Designed by Phillip Kent.
Read more about this cantilever low-wing monoplane and order plans.

Order The Alexander Bullet Plans

Written by Tom Neibuhr
As featured on page 44 in the August 2012 issue of Model Aviation.
As featured in the Model Aviation tablet app.

Order The Hobo Plans

Written by Laddie Mikulasko
As featured on page 31 in the November 2012 issue of Model Aviation.
As featured in the Model Aviation tablet app.

Order The Travel Air Mystery Ship Plans

Order the Travel Air Mystery Ship Kit (plans must be purchased separately above)

Built by Oba St. Clair, recreated by the National Model Aviation Museum
As featured on page 31 in the February 2013 issue of Model Aviation.
As featured in the Model Aviation tablet app.

Order The Miss Shirley

Build this electrified version of a Vintage RC design
Features in the May 2013 issue of Model Aviation magazine
by Dan Grotzinger

SPECIFICATIONS
Type: RC Park Flyer
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Length: 34.5 inches
Weight: 26 ounces, minus battery
Motor: E-flite Power 10 brushless outrunner
ESC: Castle Creations Phoenix-45
Propeller: APC 11 x 5.5E
Battery: Three-cell 2200 mAh LiPo
Radio: Four channels, four Hitec HS-65HB servos
Construction: Balsa, plywood
Finish: Poly-span sealed with Aero-Glass clear

The Cobra II was released as a kit in 1968 by Harold DeBolt. I built my first one in the barracks while stationed at Little Rock AFB in 1969. This is my fifth if that tells you anything. The Cobra was designed as a Formula II (slow pylon) racer and aerobatic performer with “stand-way-off” P-39 looks. It appears on the kit box in the colors of Cobra II which won the National Air Races in 1946.

It was love at first flight. The airplane, as designed, has a wonderful package of flight characteristics. For my style of flying it had one moderate and one mild shortcoming. It was designed during the transition from reeds to proportional and thus had more dihedral than necessary for use with proportional. This gave rolls the appearance of having a “wallow.”

In all versions since, I have built the wing close to flat across the top spar thus imparting a minimal dihedral. This in effect moves more of the wing area further below the thrustline so the thrustline must also be lowered to clean up the rolls. Loss of dihedral reduces rudder effectiveness, so the rudder must be enlarged also. This triad of related changes gives the Cobra the ability to perform beautiful rolls.

It is well known that double taper wings are prone to tip stall. I used to love pulling out of spins right at the ground. With the first Cobra, I once pulled out very abruptly while hitting throttle at the same time. I say once because there was no airplane left for twice. Torque and tip stall ate the airplane. My final modification is 1/8-inch wingtip washout on the 40-size aircraft.

These changes make the Cobra II a great pattern type performer with no bad habits. For the electric version, I made one other change. To counteract the instant torque and large propeller almost 3° of side thrust was added. Incidentally, I don’t think Formula II ever really took off.

Why an electric Cobra? I’ve had seven or eight scale or aerobatic electric ARFs. Most of them were structurally flimsy and designed for 3-D flying which makes them less suitable for non 3-D flyers.

I am a dedicated Vintage RC flyer. We have this great secret that we have been trying to share with the modern flying fraternity. As a rule, the old designs fly better or maybe it would be more accurate to say they fly easier. They had to—the radios of that day left a lot to be desired.

The airplanes had to be somewhat self-flying and they were since they evolved from Free Flight. Today’s jet fighters cannot fly without complex computer flight inputs called “fly by wire.” In a way our models have gone in a related direction.

The great secret in vintage models is the force arrangement. This includes wing and stab proportions and nose and tail length proportions, but in particular it is the relationship of thrustline to wing incidence and stab incidence.

The author reproduced the plans with a copy machine, then laid the copies upside down on the wood and pressed the paper copies to the wood using a hot iron. This method imprints the wood, to make cutting accurate parts easier.

The fuselage sides are matched 1/16-inch, hard-grain balsa. The square blocks pinned to the work surface helps with alignment to ensure the tail post is perpendicular.

The fuselage has no lightening holes, but it has airflow passages through the cowl blocks, bulkheads, and wing sheeting.

Small triangle-shaped balsa protects the aileron servos and EZ Link connectors during landing. Photo by Jay Smith.

The landing gear was left off to save weight and eliminate drag. Finger holes were added to the bottom of the wing to assist in launching. Smith photo.

The servo tray can be sized to fit your servos of choice. The author found the Hitec HS-65HB to be a good match. Smith photo.

The author poses with the e-Cobra. Polyspan covering provides a glimpse of the beautiful structure underneath, while the painted stripes provide contrast in the air. Smith photo.

The e-Cobra is pleasant to fly, agile in maneuvers, and fast at high throttle while exhibiting no bad habits on landing. Smith photo.

Approximately 3° of right thrust is built in to counteract the torque of the E-flite Power 10 motor. A removable hatch provides easy access to the motor and battery. Smith photo.

The first flights were still with a bit nose heavy condition. The control throws were conservative with exponential dialed in. This airplane was not touchy at all. As of this writing, I need more tail weight and maybe a little more rudder because it doesn’t want to spin. The battery saddle could be moved back into F2 a little on the next one.

It is a very pleasant airplane to fly, agile in maneuvers and fast at high throttle. It slows down nice for landing with no bad habits. All in all, the vintage Cobra II made an even better scaled down modified for electric than expected. Also it doesn’t have a bad camera angle.

Thanks to Harold DeBolt for a timeless classic design. Thanks to Jay Smith for the great photo work.

Read the entire article in the May 2013 issue of Model Aviation!

Daniel Lee Grotzinger
12460 Van Spronsen Way
Indianapolis, IN 46236

Order eCobra

Sources:

Vintage RC Society
www.vintagercsociety.org

Castle Creations
www.castlecreations.com

E-flite
www.e-fliterc.com/

Hitec RCD
www.hitecrcd.com/

Landing Products (APC Propellers)
www.apcprop.com

FAI Model Supply (Polyspan)
www.faimodelsupply.com

Features in the July 2013 issue of Model Aviation magazine and app.
Bonus content including the full parts list.
Order plans and the laser kit online.

Order The Canarrow Plans

Order the Canarrow Kit (plans must be purchased separately above)

Written by Charles S. Pipes.
A good gas design goes electric as featured in the October 2013 issue of Model Aviation.
Download free plans of the PT-19.

As World War II approached, the US Army Air Corps (USAAC) believed that a low-wing, higher-performance basic trainer was needed. The government was looking for a more demanding basic trainer that would better prepare the fledgling aviators for the high-performance nature of the combat aircraft being developed. This led to the USAAC purchasing the Fairchild PT-19 two-seat monoplane in 1939, and to quote the movie Forrest Gump, “That’s all I have to say about that.”

I need to begin by thanking Robert Somers and giving him the lion’s share of the credit for the development of this model. I converted Bob’s good gas design into an excellent electric-powered aircraft. I cannot take credit for how well it flies. The fact that it has evolved into a great-flying airplane is because Bob’s initial work produced a light, stable gas model that took minimal effort to rework.

In transitioning from the original truss design to sheet construction, I rounded the corners of the fuselage to improve its appearance.

His original design was a trussed structure built around an inverted O.S. Max .10 two-stroke with a 40-inch wingspan and weighing roughly 30 ounces dry. It had excellent flight characteristics with plenty of power for aerobatics.

As I watched him fly it my only negative thought was that the .10, being inverted, tended to be slightly finicky to start.

Shortly after seeing it fly, we decided to convert the design to a Speed 400-size electric. Bob graciously loaned me his original drawings. As a testament to Bob’s original design, the only structural change made was lengthening the nose. This helped achieve the correct CG with the lighter electric motors.

I have an older version of AutoCAD, and decided to use it for the design. Having the CAD program on my laptop allows me to work on models while traveling and to select parts on the drawings and set them up for cutting.

I chose to have John Valentine at Top Notch Product Company cut the parts. He is willing to work with builders going through the learning process of design layout. Because of the amount of travel required for my job, time in my shop is a premium and being able to email a cut file from a hotel and have the parts waiting when I get home is a great advantage.

For the diehard scratch builder, I have made sure the plans show all of the parts so that the short kit is not mandatory.

Going Electric

Having flown only glow/gas models, I have considered electrics as toys. Similar to others of my generation, I carried the preconceived notion that an electric would be heavier and underpowered compared with any glow version.

With this mentality I began working with the idea of cutting weight wherever possible, then learned that Bob is an advocate of light construction. As I made changes to switch to laser-cut parts and ease construction, I added weight to the basic airframe.

As the model neared completion I purchased a set of digital scales and had trouble believing it weighed approximately 22 ounces with a 1,650 mAh LiPo. Bob and I have concluded that the weight savings was because of the availability of all the new “light” electric hardware.

The electric motor, ESC, and battery weigh significantly less than the .10-size engine, fuel tank, tubing, and the throttle servo and its linkage. Other weight savings can be attributed to using the lighter microreceivers, servos, foam wheels, and lighter hardware. Using Solarfilm instead of MonoKote also reduced the weight.

Features

The initial effort was a trace of Bob’s design where I laid out the parts in CAD and replaced the .10 O.S. Max engine with an E-flite 450 brushless outrunner. I carried the fuselage sides past the original firewall and drew the electric motor mounted to a laminated nose block ending in a plywood nose plate.

The motor is accessed through a removable top hatch. The primary advantage to mounting the motor this way is that it eliminates the need for a separate fiberglass cowl. The most significant change at this point was to design the central fuselage into a tabbed and slotted-box design that made it easier to build the fuselage straight.

Not wanting to have to turn the model on its back or take it apart to change the batteries, I designed a removable hatch for the cockpit area, providing access to the flight battery and servos. The motor and battery hatch are held down with earth magnets.

The only other alteration I made was to change the landing gear mount from solid hardwood blocks to built-up plywood assemblies. This was done for those modelers who don’t have a small saw to do the slotting work. The airframe is self-aligning sheet wood with everything included in the short kit but the hardwood blocks and hardware.

Wing

The wing construction evolved from a traditional method of slotted LEs and TEs to a more modern version using all laser-cut parts. Cover your plans with wax paper and pin the lower spar to the plans. If you can’t get hard balsa, use basswood because the strength is worth the slight weight gain. Fit R-1, R-2s, R-3s and R-3T over the lower spar and into false TE notches. (Note R-3T is slotted to accept the wingtip former.)

Ensuring the ribs are aligned to the plans and perpendicular to the spars, pin them to the building board. Glue them to the lower spar and notched false TE using thin CA. Glue the top spar to the ribs and install the notched false LE.

If using the short kit, the bevel for dihedral is already cut and you need to correctly position it. Install 1/8-inch LE and 1/4-inch TE.

Install 1/16-inch plywood R-2As, with the 3/32-inch sheer webbing centered between the upper and lower spar. The grain should be vertical or perpendicular to the spar grain.

Install the aileron servo mounting plates. Tubes to route aileron servo wires are made up of scrap paper and glued between R-1 and R-2 prior to joining the wing halves and planking the center section.

Shape the LEs and TEs using a razor plane and sanding blocks. Glue the wingtip formers to R-3T. Glue the wingtip braces R-5 through R-8 to the top and bottom of the wingtip former—this will require bevel sanding for proper fit where the braces meet R-3T.

Glue a set of T-1, T-2, and T-3 to the top and bottom of each wingtip. Glue T-9 to the top and bottom of each wingtip. Shape the wingtip with a razor plane and sanding blocks.

Build up a left and right wing panel over the plans. The panels are joined with plywood doublers.

The landing gear blocks can be cut from hardwood or built up from plywood.

The wingtip can be built up on the wing or assembled and added to complete it.

I do my capstrips as I-beams, but other methods can be used. Don’t leave them off and be sure to make the grain perpendicular to the spar to strengthen the wing.

The wing panels are joined with epoxied 1/8-inch plywood doublers. Install the 1/8-inch center rib to allow for 1/16-inch planking. Place scrap balsa on both sides of the center rib to provide material for wing-dowel mounting.

Install 1/16-inch square stock across the LE spar and the TE to give the center planking something to adhere to. Plank the center section using 1/16-inch balsa. Install a 3/16-inch dowel in the wing’s center.

To install the landing gear blocks, build up the left and right landing gear block assemblies by gluing two L-2s to an L-1 with spacing for the 1/8-inch music wire. Glue two sets of three L-3s into a stack and attach to R-1.

Use epoxy to glue the landing gear blocks to the L-3 stack and ribs. The main landing gear is bent from the music wire and held in place with tin straps and servo screws.

Fuselage

Pin one fuselage side assembly flat on the building board and install F-3, the battery compartment floor, the wing hold-down bracket, and F-4. Ensuring that the fuselage is not twisted, install a second fuselage side. Pull the side formers together and install F-2.

Build up the motor mount and nose block by using epoxy to glue two F-1s with F-1A through F-1C. Install the nose block/motor mount assembly with epoxy. Glue in F-5 through F-8. Ensure that the fuselage is symmetrical and not twisted, bring the two sides together, and glue them at the rudder post.

Glue in ¼-inch triangular stock along the lower fuselage sides between the wing mount and the rudder post and between F-2 and F-3. This triangular stock provides support so that the lower fuselage sides can be rounded at the corner.

Using 3/32-inch balsa planks, plank the fuselage top between F-2 and F-3, and plank the lower fuselage between F-2 and F-3 with 1/8-inch balsa sheet. Plank the lower rear fuselage with 1/16-inch balsa. Glue in 1/16 x 1/8-inch balsa or basswood stringers on the turtleback. Shape the bottom edges of the fuselage.

Using 1/4 balsa sheet, build up the top and bottom areas between F-1 and F- 2 with balsa blocks. Do not glue these. Shape the nose blocks and the bottom and top hatch blocks. To expedite the process, use a power disk and belt sander to rough sand the area into shape.

Hollow the upper and lower blocks to a 1/4-inch thickness. Using epoxy, glue the bottom block between F-2 and the nose blocks. This block is critical because it carries motor stress back into the fuselage. Add guide blocks to the bottom of the upper block to align it with the fuselage sides.

Install the rudder and elevator pushrods. Glue 1/16-inch x 1/8-inch balsa stringers to the turtleback.

On a flat surface covered with wax paper, glue the hatch skin. Glue the three F-3As to the battery hatch base, then glue four 1/16 x 1/8-inch stringers into the notches in the F-3A formers.

With the battery hatch base on the edge of a table, beginning at the centerline, hold down one side of the hatch skin, allowing the excess to hang over the table as you glue.

Trim the excess skin off, allowing the hatch to rest flat on the table surface, and then glue the other side. Add scrap balsa strips to each side of the hatch base to align it with the fuselage sides. Cut out the cockpit openings.

Tail Surfaces

These are built over the plans. Cover the horizontal and vertical fin prior to mounting them on the fuselage. The area where the vertical fin meets the horizontal stabilizer is filled in with balsa blocks and covered in blue after they are installed.

Covering

The various prototypes have been covered with everything from Solarfilm to EconoKote. A slight weight savings is an advantage of this type of film covering, but does not affect its flying abilities.

Final Assembly

The motor is an E-flite 450 outrunner and is used with a 10 x 5E or 10 x 7E APC propeller. It is rated for 14 amps for Scale models in the 30-ounce weight range. Any motor in that range should work.

Power is managed with a Castle Creations Thunderbird 18-amp ESC connected to a 1,650-2,000 mAh LiPo 3S battery. Mine are from Common Sense RC. The motor current is set up using an Astro-Flight watt meter at 10-12 amps static using the ATV function on the transmitter. I used a Futaba 8U transmitter linked to a four-channel Berg receiver.

Two Hitec HS-81 servos control the rudder and elevator, and two Hitec HS-55 servos work the ailerons.

I made the aileron servo mounts out of 1/16-inch aircraft plywood.

The plywood battery compartment floor is perforated to allow air to circulate, and the cockpit openings allow heat to escape.

The receiver and rudder and elevator servos are mounted to the battery compartment floor, with the aileron servos mounted in the wings. Du-Bro aileron linkage and park flyer pushrods are used throughout. I chose E-flite wheels. The mains are 21/2-inches in diameter with a 3/4-inch diameter wheel on the tail.

Flying

Similar to Bob’s original glow version, my electric PT-19 is a pleasure to fly. It is the one model that I can say flew right off the building board.

If I had to compare it with anything in the commercial market I would say it is most similar to the Sig Four-Star. The first flight was out of a parking lot, but with 2- or 21/4-inch wheels it will fly off short grass.

The PT-19 is not twitchy when airborne and tracks straight with good response. Elevator throws should be limited to the 3/8-inch range for the first few flights.

The PT-19 is not twitchy and tracks straight with good response.

Turnaround time between flights is less than a minute because the hatch simply lifts off. The battery can be quickly swapped.

It is a true sport model that can perform aerobatics with ease. Large loops, inverted flight, stall turns, snap rolls, aileron rolls, and spins are a breeze.

With the 2,000-mAh flight packs, and my flying style (half to three-quarter throttle), flights are approximately 15 minutes, leaving the battery warm to the touch upon landing.

At a weight of 25 ounces, it is best in light air but can easily handle midafternoon breezes. Turnaround time between flights is less than a minute because of easy battery compartment access.

To land, keep the nose down and carry a little power on approach. Flare holding the nose up and let it settle.

Its wide gear and long tail make takeoffs a breeze. It tracks straight with no tendency to swing on takeoff. If you use the 450-sized motor, it only needs roughly 20 feet of runway.

Everywhere I take it people ask me which company manufactures it and I get to tell them it is scratch-built. The pride that comes from that would make it difficult for me to go back to ARFs.

Vinyl graphics from Callie Graphics provide a complete and finished look.

Thank you to Callie Graphics for the custom decals and John Valentine of Top Notch Product Company for the short kits.

—Charles S. Pipes
charliepipes@hughes.net

Bonus Photos

Download Free Plans

Download Free Builder's Guide

Specifications

Test-Model Details

Sources

Written by Robert Dance.
Build your own Short Wing Piper
Featured in the October 2013 issue of Model Aviation.
Download free plans of the Piper Pacer.

The full-scale Piper Pacer appeared in 1949 and falls into the Short Wing Pipers category which started with the Piper Vagabond in 1948, and continued with the Clipper, Pacer, Tri-Pacer, and Colt. They are referred to as Short Wings because Piper deleted three feet from root of the basic Cub wing, giving these aircraft a 29.3-foot wingspan.

The Pacer was the most handsome of these Short Wings, although the Vagabond has the cute charisma of a scaled-up model airplane. I was 15 years old when the Pacer was introduced, and I have built several versions of the Vagabond, Pacer, and Tri-Pacer. They are perfect subjects for a fine-flying model, perhaps because of their low-aspect-ratio wing, large stabilizer, and force arrangement.

My first RC Scale model was a Sterling Tri-Pacer trainer, which utilized my kit-built Controlaire reed transmitter. Shortly after that, I designed and built a small, single-channel, rudder-only Vagabond using the Ace Pulse Commander components powered by an Anderson Baby Spitfire engine. This little model also flew beautifully.

The Piper Pacer with its 18-inch wingspan, is the smallest Short Wing Piper I have built and it is the result of buying a ParkZone Ember. I was so impressed by the Ember’s amazing micro-components that I started thinking of using them in a small Scale model similar to the old Comet models I built as a boy in the 1940s.

This Pacer’s construction is similar to those Comets and to the small models designed by Walt Mooney during the 1950s and 1960s, which were offered as full-size plans in model magazines. Those who have built stick-and-tissue models should have no problem building this Pacer. Builders with a creative bent might want to convert it to a rubber-powered FF model.

The Pacer has large, balanced elevator and rudder areas, and I would recommend dual rates to lessen the throw on these surfaces. Otherwise, the model may be sensitive to control. I did not use dual rates, but to lessen the throw, I made the control horns longer than normal.

A top view of fuselage shows the Ember motor. Do not cover the top until the components and control rods are situated and the center stringer is in place.

A BSD GWJ 7mm GB Red motor with gearbox was easily mounted using two carbon-fiber rods. It also uses a very small propeller adapter.

Spektrum and ParkZone have several tiny receiver/servo bricks that can be used in this model. ParkZone’s PKZU2164 brick features AS3X artificial stabilization which might be interesting to try although I have never used it myself. This brick is also aileron capable, if you want to modify the Pacer for ailerons. The HobbyZone Champ’s components, including the motor, could be used for the Pacer.

The first motor I tried had insufficient power, so I installed a Bob Selman Designs (BSD) GB Red motor and gearbox. It mounted easily using two carbon-fiber rods. The plans show the ParkZone P-51 motor, which should have more than enough power for this model. You can look on the ParkZone, Spektrum, and HobbyZone sites for parts lists for these motor and receiver components.

For the flying propeller, I trimmed 3/8 inch from each tip of a ParkZone P-51 propeller and rounded and balanced it. ParkZone also offers control rods for these models.

Fuselage

I generally use original Titebond glue because it gives you time for adjustments and after it dries, it is easy to sand.

The entire model is built from balsa, unless otherwise noted. This is a simple model, and I have drawn the basic 1/16-inch square structure in heavy black to avoid confusion. Note that two 1/16 square pieces are used at the bottom nose area to strengthen the landing gear. I have drawn perspective views of the cowling and motor mount to aid in their construction.

Make the cowling frame using lightweight balsa, and then plank it with damp 1/32 sheet balsa. A paper pattern for the planking could help determine its shape.

The motor mount is constructed of lightweight 1/16 sheet balsa, as noted on the plans. If you decide to use another type of motor, adapt it to a mount of your own design.

I did not use acetate on the model’s side windows to assist in cooling the components. I used tiny spots of Titebond glue in four places to hold on the cowling. When I want to remove it, I carefully slice through these glued areas with a thin, double-edge razor.

Patterns are shown for the wheels and wheel pants construction. Glue the laminations and let them dry. The wheels have an aluminum tube center. I used a Dremel tool to carefully shape the wheels. A safer option would be to lightly glue a 1/16 wire in the center of the wheel, shape it on the Dremel, remove the wire, and glue in an aluminum tube.

This opening will contain the battery door hatch.





In order to determine the correct dihedral, the author made this jig from a cardboard box. He spot glued each wing to the fuselage and after drying, attached the struts.

After shaping the wheels, shape the outside of the wheel pants, then take a Dremel drill with a round carbide bit and hollow the wheel pant until the wheel has adequate clearance. Hold the wheel pant up to a light bulb to make sure you do not penetrate the balsa. Use a 1/32-diameter wire for the landing gear.

For access to the battery, I used a 1/32 sheet-silk, hinged door on the bottom of my model as shown in one of the photographs. Depending on balance, you may want to hinge your door in a different section of the bottom.

The full-scale Pacer had side stringers as shown on the J.M. Triggs three-view, but I chose not to include them because the paint scheme I used would hide the absence of side stringers. This classic paint scheme and color were taken from a Piper Pacer advertisement. If you want to see other paint schemes, search the Internet and you will find several images.

Wing

The wing is constructed in a manner similar to the open-rib design that Walt Mooney used on his small, rubber-powered Scale designs. This design makes for a lightweight wing and the upper and lower portions of the ribs are strengthened by the spars that are glued to each rib.

Make a plywood pattern for the upper curved ribs and cut them from 1/16 sheet balsa. The lower rib is 1/16 square stock. If you want a true scale rib placement, follow the placement shown on the Triggs three-view.’

The Pacer’s simple structure is reminiscent of early rubber-powered models. The wing root diagonals were eliminated on the final plans.

The tips are laminated from four 1/32 x 1/8 balsa pieces. Wet, bend, and glue them on a form using Titebond glue. Let it dry overnight before removing.

You can make the center of the wing and glue it to the top of the fuselage after you have decided where to place the brick receiver and battery. I mounted the receiver/servo brick to 1/16 sheet glued to the 1/16 square lower window frames.

After covering and painting, I spot-glued the wings to the center section in two places. You may want to construct a jig to hold the wings to the proper dihedral while gluing the wings and struts, then let the assembly dry.

Tail Surfaces

Construct the tail surfaces as shown on the plans. I used a slightly different method for hinging the rudder and elevator. I wanted to use hinges that offered the least resistance to the tiny servos. I am a fly fisherman, and I decided that my fly line leaders (or tippets) might be ideal for this purpose.

Cut a length of light leader material and draw it through a folded piece of black 400 weight emery sandpaper to give it a bit of tooth for gluing. Then take a hand pin vise with a micro drill and make holes at the hinge locations.

After the tail surfaces are covered and painted, cut a proper length of the leader and use CA glue to anchor the hinges. Be sure and use the gussets shown on the rudder and stabilizer, because without them the tissue covering may form a wrinkle on sharply angled corners.

Covering

I am from the old school and I prefer models such as this to have a finish similar to the full-scale aircraft. This model was covered with Japanese Esaki tissue, which is still available from various suppliers including A2Z Corp.

Brush three coats of nitrate dope on all of the balsa surfaces that will touch the covering, sanding lightly between each coat. A good choice of tissue color for this model would be yellow or white rather than a dark color, which would require more coats of final opaque color.

Determine the grain of the tissue and apply it lengthwise to the wings. Cut sections slightly larger than the wing area you will cover. Apply a dab of 50/50 thinned nitrate dope to the center root section of the top wing rib and to the center section of the last rib (not the tip of the wing). The dope will sink through the tissue and attach it to the wing.

The fuselage is covered with yellow Esaki tissue. A hinged door will be attached to the open area aft of the firewall for the battery.

Pull this area until it is nearly wrinkle free. You can loosen it with a brush and thin nitrate if you see an obvious wrinkle.

Attach the tissue to the outside perimeter of the LEs, TEs, and the end ribs, giving the tissue a smooth appearance. You don’t need to attach each rib at this time because the first coat of clear dope will do that.

Cut a section of tissue to cover the area from the tip rib to the tip itself. This needs covered separately because tissue does not cover smoothly on a compound surface. Once again, get the tissue as smooth as possible, but not drum tight. Cover the bottom in the same manner.

You now have covered the top and bottom of one half of the wing. Carefully trim off the overlapping tissue with a double-edge razor. Using a fine atomizer, lightly spray the top and bottom of the wing with water. Some builders use a mixture of water and alcohol, but I prefer water.

While it is wet, place the wing in a jig of raised 1/8-inch square stock and pin the wing down to prevent warps until it dries. You may want to give the wing’s TE a 1/16-inch washout. To pin it down, I slant the angle of the pins rather than pierce the balsa.

Cover the other half of the wing using the same process. After drying, paint the wings with three coats thin nitrate dope, each time placing the wings back in the jig to avoid warps.

Cover the tail and the fuselage, making sure the grain runs lengthwise and remembering that tissue does not do well on compound curves. Place the tail surfaces in a drying jig.

The fuselage needs no jig for drying, but the RC components and control rod placement need to be determined for proper access and balance before covering the fuselage and the center of the wing. Cover the cowling with tissue and sand lightly between coats of nitrate. If an area needs sealer-type filler, you can mix a bit of baby powder with the nitrate dope, but not on the open areas of covering.

Final Painting

My model was painted using thinned Brodak butyrate color dope for the final coats. I applied that dope with a basic Paasche H airbrush. You can use butyrate dope over nitrate dope, but you cannot use nitrate dope over butyrate dope.

I used Brodak Piper Cream and Brodak Brown for my Pacer. If you do not have an airbrush, you may be able to use a Preval sprayer which is available through Brodak or in many paint stores.

Each time you paint the wings and tail, place them in a jig to dry without warps. Mask the fuselage design with masking tape. You can cut the masking tape easily by applying it face down on glass and cutting it with a razor guided by a metal ruler. You can seal the edges of the masking tape with clear dope before spraying to prevent the color from bleeding under the tape.

Decals

I have provided artwork that you can scan and print onto decal paper, which is available from Micro-Mark. An inkjet printer can print them onto the decal paper in a dark brown color. Seal the decals with clear spray and following directions, apply them to the Pacer.





The completed Piper Pacer shows the paint design and the placement of decals. A non-flying propeller was used in the photo.

Flying

Using the CG shown on the plans, adjust the battery to achieve the balance. If you cannot properly balance it, try using a small bit of clay in the tail or nose.

Check your rudder and elevator control movement to make sure they move in the right direction. I suggest using a transmitter with dual rates and set the throws to minimal movement.

Charge the battery and do not use full power for the first flight. Fly on a calm day—these small models are extremely lightweight and the slightest breeze will affect their flight.

The 38-gram Pacer looks best when flown in a scalelike manner.

Adjust the motor for what you feel is enough power for it to gain altitude after hand launching. Later you may want to try takeoffs if you have a smooth surface for those tiny wheels.

Should you lack confidence for these first flights, do as I did and have an experienced RC pilot fly and trim the model. This Pacer is not meant for 3-D flying, and looks best flown in a scalelike manner. Once airborne, the tiny Pacer looks remarkably like its full-scale brother.
—Robert Dance
rbdance@robertbdance.com

Specifications

Model type: Semiscale electric
Skill level: Intermediate builder; intermediate pilot
Wingspan: 18 inches
Length: 12-5/8 inches
Power: ParkZone P-51 motor or BSD GWJ 7mm GB Red motor with gearbox
Receiver: ParkZone Brick
Battery: 1S 150 mAh
Weight: 38 grams
Construction: Balsa
Finish: Painted Japanese Esaki tissue

Download Free Plans

Or click www.ModelAviation.com/images/article/plans/PiperPacerPlan.pdf

Download Decals

Or click www.ModelAviation.com/images/article/plans/Decals-Pacer.jpg

Bonus Photos

Sources

ParkZone
(800) 338-4639
www.parkzone.com

HobbyZone
(800) 338-4639
www.hobbyzonerc.com

BSD
(417) 358-9521
www.bsdmicrorc.com

A2Z Corp
(877) 754-7465
www.a2zcorp.us

Brodak Manufacturing
(724) 966-2726
http://brodak.com

Features in the November 2013 issue of Model Aviation magazine and app.
Order plans for this 2012 Nats Winning Centaur.

Order The P-30 Centaur

Download plans for the Glastonbury Meadowlark.
Article, plans, instructions, and photos by Dennis Norman.
Online exclusive bonus content from the December 2013 issue.

In early June, Mike Nassise sent me a copy of the Tailspin newsletter. Thanks to Mike’s outstanding efforts, Tailspin is always well written and filled with three-views, clear photos, and plans. The July/August 2013 issue featured plans of the Glastonbury Meadowlark Catapult or Hand-Launch Glider designed by FAC cofounder Dave Stott in April 1986.

The grace and simplicity of the design captivated me and, with slight modification, I built a couple of them as gifts for my grandsons, Joe, age 11, and Pete, age 9, who were to have accompanied their father (my son, Chris) and me to Geneseo. Everyone chose his own color scheme, but I put them all in English markings because the design seemed to call for it.

I have included a photo of these gliders, slightly modified plans, and construction notes.

Fuselage

Total length: 111/4 inches

I. Made from 6- to 8-pound A-grain balsa sheet in two pieces that are later joined around the wing’s center line.

II. 1/64-inch plywood nose reinforcements (make two).

III. Circular ballast box cut into balsa nose (used if additional nose weight is needed).

IIII. One (1) plywood nose reinforcement is permanently glued to the model. The other is temporarily tacked to the other side of the nose during test flights. If nose weight is needed, add modeling clay to the nose. Once the balance is achieved, remove the temporary plywood, place the clay inside the ballast box, and permanently reattach the plywood nose reinforcement.

Wing

Total span: 10 inches

I. Make from 4- to 6-pound C-grain 1/8-inch balsa sheet.

II. Total dihedral: 11/4 inch (or 5/8 inch per wing half).

III. Carving the airfoil:

A. Draw carving reference lines at 1/4-inch intervals from the wing center to the wingtip, parallel to the LE.

B. The high point for the airfoil will be between 3/4 inch and 1 inch behind the LE.

C. Both LEs will be tapered using a blade and sandpaper block to a uniform thickness of 1/32 inch from center to tip.

D. The TEs will also be narrowed to 1/32 inch, but will both be carved with washout.
1. Right wing half (pilot’s right):
a. Using a straight edge, draw a line from the bottom of the right TE at the wing center to 1/32 inch below the right wingtip.
b. Draw a parallel line from 1/32 inch above the center of the right TE to the upper surface of the right wingtip. These lines on the TE will serve as a carving/sanding guide for the TE and will give you a uniform washout for the TE.
2. Left wing half (pilot’s left):
a. Using a straight edge, draw a line from the bottom of the left TE at wing center to 1/16 inch below the left wingtip.
b. Draw a parallel line from 1/32 inch above the center of the left TE to 1/32 inch below the left wingtip. These lines on the TE of the left wing will serve as a carving/sanding guide for the left TE. Notice that the washout will be less for the left wingtip than the right.

E. As airfoil carving/sanding progresses from the LE and TE toward the wing’s high point (see Wing, III, B) the carving reference lines will gradually disappear as they are sanded away. The two (2) lines at the highest point will be the last to disappear as the airfoil is completed.

F. The LEs of both wing halves are rounded. The tip portions of each LE are blended with the contour of the TE portions of each wingtip.

G. When wing shaping is finished, run some thin instant glue along the LE a short section at a time, wiping it quickly with a paper towel. This will strengthen the wing’s LE and reduce damage to the model as it is trimmed for flight.

H. The TEs of the wing halves are not tapered thinner than 1/32 inch. Making them too thin increases the likelihood of warping.

Tail Surfaces

I. Rudder/fin:

A. Make from 4- to 6-pound C-grain sheet balsa.

B. Leave LEs and TEs 1/32-inch thick for structural strength.

II. Stabilizer:

A. Stabilizer span is 5 inches and made from one (1) piece of 4- to 6-pound C-grain balsa sheet.

B. It is critical to model stability that the stabilizer be warp resistant and absolutely flat. This is particularly important if you elect to paint the model.

C. Attach the stabilizer so that it has between 0 and 3/32–inch tilt (right tip lower that left tip) when viewed by looking from the back to the front of the model.

Finishing and Painting

I. Min-Wax Spar Urethane varnish found at most hardware stores may be used to seal the raw balsa. Apply it with a small dipstick to the glider and spread it as far as possible. Do one panel at a time. After applying the Min-Wax, gently wipe it off with a paper towel and wait a day before sanding it smooth with 400-grit paper. If the varnish seems to be thick, it can be thinned 10% to 20% with mineral spirits.

II. To obtain a color finish, spray paints such as Design Master are effective, but use light coats to avoid creating weight problems.

Supplemental Files and Charts

Download plans for the Mark Rittenger’s Kingcobra.
Relive the excitement of post war racing.
Article, plans, instructions, and photos by Mark Rittinger.
Online exclusive bonus content from the January 2014 issue.

Specifications

Type: Semiscale warbird
Skill level: Intermediate
Wingspan: 57-7/16 inches
Length: 49 inches
Weight: 4 to 5.8 pounds
Construction: Balsa and plywood
Finish: Iron-on covering

Model Details

Power system: E-flite Power 32 motor; 60-amp Pro switch-mode ESC (54 amps being pulled static); Castle Creations BEC
Retracts: E-flite .25-.46 electric retracts with 90° nose and 85° mains
Propeller: APC propeller with Great Planes electric spinner
Radio system: Hitec Eclipse 2.4 GHz conversion with Optima 6 receiver
Wheels: Dave Brown Lite Flite wheels

Order Mark Rittenger’s Kingcobra

Mark Rittenger’s Kingcobra is a semiscale, electric, 57-7/16-inch-wingspan warbird. The aircraft can be built to hand launch or with retracts. Plans cost $12.00 plus shipping and handling. Please allow at least one to three weeks for delivery within the United States—longer for overseas. All domestic plans are shipped rolled via priority mail. All foreign orders are folded and shipped First Class.

Laddie Mikulasko’s Dornier Do R 4 Super-Wal
Build the multiengine, record-setting seaplane.
Article, plans, instructions, and photos by Laddie Mikulasko.
Complete build instructions and additional construction photos from the April 2014 issue of Model Aviation.





In 1914, Claudius Dornier established a company called Dornier Flugzeugwerke. Throughout its long history, the company produced many innovative designs for the civil and military markets. Until the beginning of World War II, Dornier concentrated on producing seaplanes. The most successful design was a two-engine Do J Wal.

The Wal was a popular airplane and approximately 300 were produced. European and South American airline companies used a large number of Wals. In addition to the two-engine Wals, Dornier also built 19 four-engine R 4 Super-Wals that could carry up to 19 passengers.

My model is built from foam boards that I purchased at the dollar store. The model is powered by four Turnigy 3536/9 motors. The front motors are powered by a 3S 3,000 mAh battery turning the 9 x 6 propellers at 15 amps each.

The rear motors have a 3S 3,000 mAh battery and are turning the 9 x 4.5 propellers at 12 amps each. The model could be flown using one 3S 6,000 mAh battery, but it needs added weight for balancing, so I used two batteries.

I redrew the plans to use foam instead of balsa. I made the wing in three sections for easier assembly and disassembly.

Building the Model

The first step is to remove the paper from the 3/16-inch-thick foam boards. Save the paper because you will need it for finishing.

Because the fuselage sides and the horizontal tail surfaces are 3/8-inch thick, the sheets must be glued together on top of each other to achieve the proper thickness, then glued end-to-end to make two 70-inch-long strips. Spray contact cement glue onto one side of each strip. Glue the strips to each other, but make sure that the dividing lines between the sheets are approximately 2 inches apart.

Build the tail surfaces first. The fin and the rudder are made by gluing three sheets of foam together to achieve 9/16-inch thickness. Cut out the fin (20) and the rudder (22) from this sheet. Glue the hinge spar (21) to the fin (20) and the LE spar (23) to the rudder (22).

Cut out the stabilizer (24) and the elevator surfaces (26) from a 3/8-inch-thick foam sheet. Glue the hinge spar (25) to the stabilizer (24), and the LE spar (27) to the elevators (26). Sand all of the surfaces to the shapes as shown on the plans. Cut out the opening for the stabilizer in the fin.

On the right side of the fin, make the channels for the elevator and the rudder flexible tubing. Glue in the tubing. At the bottom of the stabilizer, in the locations shown, glue in the 1/4-inch balsa blocks (29) to hold the stabilizer support struts (44).

The tail surfaces are 3/8-inch thick. Two 3/16-inch foam sheets are glued together and then sanded to shape.

Building the Wing

Cut out all of the ribs. It is important to accurately drill the holes for the carbon-fiber tubes.

The wing is built in three sections. Begin building the outer wing panels first. Because the individual sheets are only 30 inches long and the bottom wing sheet needs to be slightly longer, glue on a 2-inch strip to get the 32-inch-long sheet.

Transfer the shape of the outer wing panel onto the bottom sheet (56). Cut out the shape of the outer panel from this sheet. Transfer the location of the spars and the ribs onto the sheet. Glue the bottom main spar (52) and rear spar (53) to the sheet. Position and glue ribs W4 to W9 to the spars and to the sheet. Glue the top spars (52) and (53) to the ribs. Between the W4 ribs, glue in the plywood sheer web to the ribs and to the spars.

Cut the carbon-fiber tubes to the proper length and glue them to the W4 ribs and to the plywood web. Put this wing panel aside. Build the other wing panel to the same stage, and when it is complete, begin building the center wing section.

Transfer the location of the spars and the ribs onto the bottom foam sheet (56). Glue the bottom main spar (52) and rear spar (53) to the sheet. In the center of the wing, glue the plywood plates (54) to the bottom sheet and to the main spar. Glue ribs W1 and W2 to the spars and to the bottom sheet. Glue the top main and rear spars to the ribs.

Between the W2 ribs, glue the 1/8-inch-thick plywood sheer web to the ribs and to the main and rear spars. Plug the outer wing panels into the center panel to check the alignment. Flip the wing panels on their backs and cut out the openings in the bottom sheeting at ribs W2 and W6 for the 1/4-inch plywood blocks (60) and (65). Glue the blocks to the ribs and to the bottom sheeting (56).

The blocks (65) will hold the plastic or the aluminium clip that holds the outer wing panels to the center panel. Glue the top sheeting (57) to the ribs and to the center section spars. Glue the two foam strips (58) to the center section LE. In the rear of the center section, glue the TE (59) to the top and bottom sheeting.

Before gluing the top sheeting to the outer wing panels, sand the TE so that it tapers to nothing, as shown on the plans. Pull in the aileron servo extension wires from the F4 to F6 ribs.

The top sheeting of the other wing panel is in two halves—one is from the rib F4 to the last F5 rib, and the other is from the F5 rib to the wingtip.

Glue the top sheeting to all the ribs and spars between F4 to the last F5 rib. After that, glue the top sheeting from the F5 rib to the wingtip. Glue two strips of foam (58) to the LE and glue the aileron hinge spar (61) to the TE. Sand the wing panels.

Glue ribs W3 to ribs W2 and to ribs W4. Flip the wing panels on their backs. Drill 1/8-inch holes in the plywood blocks (60) between ribs W2 for the cabane struts and drill 3/32-inch holes into the plywood blocks between the W6 ribs for the screws, which will hold the wing struts. From a 1/4-inch-thick balsa sheet, cut out the ailerons. Cut out the opening for the aileron servo. Sand the wing panels and put them aside.

The spars are glued to the wing’s bottom skin. For easy alignment, the location of each rib is marked on the skin.

The ribs have been glued in place and top spars glued to the ribs. The top sheeting is being glued on.

This shows the sheeting nearly completed. The wingtip section is ready to be glued on.

Building the Fuselage

Transfer the shape of the hull side onto 3/8-inch foam sheets. (The actual shape of the side is shown at the top of the plans drawing number 2.) Cut out the hull sides (16). Glue the plywood doubler (7) to each hull side (16) in the location shown on the plans. Cut out all of the plywood and foam bulkheads.

Notice that most of the bulkheads have tabs at the top. Cut them out and then reattach them with masking tape. These tabs keep the bulkheads at the right height when building the hull upside down.

Pin the bulkheads upside down to the building board. Glue in the front keel (1) and rear keel (2) to the formers. Glue the top (3) and bottom (4) longerons to the bulkheads. Each front longeron—from former F1 to former F5—is cut lengthwise in the middle, so they are easy to bend when you are gluing them to the formers. Glue the hull sides to the bulkheads. Sand the longerons so that they follow the bulkheads’ contour. Glue the hull bottom sheets (8) and (9) to the hull sides and to the bulkheads.

Behind the bulkhead F8, make a secondary step by gluing the step sides (10) to bulkheads F9 and F10 and to the bottom sheeting (9). Glue the bottom foam sheeting (11) to the sides (10). Make the bottom of the hull dent resistant by using contact cement to glue balsa sheets (12) and (13) to the hull bottom.

Flip the hull right side up and remove the tabs from the bulkheads. Glue the battery floor (67) to bulkheads F2 to F6. Where bulkhead F10 is located, glue in the mounting beams for the elevator and the rudder servos. Glue in the top longeron (14) to all of the formers. Take the fin (20) and feed the flexible tubing for the elevator and the rudder through the holes in bulkheads F12 to F7. Glue the fin to the hull.

Glue the top foam sheeting (15) to the hull sides and to all of the formers. Glue the balsa nose block (16) to former F1. At formers F6 and F8, cut out the foam in the hull sides all the way to the doublers. Glue in two hardwood blocks (30) to the doubler (7). In the hardwood blocks (30), drill the holes for the cabane wire struts and sand the hull.

Between bulkheads F3 and F5, cut a large opening for the removable hatch. In the rear, where the two servo mounting beams are located, also cut an opening for the servo access hatch.

Make the wing center pylon. Glue the plywood sides (18) to the 1/4 x 3/8-inch balsa blocks. Glue the balsa sheets (17) to the plywood sides. Glue the LE (19) to the pylon, then sand to shape as shown on the plans.

The plywood doublers are glued to the hull sides and the fuselage bulkheads are positioned and pinned to the building board. Notice that the tabs are attached to the bulkheads.

The hull sides are glued to the bulkheads. The longerons will be added next.

The longerons are glued in. Each front longeron is split in half so in can easily be bent. The battery floor is also glued to the bulkheads.

Here the bottom sheeting is being glued to the bulkheads.

The entire bottom of the hull is covered with 1/16 balsa sheets.

The hull is taking shape. Next the author will cover it with paper and add scale detailing.

Building the Sponsons

Cut 1/4-diameter carbon-fiber tubes (47) to the proper length as shown on the plans. Slide the tubes into S1, S2, and S3 and then glue them to the ribs as shown on the plans. Place two shims of the same height under the tubes while the glue dries.

Glue the TE (46) to the ribs. While the shims are in place, glue the top sheeting (50) to the ribs and to the TE. When the glue is dry, flip the sponsons over and glue the bottom sheeting (49) to the ribs. Glue the LE (51) to the sponsons.

Cap the end of the S3 rib with 1/8-inch balsa sheet (63). In the location shown on the plans, cut an opening in the top sheeting and glue in the plywood blocks (48). Sand the sponsons and then put them aside.

The sponsons are reinforced with 1/4-inch diameter carbon-fiber tubes.

The Cockpit

Cut out all cockpit sides. Using thick CA, glue the sides to the crossmembers to form the cockpit and then glue on the cockpit top. Brush the sealer onto the frame and after it’s dry, sand the cockpit frame.

Building the Nacelles

Cut out plywood formers N1 to N4 and glue the magnets to them. Check the polarity to ensure that the former N1 is attracted to the N2, and N3 to N4. Next, glue in the guide dowels to formers N1 and N4.

Using a 3/8-inch foam sheet, cut out the nacelle sides (33). Glue the former N2 to the front of the nacelle and the former N3 to the rear of the nacelle and then glue the sheet (36) to the top of the nacelle. In the front, bottom part of the nacelle, glue the sheets (39) to the N2 former and to the nacelle sides (33).

Glue the sides (34) of the front cowl to the N1 former. Glue the top sheet (37) to the N1 former and to the cowl sides. Glue the sides (35) of the rear cowl to the N4 former. Glue the top sheet (38) to the cowl sides and to the N4 former. At the back of the cowl, glue a 3/8-inch foam sheet (40) to the sides. Plug the cowls into the nacelle and sand to shape as shown on the plans.

The model’s bare foam can be covered with the paper that was removed from the foam boards, or with brown packing paper. The fin, the rudder, the stabilizer, and the elevator surfaces can be covered with lightweight Japanese paper or Modelspan tissue paper.

Use carpenter’s glue that has been diluted to approximately 60% glue and 40% water to adhere the paper to the surface. You can also use a water-based clear polyurethane sealer, but don’t dilute it.

Before the covering is applied, brush one coat of the sealer on the entire model. After the sealer is dry, sand the seaplane with 60- or 80-grit sandpaper. If there are dents or other surface damage, fill them with the water-based filler and then sand some more.

Cover the center section of the wing first so you can practice covering with the paper. Cut out two sheets of the brown or white paper large enough to overlap the center section of the wing by 1 inch on all sides.

Flip the wing onto its back and brush on the sealer or diluted carpenter’s glue. Spray the paper with water until damp. Use a cloth to remove excess water. Place the damp paper onto the bottom of the wing and brush on a light coat of the sealer on the paper. Use a squeegee to smooth the paper and push out most, but not all, of the sealer, because the sealer acts as glue. Wrap the overhanging paper over the LE and TE.

When the bottom is covered, immediately brush the sealer onto the top surface of the center section of the wing and place a damp paper sheet on it. Brush some sealer on the paper, smooth it with a squeegee, and wrap excess over the LE and TE.

Always overlap adjoining sheets of paper. While the paper is wet, locate the holes for the cabane struts and puncture them. If you don’t do this, it will be difficult to locate them after the paper dries.

Anytime you cover thin surfaces with paper, such as the wing and tail, cover the top and bottom surfaces at the same time. While the paper is wet, place the surfaces vertically—allowing them to air dry. Otherwise, the surfaces will warp.

Cover the outer wing panels. Do not attempt to cover the entire wing surface in one step. Because it is a large area, if you tried to cover the entire wing with one sheet, the paper would bunch when you used the squeegee to remove excess glue. Cut the paper so that one sheet covers only one half of the one wing panel. Cover the bottom and then the top.

When you are finished covering the top and bottom of that half of the wing panel, let the paper dry. Locate the holes for the wing struts and puncture them. While the paper is drying, cover the other panel. To cover the wingtip edges, make cuts in the paper 1/2 inch apart so it easily forms around the wingtips. Cover the tail surfaces with thin paper such as Modelspan.

Use brown paper to first cover the hull sides then the top and bottom of the hull. While the paper is wet, puncture holes for the cabane struts in the hardwood blocks (30) and the holes in the balsa blocks (28) for the stabilizer struts (44).

Cover the sponsons. Before the paper dries, make sure that you punctured the holes in the plywood blocks (48), then cover the nacelles.

Lightly sand every part that was covered with paper and try not to go into the paper or the foam. If that happens, cover that spot with a patch of paper. When you’ve completed sanding, brush on another coat of sealer. Some areas may need lightweight filler. When the filler dries, sand it to prepare it for painting. Brush on one more coat of sealer on all surfaces.

Glue the center pylon to the top of the hull and the F7 bulkhead. Glue the stabilizer to the fin, smear epoxy glue onto the sponsons’ S1 rib and the carbon-fiber tubes, and then glue them to the hull sides and to the F6 and F8 bulkheads.

Glue the cockpit to the hull, and then glue the nacelles to the wing. Ensure that the motor wires are pulled into the nacelles and out of the N2 and N3 formers.

The hull is covered with paper. You can use the paper that was removed from the foam boards or brown packing paper.

The model is powered by two 2820/14 motors in the front of the nacelles and by two 2212/34 motors in the rear of the nacelles.

Make the Cabane

First, make the four cabane struts—two for the front (31) and two for the rear (32). Bend them to the shape as shown on the first plans page. Take the electrical lugs and bend the eye to roughly 90°. Slide the electrical lugs onto each strut and insert each strut into the holes in the hardwood blocks (30).

Using scrap pieces of foam sheets, cut out a V-shape cradle so that the hull can securely set in it at a 90° angle to the building board. Plug the wing panels into the center section. Slide the wing onto the fuselage pylon. At the same time, guide the cabane wires into the holes in the bottom of the wing.

Ensure that the wing is perpendicular to the hull at a positive angle of attack as shown on the plans. If the holes are slightly misaligned, rebend the strut’s wires. When the wing is aligned, slide the electrical lug until it touches the plywood block (60) on the bottom of the wing. Make sure that the eye is positioned over the hole for the screw that will hold the wing to the fuselage.

Use pliers to crimp the lug onto the cabane strut. Do the same for other three. When done, gently remove the wing. Take each strut and solder the lug to the wire. When the soldering is done, insert each strut back into the hardwood blocks (30). Place the wing back onto the pylon and onto the cabane struts.

Cut out two plywood cabane frames (41) and insert them between the struts (31) and (32). Glue them to the struts with epoxy. After the glue hardens, remove the wing and remove the cabane from the hull. Wrap fiberglass cloth around the wire struts and the plywood frame. Saturate the cloth with CA glue and then sand the cabane.

At the bottom of the cabane, smear epoxy glue onto the wires. Insert the cabane wires into the holes in the blocks (31). Place the wing back onto the top of the cabane and the fuselage pylon. Make sure that the wing is still aligned and let the epoxy cure. After the glue has hardened, use four screws to attach the wing to the cabane.

Make the Wing Struts

The simplest way to make the struts is to use K&S Streamline Aluminium Tubes. Cut them to the required length, flatten both ends of the struts, and bend the ends of the tubing so that the flat part of the strut is flush with the wing at one end and with the sponsons on the other end.

Drill the holes in the flat part of the strut. Mount the wing struts to the wing and to the sponsons. Watch for wing warping.

In the rear of the hull, glue the struts between the stabilizer and the hull. There is one more thing to do to give this model a scalelike look. As the plans show, the hull and the sponsons have antislip corrugated strips on the top surfaces of the fuselage and sponsons. To simulate corrugation, cut the 1/16 balsa sheet into 1/16 x 1/16-inch strips. Some of them will not be long enough so you will have to splice them. Before gluing in place, take each strip and lightly sand it with 100-grit sandpaper.

Seal the balsa with dope or polyurethane sealer and sand again. Using the plans drawing as a reference, glue the balsa strips to the hull and to the sponsons.

The cabane strut has been glued to the hull. Notice the electrical lugs soldered to the cabane wires.

The hull and the sponsons have antislip corrugated strips on the top of their surfaces to add scalelike detailing.

Painting and Finishing

Use your favorite paint. The seaplane is white except for the bottom of the hull, the top and bottom of the sponsons, the wing struts, and the black registration numbers. Use scrap balsa to make the dummy engine heads and the radiators, and paint them black. Glue the engine heads to the cowls.

Inside the cockpit frame, glue in the windows. Install all of the hinges, horns, servos, and pushrods. Solder the connectors to the motor wires. Solder the servo plugs onto the elevator, rudder, and the aileron extension wires. Install the motors. Because the rear motors are smaller, make and glue the false firewall to the N3 formers.

Connect all of the electrics as shown on the schematic located on the second plans page. Notice that the three speed controllers have the red wire lifted. If this is not done, the speed controllers will not properly work. Install the batteries and position them so that the model balances on the CG point as shown on the plans.

To have differential control of the rear motors, you need to install a V-tail mixer as shown on the schematic. Check the differential motor control by moving the rudder stick to the left. The rudder should move left and the rear right motor should speed up. The opposite will happen when moving the stick to the right.

Flying

Takeoffs are smooth, and the model is a gentle flier. Good luck.


—Laddie Mikulasko
lmikulasko@cogeco.ca

Plans

You may order plans by calling Greg Prater at 765-287-1256x507.
Plans cost $29.00 plus shipping and handling.

List of Supplies

Thirteen 20 x 30 x 3/16 (4.5mm to 5mm) foam boards
Foam-safe glue
Eight 1/8 x 1/4 x 36 spruce spars
One 1/32 x 12 x 6 plywood sheet
One 1/8 x 12 x 12 plywood sheet
One 1/16 x 12 x 12 plywood sheet
One 1/4 x 6 x 6 plywood sheet
One 1/4 x 36 x 3 balsa sheet
Six 1/16 x 36 x 3 balsa sheets
One 1/8 x 36 piano wire
Water-based clear Polyurethane sealer
3M 77 contact cement spray
40- and 60-grit sandpaper

See the plans for more supply details.

Specifications

Type: Semiscale amphibian
Skill level: Intermediate
Wingspan: 72 inches
Length: 62 inches
Weight: 9.5 pounds
Wing loading: 23 ounces per square foot
Construction: Foam, balsa, and plywood
Finish: Painted

SOURCES:

K&S Precision Metals
(773) 586-8503
www.ksmetals.com

AMA Plans Service
(765) 287-1256, ext. 507
www.modelaircraft.org/plans.aspx

Exploring asymmetry with an unconventional configuration
Article, photos, and design by Terry Dunn
Read the full article in the May 2014 issue of Model Aviation.

I recently set out to expand my understanding of asymmetric aircraft. When I began this quest for knowledge, I had the classic examples of asymmetry in mind—namely the Blohm und Voss Bv 141 and Rutan Boomerang. Both of these designs are proven successes, yet their unconventional configurations make one question how they can even fly in a straight line.

My breakthrough came when I realized that nearly all propeller-driven airplanes are asymmetric to some degree. With one or more propellers generating a spiraling slipstream, torque effects, gyroscopic forces, and sometimes uneven thrust (P-factor), it’s a wonder that any propeller-driven airplane can fly in a straight line! Yet, straight and level flight was mastered a long time ago.

After I realized that asymmetry is the norm rather than the exception, my question changed from “How do asymmetric airplanes work?” to “How much asymmetry can be tolerated?” I started with one confidence-building asymmetric kitbash of a Flyzone Red Hawk (see “The Joy of Kitbashing” in the August 2012 MA). Next, I set out to design an asymmetric model that would appear radically unconventional, perhaps even unairworthy to some, yet would have stable and predictable flying traits. The Parallax is the result of these efforts.

The Parallax is slightly more than a modern adaptation of the Bv 141. I make no claims that any aspect of the airplane’s performance is enhanced by its asymmetry. My position is that little is compromised despite its asymmetry. This airplane is the foam-and-LiPo embodiment of the notion that airplanes don’t necessarily have to look right to fly well.

The Parallax is built with Depron foam and requires no ribs. Here, the carbon-fiber spars are being glued into place before adding the top sheeting.

The all-foam airframe of the Parallax produces a lightweight and easily repairable structure. This unit is ready for a coat of paint and finish work.

This late 1930s-style Parallax is an example of how diverse themes can be achieved with subtle differences in shapes and colors. Note that the motor is on the right side, necessitating a reverse-rotation propeller.

You may not believe it until you see it, but the Parallax flies normally. As long as you’ve kept it light and stuck to the plans (or the allowed deviations), you should have a well-mannered sport airplane with aerobatic capability.

My adventures with the Parallax have satisfied my intent to learn more about the intricacies of asymmetric airplanes. I have also realized that understanding and utilizing asymmetry opens countless new and exciting possibilities for unique designs. I am far from finished with this foray into a seemingly untapped genre. If you’d like to join me, I think you’ll agree that the Parallax is a good place to start.

Read the entire build article and see more construction photos in the May 2014 issue of Model Aviation.

-Terry Dunn

Construction and Flight Video

Order Terry Dunn's Parallax

Asymmetric park flyer by Terry Dunn spanning 32 inches. Plans cost $12.00 plus shipping and handling. Please allow at least one to three weeks for delivery within the United States—longer for overseas. All domestic plans are shipped rolled via priority mail. All foreign orders are folded and shipped First Class.

SPECIFICATIONS

Type: Sport model
Skill level: Intermediate
Wingspan: 32 inches
Length: 33.5 inches
Weight: 14-17 ounces
Wing area: 161 square inches
Power system: 100-200 watt outrunner; 3S 800 to 1,300 mAh LiPo battery
Construction: Foam

SOURCES

Castle Creations
(913) 390-6939
www.castlecreations.com

E-flite
(800) 338-4639
www.efliterc.com

ElectriFly
(800) 637-7660
www.electrifly.com

Hitec RCD
(858) 748-6948
www.hitecrcd.com

Thunder Power RC
(702) 228-8883
www.thunderpowerrc.com

AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx

Designed and Drawn by Dennis O. Norman
Rubber Powered Peanut Scale Fokker D. VII
Featured in the June 2014 issue of Model Aviation.
Download free plans of the Fokker D. VII

It has recently been noted that there is a steady decline in the number of Peanut Scale models being flown at Flying Aces Club (FAC) meets. Chris A. Boehm, of the Cloudbusters Model Airplane Club of Michigan, Inc., and Rich Weber, president of the Cleveland Free Flight Society and editor of FAC News have started a campaign to increase Peanut Scale flying.

This plan was drawn as the subject of an early Air Ace Models plan book. The plan book and full-color tissue markings are available from Air Ace Models for $20, plus postage. A 134% enlargement of the plan is also available with the plans book and enlarged tissue coverings for $30, plus postage.

Download Free Plans

Or click www.ModelAviation.com/images/article/plans/peanutfokkerdvii.pdf

Simplicity and versatility in foam
Article, photos, and design by Charles Mackey
Read the full article in the June 2014 issue of Model Aviation.

The X-Stream is the fourth in the series of “X” designs. All were successful and unusual, but the X-Stream was different because it was a complete break from the first three in order to test the

The wing area of a typical small foam design was doubled and used as the amount of side area for the X-Stream. The Mean Aerodynamic Chord (MAC) or 25% of the side area was put on the wing’s CG. The control surfaces were doubled in area from what would normally be used.

To balance the airplane, it was necessary to move everything forward in order to use pull-pull controls. Thanks its twin I-beam construction, it was unnecessary to use external bracing. The design goal was to make a flying wing with good knife-edge qualities and a wide range of controllable speeds—especially for slow flying.

If you are new to scratch-built foam airplanes, I’ll share a few tips. First cut out all of the parts. Glue the two .008 carbon-fiber strips that form half of the I-beam in place as shown on the plans. After they are dry, turn them over and place them on a flat surface. Now glue on the two layers of 3mm foam around the edges of the airplane and in the I-beam area.

Next glue on the other two strips of carbon fiber to complete the two I-beams. Now complete the bottom of airplane as far as you can. That would include the fuselage bottom, epoxying the three servos in place, and adding the foam 45°-angle brace on one side as shown on the plans. Next add the .008 x 1/4-inch X carbon-fiber strip that runs from the motor mount to the high point of the fuselage bottom.

The next step is important. You need a way of support the airplane while you complete the top half. In the past, I had used similar-size full cans of food from the pantry, but it was frustrating.

I solved this problem by using six pieces of 2 x 6 dry wood that had been squared on a table saw and checked to be true. My friend, Ron Hudson, uses cement blocks for this purpose and he is happy with his method. Do you have some new ideas?

The X-stream (center) is the fourth of the X series that includes X-Files (R), X-File II, and Half X (L).

The author used a Turnigy 2204 motor, Castle Creations Thunderbird 9 ESC, Berg 4 receiver, and three Hextronic HTX500 servos. He used a 3S 370 mAh battery.

The Pull-Pull Control System

Long control horns and servo arms will ensure that any unwanted play in the system will be negated. Avoid short control arms. I extend my servo arms with 1mm diameter carbon-fiber rods that are 3 inches in length. Cut a slot in the servo arm to fit the rod. It doesn’t need to be centered, but leave enough room for the servo screw.

Bind the arm to the rod with thread or small soft wire and then fill in any gaps with epoxy. Install the radio equipment and control horns. Now is the time to set up your control surfaces and trims. Turn on the transmitter and install the servo horns as close to perpendicular to the foam surfaces as possible. Now use your subtrim or centering to make final adjustments. When the alignment is correct, turn the transmitter off and lock the servo arms in neutral with scrap foam and masking tape.

You are now ready to install the pull-pull lines. Attach the lines to the servo arm ends with a slip knot, tighten, and glue it in place.

I use vinyl tubing and hot glue on control horns to make them adjustable. Lock the elevator and rudder in neutral. Cut six pieces of vinyl tubing approximately 3/8 inch long. Working on one servo at a time, feed the lines through the tubing and place it over the rod ends.

Pull both the lines tight and glue with hot glue. They do not need to be as tight as a guitar string, merely tight enough to remain straight. If you ever need adjust your controls, touch the tip of your hot glue gun to the tubing, adjust the line, and reglue it.

Choosing Your Motor

I started with a 2208-14T Turnigy motor with a 3S 400 to 500 mAh battery and turning an 8 x 4.3 SF propeller and it worked well until I burned up the motor with the large propeller. Next I tried an AXI 2208/34 and it did well with a 9-inch propeller on a 3S LiPo. I now have a Hacker A20-34S with a 3S LiPo and a 9 x 4.7 propeller and I am happy with that.

The most important thing is to maintain the balance point on the front I-beam by relocating the battery.

Flying

I have a few words about flying foam airplanes. I started designing aerobatic airplanes in 1946 and I believe that foam airplanes are the best thing that has ever happened for those of us who love this type of flying.

These airplanes are inexpensive, quiet, simple to build, and I have no fear of flying them. Their other benefits include being easy to repair and capable of flying in a wide range of areas. You can fly in a gymnasium or soar with the eagles in the sky.

When you develop your flying skills, you can take off on windy days when those with big, expensive airplanes are unwilling to take that risk and are packing up. You can put on a windy-weather demonstration by flying backward, doing knife-edge hovering and rolls only a few feet away from yourself, and make spot landings at your feet. You will learn to regard the wind as a friend. Now that is fun!

I have a pleasant wish to send to you: I hope you enjoy your first flight as much as I did mine.

Sources:

The Composites Store Inc.
http://cstthecompositestore.com

Hobby Express
www.hobbyexpress.com

Aero-Model Inc.
www.aero-model.com

Hobby King
www.hobbyking.com

RCFoam
www.rcfoam.com

A simplistic FF ruber Design
Article, photos, and design by Tom Houle
Read the full article in the July 2014 issue of Model Aviation.

Leeon Davis wanted his own airplane, but he didn’t want to spend a large amount of money to achieve his goal. He looked to see what was available, then decided to design his own.

Drawing on his professional metal-working experience and skills, Leeon designed an easy-to-build, two-place airplane that only required simple aluminum cutting and bending. The design had to transport two adults and some baggage. Leeon used the Clark Y airfoil to ensure plenty of lift out of the smallish wing.

The Davis DA-2A square, boxy outlines could not be easier for the homebuilder. Leeon’s design employs a simple box fuselage. The cockpit section is framed with lightweight, square steel tubing.

All of the formers, frames, and other parts are short enough to be bent up on a small brake, and then riveted together. The airplane has constant-chord wings and V-tail, and the side engine cowling cheeks are simple curves.

I’ve always admired the simplicity of Leeon’s design and vowed that someday I’d build a FF Scale model. I searched online and turned up a pair of Davis DA-2A peanut plans by Lloyd V. Hunt and William McCombs respectively. These plans were helpful in visualizing the airframe for a larger model. A Google search turned up a number of Davis DA-2A photos. I tracked down a three-view from a 1971 issue of Air Trails magazine.

H.G. Frautschy, executive director of the Experimental Aircraft Association’s (EAA) Vintage Aircraft Association, provided me with EAA Archive photos. The full-scale DA-2A photo in this article is courtesy of the EAA Archive.

Before I get into the aspects of how I designed and built this interesting airplane, I opted to use old-fashioned rubber for power; however, there are lightweight RC and electric power systems that would fly this airplane. Had I chosen RC electric, I would have left the V-tail feathers fixed and used aileron controls.

Let’s get started.

Nose-gear strut, balsa wheels, and carved propeller

I started constructing the Davis with the nose-gear wheel and strut assembly. My goal was to fabricate a nose-gear tire and strut that would closely replicate the one used on the full-scale aircraft.

I began by cutting a 3/16 x 21/2-inch strip of brass from a sheet of .010-thick brass. Scissors will do to rough-cut the brass. I smoothed and filed the strip straight and deburred the edges. I cut the strip long to allow for handling and soldering.

I spotted a hole in the strip midway between its ends and drilled and reamed it to 3/32-inch diameter. I cut a couple of crosswise slots at one end of a length of 3/32-inch brass tubing. You can determine the length of the tube from the plans. After I flared the tube’s slotted end with long-nose pliers, I slipped the tubing through the brass strip and soldered the tube to the strip. The tube should be square to the brass strip.

I carefully formed the brass strip over a 5/16-diameter dowel and then marked the two axle holes, which are shown on the plans. I drilled these holes with a pin vise to clear a .030 brass wire axle. I inserted a 5/16 basswood block between the brass strips while I drilled out the axle holes. Finally, I trimmed the ends of the brass strip, and radiused the ends as shown on the plans.

I cut the 3/32-inch brass strut tube to its final length as shown on the plans. The tube will slip over a .045 music wire strut that extends from the bottom of the fuselage cowling. I did not attach the tubing strut to the .045 wire until after I had sheeted the fuselage cowling. CA glue will hold the tubing strut to the .045 wire.

The wheel diameters are 11/8 inches for the nose wheel and 11/4 inches for the main gear. I looked through my parts collection and on online, but was unable to find wheels that matched my required diameters. I’d heard of builders who turned their own wheels, but I had never before tried it.

I found an article that made it seem so simple I had to try it. All I needed was hard 1/16 balsa sheet, 3/32-inch brass tubing, and a Dremel or similar power tool. A small drill press would also work.

The three wheels are cross-grain, laminated, hard 1/16 balsa. Laminate enough balsa sheet to make three wheels and then some. There will likely be a gentle learning curve. The main gear wheels are 11/4 inch in diameter and require seven 1/16 cross-grain laminations.

The nose wheel is 11/8-inch diameter and requires four cross-grain laminations of 1/16 balsa sheet. I used CA glue to laminate my wheel stock. After the glue had kicked, I laid out the wheel circles and their centers. I laid out a few extra wheels just in case I botched my first attempt.

I cut the circles from the laminated balsa approximately 1/16 inch too large. I drilled holes through the wheel centers to clear lengths of 3/32-inch diameter brass tubing. I cut the brass tubes a couple of inches long. Before I glued the brass tubes to the rough-cut wheels, I checked each tube to make sure it was perfectly square to the face of each wheel.

Cut and form a .015 inch brass sheet. Slot and flare the end of a piece of 3/32 diameter brass tubing. See plans for the tubing length and forming the brass sheet.

Solder the flared end of the 3/32 tubing to the .015 brass sheet.

When satisfied, I soaked the point where the tubing goes into the balsa wheel. The CA glue will wick deeply into the balsa and retain the tubing. The tubing extension functions as the axle bearing, providing a mandrel to chuck into my Dremel hand tool.

I initially ran my Dremel tool at a low speed to check for wheel wobble. If there is any wheel wobble, make a new wheel and extended axle. To shape my wheels, I held the Dremel tool in one hand and a folded piece of 80-grit sandpaper in the other. I set the Dremel tool to a low speed until I determined how the balsa would react to the sandpaper.

As I gained confidence, and each of the wheels approached its final outline and cross-section, I turned up the speed and lightly applied the sandpaper to the wheels. A final smoothing with 150-grit sandpaper will polish the balsa. If there are any dimples in the balsa tires, you can easily fill them with Squadron white or green putty.

After the wheels were turned, I cut off the brass tubing extensions with a Zona saw. I was amazed by my first attempt at making wheels. It is easy to do; just remember to keep a light touch with the sandpaper. The entire process only took an hour or two to complete.

The 7-inch propeller dimensions came from an article on propeller carving by Bill Henn, which I found online. The propeller block layout is shown on the plans. I carved mine from hard balsa and attached a rough-shaped balsa spinner to the hub, which I final sanded after I had attached it to the propeller. With the parts finished, I turned my attention to constructing a simple pair of wings.

Wing Construction

The wings are an easy-to-build, one-piece affair. They may not look strong enough, but my rough-and-tumble initial trimming flights proved they could withstand ground contact.

I cut a rib template from Styrene, then, traced the rib outlines onto 1/16 balsa sheet. I cut the 3/32 x 1/4 -inch TE from hard balsa. I shaped and sanded the correct angular cross-section into the strip. The LE is hard 1/8-square balsa. The wing spar is a 1/16 square balsa and corner and dihedral gussets are 1/16 balsa sheet.

I built my two wing panels and the center section directly over the plans. I pinned down the wing center section, blocked up the wingtips to 15/8 inches at each tip, and glued everything together, adding 1/16 balsa sheet gussets at the dihedral breaks and corners. At the point, I shaped and sanded the LE.

The ribs with notches in their undersides accept the 1/32 aircraft plywood rectangle that holds the main landing gear .045 wire. I bent up the main gear to the true length shown on the plans, and then using soft brass wire, I sewed it to a 3/8 x 31/2-inch length of 1/32 aircraft plywood. I added the 1/32 balsa sheet wingtips to complete the wings and ready them for covering. I covered my wings with from Easy Built Models domestic white tissue.

Construction of the wings could not be simpler. Strong and light, it will hold up to first flights. The tip ribs are covered with 1/32 soft sheet.

Note the center section ribs are notched to accept the 1/32 aircraft plywood main gear leg mounting plate. The .045 music wire struts are bound to the plywood with 28-gauge soft brass wire. CA glue secures everything.

Tail Feathers

Building the V-tail feathers was easy. I used 3/32 square strips throughout for a strong, warp-free structure. I cut the corner gussets from 3/32 balsa sheet. Use the plans to ensure the correct dihedral for the V.

After gluing the two halves to the correct dihedral, I covered my tail feathers with Easy Built Models domestic white tissue. To prevent warps when I shrank the tissue, I blocked up and pinned down the V-tail surfaces and shrank the tissue in two steps.

When the tissue was taut, I added a 3/32 balsa sheet angle brace to the V-tail LE. The angle brace pattern is shown on the plans. I sheeted in the valley with 1/32 balsa sheet from the 3/32 angle brace from the LE to the TE. I set aside the finished tail feathers and moved to the fuselage.

Unassembled V-tail plates, super simple 3/32 square construction. Be sure to pin it down when the tissue is shrunk.

The assembled V-tail. Do not assemble until after the two halves are covered with tissue. Note the 3/32 sheet angle attached to the leading edge of the V-tail. The balsa angle ensures a correct V dihedral angle.

Fuselage Construction

I began constructing the fuselage, cutting and gluing formers A through E. Formers B through E are soft 3/32 x 3/16 balsa square strips. Former A is 1/32 aircraft plywood laminated to a 3/32 balsa sheet.

I cut the wing saddles from soft 3/32 balsa sheet. You will need to cut the saddles before you begin the fuselage assembly.

The basic fuselage structure consists of two 3/32 square sides and the 3/32 wing saddles. To ensure identical sides, they were constructed one on top of the other directly over the plans.

I made up a pair of curved upper cockpit bows from two strips of 1/32 x 3/32 basswood. I soaked the basswood in hot water, then laminated and molded the bows over a pair of balsa forms. After the bows had dried, I spliced them to 3/32 square upper longerons. These longerons run from the top rear of the cockpit sides to the aft end of the fuselage.

Before I erected the two 3/32-inch sides over the plan view, I notched the upper and lower longerons to accommodate angular breaks in the fuselage sides, then pinned formers B through E upside down over the plan view. Note that the canted upper halves of formers C to E are not yet attached. They are installed after the basic fuselage is removed from the plans.

Make sure formers B through E are vertical to the building board and that they align with the fuselage side uprights. At this point, I added the 3/32 upper and lower crossmembers at the nose (former A) and the aft fuselage break point.

When I pulled together the nose and tail posts, I made sure the sides were centered over the plan view. Next, I installed the rear peg uprights, which are 1/32 aircraft plywood sheet laminated to 1/16 sheet balsa.

After removing the basic fuselage assembly from the plans, I attached the three upper fuselage canted formers C through E. I attached former A to the front of the fuselage.

The .045 music wire nose strut was next. Using the side view as a guide, I bent up the .045 music strut, and then bound it to a piece of 1/32 aircraft plywood with soft brass wire. I glued the plywood into the bottom face of the nose, notching the plywood into the bottom of former B so the wire and plywood would not interfere with the 1/32 balsa sheeting yet to be added. The wire and plywood enable a solid nose-strut attachment and add needed nose weight.

The soldered brass tube nose strut slips over the .045 music-wire extension. CA glue holds the brass in place. Align your telescoped nose strut fore and aft before you CA glue the brass tubing to the music wire.

At this juncture, I attached the curved upper cockpit bows at their respective notches in upper formers C through E. The attached turtledeck longerons run to the rear of the fuselage and are faired into the upper fuselage longerons at the LE of the V tail. Now I was ready to begin sheeting the fuselage.

Because the side cheek cowls are the trickiest part of the sheeting, I started there. First, I added 1/32 balsa sheet to the flat top and bottom faces of the cowl from former A to former B. I cut a slot in the lower sheeting to allow the sheeting to fit around the nose strut. I filled in the slot with scrap balsa.

I rough-cut the curved cheek sheeting from soft 1/32 balsa sheet, then soaked the pieces in hot water. I wrapped the balsa around the curved sides from formers A to B, and held the pieces in place with my fingers and masking tape while I spot glued the curved sheeting to the fuselage with CA glue.

These are simple curves. As long as the balsa is soft and well soaked, it’s an easy wrapping process. The wet balsa will not affect the adhesion of the CA glue; water may actually cause the glue to kick even quicker.

With the nose cowling sheeted in, I worked my way aft starting at the bottom of the fuselage, then the lower sides, upper sides, and finally the top of the turtledeck. The entire fuselage is skinned with soft 1/32 balsa sheet.

To add strength to the cockpit and facilitate sheeting the curved cockpit bows, I ran that sheeting cross-grain. I then framed in a 1/2-inch opening at the rear peg to assist in installing the rubber motor. I block sanded the sheeted fuselage, using Squadron white putty to fill dings in the soft balsa.

I built the nose block from seven cross-grain laminations of 1/16 balsa sheet. I shaped it as shown on the side and plan views.

The nose plug is three cross-grain laminations of 1/16 balsa sheet. The nose plug must fit tightly into the square diamond opening in former A. I did not build down or right thrust into the nose block. Down thrust is included in the angle of former A. For flying purposes, it was about all the down thrust I needed.

I used an old Jasco ball-bearing thrust washer on my propeller. I slipped it onto the propeller shaft before I bent the rubber hook into the .045 music wire.

The finished nose strut with .030 brass wire axle. Solder the axle ends after the nose wheel is in place. Tubing slips over .045 music wire strut. CA holds the tubing to the strut.

Laminated balsa wheel turned on a Dremel tool. The 3/32 diameter brass tubing is cut off after turning the wheel. Paint flat black. Add silver paper or Styrene hub disks.

The propeller should be hard balsa, pine, or basswood. Note the slightly rounded blade tips. Start sanding with 50-grit sandpaper and work up to 220-grit. The finished propeller gets a couple of coats of clear dope, then painted silver with a red spinner. Propeller shaft is .045 music wire. Thread is bound and CA glued to the propeller hub. A Crockett or other hook is required for winding.

The two fuselage sides, 3/32 square and 3/32 sheet wing saddles. To ensure sides are identical, build one side atop the other.

Fuselage formers B through E are constructed over the plans. Use 3/32 x 3/16 balsa strips. Install the top halves of formers B to E after the fuselage sides are erected. The cockpit bows are laminated 1/32 x 3/32 basswood strips. Angle splice the bows to 3/32 square. balsa turtle deck longerons.

The assembled fuselage is ready for former A and the tops of formers B through E.

Former A and the tops of formers B through E attached to the fuselage. The laminated cockpit bows are attached next.

The brass tubing nose strut assembly ready to slip over the .045 music wire extension. The 3/32 sheet backing at former A facilitates gluing the 1/32 sheeting to the cowl cheeks.

Retain the brass nose strut tubing with gap-filling CA glue.

The cockpit bows and turtle deck stringers installed. Note the turtle deck stringers run to the L. E. of the V-tail assembly.

Fuselage sides and bottom sheeted with soft 1/32 balsa sheet. The 1/32 cockpit top sheeting runs cross-grain.

The nose strut radiator housing is built up from soft 1/16 balsa sheet. Note the opening at the bottom rear of the fuselage for attaching the rubber to the rear peg.

The fuselage sheeting completed. The three windshield supports are 3/32 strip. The instrument panel glare shield is black construction paper.

There is a built-up box under the nose cowling where the nose strut exits. I believe this is a radiator housing. Note: the fairing on the bottom of the nose block aligns with the front face of the radiator housing. I built my radiator housing per the plans with soft 1/16 balsa sheet. In retrospect, because I had to add nose weight, I could have used heavier balsa or even plywood. I slotted the housing to accommodate the nose-gear strut.

An instrument shroud on the full-scale aircraft runs from the top edge of the panel to the front edge of the windshield. I replicated this detail with folded black construction paper. At this point, I added the windshield center and corner 3/32 balsa supports. I also added paper hubs painted silver to the three balsa wheels. Except for paint and trim, this completes the fuselage.

Covering, Assembly, and Painting

I covered the wings and V-tail components with Easy Built Models domestic white tissue. I also I added washout to the wingtips. I used Elmer’s white glue to attach the wings to the fuselage wing saddles. The glue gave me some time to accurately position the wings before it cured.

Fitting the V-tail into the rear of the fuselage took some adjusting. I had to angle the inside faces of the upper fuselage longerons to enable the V-tail assembly to fit snugly into the fuselage with the LE of the V-tail set at zero incidence. I left the rear of the V-tail loose to allow glide trim adjustments.

I gave the model a light spray coat of Krylon Matte spray, then a light coat of Design Master floral spray. This lightweight spray is available in many colors at craft stores. I did the aileron and elevator markings with a black Sharpie pen.

The wing walk is black tissue. The front of the nose block is painted flat black to simulate the open cowling behind the propeller hub and spinner.

Bevel trim the inside faces of the fuselage top longerons so that the V-tail assembly rests on the top edges of the top longerons.

The top edge of the 3/32 angle gusset at the LE of the V-tail assembly should sit exactly 1/32 below the top of the turtle deck sheeting. This positions the LE of the V-tail assembly at 0° incidence. Fill the space between the V-tails with a triangular piece of 1/32 sheet. Leave the TE of the V-tail assembly loose to allow shimming in negative incidence.

The finished model was sprayed with yellow floral paint over the tissue.

Flying Notes

I added some nose weight to balance the airplane at the point shown on the plans. I made the test glides without rubber over tall grass at a park near my home. The Davis is no lightweight. It doesn’t glide well, but I was able to get reasonably flat test glides with nose weight and a 1/32 shim beneath the TE of the V-tail.

I began powered flights with six strands of braided FAI TAN super sport rubber. It wasn’t enough to gain much altitude, but eight strands did the trick. The model climbs out quickly in an open, left-hand circle. I suggest keeping that turn open with a slight amount of right thrust. It’s definitely not an endurance model, but it sure is pretty in the air.

This is Harmon Lange’s Davis DA-2 and the second one built. Photo courtesy of the EAA Archive.

Specifications

Type: Semiscale FF
Skill level: Intermediate
Wingspan: 19-3/8 inches
Length: 18.5 inches
Weight: 3.3 ounces
Wing area: 92 square inches
Construction: Balsa




—Tom Houle
thoule@wi.rr.com

Sources

AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx

Easy Built Models
(334) 358-5184
www.easybuiltmodels.com

Build your own thermal hunter
Article, photos, and design by Dick Sarpolus
Read the full article in the August 2014 issue of Model Aviation.

RC sailplanes have changed during the past 45 years. Now there is carbon fiber, vacuum-bagged fiberglass wings, ailerons, spoilers, flaps, crow settings, and highly efficient airframe designs.

My first RC sailplane was built with the wing and stabilizer from a large-class FF model, with a fuselage made to hold the radio gear. Launching was done by hand towing—like FF towline gliders. Although running across a field towing an airplane was good exercise, I sure didn’t like it.

Next I tried hi-starts, with shock cord or surgical tubing for the slingshot power. This again was a lot of work and not much fun.

Our first winches were gas-lawn-mower-engine powered, with a chain drive and clutch setup turning a large drum to wind in the line. Turnaround pulleys were another item to figure out. The gas-engine winches were noisy, messy, and we had plenty of broken lines and broken wings.

Electric winches were next, and somebody finally figured out that the old Ford starter motors with the long shafts would work for our needs. Today the winches use small, efficient, powerful modern electric motors.

I consider the best advancement in technology from those early days is the use of a powerful electric motor and folding propeller in the nose of today’s RC sailplanes. I’m not talking any sort of contest flying—just a sunny summer day, soaring for fun, looking for the thermals, and enjoying flying and easy launching without a winch or hi-start.

I wanted to do some sailplane flying and I wanted to make wood chips and sawdust to do it—not go out and buy an ARF. I wanted to do this retro style, for nostalgia’s sake. When looking back at the early model sailplane activity, nobody comes to mind faster than Frank Zaic and his Thermic series of glider and sailplane designs.

Frank Zaic and his designs are a part of our aeromodeling history and well known at least to those of us who appreciate and have a nostalgic interest in the background of our activity. Frank designed sailplanes before World War II, and many were produced in kit form by JASCO and later Jetco Models.

This isn’t the place for a review of Frank’s interesting life and model aviation activities, but it’s a topic worth researching if you enjoy that kind of reading. He’s in the AMA, National Free Flight Society (NFFS), and Society of Antique Modelers (SAM) Halls of Fame and his series of Model Aeronautic Year Books from the 1930s into the 1960s make for worthwhile reading. Most of his publications can still be found today.

I built Frank’s Thermic 18, Thermic 20, and Thermic 36 hand-launched gliders in some quantity as a kid in the 1950s, and later on used his classic Thermic 100 wing as the basis for a few RC sailplanes.

The instantly recognizable, widened and tapered wingtip shape on many of his larger sailplanes came from a full-scale German sailplane of the 1930s, the Minimoa, designed by Wolf Hirth. That wing shape is occasionally still seen today, likely for its nostalgic value rather than for any performance benefit. Some enthusiasts have built replica Thermic 100 sailplanes. Plans and reproduction kits are available for true nostalgia flying.
I decided to use Frank’s general Thermic 100 wing shape and pod-and-boom styling, coupled with some building techniques for an old-style sailplane, but have an electric motor in the nose. This project is intended to be an easy-flying model for some fun on a nice summer day, floating around and looking for that thermal lift, knowing the motor in the nose is there to help out if needed. It’s built with balsa, basswood or spruce, and plywood.

When I found I could buy the basswood wing spar material in 24-inch lengths, I laid out the wing with four 24-inch panels and 3-inch wingtips, for an overall wingspan of 102 inches and roughly 900 square inches of wing area. I built the wing in one piece, and I knew it would fit in my minivan. If the wing size is a concern, I’d make it with a one-piece, 48-inch center section and have plug-in tip panels, attaching music-wire joiners to brass or composite tubes.

I like the looks of a pod-and-boom fuselage and you can get a fiberglass tube to use as a boom. I used 1/4-inch-thick basswood top and bottom pieces with 1/16 plywood sides for an easily built, all-wood boom. Using balsa sides and plywood doublers for the fuselage section to hold the radio gear, the electric motor, and the battery pack, provides an overall structure is more rugged than light weight.

The motor I used—a BP Hobbies’ A2826-4 with a 14 x 8 folding propeller and a 4-cell LiPo battery pack—is more than is needed for relaxed flying. A smaller power setup could be used, but I enjoy the straight-up climb capability at times.

A 2,500 mAh battery is plenty for climbing high, cutting the power, and looking for thermal lift. A pack of up to 4,000 mAh can be used if you want to count on longer flights without worrying about finding the elusive thermals.

Construction

To build this model, you’ll have to round up the materials you’ll need and cut up a copy of the plans for paper templates so you can trace and cut out the parts. I’ve been getting my balsa, basswood, and plywood from National Balsa.

I took my time, cut out all the needed parts, and made a complete kit before I started construction. Then I made a number of changes while building the airplane, throwing some parts away. Hey it was the prototype! You won’t have that problem, because the plans now reflect the final version and I’m happy with it.

Because you’ll be building your own model, if you want to make changes and have some different ideas to try, go ahead and make it the way you want. This is another advantage of scratch-building instead of buying an ARF. And if you ever need to make some repairs on the airframe, you’ll be able to make the spare parts you need yourself.

I cut the plans sheet into pieces, and built the wing panels on a flat building surface. I put waxed paper over the plans to protect them. I laid the lower spar and the lower center section sheeting pieces down on the plans, and positioned the ribs over their locations on the plans. The opposite-side wing panels were built over the same plans to get the correct rib spacing, but with the ribs heading in the opposite direction.

I used vertical-grain balsa spar webbing in the center panels only, and with the top spars, LEs and TEs glued in place, I removed the wing panels from the building surface. The panels were put together with the plywood dihedral and polyhedral joiners. I wrapped the center section joint with a strip of 6-inch fiberglass cloth and epoxy.

This model uses a simple, basic structure of balsa, basswood, and plywood. No exotic materials or techniques are required. It has a polyhedral wing and control is via rudder and elevator.

This view of the nose section shows the motor with folding propeller bolted in place. Cooling air-inlet holes are used in the removable hatch, which uses a spring-loaded latch.

There is plenty of room inside the fuselage for the battery and radio gear.

The tail surfaces were built up over the plans, and I added a little dihedral in the horizontal stabilizer so its tips wouldn’t catch on the ground during a landing. That was probably unnecessary, and the stabilizer would have been easier to build flat.

I drilled and tapped the hardwood pieces in the stabilizer 1/4-20 for two nylon bolts to hold the tail assembly to the fuselage boom. The fuselage pod-and-boom sections are easily built up, and the boom glued into the holes in the pod formers. I put several cooling air inlet holes in the removable plywood hatch, which is held in place with a spring loaded latch mechanism.

The strong magnets available today for this purpose could also be used. Nylon tubing-style pushrods to the elevators and rudder are inside the boom. The wing is held to the fuselage with the plywood tab at the LE and one 1/4-20 nylon bolt at the TE.

The motor is bolted to the plywood firewall, with plenty of room for the ESC and any reasonably sized battery pack. The servos are installed under the wing position. You don’t need a towhook on the bottom of the fuselage unless you want a “pure” sailplane. Nylon pinned hinges are used on the elevators and rudder, and your favorite type of iron-on covering will do. I used a 60-amp ESC with built-in BEC circuitry to power the receiver and servos.

I didn’t even think about any hand-launched test glides before the first flight. I simply powered it up and hand launched it. The airplane jumped out of my hand, and headed steeply up. I put some downthrust in the motor mounting before the next flight.

My first flights were made in the late fall in cool and even cold weather, so I haven’t done much thermal soaring yet. I like the easy way the airplane flies, and will probably do my piloting from a comfortable lean-back chair in the summer when enjoying that sunny-day thermal activity.
—Dick Sarpolus

The Thermix is designed to be easy to build and fly while paying respect to the sailplanes that influenced its design.

Specifications

Type: Electric sailplane
Wingspan: 103 inches
Length: 55 inches
Wing area: 970 square inches
Weight: 64 ounces
Wing loading: 10 ounces per square foot
Power system: 700-plus-watt brushless motor; 60-amp ESC
Propeller: 14 x 8 folding propeller
Battery: Four-cell 2,500 to 4,000 mAh LiPo
Radio: Four-channel; two servos
Construction: Built-up balsa, plywood, and basswood

Order Plans

Sources

Frank Zaic autobiography
www.modelaircraft.org/files/ZaicFrank.pdf

BP Hobbies
www.bphobbies.com

CL model employees cardboard construction techniques
Featured in the September 2014 issue of Model Aviation
Construction article, photos, and plans by Chuck Felton

Specifications

Type: CL Scale
Wingspan: 60 inches
Length: 49 inches
Wing area: 541 square inches
Weight: 74 ounces
Wing loading: 19.7 ounces per square foot
Power system: .40 to .50 sized glow motor or equivalent
Construction: Primarily cardboard

Arado History and Setup

The Arado Ar.96 was a low-wing, single-engine aircraft of metal construction, which became the Luftwaffe’s standard advanced trainer during World War II. However, as the war progressed, it was decided to redesign the Ar.96, the chief goal being to save metal. The result was the Arado Ar.396, which was constructed primarily from wood.

These aircraft were to be built in factories in occupied France, but the subsequent course of the war made that impossible, and production was moved to Czechoslovakia. Only a few aircraft were built by war’s end and none were pressed into service. After the war, SIPA built roughly 200 in France which were used for training and as counterinsurgency aircraft in North Africa. The latter aircraft were fitted with wing racks for carrying light bombs and rockets.

The Arado Ar.396 model is simple to construct and inexpensive. It uses 1/8-inch corrugated cardboard as the primary building material, which greatly reduces building time and cost.

The design makes use of cardboard’s unique features in that it can be used in large sections and folded. Each wing panel is built from a single piece of cardboard scored and folded at the LE with cardboard ribs and a single spar.

The tail surfaces and fuselage are primarily cardboard with little internal bracing required. The result is a low-cost, fast-building model that has good, scalelike appearance and can take plenty of punishment at the flying field.

Cardboard varies in weight, but any 1/8-inch corrugated cardboard will do. Sources of this material include box manufactures and local shopping centers where you can find stacks of discarded boxes.

Look for cardboard with brown paper on one side and a white-finished Kraft paper on the other side. The white paper on the outside of the model results in a smoother finish and a neater appearance. The method of folding the cardboard and using gummed paper tape to seal the joints and exposed corrugation is explained in the construction hints.

The model has a 60-inch wingspan and a length of 49 inches. The bottom of the airfoil is flat with a curved upper surface, created by the scoring and folding technique employed.

A .40- to .50-size engine can be used. My model is powered by a .40 engine and has a fully fueled flying weight of 74 ounces. This weight, combined with the 541-square-inch wing area, results in a wing loading of 19.7 ounces per square foot.

Construction

Empennage
The fin, rudder, stabilizer, and elevators are each made from two pieces of 1/8-inch cardboard laminated together cross-grain to give 1/4-inch-thick surfaces. Add a 1/8 x 1/4-inch balsa strip to the fin’s LE and round it off.

Add 1/8 x 1/4-inch balsa strips to the stabilizer’s LEs and TEs and the elevator’s LE and round them off. Seal all raw edges with gummed paper tape. Hinge the elevators to the stabilizer with flex hinges at four places.

The empennage and elevator hinge line LEs are capped with 1/8 x 1/4 balsa strips and rounded off. The elevator is joined to the stabilizer with flexible nylon hinges at four places.

Wing
Make the three wing spar sections (one center and two outboard) from 1/4-inch balsa capped with 1/4-square spruce strips. Join the three spar segments with 1/8-inch plywood joiners, front and back, making sure to maintain the correct dihedral.

Glue the 1/8-inch plywood gear mounts into the bottom of the center wing panel. Glue the wing spar into the center wing panel. The three center wing ribs (W1) are then added. The ribs at the plywood spar joiners are shortened by 1/8 inch to account for the joiner thickness.

Add a cardboard doubler over each plywood gear mount. Apply glue to the top of the wing spar, the top of the ribs, and the wing’s TE. Fold the center top wing surface down and pin it securely in place until dry.

Glue the right side spar into the bottom of the right-hand outboard wing panel. Add cardboard ribs W1 through W6. Glue a 1-ounce weight to the right wingtip.

Build the left outboard wing panel in a similar fashion. Add the balsa tips to the wing and sand them to shape. Make a line guide from 1/8-inch plywood. Cut a slot in the left wing’s balsa tip and glue the line guide in place. Cover the TE and all seams with gummed paper tape.

The spar is glued to the bottom center section and cardboard ribs are added. Note the 1/8-plywood spar joiners at dihedral breaks and plywood gear mount inserts.

The top wing surfaces are folded down and glued in place. The balsa wingtip is made from 1/2-inch sheet with 1/8 plywood line guide. Paper tape covers the seam between the balsa wingtip and cardboard wing.

Fuselage
The flat fuselage sides are outlined with a triangular symbol on the drawing. Line the upper and lower edges of each fuselage side with 1/8 x 1/4-inch balsa strips, as shown in the fuselage side view. The strips are recessed 1/8 inch from the fuselage edges.

Bevel the strips at the aft end of the fuselage so that the cardboard sides will come together. Add cardboard supports to each fuselage side below the bellcrank and above the fuel tank.

Make firewall A from 1/4-inch plywood. Locate the mounting holes for the KM40 motor mount on the face of firewall A. Drill a hole in it for a fuel-tubing exit. Drill two holes in firewall A and install blind mounting nuts on the back side. These holes must align with the holes in C1 and are used to attach the removable cowl section.

Glue firewall A to the right side of the fuselage, making sure it is perpendicular to the fuselage side. When dry, glue the left side of the fuselage to firewall A. Attach the fuel tank to the 1/8-inch plywood support with rubber bands. Make a pushrod from 3/32-inch wire and 1/4-inch square spruce and attach it to the bellcrank along with the leadout wires.

Install the tank and bellcrank assemblies by gluing the plywood supports to the cardboard supports on the insides of the fuselage. Glue the fuselage sides together at the tail. Glue F1 and F2 in place to cover the top fuselage. Be sure to bring the fuel tubing fill and overflow lines out during covering operations. Cover the bottom fuselage with F3 through F6. Note the gap between F5 and F6 for the 1/8-inch plywood tail wheel support.

Glue the two G formers to the bottom forward fuselage, add a 1/8 x 1/4-inch balsa stringer down the centerline and cover with decking piece D4. Add fuselage formers B and C to the top forward fuselage. Add a balsa stringer down the centerline and cover with decking piece D1. Add the three D formers to the top center fuselage, add a balsa stringer, and cover with decking piece D2.

Glue formers D, E, and F in place to the top aft fuselage area, add a centerline balsa stringer, and cover with decking piece D3. Complete the forward cockpit windshield by gluing W1 in place. W1 is made from thin manila folder-type cardboard with a 1/8 x 1/4-inch balsa strip glued down the centerline for support.

The cowl is built up from 1/2-inch balsa sheet and carved to shape. The top half is glued to the model, while the bottom half is removable. The removable bottom half of the cowl has a 1/8-inch plywood C1 former glued to the back. Remember, the two holes in C1 must align with the blind nuts in the firewall A.

Sand, carve, and hollow the cowl to shape. Test fit the engine in the cowl and drill mounting holes. Use a shaft extension to ensure adequate spinner clearance. Cut holes in the cowl block for the cylinder head, exhaust, and needle valve. Apply epoxy to the inside of the cowl and front of firewall.

Glue the horizontal stabilizer to the fuselage. When dry, glue 1/2-inch triangular pieces to the underside of the stabilizer at the fuselage intersection for added strength. Glue the rudder to the fin with the TE offset 1/2 inch to the outside of the flying circle and glue in place.

Add carved balsa fairings on each side of the fin to complete the aft fuselage. Glue the wing to the fuselage.

Make each main gear from 5/32-inch diameter wire as shown. The pieces are attached to the mounting plates in the wing with nylon gear clips. Bend the tail wheel strut from 3/32-inch wire as shown, place on the plywood support, wrap with nylon thread, smear with glue, and mount in the bottom aft fuselage cutout between F5 and F6. Slip black fuel tubing over the main and tail gear wire for better definition. Adding a couple of drops of oil inside the tubing first will make this much easier.

Flat fuselage sides are lined with balsa strips recessed 1/8 inch and have cardboard supports for the bellcrank and fuel tank plywood mounts. Note the cutouts for flying wires.

The fuselage’s forward bottom section has formers and a centerline balsa stringer ready for deck covering. Cutouts help reduce weight. The pushrod is made from 1/4-inch square spruce.

The completed forward bottom section is shown. Uneven seams are later cleaned up with strips of gummed paper tape.

Cardboard bulkheads, held with a single centerline balsa stringer, are added to top fuselage. Be sure to bring the fuel tubing lines out during all covering operations.

Scored and folded top decking pieces are glued over the cardboard formers. The seams have already been covered with gummed paper tape.

The forward fuselage is ready for the balsa cowl. The front windshield, piece W1, is made from thin, manila-folder cardboard.

The cowl’s front nose block has one circular and one oblong cutout. I always use a 1/2-inch engine shaft extension for more clearance between my fingers and the propeller.

The main landing gear is 5/32-inch wire attached to plywood mounting plates in the wing bottom using three nylon gear clips.

The tail gear strut is bent to shape from 3/32-inch wire, laid on its 1/8-plywood mounting plate, wrapped with nylon thread, smeared with glue, and glued into fuselage cutout.

Finishing
Apply a coat of sanding sealer to all of the model’s balsa parts and sand smooth. Give the cardboard sections two coats of clear dope, sanding lightly after each coat with 400-grit sandpaper. Follow with two coats of color. The color scheme I used for my model is dark green on the upper surfaces and light blue for the lower surfaces.

The patterns for the aluminum MonoKote pieces used to simulate the front and aft cockpit windows are shown on the fuselage drawing. The center section canopy is not shown because it is a simple rectangular section. Apply the simulated windows to the cockpit areas and outline them with black MonoKote strips.

The striping, lettering, and insignia were made from MonoKote or designs developed in drawing program ModelCAD 3000 and printed on Avery sticky labels (#8165) with an inkjet printer.

The author displays the completed Arado Ar.396. Cardboard construction is simple and inexpensive.

Final Assembly
Pass the leadout wires through the wingtip line guide and tie them off. Attach the nylon control horn to the elevator and hook up the pushrod. Attach 3-inch diameter wheels to the main gear and a 13/4-inch diameter wheel to the tail gear. Add a 9 x 6 propeller and a 2-inch spinner to the engine and your aircraft is complete. Be sure to balance the model at the point shown on the plans.

If you have any comments, suggestions, or questions concerning the cardboard Arado Ar.396, please don’t hesitate to contact me or add a comment below.
—Chuck Felton

Construction Tips

• Before you begin building, take a look at these special tips for working with cardboard.
• Adhesive: Water-based glue, such as white glue or Titebond, is recommended. Contact cement is not recommended, because parts cannot be shifted when gluing surfaces.
• Folding: Scoring the fold lines is done with a screening tool available at any hardware store. It consists of a handle with a 11/2-inch radius wheel at one end, which is run along a metal straightedge on the fold line.
• Finishing: Cardboard gives a solid surface with no open areas to cover and is nonporous. The easiest finishing method is to give it two coats of clear dope, sanding lightly between coats using 400 grit sandpaper, followed by two coats of color dope. A wide variety of finishing materials can be used on the cardboard including coverings such as Solarfilm, MonoKote, and vinyl paper. With any of these, it is recommended that the surface not be doped, to result in a better bond.
• Paper tape: All seams, joints, and exposed edges of the model are covered with strips of gummed paper tape. Obtain a 1-inch-wide roll from a stationary store. Simply cut a thin strip to length, dip it in water, and smooth it over the seam.
• Construction: Being sure to note the direction of the corrugations when cutting out the cardboard parts. Score and fold cardboard parts as indicated on the plans.

Order Plans

Sources

AMA Plans Service
(800) 435-9262, ext. 507
www.modelaircraft.org/plans.aspx

Chuck Felton’s website
www.feltondesignanddata.com

Simplistic construction and gentle flight characteristics await you
Design, construction article, and photos by Mike Hausner.

My goal was to design a foam model that went beyond the usual flat-sheet wing. I was also interested in enticing members of our club, The Village E-Flyers in central Florida, to build an airplane from plans.

Newcomers can be intimidated by the covering process and all of the tools required, so this model is made of 3 mm and 6 mm Depron foam sheet. It had to be easy to build, but I wanted a model that flies well, too.

I made the decision to use a three-dimensional flat-bottomed wing and a simple, self-jigging, built-up fuselage. I used the basic shape of the full-scale RANS Coyote ultralight airplane and, since I only had pictures to go by, I applied model-design parameters to proportion the model.

As designed, the model has sufficient strength for normal flight loads and mild aerobatics. Don’t be tempted to overpower it. The prototype shown here flies fine on 87 watts of power.

The tools required to construct the model are limited to the basics: a hobby knife, a straightedge and ruler/yardstick, drafting triangles, a hobby saw (for the plywood parts), a 6-inch square, blue painter’s tape, sandpaper and a sanding block, pliers, wire cutters, a felt marking pen, and a flat building surface.

Most gluing on this model is with contact cement. Use epoxy or CA adhesives where noted. Before starting, read the instructions all the way through to get a better idea of the building process.

The model is patterned after the RANS Coyote Ultralight.

Specifications

Type: Electric sport model
Wingspan: 39 inches
Wing area: 239 square inches
Weight: 18 ounces
Wing loading: 10.8 ounces per square foot
Power system: 100-watt brushless motor; 20-amp ESC
Propeller: APC 8 x 3.8
Battery: Three-cell 1,320 mAh LiPo
Radio: Four-channel; four micro servos (five if you add flaps)
Construction: Foam

Coyote E Materials List

• Glues: Foam Safe CA, UHU POR (or suitable contact cement), and epoxy. 3M Super 77 (for temporary attachment of templates to foam)
• (1) Sheet 6mm depron foam 27” x 39”
• (1) Sheet 3mm depron foam 13-1/2” x 39”
• (4) Micro servos (HS-55 or 9 gram servos) for aileron (2), elevator, & rudder.
• (1) Micro servo as above for optional flaps.
• Brushless outrunner motor and appropriate ESC (E-flite 370, Super Tiger 370 or 400)
• Propeller adapter and propeller as required (8 x 3.8 SF)
• (2) .032” music wire x 36” long (control rods for ailerons, elevator, & rudder)
• (1) .047” music wire x 8” long (control rod for flaps)
• 1/16” I.D. aluminum tubing x 4-1/2” long (for FLAP torque rod bearings)
• Sullivan Gold-N-Rods #504 (control rod guide tubes – use inner yellow part)
• (1) 1/8” plywood 6” x 12” (Dihedral brace, firewall, main and tail wheel mounting plates)
• (1) 1/16” plywood 6” x 12” (Flap actuator parts, wing trail edge reinforcement)
• (4) 1/8” x ¼” hard balsa stringers x 36” (wing spars)
• (1) 3/16” diameter wood dowel X 9” long (Wing hold down dowels)
• Main landing gear (from E-flite Mini Pulse or use Great Planes #L-1 (GMPQ1810)
• Wheels as required (1-3/4” diameter) and axles as required
• Tail Wheel Assembly (World Models #PL3410030 or equivalent)
• (4) E/Z Links for .032 push rods (DuBro #849)
• (4) Micro control horns (DuBro #919)
• CA hinges (one package)
• Scotch tape (elevator & rudder hinges)
• Servo extension leads for ailerons and flaps
• (1) Optional Y harness (for aileron servos)
• #64 Rubber bands (wing hold down)
• (1) 3/16” OD Brass tube (to make hole punch)
• Paint: Use water base acrylic, plastic model paint, or Krylon Short Cuts in spray cans

Motor mounting hardware

• 4-40 screws x 1-inch long (as required)
• 4-40 blind nuts (as required)
• 2 1/2-inch plastic or carbon fiber tube (motor stand offs)
• Two 10-32 or 10-24 nylon screws (for landing gear attachment)

Building the Fuselage

The fuselage is designed to be self-jigging. Start by laying out the templates on the foam board. Spray contact cement, such as 3M Super 77, can be used to temporally attach the template to the foam. Because all of the parts are defined by straight lines, you can mark the corners by cutting through the pattern with your hobby knife and then cut between the corners using a straightedge. Try to keep the knife at 90° to the foam board.

On the fuselage sides, lay out the locations for the formers and servo rails with a fine felt-tip pen. Scribe vertical lines on the fuselage sides at the locations indicated on the plans using a dull pencil. This will aid in bending the sides later. Test to see that each crease allows the side to bend approximately 5° without cracking.

Experiment with this procedure on a piece of scrap foam board so you don’t make the crease so deep that it weakens the fuselage sides. Don’t forget to cut the holes for the wing hold-down dowels.

Glue the following pieces to the right fuselage side: F-2A, landing gear plate (foam), receiver tray, F-3A, and servo tray. Make sure all these parts are at 90° to the fuselage side. The landing gear plate and the two trays will help. When the glue has set, add 6mm x 3/8-inch strips to increase the gluing area and add strength.

Glue the right and left fuselage doublers to their respective sides. These parts will provide the proper alignment for the firewall assembly (F-1A and B).

When this assembly has dried, glue the left side in place. Make sure everything is square. As this is drying, lay out the motor mount hole pattern on the firewall, noting that the motor mount center is offset to the left when viewed from the front of the airplane. This is because of right thrust and will enable the motor shaft to be centered where it exits the fuselage.

The motor will be mounted using 4-40 screws and stand-off tubes. The stand-offs allow for better motor cooling, easier motor wire routing, and adjustment of the side- and downthrust if necessary.

The motor I used has only three mounting lugs. If yours has four, modify the firewall as required. Be sure to add the cooling holes for the battery and ESC.

Drill out the motor mounting holes with a 5/32 drill bit. Install the 4-40 blind nuts from the backside. Place a dab of RTV silicone or Vaseline in the threads to prevent them from being plugged with epoxy. Next epoxy the firewall F-1A to F-1B, and clamp until cured.

Getting back to the fuselage, install the right and left doublers. Make sure the shorter one is on the right side when looking forward as if you were in the cockpit. Now install F2C. This piece will establish the taper of the front fuselage and, together with the fuselage doublers, the right-thrust and downthrust angles for the firewall/motor mount. Install the motor mount assembly (F-1A and B) to the fuselage using 5-minute epoxy.

To create the taper at the rear of the fuselage, install F3B, F-4, F-5, and F-5B, and allow the parts to completely dry. Install the front and rear dowel supports with contact cement, then install the dowels with epoxy to keep them in place. After this has cured, sand the top and bottom edges of all formers even with the fuselage sides.

Mark and drill holes in the aluminum landing gear for the two 4-40 screws and drill them out using a 1/8-inch drill bit. Now center the aluminum landing gear over the plywood landing gear plate even with the front edge of the plate. Drill through the plywood landing gear plate using the aluminum landing gear as a template.

Enlarge the holes in the plywood plate with a 5/32 drill bit and install the two 4-40 blind nuts as you did with the motor mount. Glue the plywood landing gear plate in place with epoxy and install the tail wheel plywood plate in the same manner.

Run control rod conduits for the elevator and rudder. Note that as they cross at F-4, elevator is above and the rudder below. The elevator conduit exit at the tail is determined by the third hole in the control horn. The rudder conduit should exit lower than the elevator to avoid interference.

Cut out the elevator as one piece with a notch for a 1/4-inch dowel joiner. Cut a relief area for the joiner but do not separate the elevator halves. Epoxy the elevator joiner in place. After this assembly has cured, sand a 45° bevel on the hinge side (bottom) of the elevator. Sand the hinge side of the rudder as well. You have the option to taper the TE of the elevator and rudder. If you are going to taper the elevator and rudder, do it before you cut the elevator center. Refer to the plans for clarification.

Hinge the elevator to the horizontal stabilizer with Scotch Tape. It is helpful to clean the surfaces with alcohol before applying the tape. Apply the tape to the top of the stabilizer and elevator, then bend the elevator over the top of the stabilizer and apply hinge tape to the bottom. Test it to ensure that you have sufficient surface movement up and down.

Trial fit the fin and rudder to the stabilizer assembly. You will have to cut a notch in the rudder to clear the elevator dowel as the elevator moves up and down. When you are satisfied with the fit, hinge the rudder the way you did the elevator. Epoxy the fin and rudder assembly to the stabilizer and elevator assembly. Use a square to make sure the fin is at 90°.

Trial fit the fin and stabilizer assembly to the fuselage. Make sure the horizontal stabilizer is parallel to the top fuselage sides where the wing will be attached. Lay a straightedge across the fuselage where the wing will set and sight from the front. Make your corrections now. It is important that the wing and stabilizer are parallel to each other and that the fin and rudder are centered. When satisfied, epoxy the fin and stabilizer assembly to the fuselage.

Cut out all the parts for the fuselage, including the plywood pieces.

The fuselage is designed so that it is self-jigging. Here the landing gear support, receiver tray, and servo tray are being glued in place.

Make sure the fuselage is square.

Fuselage doublers and F2C create the front fuselage taper.

The elevator servo will be on the right, with the conduit crossing to the left rudder servo. Mark the fuselage’s centerline.

Note the glue relief area for the elevator joiner. Cut away the center area after all sanding is completed.

Use a square to make sure the fin and stabilizer are at 90°.

Battery Access Hatch

Cut and fit a piece of 6mm foam to the front lower fuselage, but do not glue in place. Read this step through completely and decide if you want this type of latching system.

Otherwise you can hold the battery hatch in place with tape or magnets.

Use foam-safe CA to make a battery hatch as shown. The two long pieces of 6mm x 3/8-inch strips of foam are glued to the sheeting to keep the hatch from falling through. The shorter piece on the left is the tongue, glued to the hatch only, and it keeps the hatch from falling out. The latch is a piece of 1/8 light plywood drilled and tapped for a 6-32 nylon screw.

The drag of the threads allow plywood pawl to rotate with the screw until it hits the stop where the screw will then tighten the hatch. I used pieces of an old plastic card to make support shims under the screw head and latch pawl and also under the area where the latch pawl will move across the foam sheeting.

Install a small plywood stop to keep the pawl from rotating after the hatch is latched. When looking from the inside, tightening the screw will rotate the pawl counterclockwise. When satisfied with this assembly, glue it to the fuselage with contact cement.

Cut out pieces of 3mm foam for the rear top and bottom sheeting. Attach them using contact cement. Trim as required when dry. If desired, you can round the fuselage corners with 150-grit sandpaper.

This shows the lower front fuselage sheeting with hatch and latch pawl.

Building the Wing

With the fuselage nearly complete it is time to build the wing. Start with the main wing spars. The wing spars are a sandwich construction using two 1/8 x 1/4 x 19-3/4 hard balsa sticks separated by a strip of 6mm foam. The balsa sticks are purposely cut longer than needed. They will later be trimmed.

Cut two strips of 6mm x 3/4-inch Depron 20 inches long. It is difficult to cut 6mm foam and maintain a 90° square edge, so after cutting, square up one of the long edges with a sanding block.

Using epoxy, glue one of the balsa sticks to the 3/4-inch wide surface of each foam strip so the 1/8-inch edge is even with the squared foam edge. It is important to use a straightedge to keep the balsa stick straight. When this has cured, epoxy another 1/8 x 1/4 balsa stick to the other side of the foam strip. Allow this to thoroughly dry then trim the extra foam to create the balsa/foam/balsa sandwich. Use the dihedral gauge found on the plans to sand one end of each spar to match the dihedral angle.

Cut the bottom wing skin from 3mm Depron 5 x 39 inches long. This is slightly long, but it will be trimmed later. Find the center and draw a perpendicular line using a fine felt-tip pen and a square or drafting triangle. Using the wing centerline on the plans, lay out the servo access panels.

Mark the left and right access panels and cut them out, separating them at the center. Align the bottom wing skin over the plans and temporarily tape it in place. Transfer the rib and hinge locations to the panel. Lay out the locations of the 7/16 LE, the 3/4 TE, and the spars on the bottom wing skin.

The CA hinges that come with the model are too big, so cut the 3/4 x 1-inch hinge material in three pieces. You will need to make eight for the ailerons and four more if adding flaps. Cut the corners of one end of the end hinge to a 30-45° angle, as shown on the plans, to make it easier to install the control surfaces. Glue the hinges to the bottom sheeting as shown on the plans using foam-safe CA.

Install the right and left spars on the wing panel with epoxy. Leave a 1/32-inch gap at the center for dihedral bend clearance. To make the alignment of the spar easier, tape a straightedge to the panel.

Next install the 3mm x 3/4-inch TE over the CA hinges with contact cement. Leave a slight gap at the center for the dihedral bend. Install the 6mm x 7/16-inch LE in the same manner.

When you cut out the wing ribs, it is easier if you take the time to make a plywood template for W-1A and W-1B. The pieces will be more accurate and uniform. Use 1/16 or 1/8 plywood and glue on a handle for holding the template in place while cutting out the parts.

Install the three outboard LE ribs—W-1A—on the right and left wing panels. The six W-1A center ribs will be installed later.

To provide clearance for the aileron servo wires, cut a clearance notch in the bottom of six of the TE ribs—W-1B (see plans). Install these ribs in their location over the servo wire cutout. Do not install the two center ribs at this time, but go ahead and install the four W1-B pieces without a clearance notch to their locations on the right and left wing panels.

Trim six LE ribs—W-1A—so that the 1/8 plywood dihedral brace will fit ahead of the wing spar. Sand a slight bevel on the bottom edge of two LE ribs (W-1A), and two TE ribs (W-1B), so that they will sit at an angle on the wing skin. Use the dihedral gauge as a guide.

Glue these two LE and TE ribs in place at wing centerline. Install the remaining LE ribs. Cut a strip of 3mm foam 3/8 x 39-inches long. Cut this into pieces to fit between the ribs. These pieces will support the servo wire access panel when it is reinstalled. Glue them to the bottom skin so that roughly 1/8 to 3/16 inch overhangs the servo wire cutout.

Sand the LEs and TEs, being careful not to sand through the hinges. Trim the spar, LE, TE, and bottom wing skin flush to the outboard ribs. Next, weight one wing panel and prop up the other until the wingtip is elevated 11-1/16 inch above the building surface. Apply epoxy to the area between the center ribs and where the dihedral brace will be installed. Install the dihedral brace and clamp. Remove excess epoxy before it dries. Once cured, clean up any mismatch between the top of the spar and the dihedral brace.

For the top wing skins, cut two pieces of 3mm Depron 5-3/16 wide x 19-1/2 inches long. Carefully form the wing skin using a broom handle or 3/4-inch diameter tube or dowel. Roll the dowel over a flat surface with the foam between the dowel and your hands. Work slowly, applying light pressure to form the skin. This will give the foam a slight curve making it easier to attach to the wing assembly. Each wing panel should look like the one in the photo.

Trial fit one of the top skins to the left wing panel. Care must be taken to align the TE and the center dihedral joint when the panel is glued in place. When satisfied with the fit, apply 30-minute epoxy to the wing spar only. Next sparingly apply two lines of contact cement to the TE. Continue along each rib, and then put two lines along the LE.

With the left wing half on a flat surface, place the top skin on the panel and lightly smooth it down so glue is transferred to the wing skin. Remove the skin and let it dry for a few seconds then reinstall by aligning the TE and center edges. Apply low-tack tape to the LE to help secure the top sheeting. Before the adhesives cure, slip a piece of 6mm foam under the outboard TE corner of the wing to provide washout in the wing, which will improve stall characteristics.

Place weights on the LE and TE at the center of the wing and one weight at the wingtip LE, not over the corner with the 6mm shim. Smooth down the LE and spar areas, making sure the skin is adhered.

Do not touch the TE except at the center rib. Give this assembly at least an hour to dry, then remove the weights and place the TE on the edge of your work surface and gently press it down. When you sight down the end of the wing, you should be able to see a slight twist—the TE at the wingtip is higher than the LE.

Fitting the right wing skin at the center will require sanding a slight curve to match the left wing skin. When satisfied with this fit, glue the skin to the wing using the same procedure as before. Don’t forget the shim under the outboard TE.

Wing spars are made with 6 mm foam sandwiched between two balsa sticks.

Lay out the rib, spar, LEs, TEs, and hinge locations on the bottom wing skin.

Cutting out the wing ribs is easy if you make a template similar to this.

When sanding the TE, take care not to sand through the hinges. This can be tedious, so take your time.

Clamp dihedral brace and center ribs until cured.

Roll form the top wing skins using a broom handle or 3/4-inch dowel.

With one wing panel weighted down, support the other panel 1-11/16 inches off the board and install the dihedral brace. Wingtip washout will improve stall characteristics.

Flaps

If you are not adding flaps, skip this section. The materials needed for the flap actuator are: .047 music wire, 1/16 plywood, 1/8 plywood, and 1/16-inch ID aluminum tube. Make up the 1/16 and 1/8 plywood flap connector parts as shown on the plans. Fabricate the flap actuator rod as shown on the plans. Make a Z bend in a 5-inch piece of .047 music wire.

To allow adjustment, make a V bend as shown on the plans. Insert the Z bend in one of the holes in the 1/16 plywood attachment piece. Align and epoxy the 1/8 plywood support and clamp until dry.

To make the flap torque rod, cut a 10-inch length of .047 wire and start by bending it into a 1/4-inch wide U shape. Install the plywood and wire flap actuator to the center of the U. See the plans for clarification of flap/torque-rod fabrication, steps, and dimensions.

Cut two pieces of 1/16 ID aluminum tube 2-1/4 inches long. The easy way to cut this is by rolling it on a flat surface with an X-Acto knife. The aluminum is soft and cuts easily. Install these aluminum “bearings” on the torque rod arms. Note the relationship to the U portion of the assembly. Don’t worry if this isn’t exact, each flap will be a custom fit. The flap actuator has a slight V that will align with the dihedral of the wing.

Test fit your flap/torque-rod assembly to the wing. You will have to cut a V groove in the wing to get the pivot point even with the wing TE. When you are satisfied with the fit, epoxy the aluminum tube portion to the wing. Take care not to get epoxy on the wire part of the assembly so that it will move freely. Secure it with tape until cured. To fit the 1-1/8 x 4-inch center TE, cut a V to allow it to fit over the flap torque rod assembly and epoxy it in place.

Note the aluminum tube “bearings” on the flap torque rod assembly.

The completed flap torque rod assembly.

Flap torque rod at the wing’s center section. Cut a clearance to allow the actuator to move forward.

Without Flaps

Cut two strips of 6mm foam, 1-1/8 x 10 inches long for the ailerons. Cut two more strips 1-1/8 x 9-3/8 long. Mark the hinge locations on the edge of each control surface and slot with a hobby knife. If you are going to taper the control surfaces, it is easier to do so before cutting out the control surface. Lay it out on the 6mm foam, mark the TE with two lines about 1-1/2mm from the top and bottom surface and sand to shape to the lines (see plans). When satisfied, cut the control surface from the main piece.

Mark the hinge side of each control surface and lay out the hinge locations using the hinges on the wing. Make a cut roughly 1/2-inch deep for each hinge. Make the cuts twice as wide as each hinge to make it easier to install. Sand the hinge side of each aileron to a “

Installing the Flaps

Cut out the flaps as shown on the plans. Mark the torque rod location on each flap. Using a 1/16 drill, drill a hole to accept the torque rod arm. For the flaps, you only need to sand the bottom at a 45° angle because the flaps will only go down. Temporarily fit the flap panels and check their operation. It is best to fasten one panel at a time. I recommend a dry run because it can be tricky.

The arm will be glued with epoxy and the hinges with foam-safe CA. When you are happy with assembly process, mix a small amount of epoxy and use a short length of the same wire used for the torque rod to feed epoxy into the hole in the flap. You don’t need much. Put a little epoxy on the arm too. Now apply CA to the hinges, both sides, and quickly install the flap. Allow it to dry and check for proper operation and bond strength. Install the other flap in the same manor.

Test fit each flap.

Installing the Ailerons

Install the ailerons by first starting the control onto the four hinges. Just get it started so that each hinge is into its slot approximately 1/16 inch. Apply a small drop of foam-safe CA to each hinge and on both sides and carefully slide the control surface all the way onto the hinge and flex the surface up and down.

Make two pieces of 1/16 plywood 1 x 11/2. Epoxy these to the wing’s TE where the rubber bands will go over the edge to the wing dowels.

Install the aileron servos and servo tray onto the wing. Use RTV silicone to install the servos. Install the flap servo by gluing it to the bottom surface of the wing. Let them dry overnight.

Bend the aileron pushrods out of .032 music wire and attach them to the servo with a Z bend. Add a V bend in each pushrod to allow for length adjustment. Attach them to the control horn with an L bend and Du-Bro micro E/Z links. Note that the servo arm is angled forward to provide aileron differential—more up than down. Aileron differential is used to counteract adverse yaw. The flap pushrod is attached to the servo with a Z bend.

Install the Y harness to the aileron servos then glue the access panels in place. You will have to trim the length of these panels and add a clearance hole for the Y harness exit at the wing’s center. The wing is now complete.

The aileron is ready to apply glue.

I use RTV silicone to install servos on park flyers.

Painting

If you want to paint your Coyote E, there are several choices available. Acrylic craft paint, plastic model spray paint, and craft spray paint are some of the choices. Acrylic craft paint is inexpensive and the color choices are almost endless.

Spray paint for plastic models is another choice. If you go this route, apply the paint in light coats and test it on a piece of scrap Depron. Krylon makes craft paint called Short Cuts. This works well, but color choices are basic. Whichever paint system you choose, first wipe down the parts with alcohol.

Flying

The results were better than I had expected. Ground handling with the steerable tail wheel was excellent. As I advanced the throttle to three-fourths on the maiden flight, the tail came up and with a touch of up-elevator, the airplane lifted off the ground as pretty as could be.

In the air, the Coyote E is responsive without being touchy. The model only requires half throttle to fly, which gives you reserve power for vertical maneuvers. The aircraft is not a powerhouse, but it will loop from level flight.

As expected with a flat-bottom wing, rolls and inverted flight require some elevator input. The flaps are effective and require up-elevator to counter the downward pitching moment and throttle to overcome the added drag.

Landing is a treat! Just reduce throttle, add a notch or two of flaps if you like, and control the descent with throttle. I have seen no tendency to bounce on landings.

The biggest surprise was how the model handles the wind. It seems to fly like a much-larger airplane. I had complete control and the Coyote E wasn’t getting kicked around by the wind like some of my other aircraft. Don’t bother with the flaps in windy conditions or you may be landing backward.

Control Throws and Dual Rates

Flight Photos

The author/designer with the Coyote E

Free Plans

Click here to download free plans

—Mike Hausner
MikeHausner@aol.com

by Dennis Norman
Free plans and build article.
Care will be given to the steps needed to specifically build the Born Loser P-6E version.
Bonus digital feature.




Al Backstrom’s construction article from the October 2000 Flying Models magazine is included as a general guide to building the Born Loser. Because the Born Loser P-6E is a modification of Backstrom’s original, care will be given to the steps needed to specifically build the Born Loser P-6E version.

Building Instructions

A. Preliminary Steps

1. Begin by taping the plans to a soft, flat, building board (ceiling tile or something similar).
2. Cover the plans with wax paper or some suitable barrier to prevent damage from glue spills, etc.
3. Most of the P-6E is built from 1/16-inch square balsa strip or 1/16-inch sheet balsa stock. On the parts sheets, you will note that 1/32-inch sheet, 1/4-inch sheet, and 1/32-inch sheet plywood are also used.

B. Building the Tail Surfaces

1. The classic warm-up technique is to build the rudder and elevator, using straight pins to hold the components firmly against the plans. To avoid weakening the structure, place straight pins around (not through) the strip stock.
2. When the glue for the rudder and elevator is dry, carefully remove the pins and gently lift the components from the plans. This is most effectively done by sliding a thin piece of metal between the balsa structure and the wax paper-covered plans.
3. Once removed from the plans, any excess dried glue should be cut away from the joints. Components can be rounded with sandpaper, but this step is optional for a model of this size and fragility.
4. Having built the rudder and elevator, set both aside until ready to cover.

C. Building the Wings

1. Like the tail surfaces, the wing is mostly built using a combination of 1/16-inch square and 1/16-inch sheet balsa.
2. Carefully cut the wingtips, ribs, and gussets from 1/16-inch sheet balsa (see parts sheet).
3. Pin hard 3/32-inch square balsa strips against the plans for the wing’s leading edges LEs). The trailing edges (TEs) are made from 1/16- x 1/8-inch balsa strips.
4. Elevate each half of the top wing by placing a piece of 3/32-inch scrap under the tips of the TEs on either side. This will create a stabilizing warp called washout in both sides of the upper wing. When building the bottom left half of the wing (pilot’s left), elevate the tip of the TE 1/16 inch using a piece of 1/16-inch scrap.
5. The right half of the bottom wing is built the same as the top wing by using a piece of 3/32-inch scrap under the tip of the right TE.
6. The steps mentioned in C4 and C5 create a warp in the bottom wing, which will help stabilize the wing in flight. The lesser washout used on the left half of the bottom wing will counteract the torque or twisting force exerted by the propeller as the rubber motor unwinds.
7. Note that the lower wing features two ribs that align with the bottom of the fuselage and help attach the bottom wing. To help anchor the covering, place a piece of 1/32- x 1/4-inch piece of sheet balsa on the side of each rib facing the wingtip.
8. Unlike the bottom wing, the top wing center uses two ribs that are placed 1/16 inch apart to form a slot for the model’s pylon. Help anchor the covering by placing a piece of 1/32- x 1/4-inch sheet balsa on the side of each rib facing the wingtip.
9. The pylon enhances the design’s stability. Make the pylon from 1/16-inch balsa sheet as shown on the plans; however, the prototype BL P-6E uses an “open” pylon in which two pieces of clear acetate are employed to create the illusion that the upper wing is held on by conventional struts.
10. Note that both wings employ 1/16-inch square balsa strips as spars. These are on the top of each wing only. For structural strength, 45°sheet gussets (WG) are added to both wings. Interplane strut receptacles are made from 1/16-inch sheet.
11. After each wing is dried, it should be removed from the building board. Sand the LEs and TEs to an airfoil shape, and then set aside to await covering and assembly to the fuselage.
12. When the wing halves are fully constructed, raise the tip of half of each wing 3/4 inch to create dihedral. Be sure to preserve the washout in the elevated wing half by placing a support beneath the tip of the wing’s TE.

D. Building the Fuselage

1. Cut the main fuselage parts from 1/16-inch sheet balsa. Use 1/32-inch sheet for the sides of the top of the fuselage ahead of the pilot’s headrest, the landing gear struts, and the fuel tank.
2. Begin by pinning the 1/16-inch square top of the fuselage side (top longeron) firmly against the wax paper-covered plans.
3. To ensure strong joints, place pins directly above of the top of each longeron at the locations where it will come in contact with each vertical upright.
4. Cut lengths of 1/16-inch strip balsa to the exact length of each vertical upright.
5. Make certain that each vertical upright, when in place, will firmly contact the upper and lower longerons. After cutting the vertical uprights, set them aside.
6. Pin an oversize length of 1/16-inch square balsa strip against the plans at the position shown for the fuselage’s bottom longeron. Next, place each vertical strip at its location on the plans. Again, the fit should be snug.
7. Apply glue to the top and bottom of each vertical upright and then set it carefully in place between the top and bottom longerons. Add sheet parts as shown on the plans to the nose, wing root, and rear motor peg area (slightly ahead of the stabilizer slot).
8. To ensure good contact with the top and bottom longerons, place a pin firmly against the outside of the bottom longeron at the strip’s location.
9. Repeat steps D2 through D8 to build the second side of the fuselage. Using the same pinhole locations from the first side should make the second side identical. Each side of the fuselage should align with the other side.
10. The inside of each part of the rear motor peg area should be reinforced with 1/32-inch plywood, which should be drilled out before placing it inside the fuselage. Make the hole slightly smaller than the diameter of the rear motor peg. The rear motor peg itself can later be snugly fitted with the use of at small rattail file.
11. At this point, the fuselage sides are ready to be joined. Begin by carefully aligning and gluing the tail ends of each fuselage side together at the rearmost vertical spacer of each side.
12. Join the front ends of each fuselage side to a temporary rectangular balsa sheet spacer cut to the inside dimensions of the nose. This will be removed after the fuselage sides are permanently joined by the 1/16-inch square spacers.
13. Looking at the top view of the fuselage shown on the plans, next cut pieces of 1/16-inch square balsa to the exact lengths shown between the fuselage sides. One pair of pieces at each location should be cut to keep the sides parallel and the fuselage cross section rectangular.
14. Add triangular fuselage top pieces 1 through 6 as shown on the plans. In building the prototype, parts 5 and 6 had to be redrawn as shown on the BL P-6E plans because they did not create a rigid enough structure to permit smooth covering of the top rear of the fuselage.
15. Following the original design, the top of the forward fuselage is made from pieces of 1/32-inch balsa sheet that join to form a triangular cross section. To make the cockpit more closely resemble a P6-E, the 1/32-inch sheet portions were extended and redesigned as shown on the plans and parts sheet.
16. Al’s Born Loser shows a balsa nose block with an optional spinner. Because this would be incorrect for a P-6E, the nose block has been reshaped to give it a more realistic look. The BL P-6E also employs a detachable nose block, which is mounted against a 1/32-inch plywood former with a 1/2-inch square hole cut in it to accommodate the nose block plug. The nose block may be carved either from a block of balsa or laminated from pieces of 1/16-inch balsa sheet as shown on the plans.
17. The landing gear is formed from .025-inch music wire. To better meet the BL P-6E’s unique wheel pant-and-strut combination, the landing gear wire was cut to eliminate that portion attaching to the wheels. Instead, the wheels are inserted and held in place in the pants with a portion of a straight pin cut to length for that purpose.
18. The landing gear struts are made by gluing two pieces of 1/32-inch sheet to the landing gear wire. To facilitate strut flexion, do not glue the struts to the lower longeron. When the landing gear struts are in place, the wheel pants are carefully glued to the bottom of the struts. Use care to evenly align the wheel pants with each other.
19. The 0.16-inch music wire tail skid shown for the Born Loser has been replaced by a tail wheel fashioned from sheet balsa to more closely approximate the look of a P-6E.

E. Covering Instructions

1. Detailed directions for applying the tissue covering are set forth on the yellow instruction sheet included.

Download free plans by clicking here.

Have fun and happy landings!
—Dennis Norman
dennis@airacemodels.com

FREE PLANS