Kitbashing

Written by Lawrence Klingberg Creating Golden Age Classics from a Cub kit Construction article Photos by the author As seen in the August 2016 issue of Model Aviation.

Bonus photos

Convert an aircraft to a model using a Cub kit

• Curtiss Robin • Waco Cabin aircraft • Bellanca Skyrocket • Fairchild FC-2 • Stinson Detroiter • Monocoupe • Travel Air 6000
Throughout the last 10 years, I have found that modifying or changing a basic Balsa USA 1/3-scale Cub kit into a high-wing classic from the 1920s to 1930s is a project that is enjoyable and might be of interest to modelers with slightly better-than-average skills. This modification is not difficult, but does require many changes to create a great scale model. Aircraft that I’ve modeled include a Monocoupe, Waco Model E, a Fairchild FC-2, and many others. In looking through the Juptner U.S. Civil Aircraft Series books or others, there are so many high-wing airplanes that are not that difficult to replicate.

The Monocoupe was designed by Don Luscombe in 1926. Throughout the years, 5,000 of the clipped-wing aircraft were sold.

If this article inspires you to build a different type of aircraft, be sure it is within your capabilities.

Fuselage

The fuselage is the most difficult part of the airplane to modify. To begin, put the Cub fuselage plans on the bench and cover it with tracing paper. These will be your plans for the side and top view of the proposed model. Draw a centerline on the paper to reference measurements for translating them from the three-views to your plans. A good starting point is to draw in the wing and stabilizer on the plans in their respective locations. They should not be changed, because it would alter the center of gravity and flight performance would be affected.

This is a side view of the Balsa USA Cub’s fuselage. Drawing courtesy of William Hannan.

For this article, the Bellanca Skyrocket will be used as the example of how to modify the Cub’s fuselage and other parts. Although the Skyrocket’s side view is a drawing of a Peanut Scale airplane by Bill Hannan, it still coveys the outline that can be used for our purposes. Let’s start to draw up the side-view plans. Start by drawing the top and bottom outlines and then draw in the upright and bracing diagonal pieces of wood. When this drafting work is completed, it’s time to cover the plans with something to protect them from glue. I use the backing from Solartex covering to protect the plans. It works better than wax paper and glue does not stick to it. While on the subject of making the fuselage sides, always make one on top of the other, ensuring two identical sides. I use gussets at every joint on the fuselage. If I make up approximately 200 pieces before starting construction, there will be enough to finish the job. When the two fuselage sides are finished, remove them and stand them up over the top view of the Cub plans and use a T square to hold up the sides. Pin them down before starting to cut the pieces of wood to create a square fuselage. Be sure to gusset each joint and check that the fuselage is straight and true at all stations. At this time, I also install crossbracing to the top and bottom of the fuselage for added strength. By now the framework should start to look like an airplane. It is often best to leave the front portion of the airplane until last to finish. This allows ample time to consider engine mounting, windshield location, what kind of cowl will be used, and whether or not a dummy radial engine, such as many old aircraft used, needs to be made.

Wings and Wing Center Section

I like to build a wing center section at this point, which is made up as a unit to be attached to the fuselage with metal pieces screwed on and also wood pieces put on with epoxy glue. Note that the leading edge (LE) is made from thin aluminum sheet. There is also a 11/2-inch hole in the center section ribs for the aileron wires to go through to connect the servos in the wing. I made a few other changes concerning the Balsa USA Cub wing. The first thing I changed was to build the wing halves with aluminum LEs (see “Tin Wings” in the July 2010 issue of Model Aviation). Another change, as pointed out in the article, would be to use a hole cutter to make holes in the wing ribs before putting the wing halves together. The 11/8-inch holes are the size of the cardboard tubes that the Solartex is wrapped around. The last modification to the wing is to build the ends of the wing so that it has the somewhat square tips, as shown in the Skyrocket wing three-view.

The ends of the wing have somewhat squared-off tips as shown in this sketch.

The Stabilizer and Rudder

The easiest job of all during this modification is the construction of the tail feathers. The stabilizer and rudder outlines are drawn so that all of the necessary ribs and hard points are in the right places. Design the ribs so that they are full-flying surfaces. If the plans are finished, go ahead and build the stabilizer and rudder. Sometimes it is a good idea to use two long 6:32 screws and run them up through the fuselage and stabilizer and then into the rudder bottom, which has T-nuts for the screws to enter. I have found this method of attaching the stabilizer to the rudder to be solid. To further strengthen the tail members, I make K&S Precision Metals streamlined tubing struts to run from the top of the rudder down to the stabilizer and then to the bottom of the fuselage. Aluminum end pieces are epoxied into the tubing and then fastened with 4:40 screws to hold everything together. The rudder can use a pull-pull system for control with the servo mounted roughly 18 inches from the wing’s LE on the bottom of the fuselage. Likewise, the stabilizer can be controlled in a similar manner.

This is the typical shape of the stabilizer and rudder ribs. A Du-Bro hinge is shown.

Wing Struts

Now is a good time to make the wing struts to hold the wings. I install two pieces of aluminum stock through the fuselage sides in two places (locate as required). The 5/8 x 1/8-inch aluminum pieces are 11/4 inches long. This allows approximately 5/8 inch to extend past the fuselage on both sides, so the struts can be bolted to the wing with 11/2-inch 4:40 screws. These strut anchors can be screwed and epoxied to the airframe. To arrive at the true strut length, the fuselage must be weighted down in the middle of an 8-foot long workbench. The wing is attached with four screws at the center section, and boxes are placed under both sides for support. We want the wings to have roughly an inch of dihedral at each end. This amount will be approximately 151/2 inches under the end of each wing half. The Skyrocket’s wing struts are slightly different from most struts, such as those the Cub uses. These struts are the lifting airfoil type.

The all-balsa LE is shown. The end view of the strut shows the 1/8-inch pine “backbone” of the strut.

To make this type of strut, pieces of 1/8-inch balsa for the ribs must be cut and glued every 3 inches onto a 21/2-inch piece of 1/8-inch pine that is approximately 34 inches long. After making four struts, they are carefully measured and the end metal pieces are attached with screws to the 1/8-inch pine strut end. The other end of the strut is K&S Precision Metals 3/4-inch aluminum. Airfoil the tubing at the ends with metal pieces epoxied into them. These attach to the wing after being measured for length.

The Engine Room

As stated in the beginning of the article, the forward section of the aircraft is the most difficult to build. By this time, most builders have given thought to how to construct this portion of the airplane from the side view. My approach to this has been to draw the front end of the airplane on the plans and make a 1/8-inch door skin “phantom” nose section to get the front dummy radial engine ring location and the real engine firewall located, both on the plans and on the airplane. The side view is cut from door skin and temporarily glued at the centerline location of the airplane, taking on the tapered shape of the dummy engine mounting ring. Don’t be fussy about these pieces because they will be cut out later to make room for the actual front ring and engine firewall. These two pieces, when glued in place, form a cross, which is the center for locating and mounting the engine on the firewall. Everything must be kept concentric.

This shows the front sketch of the Skyrocket.

Now that the dummy engine ring has been placed, you must decide to fully cowl the radial engine or to have the cylinders exposed. I prefer to assemble the radial engine with products purchased from Williams Brothers Model Products. The 1/4-scale cylinders make a realistic-looking engine, provided you make a wooden crankcase and mount it on the engine ring. They can be cowled or you can fabricate a speed ring from them. Either way, they look great and add much realism to the aircraft’s nose. For a fully cowled version of the Skyrocket, an aluminum cowl from Balsa USA, designed for a 1/2-scale Sopwith Pup, is perfect. Its inside dimensions are 131/2 inches and the dummy radial is slightly smaller. The speed ring is another option, but it must be made by the builder. Finally, the area from the end of the cowl to the start of the cabin must be considered. There are two choices. One solution is to make aluminum panels to cover the area. I make cardboard templates of everything and then cut parts from thin aluminum sheeting, leaving 3/8-inch overlap on all seams. They are attached to the framework with #1 Phillips-head screws, spaced roughly an inch apart. These screws are available from Micro Fasteners and hold the panels on nicely. Another way to cover the area is to make removable panels backed by formers and cover them with 1/32-inch sheet plywood. These can be glued on or made removable for engine access. The engine and fuel tank mounting methods are up to the builder. The instrument panel and windshield can be left until last, again fabricating cardboard templates for patterns.

This shows the front of the airplane before installing the aluminum covering. Note the instrument panel in the cockpit.

Finishing the Airplane

After all of the model’s modifications are finished, I like to assemble everything and make sure that all of the components work and all of the parts fit before final sanding and applying four coats of Balsarite to the airframe. If everything is okay, it is then time to cover with Solartex. After I’ve completed the covering, I put pinked tape on all of the seams and do all of the wing ribs, giving the airplane a finished appearance. For painting purposes, my choice is Rust-Oleum. It comes in easy-to-use spray cans, and once applied, it lasts indefinitely. If graphics are needed, they can be painted or purchased from a stationery or craft store (letters, numbers, etc.).

Landing Gear

I’ll not spend much time describing the landing gear. Most builders make them from 1/4-inch steel rods and either silver solder or braze the joints together as needed. They are usually covered with balsa shaped to an airfoil, covered with Solartex, and then painted.

Pontoons or Floats

It has been my experience in the last 25 years that the most fun is equipping an airplane with pontoons. I have constructed roughly 10 pairs of Balsa USA 1/3-scale floats and used them on all sorts of large aircraft, so I feel that they are a worthy addition to the Skyrocket. You need to build some hard points into the bottom of the fuselage to accommodate the struts that go between the pontoons and the lower portion of the fuselage. If float flying is a possibility, plan for it now.

This is a side view of the Skyrocket on floats.

Keep ’em Flying and Build ’em Big

I hope this article inspires a host of builders to try out the ideas set forth and see what they can come up with. The author assumes no responsibility for results or performance of any modified kit and has submitted the information purely for the enjoyment of creating a scale airplane from a Cub kit. —Lawrence Klingberg

Sources:

Balsa USA (800) 225-7287 www.balsausa.com Solartex www.shop.balsausa.com/category_s/119.htm K&S Precision Metals (773) 586-8503 www.ksmetals.com Balsarite www.coverite.com/accys/covr2500.html Williams Brothers Model Products (512) 846-1243 www.williamsbrothersmodelproducts.com Micro Fasteners (800) 892-6917 www.microfasteners.com Rust-Oleum (877) 385-8155 www.rustoleum.com