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Written by Bill Bambrick
WHY NOT BUILD YOUR OWN MODEL?
As seen in the October 2015 issue of Model Aviation.

I don’t recall when I was infected by the urge to build models from scratch. It seemed to evolve during my later years. It was difficult to find kits of models that I wanted to build that wouldn’t cost an arm and a leg. But it was more than that; it was the challenge of building something from scratch.

That was the beginning of a new world of model building—and it was more fun than I could ever have imagined. I’ll try to convince you that it is much more fun than simply buying something from the assortment of ARFs or RTF models that confronts you when you enter your local hobby shop.

The Search for Plans

The first thing that you must do is find plans for your project. Model Aviation and the AMA Plans Service can help with detailed sets of plans for all sorts of models from World War I and Old-Timers, to the latest wrinkle in aviation lore. The AMA Plans Service can even scale the plans up or down if you are looking for a specific size.

A few minutes on the Internet can also open a plethora of sources. You’ll be amazed at what you’ll find. A few suppliers that I have found helpful include Balsa USA, Bob Holman Plans, Sig Manufacturing Co., Brian Taylor Plans, Top Flite, and Nick Ziroli Plans. Some plans you find online are free, some have a nominal cost, and some can be expensive, but all are worth the price.

Another source for plans and kits is Ivan Pettigrew, a Canadian who designs large, lightweight airplanes, including a lot of water-based aircraft. In the case of military aircraft, Bombers of World War II and the In Action series from Squadron/Signal Publications, and Scale Aircraft Drawings by the publishers of Model Airplane News are helpful for drawing your own plans.

Construction and Building Tips

After you have decided on a project and have your plans in hand, you are ready to begin cutting wood. It is best to start on a simple part of the structure, such as the empennage or tail feathers. You must decide whether to build them to scale, or simply make them flat.

Scale implies putting a span-wise taper into the horizontal and vertical members, if called for. If building a scalelike aircraft is important to you, then the thickness and type of airfoil are significant. I prefer a scalelike appearance, which does much for the way the airplane flies, but there’s an old saying that given enough power you can make a board fly, so many prefer to make the tail feathers flat. It’s your decision.

When going for a scalelike aircraft, it is important to place supports at the extreme ends of the structure, in both fore/aft and span-wise directions.

There are many possibilities when approaching the fuselage construction. The shape of the fuselage will dictate whether it can be built using a flat-panel design of older airplanes, or whether the complex curvature of the fuselage in three dimensions is important to you.

If the fuselage is to be curved, it can be constructed in top and bottom halves, or in left and right halves, depending on its shape. Fighters are easily built in left and right halves, and then glued together. But a fuselage such as a DC-3, which is symmetrical in both directions, can be produced in either manner—left-right or top-bottom. The Top Flite DC-3 is a good example of the latter method.

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The author’s 1/12-scale Avro Lancaster is on display at the Warhawk Air Museum in Nampa ID.


If your plans don’t call out locations for your power system and radio gear, it is a good idea to do some research before going too far with the fuselage construction. Components should be placed as close as possible to the airplane’s center of gravity (CG). The CG is usually determined as a percentage of the chord length of the wing, measuring aft from the leading edge.

The desired percentage will generally vary between 25% and 33% of the root chord (or aerodynamic chord on tapered wings). Less than 25% will result in a nose-heavy condition, and greater than 33% will likely be tail-heavy. Either would require additional weight to balance the aircraft and should be kept in mind as the building progresses.

A handy formula for determining an airplane’s CG can be found in the August 2012 issue of Model Aviation.

“One way to determine the CG on larger models using three scales is to block the airplane up level. Assuming we’re talking about a tail-dragger such as the Edge, you will have to block up the scale under the tail wheel.

“Carefully measure the distance parallel to the airplane’s longitudinal centerline, from the spot where the mains contact the scale, to the spot where the tail wheel contacts the scale. Call this distance D1.

“Take the total of the weight on the mains and call this W1. Take the weight on the tail wheel and call this W2. In the following equation, the distance to the CG (DCG) is the distance from a line, perpendicular to the longitudinal centerline, and passing through the center of the mains contact spot, aft to the CG spot. “The formula is DCG = D1 x W2/(W1 + W2). Example:

“D1 = 90 inches, W1 = 30 pounds, W2 = 5

“DCG = 90 inches x 5 pounds/35 pounds

“DCG = 12.86 inches back from a line through the mains along the fuselage center

“The principle of the formula is that at the CG, the sum of the fore and aft moments will be in equilibrium. We know the forces (weights) and the distance between them (D1) and have to solve for the spot where the moments are in balance (moment = force x distance). You can also use this formula to tell how much weight you need to move to get the CG to move a given distance.”

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The author’s World War I Vickers Vimy was also donated to the Warhawk Air Museum.


By this time, you should be able to tackle the all-important wings. Cut out the template for the ribs with all of the holes and notches located. Lay them out on the rib material of the right thickness. I always lay them out on a pair of sheets so I can make two of each rib for the left and right wings. When you are satisfied with the tracing, take them to your jigsaw or band saw and cut them out. Use a sander to finish them to the correct outline.

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The author uses this drawing board to draw or modify plans. Photos by the author


The rib patterns generated by your wing design software will generally contain two outlines—one for the outer dimension, including the sheeting, and the other for the inner outline to which the sheeting is applied. It will be the inner dimension that you will want to cut the ribs to.

Several services are available that will take your plans and use laser-cutting processes to cut the ribs, making assembly much easier and more accurate. Manzano Laser Works comes to mind, but there are others from which to choose.

There are many ways to fasten a wing in place, including the use of wing tubes if the wing is in two or more pieces. The tubes fit snugly into an outer sheath of impregnated paper.

Some wings are made in one piece, and the procedure is then to fasten it in place with dowels and wing bolts—typically a 1/4-20 x 2 plastic bolt. Some wings are joined with a tongue-and-box structure.

Whatever method is used, I caution you to not try to save weight on this part of the construction. There is nothing quite as embarrassing as seeing your wings come apart in flight.

Covering and Painting

When it comes to finishing the model, the builder can apply his or her special talents for decorating. But before the application of the final coat of color, it is important to consider what kind of skin your airplane will have.

If the model is relatively small—and by small I mean something you can easily hold in your hand—an option is to apply tissue paper for the skin. Larger models require something more substantial.

Regardless of the type, the process is the same: the paper is applied with the grain running lengthwise along the fuselage or wing. It is easy to determine the direction of the grain by tearing a small portion on the edge of the tissue. It will be easy to tear along the grain, but not so in the other direction.

The tissue is glued in place then sprayed with water to tighten it. Tighten it again by applying several coats of butyrate dope. Color can be added with the final coat, if desired. This sounds simple, but chapters have been written about the process. What type of glue should you use? The answer ranges from simple glue sticks, to white glue thinned with water, to butyrate dope. You be the judge and choose whatever works best for you.

For heavier, more complex models, the aircraft can be sheeted with balsa, and then worked to a fine degree of smoothness with a planer and increasingly fine sandpapers.

Another popular technique these days is to apply an iron-on film or fabric to the surface of the airplane. This may be applied directly to the framework, or it may be preceded by applying balsa sheeting, or strips of balsa in a planking operation. Popular films include MonoKote or Coverite. Another product that has gained a good reputation among modelers is called Stits Poly-Fiber.

My friend, Sid Tanabe, from Boise, Idaho, is a master Scale builder of national repute. Sid provided me with a great deal of information regarding the finishing of airplanes, and introduced me to the Stits line of coverings, which are manufactured by F&M Enterprises.

I was especially interested in learning of the company’s SuperFil, which is a two-part filler. Typically referred to as “that blue stuff,” it is the best filler I have ever used for filling gaps and making fairings. It is lightweight, easily applied, and easy to sand or shape using a finger wetted with 90% to 100% alcohol before it cures.

When the final sanding is complete, several finishing options are available such as paint, fiberglass, or iron-on film. The decision is largely based on the model’s size and weight.

For large airplanes, it is usually best to finish with fiberglass. I use1/2- or 3/4-ounce (per square yard) fiberglass where strength is not as critical, and 2- to 5-ounce cloth for areas that will take a pounding, such as a seaplane hull. Covering with MonoKote or a similar material is easier and less time-consuming, as long as strength is not important (although these films are surprisingly tough).

Either covering might require painting, which can be completed by spray or brush. Brushing is easier, with less damage to the work area and cleanup is easier, especially if one uses throwaway brushes. Spraying, although more expensive, typically offers better results.

Work Areas and Tools

If you have a spouse or partner with a kindly disposition and immunity to all of the mess and noxious odors that will tend to infiltrate every corner of your house, you can probably work in a spare bedroom. For the rest of us, a workshop is a necessity. This doesn’t mean you need an expensive layout, but there will be some expense involved.

Depending on the layout of your house, your workshop will likely be located somewhere in your basement or garage. And if you are living in a climate that makes outdoor living uncomfortable, you will need heating and/or air conditioning. A three-car garage can be an ideal setup.

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These tools of the trade—a band saw, jigsaw, sander, and a drill press—are handy when building model aircraft.


Insulation is often necessary, and you will need to provide your workspace with a good, safe supply of electricity and plenty of outlets. You will also need workbenches, shelves, and storage.

When it comes to equipping your workshop, there is no end of gadgets you can buy, but a few items are absolutely necessary, and quality is important. These items include a jigsaw and/or a band saw, a sander, and a drill press. And each will require a mounting platform that is at a comfortable level and close to the power outlets.

A seemingly endless number of tools can be invaluable, such as drills, sanders, saws, planers, soldering equipment, etc. An especially useful assortment is produced by Dremel. Don’t forget a good bench vise with roughly 3-inch jaws. A grinder is also handy. You might already have many of these items, but you need to consider whether they are in the right place. And don’t forget a toolbox, storage cabinets, and racks. There is one additional factor you should keep in mind: an uncluttered work area is a sign of a cluttered mind, and vice versa. I’m still having trouble convincing my wife of the truth of this bit of wisdom, but I keep trying.

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A DC-3 is a good example of curved fuselage construction.


SOURCES:

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

Ivan Pettigrew ivanp2@shaw.ca  www.ivansplans.com

CompuFoil support@compufoil.com  www.compufoil.com  

Balsa USA (906) 863-6421 www.balsausa.com  

Bob Holman Plans Brian Taylor Plans (909) 885-3959 www.bhplans.com

Sig Manufacturing Co. (800) 247-5008 www.sigmfg.com  

Top Flite (800) 637-7660 http://www.horizonhobby.com/storefronts/top-flite

Nick Ziroli Plans (631) 467-4765 www.ziroligiantscaleplans.com  

Manzano Laser Works (505) 286-2640 www.manzanolaser.com


—Bill Bambrick
billbam@cableone.net

1 comments

Many thanks to Bill Bambrick on his excellent original article: "Why not build your own model" in the October 2015 issue of "Model Aviation" and thanks to AMA for re-visiting this helpful guide to scratch-building model aircraft. It is gratifying to read a "how to do it" article in contrast to the pre-built, "charge it and fly it" current approach to obtaining a model airplane.

Fortunately, scratch-built model airplanes, to fly well and far, need only to conform with Mother Nature's "Rules of Flight" (fiddle indiscriminately with Her rules at your peril, and keep a large trash bag handy to collect the many small pieces of your crashed aircraft), and since these rules are few in number to actually achieve stable and sustained model aircraft flight, just about any materials, (well, OK, perhaps not gym weights), assembly techniques, final shape, painted or not, etc., can be coaxed into a viable model aircraft that will be a happy endeavor for the builder, honest evidence of creativity for the owner, and most definitely an object-of-interest at the local flying field.

For those readers feeling this is just too cavalier, sloppy, and laid back an approach to "scratch-building", they might be correct if a builder has not enjoyed a few years of following well-reviewed plans and advice on how to design and build model aircraft, written by masters like Bill Bambrick, where one can patiently learn and apply the many principles and the few rules of how model airplanes are made and how they stay in the air.

Eventually, the persistent and bold model airplane builder may want to design and build their own R/C gas or electric-powered model aircraft using only the information and experience stored in their head; no plans, photographs, note paper, pencils, calculator, measuring instruments, drawings, books, reference materials, are required, although the addition of a large mug of good coffee is often a necessity for truly outstanding creative performance.

This "making it up as you go" primal scratch-building is not for the faint of heart. Will the resulting aircraft fly? Of course! Did you doubt it?

However one defines "scratch-built", may we all continue building model airplanes and launching them into the air. This hobby has the power to keep us sane and happy in these crazy times.

Best regards:

Frank Horine

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