Group building projects

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Written by Dave Garwood
RC Slope Soaring
As seen in the December 2018 issue of Model Aviation


Composite fuselages for production start with a plug from which the molds for the left and right fuselage halves are produced. This P-47 has a belly pan.

The joy and challenge of participating in a group build is explained by this month’s guest writer, Joe Chovan, who is an advanced builder and an ace Slope Soaring pilot.

The phrase "a team effort" is often heard from athletes, business leaders, and coworkers when describing their successful achievements. When selecting a subject for a new model, a spark of inspiration can be fanned to a flame with careful collaboration that spreads fires of enthusiasm as each participant envisions his or her role in the creation. Ideas are shared, techniques are compared, and help is enlisted toward a critical mass as the project launches.

I’ve witnessed this process many times throughout my years in the Slope Soaring community. Members of the Inland Slope Rebels (ISR) of Southern California have been working together to create Power Scale Soaring (PSS) subjects since the mid-1990s. With the maturity of the internet, the club has showcased its recent builds in the Slope Soaring discussion forums on RCGroups.

I first partook in a group build of a Supermarine Spitfire for the 2011 Spring PSS Festival. Most of the ISR group builds feature high-speed warbirds or Reno Air Race-style airplanes that span 40 to 60 inches and often employ two channels for control (elevator and aileron).

The sailplane control setup isn’t complex, but knowledge of construction methods and attention to detail is needed—all of which can be learned in a group effort. Enthusiasm is usually infectious, and experienced builders and fliers are happy to share their knowledge.

Although scratch-building methods run the gamut from balsa stickbuilt airframes to solid EPP foam construction, there is one formula that is favored by these Slope Soaring pilots to produce fast, high-performance, and durable aircraft.

Molded fiberglass fuselages with solid 3/16-inch balsa or basswood tail surfaces perform well in this size range with an RG 14 or similar airfoil. A foam-core wing sheeted with 1/16-inch balsa or plywood and basswood leading edges provides the thin, efficient airfoils we need for speed, and the strength for flight loads.

The wood surfaces can be covered with film or fabric then possibly finished with resin and painted to create pleasing military or race schemes. This combination provides enough strength to withstand 100-plus mph flights, as well as make the aircraft more impact resistant to hard landings on the slope.

For most "conventional" models that have a wing in front and a tail at the rear, when wing airfoil, loading, and tail volume attributes are understood, many designs can be copied with a successful basic formula. Merely the fuselage profile and the wing’s top view outlines, which don’t contribute as greatly to overall performance, are changed. Often, the same cores can be borrowed from one project to another, trimming as needed for slight changes in aspect ratio or wingspan.

Experienced and discerning hobbyists realize that to achieve their specific modeling goals, it is nearly always necessary to create exactly what they desire "from scratch" when current ARF offerings are found to be lacking. A scale builder might continually seek unique subjects to showcase.

Shown are wing root and wingtip template patterns that will be attached to a foam block for hotwire wing-core cutting. A spar-cutting template might be used if a spar is required.

Aircraft performance and appearance specifications present challenges that we all face when building, but a special pride arises when a builder can say, "I made this one from scratch." I wish I had more time to build this way.

Group builders commonly receive a short kit that consists of a set of foam wing cores and a molded fiberglass fuselage. Additional materials and hardware are suggested but left to the builder to acquire.

Building a sailplane from a short kit takes me approximately three weeks of four-hour evenings. My motivation to build is spurred by online banter discussing the design challenges and unique traits of a model.

The ISR and other San Diego flying clubs have many colorful and friendly characters in their ranks. After your flame is lit, you’ll find you are in great company should your travels take you to Southern California.

When making a short kit, you need to construct wing cores by creating templates for hot-wire foam cutting. A hollow, composite fuselage can be made from "lost foam" for a single production, but for repeated production of identical units, a plug must be made to the exact shape, and molds must be constructed to make fuselage parts. These processes are illustrated in articles, videos, and educational discussion threads online.

Since 2011, subsequent ISR group builds have included a Bell P-39 Airacobra, a Mitsubishi A6M Zero, a Focke-Wulf Fw 190, an original Reno racing-style Zephyr racer, a Boeing B-17 Flying Fortress, a Legend racer, a Messerschmitt Bf 109, an Embraer EMB-312 Tucano, and a North American P-51 Mustang. Other popular designs are the sport JART and Chaos, which satisfy those who like the looks of "pointy" airplanes that appear to be moving fast at any speed. All of these building and discussion threads can be found by searching the Slope Soaring section on the RCGroups forum.

Any design can be chosen for a group project and choosing is part of the fun. If you are a member of a club, you might not need to start an online thread, but having detailed descriptions and pictures easily accessible helps newcomers get up to speed and provides a historical log for future reference.

When deciding how to distribute the production tasks, consider the effort and cost involved with each task. When you are making composite aircraft, an immense amount of time can be spent producing a plug, mold, and fuselage parts—especially if they are to be delivered as a complete fuselage that is ready to be assembled with the wing and tail parts.

You’ll probably want to collect money from participants to fund the project and compensate any manufacturers for their time. It helps if someone keeps a log of expenses, who has paid, what needs shipping, and related information. At the onset, it would be a good idea to estimate time for each stage and publish this for all to see so that costs are understood. No one likes to work for free or get stuck doing the lion’s share of the work while being undercompensated.

If you are building for an event, consider delivering the necessary parts to those who are attending the event. Make that a priority over those who will be building later or are in remote locations.

A key point for group cohesiveness is to not permit too much customization. Often, requests for light, medium, or heavy lay-up (to accommodate various wind speed and durability needs) can be satisfied, but try to keep an overall conformity with wingspans, airfoils, etc.

If your goal is to fly on the slope together, it helps to keep the physical specifications (weight, wingspan, and airfoil) as close to identical as possible so that your aircraft will equally gain and lose energy in turns, but with less effort than if your sailplanes had wider variances in performance. Remember, gravity and wind speed largely determine your "throttle" capabilities on the slope, so if you all share the same design, trying to stay together is easier.

Nothing gathers attention at a flying event like formation flying of nearly identical airplanes—even seeing static displays of two or more matching "wingmen" gets extra attention from spectators.

Building toward such a goal propels one to new heights. What will you call your squadron?

Participants at the 2011 PSS Festival, held at Cajon Summit in California, collaborated to build these 45-inch wingspan Spitfires. They are fast and durable, with fiberglass and composite construction. Photo by Matin Taraz.


Joe Chovan

League of Silent Flight (LSF)

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