Planes, Trains, Bots & Games (and a few gadgets too)

The Hobby Guy

March 30th, 2009 at 8:01 am

Make ‘Em Bounce!


If you’ve had 2 or more flights on an RC airplane, you know the joy of making your airplane soar and swoop, and the agony of watching it break into pieces with an unplanned landing. Wouldn’t it be great if they could just bounce? Well, now there is a whole category of foam airplanes designed to do just that! Since the happy combination of brushless motors, lithium polymer batteries, and foam airplanes came about a few years ago, the model airplane industry has seen an enormous growth of interest in RC flying. Models ranging from simple flat surfaces, to complex molded shapes have been developed by a multitude of companies.

Of these foam materials, EPP (Expanded Polypropylene) is one of the toughest and most durable foams ever created. Airplanes made of EPP survive collisions with the ground or other objects with little of no damage, and a quick field repair if needed. EPP was developed in the 1970′s for automotive parts. Its first use was to back up plastic bumpers and absorb energy in collisions. EPP can be compressed, then bounce back to its original shape. It is also used in the interior of cars to protect occupants and absorb energy during collisions. Foam model airplanes come in a few varieties of foam including, Depron, Expanded Polystyrene (EPS), and Expanded Polypropylene (EPP). Each type of foam has its advantages and limitations. Depron is thin, light, and smooth, and makes up some of the most advanced indoor models flying today. It is fairly fragile however, and needs frequent repairs. EPS (Expanded Polystyrene) can be molded into complex shapes and has a fairly smooth finish, but it is fragile as well. EPP (Expanded Polypropylene) is flexible and can be compressed, but springs back to its original shape. Its main shortcomings are that it has a rough surface, and it requires some stiffening to hold its shape. Someone sliced a bouncy block of EPP foam into sheets, and began experimenting.

First off, EPP is far more flexible than other foams, so it had to be thicker to give it some rigidity. Carbon fiber rods and strips were added to give more stiffness and to limit twisting. Once these configurations were developed, the EPP airplane took off! Now flat foam airplanes could survive the rigors of 3D maneuvers and frequent contact with obstacles and the ground. I’ve seen these planes maneuvered around and through trees, bushes, concession tables, and inside a garage where the door opener bar was used to land on, loop around, and flop onto again. Even some informal combat seldom requires more that some CA and kicker to return to the fight! EPP makes for very durable planes! Budget RC (BRC) has developed several EPP models including an extensive collection of combat flyers and has video footage showing off the sport well. Short of a propeller chewing away the foam, most mid air collisions result in flying one or both models away, or untangling them after they reach the ground, with little or no damage! BRC also carries an aerobatic “trainer” that is a unique combination of EPP and Depron for maximum durability and lighter weight. At fairly low cost, you can have a fully aerobatic foam airplane that can hit the ground with little or no damage, and is perfect for learning aerobatics and 3D maneuvers. Another product just off the design table is an EPP jet series that hints at unheard of speeds for this flexible material! Records may soon be broken in the realm of high speed profile EPP flight! If you are looking for an airplane that can take some knocks, bounce back for more, and still give excellent flight performance, consider a foam airplane made of EPP!

About the Author

Tom Pepper has been flying planes since about age eight, when he could find five cents for balsa gliders at the local toy store. He got totally geeked about radio control planes when he saw one fly at a Boy Scout Jamboree at age 13. It took until he was 30 years old to have the means and time to build an RC glider (Olympic II) which he learned to fly on. Glow planes followed, and in the last four years he began flying electric planes. Tom has been RC flying for 28 years now. He belongs to the Hudson RC Flyers in Hudson, MI, and has been there for 27 years. His favorite plane to fly plane is “always the one I pull out of the rafters and fire up for the first time of the flying season.” Tom really enjoys electric jets, but lightweight 3D models always offer a thrill a minute too! He has combined his photography hobby with model RC planes and does aerial photography as a part time business. Currently, Tom has four land based planes, one water based plane, and a “Quad” copter that hoists a camera as well. Using video downlink, he can see what the camera is looking at and fire the shots remotely. Tom lives in Jackson, MI with his wife, Anita.

 

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