A coroplast 38″ wingspan delta wing slope soarer for 2-channel elevon control.
Read on for more pics, and all the tasty links you need to make your own.
The micro RC planes in the last post weren’t the end of the homebrew plane spree. I wanted to make something bigger, and found many designs for delta wing slope soaring planes with “elevon” control surfaces – see here, here or here for examples. These work by mixing the elevator and aileron inputs, either electronically or mechanically, so you get pitch and roll control from only one pair of control surfaces.
A slope soarer doesn’t have a motor; lift is obtaining by throwing it (hard!) off the top of a slope while wind is rushing up the slope. The inspiration for the project was that my main flying spot was just such a slope, which meant I needed something to fly when I didn’t want to pit my lovely Radian against too much wind.
A popular constuction material for these planes is “coroplast” — that corrugated plastic commonly used for real estate For Sale signs and election boards. The planes end up so rugged using this technique that they’re often flown in full-contact combat games!
The preferred 4mm thickness is hard to find in the UK, but the 6mm variant is everywhere and it didn’t take long to find a nice piece that wasn’t serving any critical purpose
Having found a piece of coroplast, I got out the scalpal and the “Chaowing” was born. It’s heavily based on the Flik – see that page for a complete construction guide. As the 6mm is quite a bit heavier than the 4mm coroplast (the Flik plans actually call for 2mm, which I’ve never been able to find), I didn’t cover the top of the plane with a second sheet as is done on the Flik. Most of the plane is a single sheet, but the electronics are mounted on an additional square of coroplast with the grain running counter to the main sheet, for extra rigidity in that region.
The side fins (yes, I’m sure there’s a technical name) are held on with thin bamboo skewers from chicken satays. The coroplast grain runs in parallel with the trailing edge (left-to-right across the plane, not forward-to-back along it). The skewers were pushed through the fin pieces and covered with epoxy, then slid into the coroplast channels. The result is extremely strong.
The electronics consist of a homemade 5-cell NiMh, the receiver and servos from our original Piper Cub trainer, and an electronic mixer from the local hobby shop. The simple 27MHz transmitter from the Cub was fine for this too, so it was a very cheap project; the only outlays were Â£8 for the mixer and Â£2 for some thick piano wire to make the pushrods. The control surface hinges use this cunning technique for strength, and the elevon control horns were fabricated like this.
The Chaowing needs a very strong wind, as it is quite a bit heavier than it probably should be. Given extreme conditions on my local slope though, it’ll stay up quite happily and is insane to fly, very flickable and great practice for delta wing flying. It’s also virtually indestructible and has taken many hard crashes without incident.
The battery pack is held onto the nose with velcro. This makes it easy to adjust the centre of gravity of the plane; I start with the CoG at the centre of the plane and adjust from there for the conditions. In extremely high winds, the CoG is moved further forward for more penetration.
With a UK general election (supposedly) occuring at some point soon, there should be a lot of raw materials around for these These simple, beginner-proof planes are a great way to learn to fly and make an excellent first project.