 New project in progress (Dec 21, 2004): Planned twin piggyback SkyDarts carried up by a D12 (and possibly staged D12) powered BT-55 booster (SkyDarts are only along for the ride, they will not stage). The SkyDarts as rudder-only R/C, BT-50 sized. To help carry the extra weight of the radio gear, the wing area is enlarged a bit to 110%. The prototype used a small GWS 4 channel receiver, pico servo, and 50 mAh nicads (total prototype SkyDart glide weight, 69 grams). There's lighter radio gear out there, but it's what I had for a sport project like this (I might use this project to help nudge me into trying out Li-Poly battery packs, since the final SkyDart models with paint and covering will weigh more than the prototype airframe). A crude prototype was built (just one SkyDart), and an old finned BT-55 model was pressed into service. It was test-flown at the December 18th Birmingham Rocket Boys launch. It was hoped it could boost straight enough without another SkyDart on the other side, but that wasn't the case. It arced on its back and went far downwind on boost. After that, a third BT-55 tube section was added, the launcher was tilted more into the wind, and the rudder was held full over to help make it roll on boost. The boosts were safe but went into the wind a lot, cutting the potential altitude and ejecting well after apogee. But the flights achieved the main goal, to see how well the model glided and how well the rudder control worked out given that the SkyDart lacks dihedral. Turned out it had far more rudder control response than it needed, so the rudder throw was dialed back in the transmitter. Next step will be to build another SkyDart, improving the radio component layout, covering the wing and tail in a lightweight model airplane covering, and painting the body and nose. Then the two will be flown to work out the kinks more, that should boost a lot straighter. Lastly, another SkyDart will be built, using another color, to replace the bare balsa rough prototype. This project is called "SkyDart Twins", as a nod to the old Estes plan #41, "Space Twins", from the late 1960's. That one had two Orbital Transport-ish gliders mounted opposing each other to balance it out (this plan pre-dated the Orbital Transport, so the O.T. actually based its glider on the Space Twins gliders). I never built the Space Twins, but in 1970 or 71 MPC had a kit of a similar type of design, two piggybacked gliders called "Lunar Patrol", which was one of my first successful glider models. I did a twin R/C glider project before, the Robart UFO twin piggybacked gliders in 1999. It worked out nicely. But it needed an F for each flight. And was a bit much to ship to NARAM in addition to other models so I only had it at one NARAM. The SkyDart Twins will be a lot cheaper to fly and a lot easier to transport. | 
Prototype R/C layout  
Ron Witherspoon photo
Ron Witherspoon photo
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