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::: Higgin's T-38 Talon
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Plane: Carver  Span 68.75" Root 10.375" Tip 6.5" MH 60 (loose interpretation - explained below) weight 48 oz wing loading 12.2 oz/ft^2 LE Sweep 28 deg Purpose - DS wing that won't elevator stall at high speed and is capable of banging out consecutive turns without losing energy. The plan was to throw everything at this project to avoid the elevator stall. 2" elevons (idea from the Razor One), flow fences and elev/flap coupling
Lay-up One layer of 10 oz. s-glass with a 1.4 veil (45 deg bias) Construction Hey, its a wing. Sink an antenna tube, bag the wing halves, drill wire tunnels, join, add tips and gear. Flying I think we're getting close (there is a small group of us attacking this problem). I'll skip the whole locating the CG deal. I don't like wings to hunt in pitch and I set the CG so that a CH farther back and they will. After trimming and setting the control throw to my liking, I quickly found coupling the flaps to the ailerons really made the rolls sloppy. Taking the easy way out I turned of the mix and will deal with that later ...if at all. The next test was to see that the flaps did in fact produce a positive pitch when deflected down -yep. Altitude was gained for a slow speed stall. Fearing the dreaded propeller spin to the ground, ya just have to go ahead a do it. One spin to an easy recovery. Now for a couple bank and yanks to see it it wants to curl into the ground. A slight tendency when turning downwind when its quartering. Test to see that the elev/flap actually makes a difference and set throws - all good. Now the true test - DS. I dropped in a whirled off a half dozen circles with the elev/flap coupling engaged and no problems staying inside the circle with minimal elevator input (smooth circles). I dropped in again without the coupling and while there was no elevator stall it required much more elevator to stay inside the circle. The elev/flap has an added benefit of stabilizing the plane in roll (I might be sniffing glue, but thats what I feel) while DSing. Tight landings are now a piece of cake. Next, lose the inboard flow fences - no change. Lose the outboard flow fences - no change. The idea was that they would control root to tip spanward flow from possibly blanketing the elevator action. I tried to bang out consecutive hard turns and the plane will perform them without losing energy, but doesn't gain energy like a conventional plane. I'm just getting started and have some more tweaking to do. I think it can improve. I'm still convinced that a traditional plane is better for this application, but after the local group lost so many swept wings to elevator stall, seeing the performance of this wing made the project a success. I learned that 2" (30% at the tips) elevons and elev/flap are good things for wings.
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All Content © Craig Toutolmin |
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:::Carver:::
