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General control line discussion => Open Forum => Topic started by: bob whitney on July 25, 2015, 09:54:06 AM
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can anyone tell me how the Flight Streak can get away with such a small elevator
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It's very short coupled and doesn't need much.
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And it doesn't have flaps. Flaps tend to act like "anti-elevators", so you need more elevator to overcome them.
The Sig Skyray (which makes an excellent stunt trainer) has no flaps an an elevator only slightly bigger than the Flight Streak's.
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It knows how to work it.
MM
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I'd disagree with Randy on the FS being "short coupled"; certainly rather long TMA for a '57-ish design, tho not as long as the years later Skyray 35. The Skyray also has a small elevator...because of the longer tail moment. The Skyray is a better stunt design, but the FS wing is a better wing...by a bunch, IMO.
Tim is correct about the flaps causing what I think Howard would call a "negative pitching moment", making the airplane want to turn opposite direction from what the elevators want. Leverage wins. Personally, I think the elevator doesn't need to be nearly as large as we typically use. Often, the flaps are also obviously too large (see Profile Cardinal!). If you look at undercambered FF airfoils, they've found that more lift/drag comes from moving camber rearward. For example...take a typical HLG with flat bottom airfoil...add a wedge to the bottom of the wing TE about 3/8" x 1/16"...blunt edge aft, pointy end forward. You'll see a big change in glide...and trim required. y1 Steve