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Author Topic: How much wing sweep is too much?  (Read 156 times)
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stuntguy13
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« on: May 27, 2021, 08:26:18 PM »

Built a couple of fun ships and been wondering about wing sweep. I know that sweep will add stability but how much is too much 30, 40, 50? What about for a flying wing design?

Best,   DennisT
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lincoln
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« Reply #1 on: May 27, 2021, 10:06:48 PM »

If I'm not mistaken, a swept wing of moderate or high aspect ratio will tend to stall at the tip unless it has quite a bit of washout. A tip stall on a swept wing will probably make the model pitch up, making the stall worse. I used to have a toy glider from Testors which had a moderately swept wing. Sometimes it would stall and spin, even though it was quite stable if it didn't stall.

30 degrees is enough, I think, to be a significant problem unless you use a lot of washout. If the wing is rigid, the washout will make the model loop when launched hard. There may be a way around this if the wing is made to flex the right way. A swept flying wing needs washout to be trimmed for level flight. There are commercially available toy gliders which are swept flying wings with a hinge in the middle. They are launched folded, but when the model slows down, a rubber band is able to open the wings. It's important to launch such a model vertically, so that it slows down enough to open the wings instead of diving back to the ground. This actually works pretty well.

Another way to deal with stall issues on swept wings was seen on the XF-91, but it was UGLY.
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