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Old 03-28-2006, 09:03 PM
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Join Date: Jan 2002
Location: Shalimar, FL
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Default RE: Ultra Stick 60 rudder design question

Ernie, I have tried many different shape of rudder and none of them made much difference. The only thing to cure roll in knife edge is anhedral or downward end plates. I did an experiment on my Little Stick with some lite ply plates. I found that 3/4 inch down below the rib line would cure the roll.

As for knife edge with a Stick, it doesn't have much side area. You can add the side force generators-very large plates at mid wing or on the tips. One thing I did years ago during my knife edge phase was to make strakes down the side. For a Stick it was easier to get a chord-long or longer piece of lite ply that was 2 inches wider than the fuselage. Put this on the bottom bolted on by the gear. Use a couple of screws at the rear. What you have made if a fence on the bottom of the fuselage just like the wing on the top. When the plane is on its side, this fence channels the air down the fuselage, rather than letting it go around the fuselage, creating lift. If you don't like it, you can always unbolt it.

In the photos, you can see the lines on the plates. I started with 1 1/2" hang down and flew. In knife edge the plane had too much effective anhedral from the long plates so it tended to roll over on its back. I would land and trim off a quarter inch and fly again. At 3/4" the roll effectively stopped. The plane originally had flat tips and would do a barrel roll with rudder, as all Sticks, flat wing or not, will do. Try it. You need anhedral or effective anhedral from the plates to kill the roll.
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