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shaping ailerons
I am building by first big plane. The plane has a trainer flat bottom wing with strip ailerons. I can’t decide which would be better, to round or angle the leading edge on the ailerons. Concerned about gap for flutter in the ailerons. They will be controlled by a servo in each wing half. The plane will be a slow lazy flier doing the standard stunts, loops, wing overs, nothing fancy. The plane should weigh in at 12-14 lbs. 85" wing. I plan on a 26cc gas engine.
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RE: shaping ailerons
What is the geometry of the trailing edge of the wing where the aileron is hinged?
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RE: shaping ailerons
I am fairley new at flying. Flunked geometry in school. Explain question please?
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RE: shaping ailerons
The ailerons are shapped the same as the wing I guess like barn doors, but the leading edge is flat same as the trailing edge.
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RE: shaping ailerons
Sorry, my question wasn't clear.
I need a drawing program or something.... (I do numbers, not graphics - see other thread :) ) The answer to your question will depend on the shape of the trailing edge of the wing that the aileron is mated (hinged) to. For example, if it is flat, then you must angle the leading edge of the aileron. If you have nice circular rounded leading edge then it won't rotate freely against the flat trailing edge of the wing when hinged. The rounded edge will *roll* along the flat edge.... yes... but won't rotate free when hinged. |
RE: shaping ailerons
Jim
Thats basically what I though. The wing training is flat and aileron sit flat against it. Thanks for the help. |
RE: shaping ailerons
Draw a line down the front of the aileron leading edge that is about 1/4" down from the top. Draw a line down the top surface of the aileron that is 1/4" back from the leading edge. Draw a 3rd line on the bottom of the aileron leading edge that is about 1/2" back from the leading edge.
Using a razor plane (Master Airscrew is probably the best you can use) start to "connect the lines" by shaving off the balsa. You'll have a 'V' shaped leading edge when you're done. The hinge line is above the center point of the leading edge for several reasons. It looks better, it allows the use of any type hinge and it provides enough clearance for "more up than down" aileron throw. This will make your flat bottom wing roll a lot better. |
RE: shaping ailerons
Do not round the LE of the aileron, cut, or sand it to a bevel.
And don't worry about the gap, or flutter. You NEED to have a slight gap for the hinges to flex. The gap can always be sealed with covering or tape, but too small of a gap can't be fixed (without a compleat hinge removal and reinstallation) and will result in binding surfaces and possible hinge failure. |
RE: shaping ailerons
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I have seen several kits that were designed by people who should have known better that to do the leading edges of the control surfaces rounded. Maybe they were Geometricaly challenged. See the illustration.
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RE: shaping ailerons
Well put dreadnaut
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RE: shaping ailerons
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......and now for the other side of the coin: :)
(I got these out of sequence; sorry!) |
RE: shaping ailerons
ORIGINAL: Bob Yeager ......and now for the other side of the coin: :) (I got these out of sequence; sorry!) |
RE: shaping ailerons
What's the source of the aero info? Interesting.
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RE: shaping ailerons
The answer to your question depends on the type of hinges you plan on using. If you're using a CA type hinge, you need to shape to a "V". If you want to use Robart hinge points (or similar), there is no problem with rounding your leading edge rather than tapering to a "V" shape. You just have to recess the actual pivot point of the hinge to the centerline of the radiused leading edge. If you want to round the leading edge, the trailing edge of the wing it buts up to should be concave to allow the aileron to recess into it. A radiused control surface looks much nicer (scale planes), but takes more work. If you decide to go that route, you can build up a surface on the trailing edge of the wing (top & bottom) either with some balsa sanded in concave shape to accept the rounded aileron, or another way would be to wrap the rounded aileron L.E. with waxed paper and temporarily mount it to the wing. Then mix up some epoxy with micro balloons and fill in the gap. Just make sure you sand it to allow enough travel up & down for your throws. (I hope that made sense!)
Pilgrim |
RE: shaping ailerons
Thanks to all. Great information.
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RE: shaping ailerons
ORIGINAL: FlyingPilgrim The answer to your question depends on the type of hinges you plan on using. If you're using a CA type hinge, you need to shape to a "V". If you want to use Robart hinge points (or similar), there is no problem with rounding your leading edge rather than tapering to a "V" shape. You just have to recess the actual pivot point of the hinge to the centerline of the radiused leading edge. If you want to round the leading edge, the trailing edge of the wing it buts up to should be concave to allow the aileron to recess into it. A radiused control surface looks much nicer (scale planes), but takes more work. If you decide to go that route, you can build up a surface on the trailing edge of the wing (top & bottom) either with some balsa sanded in concave shape to accept the rounded aileron, or another way would be to wrap the rounded aileron L.E. with waxed paper and temporarily mount it to the wing. Then mix up some epoxy with micro balloons and fill in the gap. Just make sure you sand it to allow enough travel up & down for your throws. (I hope that made sense!) Pilgrim I really like the idea of a radiused control surface and making a concave shape to house the rounded ailerons. If anyone has done this amazing work, can you please post a photo to show it looks like. Basically from your description, I am able to "imagine" and make out something, so the photo is just to confirm it. |
RE: shaping ailerons
If you have the May 2004 issue of RCM, flip to page 104, bottom left photo. It's not the best angle to show how far hinge pivot point is sunk in, but it will give you the idea. Maybe one of these guys that knows how to post graphics will help out here.
Pilgrim |
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