Thin Ailerons
 

What aerodynamic effect would one experience using an aileron that is significantly thinner than the trailing edge of the wing?

Any and all input would be appreciated. Thanks, everyone!

In the first photo, the thin white line at the rear of the TE is the aileron, viewed from the side.

RE: Thin Ailerons
 

I don't think there would be any change in the control effectiveness, as long as the gap is tight; the relationship between the leading and trailing edges is the same as a "normal" installation.

There would likely be a little extra drag from the little low-pressure area in the gap. On a full-scale plane this can add up to a knot or two; my plane has little 2" gap-sealers on the flaps that make a small difference when they are missing. It's probably negligible unless you are pylon racing or something.

Just armchair aerodynamics, FWIW.

RE: Thin Ailerons
 

In practice it has been found that ailerons thinner than the trailing edge of the wing tend to lose control effecticeness around the center. This can be particularly true at low speeds. I noticed this on a friend's trainer many years ago.

Generally, it is better to have the ailerons slightly thicker than the trailing edge. This gives better control.

If your plane is built and you do not want to build up your aileron thickness, try reflexing both ailerons up slightly.

RE: Thin Ailerons
 

I think the biggest concern I would have is control surface stiffness. Those thin ailerons will be weak in torsion, which can lead very easily to flutter. I'd go ahead and build streamlined ailerons with a thicker LE to match the cutout in the wing.

-David

RE: Thin Ailerons
 

I see it's a stunt/funfly type... they usually use flat plate ailerons rather than streamlined. I've heard lots of talk about why the thick TE is better than a streamlined one... but aerodynamically it makes no sense to me. More likely, it's easier to build an aileron from 1/4" square stock than make a real streamlined shape... so that's why they do it. ;)

-David

RE: Thin Ailerons
 

Both the above comments are very true. Thin ailerons are more prone to flutter due to less stiffness and, best control is had when the leading edge of the ailerons are slightly thicker than the trailing (hinge area) of the wing.

RE: Thin Ailerons
 

The sharp edge of the aft wing will cause flow to separate at low aileron deflection angles. For maximum aileron control the ailerons should be thicker then the wing so that flow reattaches after crossing the gap between wing and aileron. Another approach that is used on full size aerobatic planes is to hinge the aileron at about 30% chord so that the leading edge of the aileron is deflected up above the trailing edge of the wing... If you look at the Extra 300's and Sukhoi's you'll see this design.

Ty

RE: Thin Ailerons
 

Many thanks to all who took the time to respond and share their insight, knowledge, and experience. It is apparent that my time would be well spent in framing up two new ailerons, and being a little more judicious with the sanding bar.[:o]


Thanks again, and regards to all!

RE: Thin Ailerons
 

Hi Bob,
Another 2 cents worth>
Some time back the Germans did research on ailerons.
Result was unexpected. Ailerons whose leading edge were thicker than
the adjacent wing produced LESS DRAG and were more effective.
Take it for what it is worth?
Good luck!

Hal deBolt

RE: Thin Ailerons
 

Good Afternoon Hal,

Thank you for your input. Yesterday I framed up two new ailerons and build up the leading edges. I am not quite finished with them. When I finish i will post some pics, and hopefully get some input from all who have contributed to this thread. I had to be out of town today and will be tomorrow also. RC is great, but a guy needs to get in a little spring fishing! ;)

Thanks again for your input.

RE: Thin Ailerons
 

Following the excellent advice I received from everyone; I framed up two new ailerons, built up the leading edges with 1/8" stock, rounded the LE, and installed tri stock to "clean up" the "step" created between the 1/8" stock and the aileron frame.

The aileron on the left has the 1/8" stock installed, but not the tri stock. I believe the "step" created by installing the 1/8" stock is visible. the aileron on the right is completed.

The reason I added the tri stock is: I thought that the "step" would created an area of low pressure, and thus turbulence. Was I correct in my thinking?

I should have mentioned that this is a Tower Uproar .40 "Club Pylon Racer" to be powered by a TT Pro .46. I have probably defeated my purpose by adding the additional weight to the ailerons, but perhaps the increased weight will be offset by more effective control? In any event, this has been a worthwhile experience and I have learned something.

I would appreciated any comments and suggestions. I hope that reading through all of this has not been too tedious. Again, my thanks to all for the comments and suggestions.

RE: Thin Ailerons
 

Sand a taper on the ailerons. You have the meat at the front for the hinge to go into, you don't need much aft of that.