Front edge of aileron isn't constant thickness?

[astroboy]

As promised, here's the next installment of "How am I going to make THIS work?":

On previous models, I've used the covering film method of hinging control surfaces. It has the advantages of sealing the gap and, in the case of ailerons and elevators, putting the beveled edges underneath and out of sight. Well, I don't think it's going to work on this one. Not only are the front edges of the ailerons not parallel or convergent with the trailing edge, the ellipticity of the wingtips start partway along the ailerons' length. The thickness of the ailerons varies considerably, getting fatter in the middle, then tapering off to nothing at their outboard ends. So I can't very well use a full-length hinge. Even if I were to cheat the forward edges so that they were parallel with the inboard part of the trailing edge, as they approached the tips, they would still taper in thickness as the trailing edge curves forward.

Unless someone has a better idea, it looks like I'm going to be stuck with hinging on the ailerons' center line. In what I've read about sealing the gap with tape of some sort, they say to seal the top edge. I wouldn't much care for how that would look--is there a reason why the gap couldn't be sealed from underneath? If I use differential, it seems that tape that's only attached to the wing and not the aileron wouldn't be so effective if it's underneath, and if it's attached to both surfaces, I think it would bunch up when the ailerons are at neutral.

Thanks,
Jeff

[Viper Pilot]

Jeff,

Just be sure to make everything straight and square.

Then the aileron will square up nicely with the TE and there's no nned to fill the (non-existing) gap.

VP

[Ollie]

Harley Machaelis invented a hinge that would work well in this application. the hinge consists of slots in the aileron and wing along the hinge line. A flat strip of latex rubber sheet is glued into the aileron slot and fed through the slot in the wing to a point ahead of the slot in the wing and put under tension where it is glued into the wing structure. Two or more of these hinges are installed along the hinge line. The tension in the latex rubber keeps the aileron snug against the wing at all times and centered along the hinge line. Ask your dentist for a piece of sheet latex that he uses as a dental dam.

[astroboy]

Originally posted by Ollie
Harley Machaelis invented a hinge that would work well in this application. the hinge consists of slots in the aileron and wing along the hinge line. A flat strip of latex rubber sheet is glued into the aileron slot and fed through the slot in the wing to a point ahead of the slot in the wing and put under tension where it is glued into the wing structure. Two or more of these hinges are installed along the hinge line. The tension in the latex rubber keeps the aileron snug against the wing at all times and centered along the hinge line. Ask your dentist for a piece of sheet latex that he uses as a dental dam.

Hmmm. So it seems the ailerons would have to be attached to the wing before the wing is covered(See the smoke starting to come out of my ears?) Or I suppose I could glue it into the wing first, do the tension bit in the ailerons, then cover the ailerons afterwards. In any case, what glue would you recommend?

Thanks,
Jeff

[max z]

Jeff,
Funny enough I am struggling with the same problem with a scale sailplane, read my "Doppelraab" thread in the Scale Sailplanes section. I am trying to find the answer in warping the tip ribs (i.e. adding washout) to get the aileron LE back to a straight line, but sofar it is leading to rather excessive washout (6-7%). I attach a screenshot to this posting, the brownish part you see is a projection of the aileron LE. I am now working on a version with a different tip airfoil, and a smooth transition over the span of the aileron (NACA 4414 to NACA 0012), but I am not sure that that is going to help to get the washout down.

Max.

[Ollie]

Jeff,

For the straight scoop contact Harley directly at:
harleym@bmi.net

Max,

One possible solution to your wing alignment for a straight aileron hinge line is to establish the aileron hinge line, then position and orient the ribs relative to the aileron hinge line and the desired washout. In other words, locate the ribs fore and aft along the aileron hinge line, then vertically along the aileron hinge line and then rotate the ribs about the aileron hinge line for the desired washout. This shifts the problem to one of jigging the wing during construction.

Another possible solution is to transition the wing's airfoil to one of lower camber and thickness toward the tip.

[max z]

Another possible solution is to transition the wing's airfoil to one of lower camber and thickness toward the tip

Ollie, that is what I tried to say above with the NACA 4414 to 0012 transition. I've worked it out, but it does not help much.
The other method you suggested would result in an upsweep towards the tip of the top spar, very difficult to jig properly. With a flat top spar you can at least pin the wing upside down on your work surface.

Max.

[Ollie]

Max,

If you want to use the top spar as a building reference, keep the contour of the airfoil from the top spar to trailing edge constant from the inboard end of the aileron to the tip. Fit a newly designed tip airfoil to it. Draw a chord line from the trailing edge at the the wing tip to the leading edge with the desired washout angle. Put a leading edge radius at the leading edge and use a french curve to draw in a contour from the leading edge radius to the top spar. Draw in a mean camber line of the desired percent camber. Then plot the bottom contour by mirroring the top contour to the bottom using the mean camber line as a mirror. You will end up with a nonstandard tip airfoil of your own devising that will work quite well. Then transition from the airfoil at the inboard end of the aileron to your new tip airfoil. This should give you a straight aileron hinge line as well as a straight top spar.

[Ollie]

Max,
Here is another way. Keep your present airfoil all the way to the tip. Position the ribs for a straight top spar. Rotate the tip rib for the desired washout. Draw a straight line for the aileron hinge line. Adjust the washout angle for each intermediate rib so that the top of the airfoil contour falls on the straight hinge line. You will end up with a slightly nonlinear washout distribution but that is of little consequence and may even benefit the lift distribution at some angles of attack.