Yet Another wingtip question

jking · #1 07-17-2017, 12:41 PM

Apologies if this has been covered but I was unable to find anything. In fitting my right wing tip (W-715-1) on my RV-8, when the flange is seated around the perimeter the trailing edge of the tip is angled down 6 degrees or so downward from the aileron trailing edge. Its not that I cannot match the inside trailing edge to the aileron (jig in place, tooling holes aligned), but instead that the plane of the trailing edge of the tip does not run parallel with the aileron trailing edge. Is this purely a cosmetic issue? Is it commonplace?
The left side is maybe a couple degrees from alignment with the aileron and is hardly apparent. The tips have been in storage for 10 years with multiple moves and in different attitudes and I had to cut foam ribs to expand the perimeter of them to seat against the inside wing. The mis-aligned tip also has a trailing edge section of flange that bends outward and does not seat cleanly against the inside wing edge, but I'm planning on hinge attachments and this isnt a big issue.

Jerald King
RV 8
SE AZ

tgmillso · #2 07-17-2017, 11:48 PM

I just finished mine and discovered similar issues. I appears on many RV's that with the tip and aileron aligned in the neutral position, there will be some downward droop as you move outboard in the tip (about 3/32 IIRC). I also found that the tip cord was longer than the wing/aileron chord, so after speaking with Vans I sanded about 1/32" off the leading edge of the tip flange then reinforced it on the inside with 3 layers of 9oz glass. This allowed the tip to come forward a little. I then pushed the tip forward, checked that it aligned with the trailing edge and clamped it in place near the rear spar on the top and bottom sides, on the top side with a cleco gap clamp and on the bottom with a super skinny g clamp. After checking everything is perfectly aligned, contrary to the instructions I then drilled the aft two most holes first and clecoed in place, then stated at the leading edge and worked back, clecoing on the top and bottom sides as I went. If you do not cleco at the rear spar first, then it may shift. It did this to me the first time around, so I had to fill the holes and start again. Finally, you can sand the trailing edge flush with the aileron and then fill/reinforce on the inside with flox to return the strength you removed, reaching in as far as you can with a thin spatula and remembering to roughen the glass first. If your trailing edge does not line up with the aileron after you have used this method (but before you put the flox in place) you can cut the trailing edge and then re align and re bond in the position you want. There are posts on the for covering this. Good luck.
Tom.

jking · #3 07-18-2017, 11:30 AM

Tom, thanks for your help! I did contact Van's Support. They could not say whether it would have an effect on trim in flight but confirmed that cutting the trailing edge would allow me to take out the twist. I was not convinced that would work and its nice to have confirmation. Mine is much more than your 3/32". Before I do surgery on it I'm trying to take some of the twist out clamping it down with opposite twist in a warm shop for a few days. I figure it warped one way so it ought to warp back?

Jerald

JonJay · #4 07-18-2017, 11:41 AM

It is very common for the tip trailing edge not to match the aileron after flap/aileron alignment. Many "unzip" or slice the top and bottom of the trailing edge apart. The tip can then be moved around quite a bit and then rejoined back together after alignment of the training edge.
I have seen it done often and it isn't very hard to do. I am sure there are other posts with more detailed description of the process.
I wouldn't worry about it unless it is way out of alignment or simply bugs you.

jking · #5 07-18-2017, 05:15 PM

It does bug me. Its off quite a bit.

I had read about unzipping wingtips but thought it was for adjusting the vertical placement relative to the aileron. Should have know I was not the first with this problem, right? Thanks for the guidance.

Jerald

JonJay · #6 07-18-2017, 07:03 PM

It is, so I hope I didn't misunderstand your problem. Can you post some pics?
It still might be a good strategy for warping. It is just fiberglass and not difficult to work with but perhaps there is a better way. I have tried heat before with poor results.

tgmillso · #7 07-18-2017, 08:16 PM

Looking at your picture, mine looks similar. The main thing is work to have a good transition from the tip to the aileron at the trailing edge, but this droop issue is something that's very tough to address. Based on other posts I have read, most people live with it, as the droop on both sides is pretty equal. The only way I see to address this is very carefully extending outboard the recess where the wing skin overlaps the fiberglass lip. If you do this near the trailing edge, it will pull the tip upwards and correct this issue, but this will be a time consuming exercise.
Given that my droop was approximately equal on both sides (3/32") I sucked it up and will live with it. Anhedral tips will be back in fashion by the year 2025, so you will just be ahead of the curve.
Tom.

JonJay · #8 07-19-2017, 12:08 AM

Sorry, I do see the pic now. I still feel unzipping the trailing edge might work. You can then push up on the outboard corner and the two halves can slide past each other and find their new place. If that doesn't work you can epoxy and glass them back and have lost nothing but some time. I don't see any other way as you must "destabilize" that trailing edge which "locks" the top and bottom into position. The tip is relatively flexible once the trailing edge is cut. It isn't intuitive.
This is how it is done to re-align the trailing edge and I have seen that work. You are just realigning part of that edge. It may be a lost cause but I would give it a try. If it works for moving the trailing edge up and down a bit, it just might work for this.
Good luck.

Carl Froehlich · #9 07-19-2017, 10:01 AM

While I know I'll get flamed again, here is another example of deferring wingtip fit up until after the wings are on the plane, and after the flaps and ailerons are perfectly rigged (and checked by independent eyes).

The ailerons hinges may or may not need to be rehung, the flaps will need to really be in trail, the aileron alignment tools is good enough to get you in the ball park but not perfect, and the wingtip trailing edge can move up/down and inch before you drill and cleco.

The most common problem I see on RV rigging is that the aileron is not parallel to the wing, displaced up or down on one end. The fix for this is straight forward and will cure that pesky heavy wing issue.

Carl

jking · #10 07-19-2017, 10:18 AM

Thanks again for your input, guys. At this point, I dont have much to lose by cutting the trailing edge and working with it. And no Carl, not going to flame you. You have a valid point and I thank you for your view as well. I just hate the idea of doing all that fiberglass work at the end of the build-cowling, wheelpants, wingtips, windscreen and was trying to get some of it done now. For a metal plane, it seems like half my time is spent on fiberglass!

Jerald