Yet Another wingtip question

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

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.

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

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.

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

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.

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.

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.

Defer wingtip fit up

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

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

jking said:

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

Click to expand...

It does seem that way, and many people rush it to get flying (like me). The quality of the fiberglass fit and finish makes a huge difference as those parts are very visible. You are doing the right thing. Hoping for a successful outcome. Let us know how it goes.

jking said:

. SNIP.... 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

Click to expand...

The other side of the coin is if you defer all the glass work to the end, you only need to get up on the proficiency curve one time. I also glass in all the showing ribs so having just the one big fiberglass hill to climb works best for me.

And if you really want to loose your religion, do the glass work on an RV-10!

Carl

Jerald,

Like you the droop bugged me. I wanted a razor straight line from root to tip. I would estimate it took about 60 hours of work to accomplish getting it straight. Here's what I did. After getting the flaps and ailerons on the wing I built a wood devise to hold the flap and aileron together while the aileron jig is in place. The aileron jig that vans sells works great for this. I double check alignment at the aileron tip with a straight edge and the tooling holes in the outboard ribs per the plans. Next I fit the tips and used the hinge method to mount the tips. Now taking string I ran from the flap trailing edge at the root to the very edge of the fiberglass tip and noted the droop. Like yours mine was about 5 or 6 degrees. The only way to correct for this is to cut not only the trailing edge but also about 14-16" off the side. Next I was able to tack glue the trailing edge to get the proper fit. Then I began the process of glassing the trailing edge back together with the proper angle and degree of twist to match the aileron and flap on that wing. "CAUTION". If you use the hinge method the slight play in the hinges cause more droop when you take the wings out of the cradle and lay it flat on a table causing you to have to start the cut and re-align process over again!!! Ask me how I know The final product came out razor straight and very strong, although it did add a small amount of weight per tip. I visited the Vans factory recently and checked all of their demonstrators. Several had a small droop or twist in the fiberglass tips. So is it worth the extra work? Honestly, each builder has to answer that. I don't think it will cause a huge roll issue if you don't as long as you install the Vans aileron trim system. We'll see. Here is a link to my builders log. Good luck!

http://websites.expercraft.com/markm1/index.php?q=log_entry&log_id=88435

https://s3.amazonaws.com/expercraft/markm1/43558026257edd24489258.jpg

I have no dog in the droop or no droop hunt, but if it helps, here's some empirical data on roll influence. I'm aware of several different models of experimental a/c that have tried roll trim tabs near/on the wing tip, including attempts to use them for autopilot roll control. None were at all effective, and all had to move the tabs to the trailing edge of the aileron to get them to work (so the tab drives the aileron; same as the elevator trim tab drives the elevator).

Just a FWIW....

Charlie

Yay Mark - someone who has actually done it! I agree with Charlie. It is a cosmetic issue and I too would be very surprised if the droop affected anything.

I find it interesting that this issue didn't seem to be there in the early days. (We had others). Perhaps the new wing tip molds or design is off here. Seems like a lot of folks have this issue and with a match drilled kit, consistency should be better in regard to the wing making this fit up easier, not harder.

Jerald,

One other thing I thought I might mention. I have a prior life in auto collision repair. With the exception of using wet epoxy and 8oz glass for the layups I relied heavily on a thick slurry of glass bubbles for blending the outer surface. I shaped and cut with 36 grit paper and did a final sand with 80 grit. Before priming, I used a glazing putty and did a final sand with 180 grit before priming with a fill and sand epoxy primer. I detailed the process in the builders log. I thought I would mention it because if you go down this road you will go mad shaping and sanding with a finer grit and trying to achieve a razor straight edge. Once again good luck!!

Thanks for sharing your experience, Mark. When I first saw the angle I thought I would have to split the trailing edge and continue along the outside for some distance. I have checked out your builder site. I guess you keep going until it gives enough to take the angle out. I am still working on other things and hoping my "reverse twist" clamps will take at least some of the twist out. Or maybe by then I can live with it...

Jerald

Honestly the only two people that are going to see the slight droop are you and a OSH lindy award judge. I think the most important thing is that the aileron and tip meet when the ailerons are nuteral.