Left Wing Tip Problem

Time: 6 Hours

As Glenn and I were talking and looking at the left wing tip as it was installed we noticed a problem. With my installation I didn’t notice how the trailing edge line looked! I was concerned that the trailing edge matched up with the aileron hence the need to split open that edge so I could make it rise or lower as needed. What I didn’t do was sight down the entire length of the wing. What we found was that the wing tip drooped down almost 3/4″ over the run of the tip!

Thats not good, so I thought maybe there will be the same dip in the right wingtip keeping things symmetrical so I grabbed the right wing tip and installed it. Yep that’s right it’s perfectly straight unlike the terrible left tip! 

Ok so now how do I fix the left side. The intial plan was to split the aft end and see what we can do. That didn’t give us much results. So we started splitting the outboard from aft to front a little at a time to see what we could get. No luck every time we moved or manipulated we ended up getting bulges or stresses. So I cleaned up my work area and called it a night to go home and think. I was deflated on what to do and did a bunch of research to come up with some plan. Well this morning I had no idea what to do and was going to order a new wing tip and start over. That was going to be around $300 with shipping and I was looking forward to that. So one option Glenn and I are talking about was to shorten the top edge that runs along the wing skin, where the hinge is. This would require drilling out all the rivets and chiseling off the hinge and fiberglass. I figured it was worth a shot before buying a new one. So I removed the tip and started drilling. It didn’t take too long to get all of them done and removed the hinge. So I marked a line along the top of the tip inset 3/16″ and removed that material with my orbital sander.  Why 3/16″? It was just a guess on my part and I went with it. I then returned the tip to the wing and put the lower hinge pin in and pushed the top up tight. To my surprise it fit pretty good and the outboard tip matched up to the level meaning it was inline with the aileron! Ok so I removed the tip and grabbed a new section of hinge for the tip side and cut it to size. I put it in place on the top hinge of the wing side. With it I place I returned the tip using the lower hinge pin. I then pushed the top up tight and clamped it in place. I drew a line 3/16″ outboard on the top of the tip, this will be the new rivet line since I moved the top that much inboard.

 I drilled one hole at the aft end of the rivet line and put a clecko in to check the trailing edge alignment.  Wow it looked great! So I drilled the rest of the rivet holes and clecko’ed them. So I then made some shims to keep the trailing edge the right thickness since I split it open. I mixed up some epoxy with flox and buttered the split edges and clamped them in place with the level. 

So I will let that cure before unclamping to see how it turned out. What a new experience working with fiberglass. While the left side was sitting I removed the right tip to finish work on it.  First up was to cut the rib that closes the aft end of the tip. Since I decided to use hinges this rib needed a little modification to get it fit.  

Second was to address the flimsy middle section of the top. From what I have read and Glenn told me is that the flimsy top will flex and move a lot in flight potentially causing paint cracks and just looking terrible in flight. Guys have used rigid foam cutbtonshape and epoxied in place.  For me I decided to follow Jason Beavers advice and use some foam backer rod, this is a foam rope that made to fill concrete gaps before caulking. This rod is just used to create a shape for an overlay of fiberglass to make a stiffening layup. The idea is that after the layup cures it acts as a rigid vertical element to the flat part to give it rigidity. So I figured out where the flexing would occur and cut a couple peices to length. Then I used my hot glue gun to tack the ends in place. 

I then cut some 3″ fiberglass to cover the rod with an inch or two overhang to finish the look. I mixed some epoxy and wet the glass into position.

That was enough fiberglass for one day and I cleaned up my messes and called it a day. 

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