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I'm at the point of installing the W-412 wing tip rib in my new tips. In a prior wingtip installation, I did not like the way the wingtip came out after I mounted the W-412 using rivets. When the countersunk rivets were squeezed the gel coat cracked around the factory head in a few places. The cracked gel coat would have to be removed prior to painting or the crack would eventually show up in the paint. And the area along the length of the rib was visible after installation - but don't know what caused that. Perhaps I had the W-412 shoved too far aft when I permanently attached them which caused the appearance issue which was a noticable waviness between rivets.

So after giving it some thought (very dangerous I know), I wonder about the feasibility of not riveting them at all, but rather bonding them to the fiberglass using Proseal. I'd drill a number of #40 holes along the top and bottom flange and use clecos to hold the W-412 in place while the Proseal set up, and later fill the holes with flox. And since Proseal is flexible there is little chance of it cracking later and the rib coming loose. Another advantage is I can easily mount the rib 'reversed', that is, with the rib flanges facing outboard, which will give the wingtip a better look when finished. I can't think of a downside to this as this should be an area of little or no flight induced stress, but seek advice from those who have been there, done that. Thanks

 

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Bump on this thread.

After giving it even more thought (more dangerous...) I remembered that when I built a Christen Eagle II in the mid '90's the canopy assembly, which is much like Van's (steel frame, plexiglass bubble, fiberglass skirt, plus aluminum side rails), was bonded together using 3M Scotchweld structural adhesive. So I'm thinking now that I'll use this product for the W-412 tip ribs instead of Proseal. But I still have the same question - has anyone ever just bonded the rib to the fiberglass? Also, thoughts on having the flange of the rib facing outboard? I did see one or two at Osh this year that was done with the rib reversed and it did look nice and I don't see a downside, but....?

Thanks

 

[robertahegy]

When I built mine, I countersunk the rivet heads into the fiberglass and smoothed filler over them. Never had any cracking or chipping issues in the finish. Sink them enough to bury the entire head below the surface.

Roberta

 

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Thanks for the response Roberta. Perhaps on the prior installation the countersinks were not deep enough. I'll do some experimenting...