What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Glassing Cowl Rivets

Frankster13

Active Member
Several people have said to glass the cowl rivets on my RV-14A so later they don't get cracks in the paint and show through. I am interested in any recommendations on the weight of cloth and techniques.
 
Cowl rivets

Wow. I can’t imagine glassing over the rivets personally. If you over counter sink so the rivets are below the surface, you can then apply West System epoxy with 410 filler (easiest to sand). Sand the surface flush, prime with a filler epoxy primer. Sand, wet sand to 400 and be done. You will never see those rivets bellow the primer and finish paint.

Glassing over the rivets would be a nightmare trying to get the surface flush.
 
Just food for thought

I did not build the cowling on my 3B, but I noticed one rivet was working loose over time. This sensitized me to the challenge of a better way. So on my 4 project, I bonded glass tape inside the cowl to provide an invisible platform for riveted hardware. This worked for 1/4 turn Skybolt fasteners and could work for top/bottom hinge approach. Bottom line, no rivets to spoil your finished cowl, ever.
 
I used fiberglass strips inside the cowling to beef up the areas where the hinges are attached with rivets. Those areas are pretty thin and flexible, IMO. In addition to rivets, I used proseal to glue the hinges to the cowl.

No external fiberglass tape, no cracks around rivets after 20 years.
 
Add to Kyle's point

You can use proseal,3M2216, JBweld and other semi-rigid epoxies to complement the Hinge/rivet/cowl interface.
 
A single bid of medium weigh glass over the rivet heads works well.

What I do:
- Put a skim coat of micro over the rivet heads. Sand flat after it sets. Don’t glass over a gap.
- A bid of glass on top of the micro.
- Skim coat of micro over the glass after is sets, sand flush and feather the edges.

Rivet head in fiberglass tend to eventually pop the paint if your don’t glass over them.

Carl
 
Although I’m not a fan of glassing over rivets, I think of you wanted to do that, you should put a thin layer of cloth over the rivet line. I have some very thin fiberglass cloth, and it would not require much filler to hide the edge of the cloth edge, or the fine weave of the cloth. If you use just micro fill and sand, you will likely eventually see cracks in the paint around some of the rivets. This doesn’t mean the rivets are working. Different coefficient of expansion between the fiberglass and the aluminum rivet can cause this (I think). The layer of cloth helps to hold all this together. It’s worked for me in other areas - like fiberglass elevator fairing attach, without any cracks, and it’s held up for many years.
 
20 years ago, I put a single bid of 1522 cloth over the rivets. No evidence of cracking in the paint. My feeling is that removal of the hinge would involve repainting the cowl in any case and sanding off the thin layer is relatively easy.
 
When I did this years ago a friend put me on to using narrow fiberglass "tapes" used by R/C aircraft enthusiast. Instead of the 6 or 9 oz. cloth it is like 2 or 3 oz., and 0.5 to 1.0 inch wide. I don't remember where I got it, but it is very thin and a couple of layers of tape followed by micro should ensure rivet hiding and prevent future "nail pop" problems.
 
Yep. G-Flex is a great epoxy for many things. It remains relatively flexible over a fairly wide temperature range, similar to their (Gougeon Brothers/West System) Pro-Set epoxy. Pro-Set is the structural adhesive that I attached my Fastback canopy to the frame on my original RV8, and what was used on Spaceship One that went into outer space. As a finished product that you want to paint, I would put on a layer of cloth and micro for a final finish prior to primer.
 
Definitely

When I riveted on the aluminum plates for the Skybolts, I had a layer of West Systems and micro balloons on the aluminum against the cowl. Then clecoed in place. The rivets were squeezed with the epoxy oozing through the holes. After squeezing, card the excess epoxy to fill any voids.

You can use 2-3 ounce glass cloth from CST Sales or most hobby distributors. Use Peel Ply for a nice finish. Fill and sand as needed. You won't have any rivets coming loose.
 
Back
Top