What's new
Van's Air Force

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

fiberglass cowl crack repair

larryMar

Well Known Member
I have a 1966 fiberglass nose bowl that has "spiderweb" looking cracks in the gelcoat. A couple years ago (about 200hrs) I sanded it down and sprayed a filler coat and repainted- only to have them show up again. Is there a longer lasting way to take care of this problem of cracking? It's a certified airplane and new cowls aren't an option, so I have to deal with repair. The cracks are not structural, bit cosmetic only.

Thanks,
 
I have a 1966 fiberglass nose bowl that has "spiderweb" looking cracks in the gelcoat. A couple years ago (about 200hrs) I sanded it down and sprayed a filler coat and repainted- only to have them show up again. Is there a longer lasting way to take care of this problem of cracking? It's a certified airplane and new cowls aren't an option, so I have to deal with repair. The cracks are not structural, bit cosmetic only.

Assuming the nosebowl has no significant mechanical load...

Remove all the gelcoat, make any necessary repairs to the underlying POS polyester/glass, overlay with one ply of epoxy/glass, sand dull, seal with neat epoxy, sand dull, spray epoxy primer and urethane high build, block sand, spray color.
 
Assuming the nosebowl has no significant mechanical load...

Remove all the gelcoat, make any necessary repairs to the underlying POS polyester/glass, overlay with one ply of epoxy/glass, sand dull, seal with neat epoxy, sand dull, spray epoxy primer and urethane high build, block sand, spray color.

+1 To Dan's method
 
Thanks Dan!

Neat epoxy - the floor stuff? Can aircraft fabric be used as a ply of glass? I am thinking it's a fine weave and I have excess.
 
Thanks Dan!

Neat epoxy - the floor stuff? Can aircraft fabric be used as a ply of glass? I am thinking it's a fine weave and I have excess.

Oh boy. Are you an EAA member with their membership web access? They have educational videos on fiberglass work. If not, take a look on YouTube and VANS Aircraft's fiberglass videos on the RV14 windshield/canopy fairing work. That will get you oriented to the concepts of glass work. 'No' to your questions above. West Systems 105 resin with 206 hardener along with some lightweight fiberglass bi-directional cloth is what you'll likely wind up with.
 
Spinner

Hopefully there is nothing causing the cracking and it's just gel coat fractures. I agree, sand it off.
If you want a thin layer try 120-38 Standard E-Glass Fiberglass Cloth 38. Very thin and light.
Neat epoxy is simply epoxy (West Systems 105) with nothing added. It's skimmed on after the fiberglass is cured to fill and seal pinholes.
You might want to read Dan's Sticky in the Fiberglass section.
Usually the process is
1. Layup fiberglass & cure
2. Spread a layer of micro & cure
3. Block sand flat
4. Apply (skim) neat epoxy & cure
5. Block sand flat
6. Spray primer
7. Wet sand
8. Spray paint
9. Cut & Buff
 
Thanks Dan!

Neat epoxy - the floor stuff? Can aircraft fabric be used as a ply of glass? I am thinking it's a fine weave and I have excess.

Neat epoxy means pure epoxy without any fillers.. guys here started using that to fill pinholes.

By “aircraft fabric” do you mean fiberglass weave or ceconite fabric covering?
 
Thanks for the clarification. I hadn't heard of "neat" epoxy, and when I search - it was all flooring stuff! I didn't think that could be right, but I'm a tube & fabric guy... I was thinking ceconite. I will discard that thought and get the suggested proper stuff. Thanks again for the direction.
 
"Neat" is resin plus hardener, but no fillers.

Minimum 5oz plain weave glass cloth if the nosebowl is not too curvy. Look for a crowfoot weave for easier compliance with compound curves. For example, 4-harness has less compliance than 8-harness, which is extremely compliant.
 
Thanks for the clarification. I hadn't heard of "neat" epoxy, and when I search - it was all flooring stuff! I didn't think that could be right, but I'm a tube & fabric guy... I was thinking ceconite. I will discard that thought and get the suggested proper stuff. Thanks again for the direction.

Ceconite fabric is very useful for fiberglass work.. we use it as peel ply. You should look into taking one of those EAA fiberglass classes.. it will answer so many of your questions. It’s hard to learn these techniques over the internet without having someone show you and help you.
 
Back
Top