Talk Composites - The Forum for Advanced Composites

Gelcoat surface problem

http://www.talkcomposites.com/Topic22445.aspx

By Zymka - 12/16/2016 10:45:05 AM

Good day everyone!

  I have been doing some carbon fiber stuff with vacuum infusion, and have had great results for most smaller parts. But once I make a bigger flat panel (bonnet top) I get this problem:
The gelcoat has small holes mainly between the fibers
This is how I made the parts:
PVA + wax on surface
sprayed gelcoat about 0,6mm GC50 + 15% styrene and 2% mekp , let it cure fully overnight
twill carbon 200gsm + 2 layers of 313gsm biaxial carbon fiber
peeply, perforated film,  mesh
infused with in2 mainly with fast hardener(as I ran out of slow one) and feeded with extra resin after clamping vac hose
postcured 10h at 50C and 5h at 60C

http://www.talkcomposites.com/Uploads/Images/c3e9b3fb-afe4-4f63-bd34-a48e.jpghttp://www.talkcomposites.com/Uploads/Images/675ed7ec-605d-4ae8-a4bb-8f55.jpg


Could this be because of the part shrinkage when postcuring?

Thanks!
By Zymka - 12/19/2016 3:49:03 PM

Yes, I like it when its flatter , because the top layer looks much better when fillaments are laying straight, I don't know how to say , you know when you brush gelcoat with a brush, you get uneven surface of carbon beneath the gelcoat, so when i spray it without thinning I get some hills and holes, which will be visible as well, especially when using 12k carbon weave.
So thats great news , I will sand it down to make it flatter 

Thank you Waren and Hanaldo for your help!