Talk Composites - The Forum for Advanced Composites

Carbon and resin not taken to gel coat

http://www.talkcomposites.com/Topic17766.aspx

By Howie7 - 6/6/2015 9:35:33 AM

Hi everyone, first post on here.

I have a small background doing some fibreglass repairs and mould making so have a slight clue about what I'm doing. But obviously not too good as I'm having a nightmare here. 

Recently got myself some carbon and making some small stuff and decided to take on the rather ambitious task of taking a mold of the splitter from my car (Honda civic type r ep3) and making a cf replacement. 

First time round making the mould I used easy composites tooling gel coat followed by resin and a fair few layers of csm. When I tried to release it the gel coat had taken to the bumper and the csm and resin was separate from it.

Absolute nightmare so stripped it all off and started from scratch and my mould was complete without a hitch.

After that I gave the bumper 2 coats of wax and 2 coats of clear gel coat. I ran out of time and had to leave it 4 days because of work. Then I gave it a coat of resin followed by 2 full layers of cf mat and some reinforcement cf around the edges with finally some honeycomb core material in the centre for extra strength.

I gave it 24 hours to cure and when I tried to release it the same thing has happened as what happened with the first mould and the gel has taken to the mould leaving it basically stuck in the mould. I have tried to get it released but it's just releasing between the gel and the cf/resin.

I'm aware albeit slightly disheartened that I have made a booboo and wasted a fair amount of material. But I am more so concerned about where I went wrong and how to ensure this doesn't happen again. 

Thanks in advance for any advice or help, thoroughly appreciated

Howie.
By alex.mc - 6/10/2015 7:29:32 AM

I use wax only, and yes it can be tricky!

Wax only is not dissimilar to semi-permament in that you need to be fastidious in it's proper application. A bumper or splitter on a car with mixed materials is a difficult subject. The rubber may have absorbed any number of chemical deposits that the wax is incompatible with. thorough cleaning first with panel wipe(petroleum distillate) would help.
As others mention, 2 coats is not enough. A minimum of 5 on an "easy" mould, and 10 on a difficult mould would be appropriate.
My seasoned moulds however only require 1 coat between pulls now, I use wax only to get a high quality of surface finish from the mould.

PVA is your friend! Applied correctly it WILL work!
Solvent based are easiest, water based will give a better finish but be more sensitive to runs and dirt inclusion.