Carbon and resin not taken to gel coat

[Howie7]

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.

[dbayton]

I’m willing to bet that you’re using a polyester gel coat, and epoxy resin for the reinforcement. Is that the case? Polyester gel doesn’t bond well to epoxy, which would explain why your gel coat is delaminating from from the resin/CSM.

Use epoxy gel coat if you’re going to use epoxy laminating resin. If using polyester gel coat, use polyester laminating resin.

[steyrn]

If the gel coat stick to the bumper or the mould you have a problem with your agent release, not good quality, not enough or not good application.

[Jonty]

Use easy composites easylease release agent. Wipe it over the surface, allow to dry, do 5 layers 15 mins apart and it’ll come away just fine. Don’t buff like a wax… That was my first mistake!

I use their UniMould tooling system, it’s a good place to start. You may find cheaper alternatives later, but you’ve already discovered that error are a pain in the arse, so go with tried and tested.

[Howie7]

I’m willing to bet that you’re using a polyester gel coat, and epoxy resin for the reinforcement. Is that the case? Polyester gel doesn’t bond well to epoxy, which would explain why your gel coat is delaminating from from the resin/CSM.

Use epoxy gel coat if you’re going to use epoxy laminating resin. If using polyester gel coat, use polyester laminating resin.

Thanks for the reply mate I’m using polyester gel and resin. I’ve had this problem before unfortunately lol.

If the gel coat stick to the bumper or the mould you have a problem with your agent release, not good quality, not enough or not good application.

Thanks mate I’ve used a different wax this time and gonna see how that goes.

Use easy composites easylease release agent. Wipe it over the surface, allow to dry, do 5 layers 15 mins apart and it’ll come away just fine. Don’t buff like a wax… That was my first mistake!

I use their UniMould tooling system, it’s a good place to start. You may find cheaper alternatives later, but you’ve already discovered that error are a pain in the arse, so go with tried and tested.

Definitely errors are expensive, time consuming and more than anything stressful.

Thanks for all the advice and suggestions guys!

[Roger]

2 coats of any release agent, be it paste wax, polymer release (Frekote, Chemlease, etc) that I know of is not enough. Paste wax needs 6-8 good coats. polymer release agents have their own requirements but they are generally somewhere around 5 coats.

For things like what you are doing, PVA is my go to. I like to spray 6-8 very thin coats, letting each coat dry before applying the next. A coat of paste wax over the PVA will aid in release.

[Howie7]

2 coats of any release agent, be it paste wax, polymer release (Frekote, Chemlease, etc) that I know of is not enough. Paste wax needs 6-8 good coats. polymer release agents have their own requirements but they are generally somewhere around 5 coats.

For things like what you are doing, PVA is my go to. I like to spray 6-8 very thin coats, letting each coat dry before applying the next. A coat of paste wax over the PVA will aid in release.

ive been using silicone release wax. also started using briwax aswell. after this mess up ive been putting more coats of wax on stuff ive been doing. only thing is with the silicone release wax is that you cant use pva on top of it. thanks for your advice mate.

[AJHR]

Sounds like you may have let the gel coat over cure since you couldn’t continue with it till 4 days later. I also prefer PVA on parts when making moulds. A few coats of a non silicone release wax, then several coats of PVA is pretty much full proof. I’ve never had a realease issue with that technique.

[wyowindworks]

Does your polyester gel-coat contain wax? Some do and some do not. You want to use one that doesn’t contain wax for in mold coating. Some gel-coats include a wax to ensure that they cure to a nice hard finish. Was the gel-coat tacky (after 4 days) when you started the layup?

[Hanaldo]

A gelcoat that contains wax is no longer a gelcoat, it’s a flowcoat.

[Howie7]

Sounds like you may have let the gel coat over cure since you couldn’t continue with it till 4 days later. I also prefer PVA on parts when making moulds. A few coats of a non silicone release wax, then several coats of PVA is pretty much full proof. I’ve never had a realease issue with that technique.

Yeah mate I asked in the suppliers I use and they said the same thing. Now I know to lay up on top of my gel coat within the day.

Does your polyester gel-coat contain wax? Some do and some do not. You want to use one that doesn’t contain wax for in mold coating. Some gel-coats include a wax to ensure that they cure to a nice hard finish. Was the gel-coat tacky (after 4 days) when you started the layup?

It wasn’t too tacky but a slight tack. It doesn’t have wax in it though as I also got s wax solution when I got my gel coat for doing repairs so that it doesn’t stay tacky.

[eXtremist]

I’m willing to bet that you’re using a polyester gel coat, and epoxy resin for the reinforcement. Is that the case? Polyester gel doesn’t bond well to epoxy, which would explain why your gel coat is delaminating from from the resin/CSM.

Use epoxy gel coat if you’re going to use epoxy laminating resin. If using polyester gel coat, use polyester laminating resin.

Is there some sort of cheat sheet or rule book that people can use as a reference as to what will work best with what etc…

[zac]

scott bader among others make a low styrene polyester gelcoat that is compatible with epoxy resins.