Using gel-coat

mandalore697

Active Hunter
OK folks,

I'm making a cast of my heavily modified Kelloggs Clone using the RTV silicone mold I made.

To make a good cast I want to use a gel-coat lining. Do I need to let it fully cure before applying the layers of fibreglass?

How thick should the layer be? Should I "paint" it on or use another method?

Your advice would be most appreciated!

Thanks

Dan
 

MARROW SUN

Active Hunter
mandalore697 said:
Do I need to let it fully cure before applying the layers of fibreglass?

How thick should the layer be? Should I "paint" it on or use another method?

Dan

A good rule of thumb to follow is that if you can touch the gel coat and it feels tacky but NONE comes off on your glove then your ready to apply the second layer.
You don't have to go to thick, 2 coats that cover evenly will do fine. I personally always use a cheap paint brush to apply my gel coat. When I'm done, I squeeze out the extra gelcoat from the brissles and store it in a paint can full of acetone.

Hope this helps,

MS
 

evan4218

Active Hunter
mandalore697 said:
OK folks,

I'm making a cast of my heavily modified Kelloggs Clone using the RTV silicone mold I made.

To make a good cast I want to use a gel-coat lining. Do I need to let it fully cure before applying the layers of fibreglass?

How thick should the layer be? Should I "paint" it on or use another method?

Your advice would be most appreciated!

Thanks

Dan

I am looking to do something similar with a custom sculpt and would love it if you took progress shots of your casting method! :)
 

Q99213

New Hunter
From my experience the best results come from using an air gun. Spray a very light coat over the mould, but thick enough that you can't see the mould underneath. Let it dry about 5 min and then apply the fg. If you let it dry too long it won't stick to the fg and will peel. Also, just apply one layer of glass as the gelcoat will shrivel from the heat of the resin.

I've found it easier to forgoe the gelcoat and just thicken either epoxy or polyester resin and brush that on as a first coat. Comes out very nice.
 

Ronin677

Well-Known Hunter
Dan

I am taking a trip over to a company called Marplas next Saturday (they are based near County Hall just off the southern by-pass). They specialise in moulding and are going to advise me on exactly how to make the female mould and on making FG copies from the moulds. I will gladly share the info i get with you.

Let me know if there are still any questions you need answering and i will try to find out the answers next weekend.

btw thanks for your tips you have shared so far with me

Jon
 

mandalore697

Active Hunter
Ronin677 said:
Dan

I am taking a trip over to a company called Marplas next Saturday (they are based near County Hall just off the southern by-pass). They specialise in moulding and are going to advise me on exactly how to make the female mould and on making FG copies from the moulds. I will gladly share the info i get with you.

Let me know if there are still any questions you need answering and i will try to find out the answers next weekend.

btw thanks for your tips you have shared so far with me

Jon

Jon,

That would be great! That would be some experience to actually go and be shown/told what to do.

My only questions were whetehr its best to paint it on, what sort of thickness it should be and how much would be needed, basically everything in this thread!

I'm glad I could help you out too.

Cheers

Dan
 

TD1536

Active Hunter
Do folks generally use GelCoat for the top, exposed layer, then back it with fiberglass AND polyester resin? Or just use Gel Coat and Fiberglass?
 

psberetta

Active Hunter
TD-1536 said:
Do folks generally use GelCoat for the top, exposed layer, then back it with fiberglass AND polyester resin? Or just use Gel Coat and Fiberglass?

And to add to this question....do you put down a release agent of some kind
before you put in the gelcote ?
 

fettpride

Well-Known Hunter
If you're using a silicone mold, there really is no need for a release agent when pulling polyester. If you're concerned about the life of your molds, a release can extend the production life of the mold, but it's not needed because of the releasing properties of the silicone. If you're casting gypsum or cement that is a different story, use a release agent as that's harder on the molds than polyester. I tend to not use a release when I'm pulling polyester because it can get a bit too slippery for the gelcoat layer on sharp detail where it won't stay in place and slides off before it sets up for your lamination layer.

The order you're looking for is gelcoat first, then your fiberglass mat or cloth, and you're polyester. The polyester is used to saturate the fibrglass mat/cloth and make it stick to the gelcoat layer (lamination). Fiberglass reinforced.

FP
 
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