Releasing fibreglass from the mould, any tips?

[dtype38]

I used to use wax only and once got a moulding stuck in a mould and things got damaged trying to get it out. Since then I've used release agent and never had that problem. You're right, the finish isn't as good as just using wax, but in my case, I always sand/primer/paint anyway.

[trikesrule]

O h dear I've read some horrible things and theres been a couple of descent tips here. I've been a fibreglass laminator for thirty years and still doing it here in Tasmania. So Al have you done the job yet? If not hold up for a minute the repairs need time to cure and to have the Styrene come out. Styrene will eat any mould release wax or PVA. Firstly how did you repair the mould after the last release damaged it? Sorry I need to check the quality of your repair(s). What was the smoothest grade of paper you used to finish it with.........trikes

[Al Weyman]

Hi trikes, not completed yet , I have made the repairs with standard body filler and have yet to finish them of, should I prime or paint the inside of the mould before starting.

[trikesrule]

Repairs done with bodyfiller thats ok. Does your mould originally (before damage was done) have gelcoat on it?

[Al Weyman]

I'm not sure a mate gave it to me.

[trikesrule]

Whats on it now Al?

[JohnD]

Al,
Don't know what Trikes will think of this, but mould repairs, for damage to the finish, not structural, can be done instantly with Plasticine. Yes, the kid's modelling clay. It will take polish, if done gently and release easily. You may end up with bits of Plasticine on the product, but that will wipe off.

The other 'quickie' repair is brown parcel wrapping tape. It will cover defects in the mould gel coat, and GRP does not stick to it. You will have a microfine line on the product at the edge of the tape, but that will smooth with some fine body-filler or sand out. Yes, this is deferring work from the mould to the product, but it is usually easier to work on a solid, convex surface, rather than inside a mould.

Trikes,
I'm sure that both these will be bodges in your eyes, that a pro would not consider. But the pro is looking for a mould that will make many products, time and again, once it is made perfect. Your average racer who gets into DiY GRP work, is looking for one piece, maybe another later, so that a quick way of getting the product is acceptable. Some don't even bother with a mould, but make a positive buck, layup on that and then smooth with body filler. Yuck!

John

[Al Weyman]

Yes you are right the mould I have had actually been fitted to a car! I think it looks like black paint trikes.

[jaysalv]

can anyone help?
i have recently resprayed a mk4 davrian which is totally made from fibreglass i had trouble with the bonnet from the start but finally got it looking ok when i painted it or should i say as i was painting it a small split started to appear in the bonnet which gradually grew to about 10 inches long . the car was not baked as i expected something like this to happen . when you look closely at it its not the fibreglass thats cracked it seems that it has seperated from the gel coat . any ideas as to what to do with it / its for a costomer who needs the car by the end of july to race in the nurburgring 700 so time is not on my side . what is to blame .

[StephenRae]

Glass fibre boats suffer from osmosis which results in moisture getting under the gel coat, unfortunately the fix is to grind/sand off to reveal the matting, dry off and do a body repair.....Going back to water soluble release agent it will only work on a totally sealed surface...a couple of coats of paint cannot guarantee that it will not leach out.

[Al Weyman]

So what do we seal it with steve, the Bees wax?

[StephenRae]

Originally Posted by Al Weyman

So what do we seal it with steve, the Bees wax?

That's about it Al, have faith... the last mould I took was from a £166000 Aston Martin Vanquish...I did have a couple of restless nights but all was well.

[trikesrule]

Al use PVA BUT not all PVA's are good reliable products. Some of them a utter rubbish. So head to your F/G store and if the guy there hasn't used and had a successful 'pull' with that PVA go else where. Applying the stuff you can brush it on but for a small thing like a spoiler I spray it on in thin coats till I get a uniform sag running off the product. This leaves a uniform layer of PVA. BUT if you get what looks like the PVA separating you have to wipe the lot off and reclean the surface. Use only Acetone not Thinner. PVA separation is an annoying thing to happen but you can test a surface cleanliness by just brushing a little PVA on. Tip Always wear latex gloves never touch a surface thats to have glassfibre laid up on it with bare skin.

[trikesrule]

Jay you have a bit of a problem there for sure but it's fixable. T'was caused by somebody probably touch testing gelcoat without GLOVES. Either way theres a contaminant in there between the layers so as Steve suggested grind it out stopping often to cleanse with Acetone. The surface should be wiped once and the rag discarded after each wipe. If it hasn't been wiped at least five times it's not chemically clean. Take your time doing the repair so as the Styrene starts coming out straight away. Before applying any paint stick it in the sun and let the UV go to work. But don't let it get hot warm is good. Rewash with Acetone after a day or so then leave it for a week then go ahead and paint. Do not use thinners on a fibreglass surface it reactivates the resin! ........trikes

[trikesrule]

JohnD The brown packaging tape comes in pretty handy at times hey lol. Al Is that paint at least a year old on the spoiler? Needs to be nice and hard. Be careful not to soak the rag with too much acetone. Don't want the acetone starting to break the paint down and don't forget the gloves...trikes

[Al Weyman]

Its years old but will have to be redone for the repairs if painting is suggested. I will use the gloves, actually I alway do as its horrible stuff to clean off!

[jaysalv]

thanks for you advice guys last night i got a belt sander(sounds a bit extreme i know) and ground out the crack right back to the matting . i then fibre glassed the repair low then put a fine scim of filler over the top of it . i then primed the area and let it air dry . so far it has stayed ok but im painting it tonight so wont know till tomorow really if i have solved the problem. but its all experience i spose.. look at the website later this week to see the results

[peenuts]

AL i use to build racing yachts and boats in cornwall we always washed the mould out if new .
then styrene wipe. but as this only a small mould i would surgest
1 three polishies of mirror glaze wax put on then leave to dry and polish off
leave at least 1 hour between each coat.
2 use the blue p.v.a we used a 50/ 50 with water put on with a piece of sponge leave to dry.
3 if you require alight weight rear spoiler then i would use 1 gel coat and 2 layers of 1oz matting only reforce the areas that are used for bolting down
4 the p.v.a is a release agent as does not need any wax over the top as this in some cases takes the p.v.a off
5 once the mould has been used you only need to wash out with water dry off and 1 coat of wax and reapply the p.v.a
would surgest buy a air connection drill small in mould then glass metal plate with air connection on to back of mould remmber to put a piece of tape over hole inside mould before you gel up. when you need to release apply air start of low and in crease pressure then the moulding should just pop out.......

[Al Weyman]

Thanks Peenuts.

[peenuts]

Al if you have that much trouble let me know . have done work for the cherry brothers Alan and Andrew plus other bits and pieces in my spare time for the one with davrian as commented in this thread.......
phil

[Al Weyman]

Thanks, I have done 6 coats of Bees wax and am about to apply the release agent and will try laying it up Saturday, fingers crossed.

[Al Weyman]

It popped beautiful with no damage whatsoever to an already delicately repaired mould and looks great and very light! You guys are the nuts thanks for the advise it has really given me confidence to do more and I have a fair bit to do on my IROC project!

Just one other question, the difference betweel Gel coat and Flow Coat, is Flow coat for making the mould from the original or what?

[trikesrule]

Hi Al nice to hear of a successful 'pull' and I reckon the other guys would all be pleased as punch with your success. Flowcoat is used mainly as a covering for areas that don't need a smooth finish like speed boat floors for one. Flowcoat contains 'Wax in Styrene' so that it dosen't have that sticky feel to it after it's gone hard Gelcoat dosen't have W/S. If it did the f/g wouldn't stick to it. Also f/g is low in strength. Gelcoat is sprayed or brushed into a super smooth / shiny moulding then f/g is laid over that then the product is popped from the moulding and you have a finished product that dosen't need paint. I have a suggestion for future spoilers use Dyneema and Epoxy Resin (same release agents are ok). You can end up with a product that weighs in a 1/4 or less than your glass product and Dyneema has a high abrasion resistance and will resist the magnetic pull of those gravel traps you mentioned...........trikes

[Al Weyman]

Thanks for the informative answer again Trikes, good stuff.

[zefarelly]

Wahey . . .Als pulled . . . . . good work Fella

let us know . . . .with pics . . .when its all done and polished !