mould release wax

[ghostlymoron]

30boat, thanks for your advice, that makes sense. What do you mean by thickened topcoat? And where would i get talcum - from grannies bathroom?

 

[ytd]

you can also use micro balloons to turn resin into filler.

I have a book on automotive fiberglas which says to use car wax with a high percentage of carnauba wax and confirms that the mould must be completely smooth and very high gloss.

 

[30boat]

30boat, thanks for your advice, that makes sense. What do you mean by thickened topcoat? And where would i get talcum - from grannies bathroom?

You can use unthickened topcoat (don't use gelcoat as it won't fully harden if exposed to air) but I find that a little bit of talcum powder makes it less runny.You can usually buy it by weight at fiberglass and resin stores but for a small amount scented baby powder will do perfectly.
Polyester resin is good enough for this repair providing you abrade well and clean off all contamination.Actually that also applies to epoxy but polyester is much cheaper.

 

[nigelmercier]

Personally I would use PVA Release Agent: http://amzn.to/1lLx772 If you only need a small quantity I could send you some.

Having now seen the picture, I agree with the others recommending an in-situ repair. I had a totally different idea of the problem. This would be better fixed with epoxy and glass cloth from the inside out, then paint on resin topcoat with a foam roller. Cut away any damaged areas first.

 

[ghostlymoron]

Decided against moulding and did a conventional repair. Mat on either side and build up flowcoat outside. It's taken forever, not full time, specially building up flowcoat which i didn't thicken. Overall I'm quite satisfied and will put up some photos of finished article soon. I didn't bother with color matching but quite like the mottled effect.

 

[coopec]

It's probably a lot stronger than making up a mold and then gluing the piece into a place

 

[ghostlymoron]

My original plan was to make a female mould and lay up behind it directly on the hatch which would have been quite strong but require other materials.

 

[Javelin]

This is the kind of thing I do on a weekly basis.
Grind old gel out till you get back to nice gel.
Shamfer the gel and glass as shallow an angle as you can.
Tape up the surface gel edges so you dont get resin/glass on it. (can clean/sand after but easier before)
Apply a backing with the internal shape and use parcel tape on its surface. (I obviously use resin resistant tape)
Build up the repair with grp with either a bit of mat or at a pinch fibreglass repair paste but it really needs something inside the paste to give it strength.
Remove tape and or clean the old gel coat edges with 150 grit or similar.
Then I'd use topcoat gelcoat, which is gelcoat with wax in it.
Alternatively use Gelcoat filler such as Plastic Padding Gelcoat Filler. It goes off in 10/15 minutes.
To get a colour match is a little harder and a bit of trial and error but a tiny touch of yellow and or gray pigment/paint mixed in with the paste before you add the hardener.
Then sand with 240 grit and apply another thin coat of filler as smoothly as you can.
Then its a question of wet n dry using 500 > 1500 grit
Finally cutting compound and polish.

 

[coopec]

Javelin

Pity you didn't post a whole lot earlier: nice to get advice from a professional!!!

 

[Javelin]

sorry I came across this thread a bit late obviously.