Repairing damaged fibreglass

[Daston]

Hey guys,

I am picking up a rather sorry looking bonnet for beer money. Most of the damage is cracks and gelcoat that I can fix pretty easily.

However the main issue is one of the corners that wrap Round the scuttle has snapped off.

My initial thoughts is to make a fibreglass mould from my existing bonnet but I fear this will damage the paint?

Here are some pics I've been sent






Any tips would be great

[paintman]

I've done this a couple of times on motorcycle mudguards and - so far! - haven't damaged the underlying paint.

Plenty of wax polish on the paint surface.

Thin plastic sheet on the painted surface to protect it - I used several layers of clingfilm. Make as smooth as possible & use sticky tape to pull it taut. You may get a few imperfections in the finished mould this way as it would be usual to coat the pattern with release agent & then apply gelcoat but I didn't want to apply sticky stuff directly to the paint surface!

Wax polish the plastic.

Brush on thin coat of activated resin & allow to go tacky - gives a smooth surface to the inside of the mould. You could always use gelcoat.

Apply another coat & allow to go tacky.

Couple of layers of grp tissue & allow to go tacky

Couple of layers of csm.

Allow to go off.

Remove from the pattern & peel off the plastic.

Don't be tempted to pile stuff on as the curing of the resin produces quite a lot of heat. Whether that would harm the paint I don't know but I'd rather not take the risk.

ETA if it's not too big a piece would making a mould with plasticine, modelling clay or similar work as I'm assuming it would be a one-off & a lot less faff?

Edited by paintman on Thursday 14th December 11:23

[Daston]

I like the idea of clay, the break looks to be the top corner so cant be more than 100mm. I take it its as simple as laying clingfilm over the panel, adding releasing agent to it and then wacking clay on?

I am pretty handy and making moulds for models using milliput and the like and we use petroleum jelly to stop it from sticking to the original part. I assume its similar for car parts.

[paintman]

I'd use clingfilm to protect the original surface then just press the clay/plasticine etc onto it.
I'd expect the clingfilm just to peel off the clay although I don't suppose some sort of release agent would hurt.

[Daston]

Sounds simple enough Will know more when I see it and compare it to my current one.

Thanks for the advice.