Fibreglass repairs

[HRG]

I'm just doing my first fibreglass repairs How long should you leave it before:

A) Applying a second layer.
B) Drilling/sanding it.

Also, how many layers of regular matting constitutes a "strong" repair?

Any top tips always welcome... It's not cosmetic, I'm just strengthening the seat base as there were a couple of hairline cracks that I wanted to nip in the bud. (Yes, I've drilled tiny holes at the end of the cracks before I applied the first layer!)

[SC500]

You can lay up three to four layers at once without concern of too much thermo build up.
6 layers is strong enough for what you want.

You can trim it while its still green. Drilling and sanding depends on how much cat you used plus the temperature you did it in.
Just wait till it feels dry to touch, 1 to 2 hours maybe.

[SC500]

Thinking about it 6 layers will be ott
just put down 4

[Gandalf]

Rob in answer to your GRP repair

A) Applying a second layer.

- You can apply next layers as soon as the first is cured enough to touch, you can put a couple of layers on at once to speed things up, see below

B) Drilling/sanding it.

- leave it for a good 24hrs minimum, if possible. And the longer the better as it generally takes about 7 days to cure fully, but will be strong enough to reinstall seat after a day or so without trouble.

Also, how many layers of regular matting constitutes a "strong" repair?

[i]As this is the seat mounting area and you have the usual 450 grm/m2 chopped strand glass I would suggest putting at least 6 layers down
(ps. you can safely put 2 or 3 layers down together, should not cause a problem)[/i]

Tip: Rip the glass rather than cut it - as this disguises the edge of the repair

And make each consecutive layer 20mm or so smaller all round to create a stepped edge to your repair it`ll make for a neater finish and dissipate stresses more gradually.

[HRG]

Thanks folks... That should do it