Newbie question, any info would be good!

[system]

I intended to make, what I would call a Carbon Fibre skin for a door mirror, purley for cosmetic reasons.

I used your basic hand lay up for the mould and the plug. I was shocked to find the plug, which was three layers of light, chopped strand, fibre glass would not slide over the original mirror, as it was exactly the same size as the original mirror (Doh!!).

Is there a technique for making the mould a bit bigger so that the plug and/or the finished item fits over the part it was made for, or am I stuck?

I accidently dropped both the mirrors, they fell about 4ft, the clear gel coat cracked, I wouldnt have expected this,why did it happen??

Does Carbon Fibre shrink in the same way Kevlar does through the mould/plug process?

[system]

Abe,

If you’re trying to produce a part that is going to fit over the same part, then you’ll need to account for the size difference. Here are some options that you have:

1. Get a high build primer and spray it over your original mirrors. Build up the thickness that would emulate the thickness of your final product and make a mold off of that.

2. You can also buy a material called “sheet wax”. They come in different thickness and you can place this over your mirrors. Then you can make your mold off of that.

There are several reasons why your gel coat could have cracked. I can’t say for sure unless I can see it. Carbon and kevlar do not shrink. What shrinks is the resin matrix that you use. Epoxy shrinks the least (approx 1% give or take) compares to polyester which shrinks at about 5% give or take.

[system]

Is there an simple enough method (not sanding!) of making both the outside and the inside of a piece smooth, so that the Carbon Fibre final mates well with the mirror surface?

[system]

You probably don’t want the inner surface to be smooth. A rough finish would bond better than a smooth one. If you’re reffering to a consitent finish then that can be achieved by using fine weave cloth or vacuum bagging.