Mold making Q?

General Composites Discussions Articles and Tutorials
#1

Ok this is how im laying up my mould ???
polyester mold

1.wax

2.Tooling gel coat.

3.Chopstrand mat for first skin layer (how long do i give the gel coat befor i put this on?) and do i need to sand the gel coat?.

  1. Again how long should i give it befor next layers of chop(how many layers at a time?) should i be letting it fully go hard then sand or do i let it go green and lay over or scuff up?

  2. More layers of chop?

  3. More layers of chop (how thick should i make the mold)?

Should i be putting in a core mat and or stiched cloth as well?

  1. Then bracing timber/ply

hope this is not confusing:(

And is this the way??

Thanks for any help

#2

you can leave the gelcoat to dry completely. however, for best chemical bond, you lay up the glass when the gelcoat is at B stage=

A stage = wet
B stage = dry but tacky surface. you touch it and leaves a fingerprint, but no stuff is left on your finger. Polyester dries from the inside towards the outside. IMPORTANT : if your gelcoat layer is too thin, or you lay fiberglass too early, its very likely the gelcoat will wrinkle. If your gelcoat is too thick, it may chip off…

if you let the gel coat dry completely, sand it with a large grit sandpaper (like…60-80) for better mechanical bonding.

for the first layer you should use the thinnest glass, both to have a bubble free surface, cause it wets out easily, and to prevent fiber print through.

you can build up to 3-4 mm thickness of chop each time,which is enough for most molds (for me)

as for coremat etc, its up to you…