Hi, just wondered what some of the guys use to make moulds in the UK? I was looking at using East coast fibreglasses tooling gel coat and Optimould to back it but it says the gelcoat takes 2 - 3 weeks to cure fully at 20 degrees. The optimould only has a shelf life of 6 weeks and I wanted something last a little longer as I not sure how much I would use. Thanks!
What does everybody else use?
I’m not in the UK, but i use polyester tooling gel coat, catylized with 2% mekp. I let that get well into the gel stage, then i lay up with fiberglass and vinyl ester resin, also cat’d with 2% mekp. It is probably very cold there in the uk so you may want to catylize with 3% mekp for a faster cure time.
What type of production run will you be using the tooling for?
Polyester systems will give you a low production run. I suggest browsing though the forums. There is plenty on information 
Fastrr, why are you using a polyester gel coat with vinyl ester resin? You should be using a vinyl ester tooling gel coat if your using vinyl ester resin system.
What is Mekp? I will be making aroun 50 parts from my moulds.
MEKP is a reactant that reacts with a reagent in polyester or vinylester to create heat and cure the resin. When you buy either of those you should ask if you get MEKP with the order.
there are also many different catalyst, MEKP is just general. You should really read the spec sheet to use the recommended catalyst. we use 7 different catalyst here.
when you use mekp is the % by weight or volume?
Usually by weight, although the error you make by doing it in volume is not so big.
Read the datasheets on your resin, it should also say a recommended percentage, by weight.
For smaller moulds I am working on a very rapid system, from start to finish in under 5 hours, including waiting times. Will publish about it soon.