Advice needed on roughage glassing? I'm looking into constructing a fibre cup tank, 8ftx4ftx4ft. If I kind a...

I'm looking into constructing a fibre cup tank, 8ftx4ftx4ft.
If I kind a mould out of timber, then gel coat & laminate, will this size of mould release
Or am i better bad constructing the tank out of ply next laminating the ply ,can i then gel coat afterwards, this is a one sour project.
Adding 3/4 tub to a finished attic -...
Answers:    before you start,procure a catalogue from www.caktanks.co.uk They form holding tanks for motorhomes and caravan...a fraction of the price of the marine suppliers,and a short time ago as good talent. They have a substantial range within stock,so you should be able to win something to fit.
Plastic binding epoxy resin?
what is the intended use of the tank?