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Another massively net negative day for this project.
At least I think I have worked out why the gel coat blistered. After I had rubbed down with the 2000 grit pads I thought I would give the patterns an extra polish and I used car polish (turtle wax) before I put the release agent on – some residue of it obviously migrated through the release agent and caused the blistering. Odd though that it did not show up on the first coat.
Closer examination of the blistering showed that it started at the junction between the first coat and the pattern not between the coats. That meant there was no point in continuing with them so most of this morning was spent removing the gel coat from all the patterns, like peeling a lot of hard-boiled eggs only more difficult and a lot harder on my right thumb nail.
My inability to remove the gel coat (admittedly in unsupported form) in substantial pieces also told me:
a) that most of my patterns will need to be modified (bugger!) to eliminate all sharp corners/right angles. The gel coat simply would not release either side of a right angle, presumable because it shrinks a bit during curing. This means at least an extra 30 hours filing radiuses, then priming and top-coating and multiple rub downs in between; and
b) that if I want to ensure that the moulds release from the pattern they will all have to be split moulds meaning that I will have to decide where to split the mould, cut polypropylene sheet to the contour of the cross section where the split is to be made and then make the half mould twice. This is also I estimate a further 30 hours work (double bugger!!)
c) my battery carrier mould may not be manufacturable at all using this method.
I started this project to learn how to do stuff, sometimes I just wish the lessons were not so hard learned.
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