Further investigation of the problem with, what I’m calling the Mk1 mould, seems to be a mechanical lock. Although I set the pouring gate and risers accurately at the latex stage it looks as though they’ve moved during the fibreglass stage so I won’t be using this method again.
So what am I going to do?
I think I’ll use silicone pouring resin instead. Much more expensive but in light of the previous failure it stands a greater chance of success.
First job is calculate how much resin I need. Simple job, just measure the size of the pattern (the main part of the calipurr) allowing about 10mm thickness over the whole area. The SG of silicon rubber is about 1.1. If it’s not enough the cure time will allow me to mix more but you need to allow for it when you estimate if you’ve got enough. No FG will be required as a top, foam board being enough but you still need a pouring gate and risers. I’m going to make these bigger (diameter) than before and out of something flexible. (Hose or nylon 11 or12). This won’t stick to the silicon so they can be removed easily once the silicone has set so there won’t ( I hope) any problems with mechanical lock.
More after the Mk2 cast.
(Edited). This works out at about 3.5 litres. That’s a lot at about £18.00 a litre.
M