I’ve taken a mould from this, and made the flat sheet for the top plate (2 layers of 300gsm, one layer of 200gsm gives 1.05mm thickness).
I then made the adhesive to bond the two – infusion resin mixed with glass microbeads to make a paste. All good.
I filled the bottom panel with adhesive, clagged the two together and clamped them. After that, I popped it in the oven at 60C for about 30 mins to kick the exotherm off (with fast resin) and I left it alone for a while. I even remembered to cover the facing side with bagging film to stop it getting mucked up when the adhesive ran out as the parts were compressed.
It’s not easy to see from this, but what I think has happened is that the heat from the oven has started to set the adhesive from the outside in, sealing it. Then this has kicked off the exotherm inside which has caused the adhesive to expand, but because the outside edges are setting and gripping, and the adhesive wants to expand and can’t. So, it warps.
I now need a different and better method, which I’m cooking up right now. Either a much slower cure, or cross drill it (where the hatch needs to be drilled anyway, and leave a few extra drill holes in the base only in the middle. Then bolt it through with a couple of plates on the outside help reinforce the shape and a tube inset at each bolt through hole to stop over clamping. I will then inject the adhesive in through the spare holes and let it go off. The open holes will give the expanding adhesive somewhere to go.
I have bunch of stuff to do, and am feeling a little overwhelmed about which job to tackle next (at 19:30 on a Sunday night). I’m now getting over the disappointment, time and materials lost, and have a plan. The plan is:
- buy beer
- make savoury bacon cupcakes with my daughter
- watch The Blues Brothers with the kids.