Some success, some failure. TBH I never really expected this to work first try, fortunately polyurethane is reasonably cheap and I still have enough left over for at least one more attempt.
Plan was to always make a mould the ‘old fashioned way’; carve out a male plug, and take a fibreglass female mould from it. However, I found a local company who specialised in CNC machining various types of foam. Quote wasn’t too bad, just a little more than what it would have cost me to do it the ‘old fashioned way’, so thought why not.
Measured up the Trampa deck, and set about designing something I didn’t mind the look of.
Month passed before I was able to pick up the machined mould. A little longer than expected, but I don’t think they were really making any money out of this so really didn’t want to be pushy.
It’s a urethane foam, quite dense and somewhat heavier than expected when you first pick it up. I sealed it with about 5 coats of a water based polyurethane paint. While denser that polystyrene, I’d still expect it to soften if exposed to any sort of solvent.
Relieved to see the CAD geometry, and that of the actual board measured up ok.
Modelling clay to build up the flange areas.
Few coats of mould release wax were applied, followed by a single coat of PVA (blue stuff).
Finally the black stuff goes in. This is a 65a polyurethane, usually a yellowish colour, but I mixed in a black pigment. This particular type has a long’ish work time of 25 minutes. Initially I painted the mould, then added a thickener to the resin. Theory being the thickener would allow it to stick to the vertical surfaces.
Spent the next hour or so trying to smoosh the thickening polyurethane away from where it wanted to pool. . . with limited success. Left it sit in the mould for the next 48hrs just to be sure it dried.
It released really well from the mould which was nice as I’d like to use it again. However it was immediately obvious it was somewhat more flexible than I’d like and had expected.
Main problem is that the vertical surfaces are really quite thin (no real surprise), as in less than 0.5mm thin .
Still, there’s some success in that I do actually quite like the way it turned out from an appearance perspective, and there’s certainly no concerns about it stiffening up the board .
Figure I have a few options, open to suggestions here…
- Give up and use CF / fibreglass in the mould.
- Manufacture a top half of the mould somehow. Could also include a few internal walls that run between the battery segments.