The beam mould released without any drama
and then it was the usual wax-on and wax-off a few times to prep the surface, and then some PVA release agent.
I also got a piece of 5mm clear perspex with which to close off the mould - the idea being that I'd be able to keep an eye on what's happening inside.
The cool thing of having this mould is I can use it to create a foam core, and then I can wrap the core in fibre and stick it back into the same mould to get a perfect surface finish.
To create the core I went shopping and after handling a few samples decided on a polyurethane foam that expands up to 8 times by volume - this had the right amount of rigidity without being too heavy.
This is a two part foam that you mix 1:1, and then you have around 2 minutes to get it into the mould before it starts expanding.
I drilled a 16mm hole in the middle of perspex to serve as a pouring opening, and then clamped the sheet to the mould. Then I mixed up a batch of the PU foam and started the pour..
Only, the foam was expanding faster than I could pour it and eventually filled the mould only partially.
The solution: put the seperate parts in the fridge prior to mixing and you can extend the pouring time to about 4 minutes, which turned out to be enough time to get the mix into the mould and evenly distributed before it started expanding.
The end result is a very nicely formed core that just needs the edges trimmed a bit. Total weight is 103g.
Next I'll be wrapping the core in two layers of 200gsm glass. At around 0.14sqm per layer I expect the laminate to add a further 50g-80g.