Ok this just wont do. I managed to get a few hours to myself (ok so I stayed up way past my usual limit) and cast some more open moulds. This time it was the turn of some of my trench pieces.
Most of it has been successful... but and there is always a but. One mould had a small bit of RTV that hadn't been mixed and was still liquid when I prised the mast out of it.
You can see the offending area circled in red.
The rest of the moulds are producing some decent pieces.
There is only one more piece to cast but this is going to be a two piece mould. Hopefully the 3kg tub of RTV should arrive this Wednesday. Once it does I'll recast the wall section that failed.
One other issue I need to resolve is the floor section. For some reason I've made it about 4mm to long. This obviously means that all the wall sections don't line up. Pretty easy to correct but this also will need to be remoulded.
I can easily cut the the old mould into strips and reuse them in future moulds as packing material.
If anyone finds themselves in the same situation as I did and can't be bothered with the hassle of creating one from scratch or the astronomical costs on ebay. I would be happy to cast some up for you for cost of materials and postage,