Fasta (23/02/2014)
Even simpler is to use a solid silicone intensifier or core.
So you would need to cast the silicone less the skin thickness in your mould using CSM or sheet wax.
Silicone expands a lot with heat and makes good pressure so no need for bags, bladders, pumps or compressors but you will need an oven for pre preg.
You may need to form some kind of extension to the silicone so you can grip it to remove. If you wanted you could also cast it with a metal tube down the centre simply to reduce the silicone since it is expensive. Maybe the tube could be withdrawn and then the silicone would also release/remove even easier?
I have made small yacht parts like this and it works great.You don't happen to have pics and/or a silicon product link do you?
I like the idea of undersizing the silicon. And using wax sheets seems like a good way to get the thickness I want/need. I COULD cut a foam mold for the silicon, but if I don't have to cut two molds, then all the better! Not having to keep positive pressure throughout the baking seems like a plus. But I agree with the idea that I might want to stengthen the mold halves as much as possible. Good thought on the metal tube as well.
Someone above wrote on CNC and my budget. I have Free CNC. That is, I do all the CAM and run the CNC router at my work, after 5pm it might as well be mine, unlimited use.
To everyone else, I'm actually still not understanding how this could be done with a vacuum...?