Hi, have been away from this site for so long - sorry. The Gato build is soon to be resurrected but I've become interested in building a scaled -up version of HMS Unseen - a wooden model, the plans for which have been published in IMM magazine recently. The sub model (based loosely on a RN "O" class such as the preserved HMS Ocelot - (google it!)) is now long and wide enough for me to convert it, eventually, from a dynamic diver to one which has ballast tanks. I favour the Sherwood design of a water pump pumping water into a sealed and thus pressurised tank; my question is, after a long preamble, is what water pump to use? Some, I know, deride the use of car windscreen washer motors and I also realise from another UK-based member that there is also http://www.micropumps.co.uk/
-(but perhaps too weak?).
Also, I'd welcome messages from other IMM "Unseen" sub-builders.