Get yourself a copy of 'Model Submarine Technology' by Norbert Bruggen.
It's available from Amazon and also the publishers Traplet.
It's a good book, although it has some errors, notably in the electronics section. Also some of the formulae aren't clearly explained, and can be quite baffling, even for someone from an engineering backgound.
That said, this book stands alone as a source of information for the model submariner.
Back issues of the Sub Committee report are another goldmine of ideas.