For those of you contemplating the $$$ purchase of an expensive relic...here's the best virtual slide-rule out there. Oh, I have a good collection of the real things; but this is for those who would like the feel of what the WWII skippers had to endure, without spending the big bucks/euros.
http://www.sliderule.demon.co.uk/
May I suggest D/L the newer version 2.1...version 2.0 is good too, btw.
I play SH3/4 in the Windows mode so I keep my virtual sliderule minimized along the bottom of my screen until needed.
...also, the virtual sliderule comes with complete instructions.
cheers,