Counter-roatating vs pump-jets - Just wondering...

[terry weber]

I was just wondering, what are the benifets/draw-backs of these two different types of props? I know pump-jets are quieter, but are they more stable over a range of speed? What about Counter-roatating props? What was the reasone for having them on the Albecore phase III? Was it for more speed, or to help keep the boat stable underwater? Thanks,
Terry Weber

[stevel14]

The contra-rotating props were primarily

The contra-rotating props were primarily an attempt to increase propulsive efficiency (ie-more speed for the same power or the same speed for less power) while the pump-jet is to make the boat quieter by reducing the effects of cavitation. I have not heard if there is any increase of efficiency with the pump-jet or not.

Steve
#2442