Re: Screw size and speed

[Dick Morrisson <rmorrisson@unidial.com>]

John,
This not an answer to your question, but a related one.

Fish have a pretty good propulsion system for underwater use that works at both
high and low speed and it almost never gets tangled in the garbage (they may
choke on it but their propulsion system nearly always remains clear!).  Does
anyone in the group have experience with "non-propellor" (fish style)
propulsion?  Is this a possibility for a small sub?  And for those who need
lots of horsepower, think "blue whale"!

Dick Morrisson


John Brownlee wrote:

>         In RE: Superiority of big geared-down screws, any thoughts or
> experience on fouling? Problem with being a "bottom dweller" is that there
> are -things- you can wind up amuck in, like cables and so on. I worked
> around ducted small screws to keep a clean smooth profile, but realize the
> performance penalty. Hearing more about the Perry subs has really piqued my
> interest, though.
>         Did any of the Perry boats ever have trouble with those big screws
> and entanglement when they weren't under power?
>
>                                                         John
>
> John Brownlee
> Lunar and Planetary Lab
> University of Arizona
> jonnie @ lpl . arizona . edu