RE: [PSUBS-MAILIST] Thrusters behind vs thrusters at sides?

[Lew Clayman <lew_clayman@yahoo.com>]

--- Alec Smyth <Asmyth@changepoint.com> wrote:
> Please see below... note that in spite of playing "devils advocate" I am
> coming down on the side of putting the thrusters aft. I just thought it was
> a good topic for discussion, and thanks for the feedback!

LC: I wasn't really advocating either solution, I see general advantages each way and don't know
enough of the specifics to weigh them on this design.  But it is a stimulating discussion, thanks
for tossing it out.
 
> AS: A tank always adds weight, but if outside the hull it also adds
> displacement, so the net result is zero. If carried inside, it means I have
> less lbs to use for other useful purposes such as the hull or batteries. 

LC: Not sure that I buy that the displacement (based on volume) precisely offsets the weight of
tank, but your point is well taken nonetheless.  They offset somewhat, in any case - not at all if
internal.
 
> AS: Problem is, my rudders will be mostly up in the air unless I'm
> submerged! But yes, I could submerge at least a little to steer. I also
> liked Carsten's suggestion of angling the thrusters slightly.

Slick solution, angling to compensate.

Given that most trolling motors have a reverse mode, and that the cheap kinds run backwards if you
reverse the polarity of the DC power supply (battery) I wonder if counter-rotating props are in
fact all that hard to accomplish?  Although, the props themselves (rather than the motors) are not
optimized for counter-rotation... hmmm, a niche market here?  A clever tinkerer could no doubt run
two counter-rotating props from a single motor, saving weight at the cost of complexity and the
reliability of a fallback (one-prop) option...
 
> AS: You're right, its not absolutely necessary. However, there's
> considerably more mounting hardware involved aft than carrying the thrusters
> on the side, so without a fairing it would be fairly messy, which translates
> as slow and entanglement-prone. On the side, all they would really need is
> prop guards. 

LC: Just as you say.

-L

=====
"Yo no soy marinero / Soy capitan"
          - Traditional Mexican Lyric (La Bamba)
=====

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