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

[Alec Smyth <Asmyth@changepoint.com>]

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!

- Alec

-----Original Message-----
From: Lew Clayman [mailto:lew_clayman@yahoo.com]
Sent: Monday, July 30, 2001 5:16 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Thrusters behind vs thrusters at sides?


--- Alec Smyth <Asmyth@changepoint.com> wrote:
> - Carrying the tank outside means it does not add any weight to the hull.

Sure it does... ok, technically perhaps not to the hull, but certainly to
the sub as a whole.

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. 


> - If one motor dies, I think its more likely the survivor can be used for
> getting home (as opposed to going in circles) if its close to the
> centerline.

Either way, you'll have to steer to compensate. 

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.

 
> But on the other hand, if I mounted the thrusters in fixed positions one
on
> each side, near the stern but on the side of the hull (like an MD-80
> airliner):
> 
> - There's no fairing to build or break.

You could have fairings there, too.  On the other hand, on the center, why
is fairing necessary?

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. 




-Lew


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

__________________________________________________
Do You Yahoo!?
Make international calls for as low as $.04/minute with Yahoo! Messenger
http://phonecard.yahoo.com/