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Re: [PSUBS-MAILIST] Thrusters behind vs thrusters at sides?
> Alec Smyth schrieb:
>
> Now the pictures are on in the PSUBS picture gallery, may I put out a
> general question for discussion?
>
> If you look at the concept drawing, I have two thrusters plugged in at
> the stern, a la Deep Flight. This has a couple of advantages:
>
> - I can carry a SCUBA tank (or two) easily on the thruster chassis.
> Because this is external, the tanks can also be easily replaced.
>
> - Carrying the tank outside means it does not add any weight to the
> hull.
>
> - Less chance of entanglement, and better protected at dockside.
>
> - I have not yet found a set of counter-rotating props for trolling
> motors, so this should minimize the torque due to both props turning
> in the same direction.
>
> - 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.
No point - you can build in the MD-80 configuration both thruster
with a 2-3 degree outside angle from the middle axis. Depents on
speed the boat will drive strait forward with one engine running.
>
Best point :
In this configuration both motors are well protected and will not
catch a rope or net (like in the MD-80 config.) From a prone position
sub you can no look to the stern..
.. so you never will find out which dammed force catch your sub and
force
you on the bottom - maybe for ever.
Also in this configuration the thruster can use some of
the frictional wake of the hull - this can be save on a submarine
up to 10-20 % of thrust power consumption (Depents on the speed and hull
configuration.)
>
>
> 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.
>
> - I would have greater maneuverability at dockside.
>
> - The boat gets several feet shorter, which would make it easier to
> trailer, and perhaps more maneuverable in flight.
The boat get shorter - thats a good point.
>
> The big unknown to me, since I do not know much about aerodynamics
> (ok, hydrodynamics), is which of the two configurations might be the
> more efficient in terms of drag. And this is probably the most
> important consideration of all. Any feedback would be very welcome!
>
> thanks,
>
In which way you have side control ?
Carsten
> - Alec