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



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.

 

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 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,

- Alec