The only moveable Kort nozzles that I know about were used on the American DSRVs. I believe the nozzles turned around the prop, deflecting thrust. Potent lateral and vertical maneuvering thrusters were used in concert to assist. I don't actually know any of the Navy drivers, but the vehicles operated for many years without (visible) change.
I have to back up and explain the live rudder issue. Without it, you depend absolutely on propulsion for steering. A rudder continues to deflect water as long as the vehicle is in motion, which is a very valuable contribution to the overall maneuverability of the vehicle. If you don't have control surfaces the sub will "skid." In other words, it will continue in the direction it was going when you stoppedd the prop, even though you wanted to keep turning. If you are partway through a turn, for instance, but closing on an obstruction or target, you can't keep swinging into it without a rudder. You basically are forced to "drive" the boat everywhere. And the sub will wander a bit on course, which has to be constantly corrected, an exercise that will wear you out over time.
We have discussed this on the forum a time or two. A Perry main propulsion system (motor, reduction gear, seals and all the external gear weighs nearly 900 pounds. It is an enormous penalty for what we normally think of as a psub. For our purposes in the Perrys, and I mean using a sub hard in all kinds of conditions, the more capability the boat had the better off we were.
Building a small sub is all about trade-offs. Your diesel system will be heavy, and include a reduction gear. If you turn a big wheel, then I would recommend strongly that you look into all avenues for utilizing that power. Kort nozzle technology has come a long way. Perhaps you can do all you need to do with just that. I just don't know, but my tendencies are conservative and, as I said, the more options the better.
Vance
-----Original Message-----
From: Jens Laland <laland@artematrix.org>
To: personal_submersibles@psubs.org
Sent: Fri, Mar 26, 2010 8:32 pm
Subject: Re: [PSUBS-MAILIST] Rudder Indicator using 3 Reed Relays
Vance
Thanks for your feedback, and I really appreciated your points of view.
** I don't think the spaced readouts would do much for you
** if they are either on or off.
This circuit will always have one of the 5 LEDs lit, as the magnet will
always be over one or two reed relays at any moment in time (hence the
short spacing between the reeds).
However, it could very well be that I misunderstand your point here. If
so, please clarify.
** Live steering (movable thrusters without control surfaces)
** are even more critical than a rudder.
Now this is very interesting, as I am considering (dreaming of) having one
large steerable Kort-nozzle (using a constant-velocity joint) in my small
diesel-electric psub design. I believe this would provide a much improved
maneuverability (up/down & sideways), even at very slow speed.
Therefore, my own idea of a visual control and feedback instrument for the
steerable Kort-nozzle will be based on a rebuilt (vintage) aviation
instrument(Zero Reader), ref
http://traktoria.org/sub/zero_reader_indicator1.jpg
For the control system itself, I will most likely use some homemade
inductive sensors (easier to pressure proof than potentiometers). And I
will use a simple 4-20mA current loop (one twisted pair) to feed the
analog signal to the said instrument in real time.
I am curious to know if such a scheme would be in accordance with what you
consider to be practical in real operation of a craft.
Best regards,
Jens Laland
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