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Re: [PSUBS-MAILIST] bionic propeller
On 11/21/2010 2:45 AM, ShellyDalg@aol.com wrote:
In a message dated 11/20/2010 10:37:23 A.M. Eastern Standard Time,
JimToddPsub@aol.com writes:
eliminate the possibility of snagging on something as much as
possible, and a Kort is part of that.
I imagine there is some loss of efficiency but I have seen a few
thruster designs where the props and motors are enclosed inside a
"fairing" and water flow is "ducted" to the props. This eliminates
entanglement issues but again, probably would slow the boat a bit.
A properly designed duct will improve propulsive efficiency at low
speeds, which is the typical operating regime for small submersibles.
The reason is that, at low speeds, the lip of the duct or shroud (again,
assuming proper design) develops about as much thrust as the propeller
itself, at the cost of only a small reduction in the thrust of the
propeller (and under static conditions, even the propeller thrust is
improved).
Marc
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