T-Pain Is On A Boat: RE: [Electric Boats] Emerging technology

Friday, November 6, 2009

RE: [Electric Boats] Emerging technology - hopefully lower cost

Here is a video showing the Kort Nozzles on a tug boat. Notice the shape of the propeller inside the nozzle. The maximum blade width is right at the interface of the nozzle and the propeller. Using a standard propeller that has not been modified in a Kort Nozzle shape is worse than no Kort Nozzle at all. The increases thrust at low speeds comes from being able to eliminate the 20-25% of the prop blade tip that is inefficient and using the nozzle to contain any off-tip water flow. For the same diameter propeller, the Kort Nozzle prop can have significant more surface area interacting with the water resulting in greater amounts of water being moved which equates to more power.
http://www.youtube.com/watch?v=QdSH6SBl5hY

--- On Thu, 11/5/09, Myles Twete <matwete@comcast.net> wrote:

From: Myles Twete <matwete@comcast.net>
Subject: RE: [Electric Boats] Emerging technology - hopefully lower cost
To: electricboats@yahoogroups.com
Date: Thursday, November 5, 2009, 11:56 PM

While not technically a Kort Nozzle, there are many types of prop guards that one can purchase, install and use.

One is here: http://www.propguar dmarine.com/

And it's one of those ( a 14" diameter one) that I have used for some 5 years now after using a smaller, 12" diameter one.

While I am not using a standard stock propeller, I do use a 12x12x3" brass prop that was some standard prop for some outboard some time back (50's?).

And what I have is very efficient in my estimation despite the fact that I should be using a 14x14x11" or so prop.

So yes, I could come up with a better prop configuration that works best with the nozzle, but the ordinary propeller I do have works well enough.

As for Florida, I cannot comment except that whatever folks can do to protect those gentle creatures called Manatees, they should do.

They're dang cute and graceful. Florida should do the right thing and mandate these nozzles, especially for boats that have top speeds under 15mph.

I am very happy with my prop guard and it looks cool also.

-Myles Twete, Portland, Or.

From: electricboats@ yahoogroups. com [mailto:electricboa ts@yahoogroups. com] On Behalf Of James Graham
Sent: Thursday, November 05, 2009 8:14 PM
To: electricboats@ yahoogroups. com
Subject: Re: [Electric Boats] Emerging technology - hopefully lower cost

- - Kort Nozzles are comprised of special shaped propeller working inside a circular "collar".

You cannot use an ordinary propeller in a Kort system.
- - There was a movement in Florida to required outboard motors to have a Kort Nozzle system to minimize the impact damage to Manatees caused by "slicing" propeller blades. But it never got off the drawing boards as it was too expensive and not needed in other areas of the country. So the outboard motor companies said - No. and stayed with the ordinary propeller system.