kort nozzle

[Brian.Lin]

I plan to design a tug.

I have no exeperience for kort nozzle.

Does anyone know about it?

could anyone supply me the study information?

I need some document to decide the diameter of duct and propller, the clearance between duct and hull or any others have to notice.

[gonzo]

"The propeller book" by Gerr will give you the basics. A nozzle has more low end thrust, but more drag.

[dskira]

I used to put nozzle on every displacement comercial boat, (small tug and offshore fishing boat) and I find the drag was not a problem against the thrust we gain at high and low range.

[marshmat]

There's a fair bit of literature regarding Kort nozzles and related devices.

In very general terms, they tend to improve thrust at low speeds, but create considerable drag at higher speeds. Heavy, pure displacement hulls that need high bollard pull tend to benefit the most.

[dskira]

I never used it on high speed boat, but on displacement it was quite a change with and without.
I used the Ulstein brand.
But fo high ot medium speed I tried one on a outboard and it was fantastic. The drag do not seams to be a problem at all.
The Navy is putting on the small intervention rib boat 200Hp outboard with nozzles and they find the speed was better with them.

[DMacPherson]

We prepared an article some time back that might offer some insight:

http://www.hydrocompinc.com/knowledge/techexchange/tex0801.pdf


Regards,

Don MacPherson
HydroComp, Inc.