[MHml] horsepower & sleds

[Michael Conley]

Bill
     Durajet was developed by evinrude for the seals and the likes because they could not get a rib  up on a plane with men and equipment to much power lost from the tips of the props. they inclosed it with a tube and the problem went away. plus no side thrust from the prop
  mike

Russell_P_Davis at cox.net wrote:
  Gear shifting like modification of a jet ski for heavy tow service:

An edutor can distribute the force of a high speed water jet over a large
bulk of water so that much less power is lost in slip, turbulence and shear.
I think the idea maybe to move a lot of displacement water - not heat up a
little bit of water.
Russell

----- Original Message ----- 
From: "Diane Selkirk" 
To: "Informed discussion of multihull issues" 
Sent: Thursday, February 01, 2007 11:00 PM
Subject: Re: [MHml] horsepower & sleds


> Bill Gibbs wrote:
>> Hmmmm...
>> Hadn't thought of a jet ski.
>> Aren't jets a lot less efficient than props, especially at lower speeds?
>>
>> Bill
>>
>>
> Generally yes, the cross over is about 25 knots. Jets have smaller
> diameter impellers (less efficient than a big prop) but make up for it
> with less drag from strut/shaft/rudder.
>
> I can't see the pitch of a jet ski impeller as being suited for pushing a
> big 10,000 lb boat.
>
> Evan Gatehouse
>
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