[MHml] horsepower & sleds

[Russell_P_Davis at cox.net]

With an undersized over speed  propeller? Agreed.

In most applications efficiency is as defined by money and design 
constraints.  A numerically 'perfect' but unworkable solution won't help us 
much.

For this particular problem domain:
1) Detachable high speed mule boat
2) With bollard pull enough to serve as a tow boat pulling a bulky load 
against the wind
3) With no extra labor needed to run the mule as a push boat
4) Modestly economical in fuel and weight in high speed operation
5) Modestly economical in fuel and weight in high bollard pull operation
6) Modestly economical in capital
It seems that Hamilton came up with the most economic solution a long time 
ago - Just make sure the high speed water is ejected above the water level 
and into the air.
http://en.wikipedia.org/wiki/Jetboat

That fabrication is a lot less complicated than an eductor. And possibly 
off-the-shelf

----- Original Message ----- 
From: "Diane Selkirk" <ceilydh at 3web.net>
To: "Informed discussion of multihull issues" <multihulls at steamradio.com>
Sent: Thursday, February 01, 2007 11:51 PM
Subject: Re: [MHml] horsepower & sleds


> 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
>>
>>
> Yeah, (slight sarcasm) that's what you get with a propeller.  Large 
> diameter is always more efficient.  That's why a big 32m tugboat may have 
> a 2.5m diameter propeller.
>
> Evan Gatehouse
>
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