[MHml] Engine power

[Bill Gibbs]

WOW!

Bill 

-----Original Message-----
From: multihulls-bounces at steamradio.com
[mailto:multihulls-bounces at steamradio.com] On Behalf Of Martin Schöön
Sent: Sunday, February 04, 2007 5:35 AM
To: Informed discussion of multihull issues
Subject: Re: [MHml] Engine power

On 2/3/07, roy mills <rsirfj at shaw.ca> wrote:
<snip>
>
>     Are you quite sure you want to go at 20 knots?  14 would be twice 
> as fast and would only need provide about 4.5 times as much thrust 
> instead of 10. Besides 90 hp is not as big a challenge to find.  You 
> were concerned that a tall standing outboard would bang up against the 
> underside of AB. If you did not use an outboard that height would not 
> be a problem. Sure Diesel is heavier, but fuel is heavy too and you 
> would burn a good deal less. Prop efficiency is the key factor in
converting hp to thrust.
>
>     Cheers anyway   Roy, who looks forward to a similar blizzard of
> technical advice to what you got with your initial query.

I agree with Roy when he questions your need for 20 knots. High speed is
costly in terms of power (and fuel cost).

I have done some (w)reckless number crunching. The results are summarised in
a pdf-dcoument that can be downloaded at:
http://hem.bredband.net/mschoon/Modelling_Afterburner.pdf

-- 
Martin Schöön              "Problems worthy of attack
                                         prove their worth by hitting back"
                                         Piet Hein
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