[MHml] Engine power

[K38BOB at aol.com]

Pretty cool thread: here's some thoughts
 
1- Cross check/calbrate hp vs speed on sailing cats with motors with these  
guys and woods comments and goldcoast motorsailers etc
_http://www.catsailor.com/wildthang/wild_thang.html_ 
(http://www.catsailor.com/wildthang/wild_thang.html) 
 
2- Smalloutboards dot com (no connection) has some interesting choices like  
100+hp for 6grand as source
Design some mounts for the transoms and hang what size you decide (or the  
sled/s but I like the transom mounts)
 
3- For extra fun ( I mean efficiency) lift the bows above the chop for  
reduced drag and improved speed in chop
_http://wingo.com/dakh/beachcats.html_ (http://wingo.com/dakh/beachcats.html) 
 (  how is Tom Speers work progressing?) 
cheers
bob (contemplating a repower of my yanmar 2gm20 with a 3ym30 or beta  902)
_http://www.sfbama.org/members/Devoras/index.html_ 
(http://www.sfbama.org/members/Devoras/index.html) 
 
 
 
In a message dated 2/4/2007 5:38:04 A.M. Pacific Standard Time,  
martin.schoon at gmail.com writes:

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





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