GL: Fuel burn

[LRZeitlin at aol.com]

In a message dated 6/29/08 12:00:40 AM, Bob writes:


> I have been following the design and production of the Maine Cat P-47 for 
> the last few years. The performance of this boat (from their real life test 
> boat) has been?extraordinary?in speed vs fuel burn. See chart below.
> 
> 10.13 NMPG at 8.1 knots. !!!!
> 
> 

I admit that I know nothing about the Maine Cat P-47. I've never even seen a 
picture of one. But it is possible to get what seems like extraordinary fuel 
mileage with some nontraditional designs. At 8.1 KT, the Maine Cat is probably 
traveling at about a S/L ratio of 1 or slightly less. This is a very 
economical speed where form resistance and skin friction are almost in balance. Cats 
are also lighter than monohulls, not requiring ballast to keep the top side up. 
This means that the thinner dual hulls are less submerged and have less skin 
friction. Long slim boats move through the water far more easily than shorter, 
fatter boats with equal volume. To carry this to an absurd extreme, I get 
almost 50 MPG in my 15' Grumman canoe powered by a 2 HP Honda 4 stroke. On Boy 
Scout trips my son used to be able to do the same on a 6 pack of Cokes and a 
couple of Twinkies.

Larry Z


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