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A modern cruising
Ailsa Craig
, around 13,700 pounds,
would be fitted with, say, a single 300-hp diesel or twin
150s. Cruise would be around 13 knots making the trek
from New York to Bermuda in just over two days. T
would cost you no more than 520 gallons in fuel for
the hop over, and you could take your whole family,
friend or two, and all your belongings along. Spend
seven or eight days exploring the islands, then turn
around and head home. This would be one pleasan
and economical vacation. Slow down to 11 knots a
the crossing would take you all of two and a half da
and you’d use only 370 gallons of diesel.
How to Make an Efficient Boat
I’ve read a lot about efficiency on boats over the ye
and much of it hasn’t added up. Almost any knowl-
edgeable designer will tell you that just three basic
things make for efficiency:
1) Going slower
2) Long, slender hulls
3) An efficient propulsion package
I’d like to make this seem more complicated, but
that’s it. Yes, you can improve efficiency with tweak
and adjustments to the hull form—refinements in
shape. Also, certainly, the hull form must be properl
matched to the intended operational speed, but hul
shape refinements add small percentages to effi-
ciency, the three items above are—by a good margi
the overriding factors.
Transport Efficiency
The bottom line is fuel consumption and this is wha
determines a powerboat’s efficiency. How much fu
takes to get it from point A to point B. Naval archite
have a specific formula for efficiency, which is calle
“transport efficiency,” or “E
.” There are minor varia-
tions of E
. Ship designers are really interested in th
weight of cargo moved from place to place efficient
Transport efficiency for cargo ships is thus:
= speed x cargo weight
Since fuel consumption is directly proportional to
power, dividing by power gives you the efficiency.
In yachts, patrol boats, small passenger vessels, it’s
really the entire weight of the fully-loaded boat that
should be evaluated, so for our purposes transport
ciency would be:
= speed x loaded displacement
Engineers are fussy about units (for good reason), a
to be more accurate we should define transport effi
ciency, E
—57-ft. Voyaging Motorcruiser
—66-ft. Voyaging Motorcruiser
—45-ft. Ultra-Shoal Motorcruiser
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