Jere Lull wrote:

In article ,
Albert P. Belle Isle wrote:


As a quick calculation, 24ft DWL would yield a hull speed of about
6.6kt with a speed-length coefficient of 1.34. To get to 7kt, the
effective DWL at 1.34 would be a little over 27ft - not 35ft.


We've sustained much higher speeds, but don't feel like opening myself
up for someone saying that it's impossible, that I'm surfing, my
knotmeter's off, there's a current, or some such.

I would agree except that I eliminated all those things. We really have
done "impossible" things. Would love to know how, but gave up and simply
enjoy.


It isn't a trick. The rule isn't a natural law, it's a general
guage, and it is inaccurate in most cases. It might hold true for
any one hull shape and weight, but it does not imply any limit, it
is only an estimation of a constant of some sort we call hull speed.

It's really all a question of fuel or propulsion force mileage. If
you can ignore current and wind, the distance per gallon would be
less at high speed than at low. There might be a "resonant" speed at
which you could get the best mileage for your hull form and weight.
You could plot a few speeds and fuel economies, and calculate a
number which might express some value for, call it formatic drag,
for want of a higher education...

Each boat would have it's own value.

A good comparison might also formulate the "answer" as an expression
of fuel cost per mile / hour, or in effect how much it would cost
per voyage in terms of dollers per hour wasted or saved in transit.
In other words, to express the cost in fuel efficiency as a term
that implied impatience, or something. Me, I like to spend as much
time as possible on the boat, so don't count "slow" as a cost. A
floating raft is almost as much fun, and you can fish!

The more time wasted, the better fuel economy? How much per hour to
save each hour wasted? How do you value your time?

Terry K

I use english measure for the sense of familiarity. Old rules of
thumb last just as long as the thumb, I guess.