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Hull Speed Doesn’t Exist…
I’ve been kicking around this business for almost 30
years, most of the time dealing with displacement boats. When I began in
the early 80’s most folks found that choice a curious concept. I
remember taking our wares to Ft. Lauderdale Brokers and Execs only to be
greeted by blank stares. I expect our departures were greeted with
snickers and more as they imagined “why anyone would want to go that
slow ”. Years later after increased oil prices, maturing sailboat
owners, and other issues, the best and the brightest decided that
displacement boats were Cause Celeb.
My quibble here is not with the people or perception; it is the fact
that there’s really no such thing as “hull speed”. This comes to mind
because I got caught again in the hull speed trap the other day talking
with a boat owner. The supposition is that there is a speed beyond which
boats of certain shape will not go, i.e. boats have a finite speed.
There’s no room here to get really technical, but hull speed is
generally considered to be 1.34 times the square root of the boat’s
waterline length. The short description goes that beyond some such
speed, boats must climb their own wave, overcome squatting, eat their
own young or do something else likely improbable. Unfortunately that
assumption is more over simplification than an expression of the physics
involved.
The truth is “hull speed” is simply shorthand for suggesting a point at
which the addition of more power is increasingly more inefficient. At
least in theory you could water ski behind a tugboat if you could
install enough power (without sinking the boat). If you think I’m wrong
consider the shape of NASA’s space shuttle at lift off. Though far from
sweet and aerodynamic; the bulky shape is a clear picture of what
Horsepower can buy.
But that’s just my opinion.
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