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following day. I told Olin about the above-mentioned re-
search. Olin smiled and replied, “Dave, a few years ago I
engaged the services of a physicist in California to test an
America’s cup 12-meter. My phone rang at 3:00 o’clock in
the morning. It was the physicist screaming in my ear, “
we are going the wrong way. We are going the wrong way.
The boat is much faster going
” Olin and I both
spoke the next day, both of us
told the above story and we
were video tapped.
I believe the hollow waterlines
forward on the
in reverse left the stern wave
slip past the stern, which
eliminated the so-called dis-
placement hull brake at 1.34
times the square root of the
waterline length. The model
test of
with two bows
and no stern certainly proved
my theory.
Look at the book
Philip L.
Rhodes and His Yacht De-
. Turn to page 164,
Karawan II
, Unique at Both
Ends.” Notice the hollow wa-
terlines aft on the lines draw-
ing. Notice the rudder at-
tached right at the aft end of
the hollow waterlines, which
further straightens out the
water flow leaving the stern.
In 1955
Karawan II
was re
rigged under Rhodes’s direc-
tion for a new owner who
changed her name to
She won the Bermuda Race
and cleaned up in 29 of the
next 33 races she entered.
Looking at photographs of
reaching in a stiff
breeze I would bet she is ex-
ceeding 1.34 times the square root of her waterline length.
went backwards at a speed length ratio of 2. What
this means is that sailboats could be designed that would
win races and cruise under power at a speed length ratio of
at least 2. A 25-foot waterline sailboat could cruise under
power at 10 knots, a 36-foot waterline sailboat could cruise
under power at 12 knots, and a 64-foot waterline sailboat
could cruise under power at 16 knots.
The Viking ships were double-enders with pronounced hol
low waterlines aft. I wonder if they could exceed a speed
length ratio of 1.34?
Look in
The Common Sense Of Yacht Design
, volume I, by
Francis Herreshoff. Turn to page 47 and look at the 85-fo
waterline double-ender
cruising at 16 knots for a
speed length ratio of 1.73
Look at
’s stern wave
Maybe some ambitious
young yacht designer will
read this, follow the trail o
those of us mentioned ab
make some successful
model tests, design a nice
looking boat with comfort-
able accommodations, m
a royalty deal with an hon
able builder, win a lot of
races, and build and sell
thousands of auxiliary sail
boats that can cruise from
New England to Florida in
half the time it takes the e
isting auxiliary sailboats t
make the trip.
Westlawn graduate Davi
Martin has spent a lifeti
designing all types of boa
His book,
The Book of Da
Martin Designs
, is
available on CD from
to purchase t
Book of Dave
Martin Designs
on CD,
Wrong Way Martin and Stephens
. . . continued
The original 24-foot Atlantic City catboat, before the 3-foot
transom extension.
About Theoretical Hull Speed
We now know that so-called theoretical hull speed is no
real wall or barrier and that so-called displacement hull
can achieve higher speeds than theoretical hull speed. I
fact, hull speed is really a function of DL ratio. For a co
plete discussion and formula see the
This still doesn’t explain boats
going so much faster backwards than forward.