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Copyright © 2009, David P. Martin, Naval Architect
Westlawn graduate David Martin has spent a lifetime
designing all types of boats. His new book, The Book of
Dave Marin Designs, is available on CD from Ama-
zon.com.
The Masthead
will feature excerpts from this
fascinating new work over the next few issues.
70-Ft. and 73-Ft. Ocean Yachts Super Sport
A New Hull Form for the New Century
On this, my first design of the new millennium, I was deter-
mined to develop a new hull form that had a much
smoother ride than my twentieth-century designs without
losing any speed or fuel economy. Three models were made
to 1/2" = 1' - 0” scale. First a 66-ft. Ocean, many of which
were built so that very accurate data was available on
speed, power, displacement and sea keeping. The second
model was a 73-footer with a hull form derived from the
best performing of my designs, as a parent form. The third
model was an entirely new radical departure from anything
previously done by me. It had considerably more deadrise
than the other two models. There were two deep lift strakes
with a 33-degree down angle. Both lift strakes were farth
apart forward than they were aft.
The new models were designed to 73 feet. It was Ocean’
intention to build the mold to 73 feet then dam it to 70 f
initially, and a few years later, remove the dam and prod
a 73 footer. The 70-footer was estimated to be 50% heav
than the 66-footer. It was tested at displacements betwe
112,000 lb. and 127,000 lb. The Ph.D. Professors operat
the model basin test tanks will cringe at what I am about
say. The models were towed from a yoke on an outboard
boat at scale speeds using a GPS to measure speed. The
footer was towed from a line proportionally inboard from
73-ft. model due to its lighter displacement. The radical
model was fastest at all but two speeds, 29 knots and 4
knots. Probably, this was due to the 66-ft. models higher
speed/length ratio as a result of its shorter waterline len
When the speed tests were complete, we whipped the ra
cal model through the wake and let the tow line slack so
model was on it’s own, in a gigantic following sea. The ra
cal model was definitely the better boat and amazing in
following sea. Next the radical model was tested against
73-Foot Ocean Yachts Super Sport