PAGE 24 • SPRING 2006 THE JOURNAL OF THE AMERICAN SAILING ASSOCIATION
INSTRUCTOR TIP
By Capt. Paul Miller, California Sailing Academy
Understanding sail power, sail construction and shape
Part 3 of a 4-part series on proper sail trim and shape
A
sailboat’s sail can be compared to an aircraft
The method of obtaining these shapes is achieved by
wing. A crop-dusting aircraft flies at a slow speed
sewing elliptical sections of sails together into a total
and has a very thick wing in order to produce
triangular sail shape. In the world of high-tech race
sufficient lift at lower air speeds. High performance jets
boats, the sails are formed over a bent surface into the
have very thin and adjustable wings since they fly at high
desired shape and then bonded. The sail material is
air speed. In the same manner, sailboat sails are
much lighter than the sail material used in cruising
generally cut differently for the conditions in which the
sailboats.
vessel will sail.
When I was sailing at the Naval Academy, we had many sets
of sails on our Annapolis 44s, which ranged from the
A vessel that is to be sailed in an area known for lighter
baggies to the flats, numbered one through four. The #1
wind conditions will have the sails cut larger and with
was the fullest and thinnest sail, and #4 was flat and thick.
more fullness, similar to the wing of the crop duster
aircraft. A vessel that sails in San Francisco Bay, known
Good sails can be costly. Often it is necessary to have
for strong breezes, will have its sails cut flatter and may
more all-purpose sails and use sailboat rigging to change
have less sail area.
the shape of the sail.
R
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