PAGE 24 • AUTUMN 2005 THE JOURNAL OF THE AMERICAN SAILING ASSOCIATION
MARLINSPIKE SEAMANSHIP
By Capt. Paul Miller, California Sailing Academy
Key Tips for Optimizing Mainsail Power
Part I of a 4-part series on proper sail trim and shape
T
he primary considerations in controlling sail power
In strong winds when sailing to windward, tighten the
are sail trim, shape and twist. Over the years, we
main halyard, downhaul or Cunningham, and clew
have accepted the fact that when the winds over
outhaul to move the sail draft into the designed position.
the water (true) are lower velocity (light), it is best to
A fractional rig mast may be bent forward in the middle
make the sails fuller (power up); and in strong winds, it
to flatten (de-power) the mainsail. The vang can be
is best to make them flat (power down).
tightened for leach tension and reduction of twist if
necessary and the traveler can be eased to leeward
The mainsail shape is obtained by adjustment of the
particularly in the gusts. As the vessel is sailed off the
halyard, downhaul, Cunningham, outhaul, boom vang,
wind, the boom moves out over the water. The traveler
mast bend and mainsheet tension.
becomes less effective for sail twist and the boom vang
becomes more effective.
As a sailor drives the boat to windward in a breeze, it is
often noted that the main sheet is over-trimmed and the
outhaul is loose causing the battens to angle to
windward. This induced drag at the tight leach is very
slow and causes excessive heeling in a breeze.
(L) Ease the traveler to leeward to reduce excess weather helm in
higher winds. (R) Center the traveler in lighter winds to improve
sail performance.
Paul Miller has been the owner and operator of the California
Sailing Academy and Coast Guard School at Marina del Rey,
Calif., since 1968. He graduated from the United States
Naval Academy and did his graduate studies at George
Washington University. As an officer, he returned to the Naval
Academy as an instructor and sailing coach. He and his wife
Example of a loose outhaul greatly distorting sail shape and
Jeanne are full-time instructors at the California Sailing
greatly decreasing sail performance.
Academy.
R
AMERICAN SAILING ASSOCIATION
P.O. BOX 12079, MARINA DEL REY, CA
PRESORTED
90295-3079 TEL: 310/822-7171
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