Navigation Under Sail - Lagoon 421 Owner's Manual

NAVIGATION
N a v i g a t io n u n d e r s a i l
• BEWARE
A catamaran presents 6 times greater heel resistance than a single-
hull vessel. In terms of ship design we speak of righting moment
(multiplication of the vessel's weight by the transverse distance
between the centre of gravity and the centre of flotation (or buoyan-
cy)).
See illustration on previous page.
This fact has real consequences for the handling and sail-trimming
of a catamaran.
The fact that the boat will not heel over could conceal an excessive
sail surface area in use, which could be dangerous for the crew and
the vessel. It is therefore essential to constantly monitor the real
wind speed and to trim the sail surface area as a priority in accor-
dance with this speed.
These latter adjustments are valid in calm seas. In rough seas one
should take the precaution of reducing 10% earlier in terms of real
wind speed. Generally speaking, it is essential to constantly look to
relieve the vessel rather than to put it under stress.
One should always look for the sail angle of attack to be headed to
the apparent wind and the sails to be not over-trimmed so that the
airflows leaving the sail are parallel to each other, that is to say they
do not create turbulence behind the sail.
Failure to follow the above recommendations can be dangerous for
the boat and the crew, and the manufacturer cannot be held respon-
sible in the event of an accident.
LAGOON 421
• CLOSE HAULED TRIMMING (between 75 and 50° to true
wind)
Given wind force in apparent wind
- From 0 to 16 knots: full sail ; mainsail traveler 30 cm to windward
of center, mainsail trimmed with a slightly opened leech (boom
centered).
The Genoa jib is trimmed near the spreader,the Genoa traveler is
placed so that the angle of the Genoa sheet forms a straight line
with the clew and the luff, at 40% of its height.
- From 16 to 20 knots: full sail ; the mainsail traveler moves up to
60 cm to windward of center, mainsail trimmed with a slightly more
open leech (boom still in line: so the sheet will have to be slacke-
ned).
The Genoa traveler does not change position but adjust the sheet
so that the leech is 10 cm from the spreader.
- From 20 to 26 knots: 1 Reef, full Genoa ; the mainsail traveler co-
mes back to 30 cm to windward of center.
The Genoa traveler does not change position but adjust the sheet
so that the leech is 20 cm from the spreader.
- From 26 to 30 knots: 1 Reef, 75% of the Genoa ; the mainsail
traveler comes back to 60 cm to windward of center.
The Genoa traveler remains in place or moves slightly forward but
it is adjusted so that the leech forms a propeller, the upper part
dumping air out under strong gusts of wind.
- From 30 to 36 knots: 2 Reef, 60% of the Genoa ; the mainsail
traveler returns to the 30 cm to windward of center, the boom is
slackened to fly 50 cm leeward.
The Genoa traveler is moved slightly forward, the adjustment re-
mains the same.
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NAVIGATION
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