LAGOON 400
1
NAVIGATION
11
•BEWARE
A catamaran presents 6 times greater heel resistance than a single-hull
vessel. In terms of ship design we speak of righting moment (multipli-
cation of the vessel's weight by the transverse distance between the
centre of gravity and the centre of flotation (or buoyancy)).
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 ves-
sel. It is therefore essential to constantly monitor the real wind speed
and to trim the sail surface area as a priority in accordance 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 crea-
te 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 responsible in
the event of an accident.
• 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 cente-
red).
The Genoa jib is trimmed near the spreader,the Genoa traveler is pla-
ced 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 slackened).
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 comes
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 trave-
ler 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 trave-
ler 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 remains
the same.
Navigation under sail
NAVIGATION
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