Lagoon 380 User Manual - page 13
NAVIGATION
11
NAVIGATION
1
LAGOON 380
Navigation under sail
z
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
buoyancy).
See illustration opposite.
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
windspeed and to trim the sail area as a priority according to 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
windspeed. 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
responsible in the event of an accident.
z
CLOSE HAULED TRIMMING (between 75 and 50° to true wind)
W
Wiin
nd
d ffoorrccee g
giivveen
n iin
n aap
pp
paarreen
ntt w
wiin
nd
d
- FFrroom
m 0
0 ttoo 1
16
6 kkn
noottss: full sail ; main sail traveller 30 cm above the
boat centre, main sail trimmed with a slightly opened leech (boom
centred).
The genoa jib is trimmed to near the spreader, the genoa traveller 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.
- FFrroom
m 1
16
6 ttoo 2
20
0 kkn
noottss: full sail; the main sail traveller moves up to
60cm above boat centre, main sail trimmed with a slightly more open
leech (boom still in line: so the sheet will have to be slackened).
- FFrroom
m 2
20
0 ttoo 2
26
6 kkn
noottss: 1 reef, full genoa; the main sail traveller comes
back to 30cm above boat centre.
The genoa traveller does not change position but the sheet is
slackened slightly so that the leech is 20 cm from the spreader.
- FFrroom
m 2
26
6 ttoo 3
30
0 kkn
noottss: 1 reef, 75% of the genoa, the main sail
traveller goes to 60 cm above the boat's centre.
The genoa traveller remains in place or moves slightly forward but it
is adjusted so that the leech acts as a propeller, the upper part
dumping air out in strong wind conditions.
- FFrroom
m 3
30
0 ttoo 3
36
6 kkn
noottss: 2 reefs, 60% of the genoa, the main sail
traveller returns to the 30 cm above centre position, the boom is
slackened to fly 50 cm leeward.
The genoa traveller is moved slightly forward, the adjustment remains
the same.