Trimming the mainsail
Using the kicker, mainsheet and traveller to best
effect.
The mainsail is primarily set and controlled using the
mainsheet, kicker (vang) and traveller.
Their combined affect is to adjust the sail angle to the
wind and the amount of twist in the sail.
Twist
Wind speed increases and frees a little with height.
Therefore the top of the sail is trimmed freer than the base
of the sail.
The amount of twist is judged by looking up the leech to
see if the top of the sail falls to leeward more than the
central sections. A more precise method is watching the
telltales streaming from the leech.
When going upwind, the mainsheet and the traveller are
used to control twist. When sailing off the wind, the kicker
takes over.
Mainsheet
The mainsheet not only adjusts the angle of the sail to
the wind, it also affects twist when sailing close to the
wind.
The sheet exerts a large downwards force on the leech of
the sail when the boom is directly above it, much more than
the kicker.
Adjust the mainsheet so that the top batten is roughly
parallel with the boom or the top telltale streams straight
out from the leech.
Too much sheet tension and the top telltale will fall to
leeward as the leech closes and twist is reduced.
Once the sail set is correct for close hauled or fine
reaching, the mainsheet traveller is used to quickly depower
the sail in gusts, without spoiling twist.
Traveller
When going upwind, once twist is set using the mainsheet,
the traveller is used to power or depower the boat.
It is normally centralised but can be hoisted to windward
in light airs or to leeward in heavy airs.
Moving the traveller to windward, easing the sheet and
kicker allows the boom to stay near the centreline with the
sheet eased.
The eased sheet allows the boom to rise in the light
airs, creating twist.
If weather helm is detected or boat heel increases, ease
the traveller to leeward. This retains sail shape and twist
but reduces heeling force. The luff spills wind but the
leech keeps driving.
If you are still over-pressed with the traveller to
leeward; reef, centre the traveler and start the process
again.
Kicker or vang
The kicker controls leech tension and twist when the boom
has passed to leeward of the traveller.
Easing the kicker allows the boom to rise, opening the
leech and increasing twist.
Tightening the kicker will close the leech decreasing
twist.
Often the kicker needs adjusting to stop the top of the
sail twisting too much when sailing off the wind and on a
run.
Rod kickers
Contrary to belief, rod kickers do not exert more force
downwards. Their role is to create more upwards force in
light airs.
They push a heavy boom upwards using gas struts or
springs allowing the leech to open instead of the weight of
the boom pulling down in light airs, closing the leech.
Twist rules
Going upwind
- Light airs: traveller to windward, sheet eased to
centreline or just to leeward.
- Medium airs: traveller centralised, main sheeted
normally to achieve twist.
- Gusts: leave the sheet alone, ease the traveller.
- Increasing wind: reef, centralise the traveller and
start as (2)
Reaching and running
- Use the kicker to adjust twist once the boom passes
outboard of the traveller.
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