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9
HEADSAIL TRIM
‘As a pretty simple starting
point for headsail trim, it
should match the mainsail
trim in both twist and
angle of attack,’ says
Gladstone. ‘An
overtrimmed headsail is
something we see all too
often and I believe it is for several reasons.
‘Upwind, we learn to set the jib leads
or cars so that the telltales break evenly.
When they are too far back, the top telltale
breaks before the bottom, when leads are
set properly, then telltales break evenly.
However, when the jib leads are too far
forward, the telltales still break evenly, so just
seeing that our telltales are all flying does not
tell us if we are overtrimmed, only that we’re
not undertrimmed. To correctly control the
twist in a headsail you need to move jib cars
aft until the top telltale is just breaking and
then move them a fraction forward.
‘Of course that all assumes that cars are
able to be moved while the sail is trimmed
in, which is often not the case on cruising
boats so this can involve a bit of luffing to
take the load out of the sheet and then
moving the cars – or slowly getting there
over a series of tacks.
‘If the jib is overtrimmed it has negative
effects; it increases the depth of the sail,
upsetting the balance of the boat and
creating weather helm. It also stalls the air
coming off the leech of the sail which spoils
the flow over the leeward side of the mainsail.’
Gladstone adds that with both the mainsail
and the headsail it is wise to consider what
you are setting your boat up for. If you are
sailing shorthanded, with only one or two
onboard and are likely to be using the
autopilot then sailing with more twist in
both sails is important as it provides a wider
groove for the boat to sail in. The effect of
this is it allows the boat to be hit by a gust
with the autopilot on, but maintain decent
pace and not trip up. ‘If you have too little
twist in the headsail and mainsail then you
reduce the ability of the autopilot to adjust
the boat’s course and get back on track.’
REMEMBER: Your jib telltales will not let
you know if your leech is too tight as they
will still stream. Move cars aft until telltales
break and then move them forward
fractionally. More twist will help keep the
boat moving when the autopilot is steering.
10
TIDE EFFECTS
Falk feels there is still a gap
in many sailors’ knowledge
when it comes to tides and
properly anticipating their
impact on sailing. Tibbs
agrees this is often
overlooked. ‘The basics of
how apparent wind changes
when the tide is under or against us is relatively simple. If there
is 5 knots of wind blowing and 5 knots of tide running, if you are
running with the tide the actual wind you experience would be
close to zero as the tide is carrying you as fast as the wind. We
all know we are not going to go to Portland Bill wind against tide
as there is signification seaway, but the tide changes your
apparent so much too. Beating in a flood tide out of the Solent
you’ll have 2-3 knots of tide under you. With a true windspeed of
20 knots, a few knots of tide can bring that to 23-24 and your
total apparent wind speed is pretty quickly up to 28 knots!’
REMEMBER: Tide affects how you experience wind in real
terms. The wind effect should be considered in passage planning.
EXPERT ON BOARD
Tidal gates are well
understood but the effect
tide has on apparent wind
is not always fully
considered
Both mainsail and headsail
should be trimmed together – it
is easy to overtrim a headsail and
close the slot, stalling the sails
