North Sails tuning guide is written to help you get the best
performance from your North Sails. The measurements and settings
included in this guide are the ones that we have found to be the fastest
settings for the IF-Boat. Since crew, wind and sailing conditions vary,
you may find slightly different settings are better for you. However,
by following these instructions, you can be confident that you are well
set up to win at any level. We believe this guide will make your sailing
experience simpler, more sucessful and most of all more fun.
The tuning guide was written by Björn Österberg at North Sails One Design.
This chapter explains rig tuning and the trim control systems
required to be able to get full potential from your North Sails. Always
consult the Class Rules while working with your boat and equipment.
The IF-Boat has relatively little helm and is, unlike most boats, even
more neutral when heeled. To get enough helm for good pointing ability
upwind the mast is raked aft. The length of the headstay determines the
amount of rake. We recommend a total headstay length of 8400mm. You will
most likely need to add one or two toggles to the original headstay to
bring it up to this length. A popular alternative is to get a new
headstay without turnbuckle made to the total length of 8400mm.
While measuring the rig you can also check other measurements including
J-measurement an spinnaker pole length to make sure they are on maximum
and according to the class rule.
IF-boats are typically 20 –30 years old and therefore checking points
that effects rig tension can be worth while. The cabin top underneath
the mast step and the hull around the chainplates are the most critical
areas. A ”knee”, which strengthens the hull and deck at the chainplates,
is allowed. This procedure is described in the class rules.
The settings for rig tension and prebend should me taken with no load on
the backstay. Using a tension gauge helps finding and repeating a
desired rig trim. We use the Loos Tension Gauge mod. B rig. The base
setting is 22 (220kg) headstay tension. To achieve that the values for
the upper and lower shrouds are 37 and 20. In certain conditions, when
the boat needs a lot of power, a looser rig set-up with a headstay
tension of 18, can be worth trying. A looser headstay adds power to the
genoa, making it easier to build and maintain botspped.
The tension of the lowers affects two things. Adding tension to the
lowers increases tension in the forstay. It also affects the amount of
prebend in the mast. The amount of prebend determines the amount of
camber in the mainsail. Your North manisail is designed to a prebend of
20 mm. Setting your rig with a greater prebend will flatten your
mainsail. Setting the mast with less prebend, a straight mast, will add
more power to the mainsail.
According to the class rule the spreaders has to be able to move for and
aft in the spreader brackets. Reducing the aft movement of the
spreaders creates a better support for the mast. Using a string, tie the
shrouds to pull the spreaders back as far as they will go. Then measure
280 mm from the string to the aft face of the mast to get the
Your sail is delivered with 4 small and 6 large trim decals. The small
decals can be used for outhaul and other small range adjustments. We use
the large decals for genoa halyard, genoa cunningham, genoa- and main
tracks. Cutting the decals into “loose” numbers allows you to match the
numbers to positions on genoa track.
The main traveler has to be easy adjustable. A low friction traveler car
with a 2:1 purchase will ensure that adjustments can be made even in
With eased outhaul the elliptical foot panel gives the mainsail a deep
and smooth shape. When tensioned for upwind sailing the lower half of
the mainsail is flattened. The purchase of the outhaul should be at
least 6:1. The tailing end can either stop underneath the boom (as
shown) or be lead to the cabin top.
Cunningham adjustment affects draft position. With loose cunningham the
draft will be further aft. When the cunningham is tensioned the draft
will move forward and open the leech of the mainsail. A 3:1 purchase
lead back to a cleat on the cabin top ensures easy adjustment.
We use the vang mainly to adjust mainsail twist on downwind legs. The
vang can also be used to help the mast bend in the lower sections on a
heavy air beat. Using a tight vang while manoeuvring in the pre-start
will make the boat accelerate faster. An 8:1 purchase with an easy to
reach cleat is recommended.
The backstay is the key to balance and speed in medium and heavy
air. It has to be easy adjustable even when the crew is hiking from the
windward side of the cockpit. The backstay can either be lead to both
sides of the cockpit or to a center cleat with the line lead underneath
the hatch (as shown). We recommend minimum 16:1 purchase.
Inner Genoa tracks
The genoa has a flat leech section that allows us to sheet the genoa
on an inner track in all conditions. The position of the track is 100
to 150 mm inboard of the standard track. The aft end of the track is 600
mm forward of the cut-out in the gunwale. The track is 500 mm long.
Because of the low clew of the genoa it is important to have the spacing
of the trim positions tight enough. Drilling an extra hole between
factory holes, bringing the spacing down to about 50 mm will do the job.
Genoa sheeting winches
Sheeting the genoa from winches on the cabin top gives the trimmer a
better position. Further forward and facing in to the slot between genoa
and main it is easier to get the right genoa trim. With low handle
winches, such as Andersen, the handle can be left in the winch while
Put a mark on the genoa halyard in front of the cleat. A “North Sails
Trim Decal” underneath the mark helps keeping track of the hoist.
Adjusting luff tension can be done with either halyard tension or a
The cunningham alternative has the advantage of not affecting the head
of the sail and therefore leaving the sheeting position unaffected. It
is easy to underestimate the force in the cunningham and use a too
stretchy rope. We use a 6mm spectra core with a 6:1 purchase arrangement
on the aft starbord side of the cabin. Since the tack of the genoa is
about 200 mm above deck it is important to keep the sail forward towards
the forstay. If this is not done properly the sheet tension will pull
the tack of the genoa aft, causing a wrinkle from the firs luff hank. If
you use a rigging screw at the lower end of the forstay, just tie a 4mm
spectra loop twice around the rigging screw and the trough the tack
ring. If you are using a cunningham you might want to put a thin
aluminium pipe around the rigging screw to reduce friction. Having a
full-length forstay use the extra luff hank right close to the tack
Tweekers (twing lines) serve many purposes: they keep the aftrerguy out
of the way of the crew on reaches. They reduce the need a forguy and
keep the spinnaker more stable in manoeuvres making it easier for the
bowman. We put the tweeker blocks at the forward end of the standard
genoa tracks where the boat is at maximum width.
The IF sails well unreefed even in heavy air. Using the jib in winds
above 18 knots will make both manoeuvres and keeping boatspeed easier.
Because the centre of effort moves forward with the jib, pointing is the
critical thing with the jib. The confident crew will therefore use the
genoa in all windstrenghs because of the importance of good pointing,
especially in bigger fleets. We recommend using the inner genoa track in
A good way to move quickly up the learning curve is to mark all trim
control lines and positions. This will enable you to copy a trim you
have found fast in the past, giving you confidence in boatspeed and
allowing you to concentrate more fully on tactics.
In very light air the mainsail should be trimmed with an open leech
to allow the windflow to follow the sail. The traveler is kept about 300
mm to windward of the centerline with the sheet tensioned to position
the boom about 200 mm to leeward of the centerling. Check that the top
telltales flow to make sure the leech has enough twist.
Keeping the crew weight to leeward in these conditiond helps opening the
leeches of the sails. The outhaul is set at #3 on the small trim decal
on the boom. When the breeze builds to about 6 knots the sail can take
more sheeting while still maintaing good windflow. The traveler is
dropped to about 100 mm to windward and the sheet is pulled to centre
the boom. In light air when the mast is straight the cunningham should
be slack and small horisontal "sped wrinkles" should bee seen in the
luff of the sail.
In the 6 to 12 knots wind range the mainsail can be sheeted tight,
letting the top telltale stall at about 50% of the time. A closed leech
puts priority on pointing whereas a more open leech gives extra speed.
In choppy conditions it pays to ease a few inches in the sheet after
tacking to help acceleration. When the boat is up to speed the sheet is
pulled tight and the focus is back on pointing. At 10 knots you can
start flattening the main by pulling the slack out of the backstay and
tightening the outhaul.[mi:1758 p=s mw=400]
In about 14 knots of wind the boat will start to heel with the trim
described above. The solution is to tighten the backstay. This will
depower the main and twist its upper part. The boom can still be held on
the centreline to match the overlap of the genoa. To keep the draft
position in the middle when bending the mast you need to pull the
cunningham. A new sail needs only little cunningham tension whereas an
older sail requires relatively more luff tension.
In winds above 16 knots the mainsail is depowerd and used mainly for
controlling helm. Controlling the power with backstay works well in
steady wind conditions. In gusty conditions this method is too slow and
we have to work the traveler instead. Make sure the boat is
well-balanced in heavy seas. With the right trim the boat should flow
naturally through the waves. If the boat feels “sluggish” it can be a
sign that the main is giving too much power. With the right, open-leech,
trim the boat will be easy to steer and accelerate quickly after big
To get the right clew height you need to set the tack about 150 to
200 mm above deck. Regardless if you use cunningham or not, it is
important to make sure the tack does not move aft with increased sheet
tension. If you use a rigging screw at the lower end of the forstay, tie
a 4mm spectra loop twice around the rigging screw and the trough the
tack ring. With a full-length forstay use the extra luff hank right
close to the tack ring. The best reference for genoa trim is the
distance between the leech and the spreader tip. The following
measurements refer to spreaders with reduced sweep (as described
earlier). For standard sweept spreaders add 50 mm to the measurements
Light and medium air
The right genoa lead for light and medium wind is set when the luff of
the genoa breaks evenly from top to bottom. If the top luff breaks
earlier the lead is too far aft. In light air the luff should be
tensioned so that a few wrinkles remain. Under 6 knots the distance
between the leech and spreader tip is 100 mm. When the breeze builds to 8
knots the luff is tightened to remove wrinkles and the genoa is sheeted
to 20-30 mm from the spreader tip. In flat water the sail can be
sheeted all the way in to the spreader. With tighter sheeting the car
has to be moved aft about 50 mm to ensure an even break in the luff.
As with the mainsail the genoa should be flattened and twisted in
heavy air. The luff is tensioned and the lead is moved another 50 – 100
mm aft. The upper part of the luff will now break earlier than the
bottom part. The foot of the sail is sheeted tight around the
chainplates and the leech is further away from the spreader. In 14 knots
the distance is 100 mm. With winds above 20 knots the lead is moved
further aft and the distance from leech to spreader is 250 mm. This
allows the mainsail traveler to be dropped without closing the slot too
much. The harmony between main and genoa is important. An adjustment in
the genoa is normally followed by a matching adjustment in the main. In
stronger winds the amount of backwind in the main will give a hint about
the relative trim of the sails. Compared to other boats the IF can be
sailed very close to the wind (with a considerable break in the genoa
luff) in strong breeze and flat water.
Because we no longer sail reaching legs this part only describes
downwind (VMG) sailing. The rule-of-thumb for spinnaker trim is to keep
both clews on the same height and the spinnaker boom in right angle to
the apparent wind. In light winds this will mean a lower boom and for
heavy air the boom can be carried higher. If the spinnaker boom is on an
adjustable track on the mast, keep the boom horizontal to get maximum
effect. The afterguy (brace) should be set with a tight tweeker. The
exception is when the boat is sailed on very deep angles where the
tweeker should be eased 500 mm to avoid a sharp bend at the tweeker
The spinnaker sheet is eased just to get a slight curl in the luff of
the spinnaker. In light airs sailing higher angles even on downwind legs
can use the effect of the apparent wind. The angle determines by the
spinnaker sheet pressure. Communication between spinnaker trimmer and
helmsman is the key. When the pressure builds the trimmer tells the
helmsman to bear off and when pressure drops the trimmer tells the
helmsman to luff up.
In winds above 10 knots the main is eased all the way to the shrouds. In
lighter winds when steering higher angles she main is sheeted tighter
to provide a slot between spinnaker and main. To give the mainsail
powerful and even camber, make sure the outhaul is eased to #5 and the
cunningham and backstay is slack. The vang should be tensioned just
enough to keep the top batten parallel with the boom.
Spinnaker sailing is easier if you get rid of the genoa. Roll the genoa
parallel to the headstay. Start with the clew and roll the sail vertical
behind the headstay. Have a 500 mm rope and tie it around the sail and
headstay. When the genoa is not furled make sure the genoa sheet is
loose. An overtrimmed genoa will create turbulent air for the spinnaker,
making it unstable and hard to trim.
The IF is normally raced with 3 persons. It is not possible to
describe the “perfect” crew organisation for all boats. The knowledge,
experience and the ambitions of the crew should determine who does what.
The idea with the following chart is to present a proposal and an
inspiration to make your own chart for your boat. By making a chart you
have to think and talk trough the crew work. By assigning a job
description to each position, a new crew member can be easily integrated
into your boat handling team.
In organising the crew of your boat your goals should be to:
· Involve all crew members in each manoeuvre
· Avoid having crew members cross paths with each other
· Talk about and decide tactical matters to involve the whole crew
We hoist and retrieve the spinnaker trough the fordeck hatch. We like
this method because the spinnaker has a shorter distance to get from
stored to set, especially at gybe sets. With the traditional way of
hoisting from the cabin hatch the spinnaker has to be led past the boom,
vang and shrouds before getting in position. Another advantage is to
have the bowman work from a position around the mast. This will make the
cockpit less crowded and keep the crew weight well forward.
A short description:
To allow the spinnaker to be hoisted from the mast, exit the spinnaker
halyard 2000 mm above deck on starboard side. Mount a cleat 400 mm
underneath the exit. The forward closing fittings of the fordeck hatch
can be removed while racing. The hatch is heavy enough to keep the water
out even in rough conditions.
Store the spinnaker in the fordeck hatch. Have the head and clews
sticking out a few inches. The halyard is led forward to the forstay to
keep it out of the way of the genoa. Use the gunwhale fairlead or a hook
mounted close to the headstay.
|Organisation ||Helmsman ||Cockpit ||Bowman |
|Before the start ||Steering, strategy||Sailtrim, strategy||Wind observations, compass, bearings, strategy|
|Start||Steering, strategy||Genoasheet, leeward lookout,|
|Compass, time, flags|
|Upwind||Steering, boat to boat tactics, mainsheet||Tactics, genoa trim||Wind and boat observations,|
|Tacking||Steering, tactics, mainsheet ||Genoasheets, both in light air, new sheet only in heavy air||Release old sheet in heavy air|
|Preparing top rounding||Steering, mainsheet traveler||Toppinglift and forguy (bearaway set), set tweekers||Pole on|
|Bearaway set||Steering, boat to boat tactics, mainsheet||Spinnaker sheets. Pay out spinnaker if cabinhatch hoist||Hoist spinnaker, roll genoa, release outhaul and main|
|Jibe set||Steering, boat to boat tactics, mainsheet, jibe main||Pull around genoa sheets, trim spinnaker sheets, pull topping lift||Hoist spinnaker, pole on, roll genoa, release outhaul and|
|Downwind leg||Steering, boat to boat tactics||Trim spinnaker sheets||Wind and boat observations,|
compass bearings, tactics, clear halyards, fine tune vang
|Jibe||Steering, boat to boat tactics, mainsheet, jibe main||Trim spinnaker sheets, jibe tweekers||Jibe pole, adjust forguy (if in use)|
|Preparing leeward rounding||Steering, pre-set main traveler and backstay||Trim spinnaker sheets, jibe|
|Stretch cunningham and outhaul, remove spinnakerboom|
|Takedown||Steering, mainsheet||Spinnaker sheets, genoasheet||Remove spinnaker|
|Leeward rounding||Steering, mainsheet||Genoasheet||Fasten spinnakerfall|
If you have any questions regarding trim or IF-Boat sailing in general, please contact Theis Palm.
Good luck on the water!
| ||IF On the Water|
Genoa lead position
#3 on trim
Slack - remove
2-0 on trim
0 on decal
* Add 50 mm for spreaders with unrestricted sweep
Contact the IF Racing Experts: