Fireball Tuning Guide Draft update 1997
The
following suggestions are meant to be a guide and should not be misconstrued as
being the only way to make your boat go fast. There are many variables in yacht
racing and we can only offer information that we have found to work for
ourselves, but for your crew weight, wind and water conditions, a slightly
different approach may be necessary.
These suggestions should be a great starting point, but whatever makes
you go the fastest is the best! As you
read this, write down any questions you may have and we will be happy to
discuss them with you in more detail.
Spreader Deflection: For the
DT mainsail.
Spreaders: 3100 mm above heel
Where
x is the distance from the centre of the boltrope slot to the shroud.
Wherey
is the distance from the back of the mast to a straightline between the
shrouds.
X:
405mm Y:
185mm
Mast step: The mast
should be as far forward as is practical for your boat. Further aft than 1.5" from the bulkhead
to the front of the mast would start to be un-acceptable.
When the forestay is loaded to 350 lbs
the mast should have a prebend of 45-5 mm.
The mast should not invert (ie. tip bending over towards bow).
Note that these figures will produce the
prebend only if your chainplates are in the same place as ours (264.5 cm
forward of transom). If yours aren't
then you will need to adjust your spreaders so that you attain the 5 cm. of
prebend.
Symmetry: Be sure your shrouds are the same length and
your spreaders are set at the same angle and are the same length. In order to test this load the rig and sight
up the mast. Does your mast bend to one
side? If yes, then you have a symmetry problem.
Rake
& Tension: You should
always know what rake and tension you are sailing with at any given time. To do this, draw calibration lines on your
mast which can be lined up with your jib halyard. The ideal tension minimizes
headstay sag. In higher winds, and
especially in flat water more rig tension will be required. Adjusting rig
tension has various effects. As tension
is increased the mast will get more pre-bend making your main flatter. Also more rig tension reduces headstay sag
also making your jib flatter. Of course
the opposite is true when you reduce the rig tension.
To measure rake, we put a tape measure
up the main halyard so that the end of the tape is at the bottom of the top
most black band. When the tape is up
pull it taught and measure where the aft deck meets the transom on the
centreline of the boat. The starting
rake is 22' 7.5". This rake is
good up to 11 knots where you should increase rake by 1 chainplate position. Above 15 knots you should drop another
chainplate hole and another at 19 knots and another at 22 knots. In high winds (22+) it is not un-heard of to
have rake measuring as little as 22' 0".
Mast
Ram: Before sailing
you should determine the neutral position of the ram with the boat fully rigged
on land. Mark this position on the
mast. Then place another mark 1 above
and 1 below the neutral point.
When the
crew is inside the boat (0-5 knots) the mast should have some induced prebend
with the ram (up 1 from Neutral) as well as the prebend that is set up with
spreaders. Gradual reduction from 5-8
knots, where the mast is nearly fully powered (firm down pressure (1/2 from
neutral) on ram) by 10 knots. When the
crew is solidly on the side tank, or marginally trapping, the ram should be
down 1 . The mast should be fully
rammed until you begin to be overpowered.
At this point the ram should be released back to the neutral point and
vang applied progressivly as the wind rises.
This will make the mast bend.
This depowers your main by flattening it. The total release of the mast ram could result in mast failure
in high winds when the vang is on hard so be aware of the loads.
Cunningham: The cunningham control the position of the
draft in the sail. As cunningham
tension is increased, the draft is pulled forward in the sail, straightening
the leech and decreasing the heeling force.
Too much cunningham in lighter air, or when the breeze dies, reduces
power and can hurt pointing and speed by norrowing the slot.
When in
doubt let the cunnigham off. Wrinkles
in the luff are not a bad thing. Due to
the narrow sheeting angle of the jib it is imperative you do not pull the draft
too far forward choking the entire sailplan.
Outhaul: The lens
foot, the mainsail panel nearest the boom, should not be fully open when sailing to windward. The outhaul should be kept firm in all
conditions, except in choppy waves and medium air when it can be eased about
one half inch. In 18 + knots, the
outhaul should be at maximum.
Mainsail
Trim: The top batten
telltale is a critical indicator of mainsail trim. It should be flying about 30 to 50% of the time in light air and
flat water and 60% of the time in chop.
If the boat hits a bad wave or there is dirty air, make sure the
telltale is flying. Keeping the upper telltale
flying is a joint effort of the sheet and vang. There should be no vang tension and all sheet tension up to 10
knots, or when the crew is solidly on the rail. As the wind rises, the vang should be increased while watching
the upper telltale. As you get
overpowered and begin to release your mast ram, more vang must be applied to
help flatten the whole main by assisting in bending the mast. Sheet and vang tension are critical
adjustments and should be checked and adjusted constantly to ensure proper main
trim. Always try to get your boom to
the centreline. In full trapezing
conditions the boom should never be beyond the aft corner. If you find it out there release a small
amount of down pressure on the ram and add more vang.
Jib
Trim: The standard method of determining jib lead
position is to head up slowly and watch the jib luff. If the top breaks first, it is because the foot of the sail is
trimmed too hard relative to the leech of the sail and the top is twisting into
the breeze. Move the lead forward to
increase leech tension and reduce twist until the sail luffs evenly. If the bottom of the sail luffs first, the
reverse is true and you have to move the lead back. In light air the sheet should be eased very slightly
(1") from the maximum trim
setting. In heavy air, when the boat is
overpowered, the sheet should can be eased significantly (2-3") in the
puffs to open the slot. We have found
that the ideal inboard/outboard position of the lead is 10" from the centreline in 0-15, and 11-12"
in winds above 15 knots. For starting
you can bring the lead into 9-9.5 inches but this is a high pointing mode and
is not an easy technique to master. The
mainsail and mast must also be trimmed perfectly to match the jib. If in doubt leave it outboard for an more
all purpose setting.
Centreboard: The front edge of the centreboard should be
straight up and down until you become overpowered and begin to rake your
mast. At this point, raise it so that
the aft edge is straight up and down.
The centreboard pin should be located 269 cm. forward of the transom.
Spinnaker
Trim: For successful spinnaker handling good communication
between the helm and crew is essential.
For and aft pole trim ranges from 3" from the forstay when close
reaching and 60 degrees aft when
running. Pole height can be adjusted so
that the luff curl starts just above the mid-point. In very light air lowering the pole a little extra can help the
spinnaker fly when there is not enough pressure to lift it. Communication is most important when running
on gybing angles. The crew should be
able to feel pressure on the sheet and guy and know whether the helm is
pointing too high or too low. If the
crew feels very little pressure on the sheets then the helm is likely sailing
too low. The crew should communicate
this and advise that a higher angle may prove faster. Head up until more pressure is felt. The helm should always try too sail as low as possible without
sacrificing boat speed.
The crew should also feel the wind
shifts before the helm, so tell him/her when they come. Shifts lost running can be many boat lengths
lost, often more than on beats.
Upwind
Tips: In the Fireball
the water conditions are a critical factor.
In flat water keep the sails flat for high pointing. In chop, power is needed. Make your sails fuller. Sacrifice pointing for extra power to punch
through the waves. If the wind is high
enough this principle also applies so you can get on an upwind plane.
Downwind
Mainsail Tips: Ease the
main until it just luffs, then trim it in a little. When in doubt, let it out.
Set the vang so that the top batten is parallel to the boom. Ease the cunningham, outhaul to power up for
downwind. If you anticipate a close
reach, ease the vang but wait to ease the other controls until you feel that the
boat is under control and needs more power.
Keep the boat flat. If you are
having trouble close reaching you can raise the centreboard more, apply
excessive cunnigham and raise the pole some.
Dead downwind raise the centreboard almost all the way.
If you
have any further questions, please do not hesitate to call us here at the loft.
Good
Sailing,
Tof Nicoll-Griffith
North
Sails Fogh One-Design