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Tuning Tips |
Nacra 6.0. Tuning Guide
Starting Point: Hull Alignment The first place to start is to make sure the
front beam is seated with theends of the dolphin striker resting against the stop on the
inside of the hulls. Set the rear beam in the saddles and adjust the movable stops to
allow the hulls to be aligned. I have been taking my measurements from the middle of the
bows and comparing it to the measurements from the center of the lower gudgeons. Set the
alignment so there is zero toe in or out. I have tried to measure my boat diagonally
and it hasn't worked out, because the boat is not perfect. One hull is a little more
forward than the other. When every thing is lined up make sure a set screw is installed in
the rear stops. There is a open hole for it on the stopper. This is very important, the
boat won't stay lined up if this isn't done. Rudder Alignment The rudder alignment should be set for 0 to 1/32 inches of toe in
to compensate for rudder lash. Set the rudders with the tramp installed and
tensioned. Shims can be used in between the rudders and castings to remove slop.
This will reduce that loose feeling in the tiller.
Daggerboard and Rudder Tuning Rounding of the leading edge is more important
than thinning the trailing edge. Fill in any perfections to achieve a nice rounded shape.
For the trailing edge, thinning the board from about 2 inches in to an edge about 1/16 of
an inch should do it. The boards come new with a small ridge that runs along the
back edge on both sides. The ridge is very subtle but should be removed in this
process. Mast Set-UP Set the spreader rake to about a minimum of
2". This measurement can be taken by placing a straight edge across the tips of the
spreaders and measuring the distance to the back of the mast. Start with the outer
diamonds and set tension to about 500lbs. This should result in the mast being pre-bent
about 1 -3/4". Then set the inner diamonds to be just tight but not enough to
increase pre-bend. Final measurements should be made with the mast on it's side. A wire
tension gauge should be used to accurately measure wire tension. Rig Set-Up We have tried several positions of mast rake
and found that about 15" to 18" of mast rake seems to be a good start. I have
seen people sail fast with the mast perpendicular and raked back all the way. We measure
rake by putting the trapeze hook down and moving it to the point where it just touches the
top of deck forward and aft of the front beam. Then measure the distance from the center
of these two points to the front of the front beam. Shroud tension shouldn't be too tight
to allow full rotation of the mast. A more accurate way to measure mast rake is to level
the boat at the front and rear beams. Hang a weight from the halyard a measure were the
weight hits the trampoline. The distance from the weight to the front beam is the mast
rake. Mast Set-Up for the Big Guys
Spreaders should be set to 1-3/4" of rake. Tighten outer diamonds for 1-1/2" of pre-bend. Tighten inner diamond wires just short of adding anymore bend. Final measurements should be made with the mast on it's side. NOTE: Never let pre-bend to go under 1-1/4.
INTER 20 TUNING GUIDELINES
Mast: Diamond wires: With the diamond wire tension released, lay a straight edge across the back of the spreaders. Measure the distance between the straight edge and the back of the mast. This dimension is going to vary depending on your total crew weight. 300-325 lbs. 2.625" of spreader rake is used, 325-350 lbs. 1.5 " of spreader rake is used, and over 350 lbs. a rake of 1.0" is used. (note: Factory recommends at least 1.5") VERY IMPORTANT; Be sure that when you are making adjustments to your spreader rake, you adjust both halves the same distance. Spinnaker halyard: Run a twing ball up the halyard,
this will stop the head to the spinnaker from jamming in the bail. Now your
halyard will run up through the bail to the cheek block and down through the
bail. This will allow your crew to pull the spinnaker up until the twing ball
reaches the bail. This will alleviate the problem of pulling the spinnaker through
the bail. Prebend: Rudders: Your rudders are adjustable fore and aft. This is accomplished by the adjusting screw on the top of the rudder casting. For the first couple of times of sailing, you should start with the screw in all the way. Now as you become more comfortable with the boat start moving the adjusting screw out. This will lighten the helm the more you unscrew the adjusting screw. Be careful not to go too far at one time, if you go to far the helm will not be neutral, but will be divergent. Daggerboards: The dagger boards work well out of the box, but if you experience
some humming, simple sand the ttrailing edge of the boards. Do not sand them to a
razor sharp edge, but an edge thicknes of approximately 0.090". Battens: The stock performance battens work well and should be
used. Batten tension should be applied to remove wrinkles only. Spinnaker: The spinnaker is one of the most interesting parts to the Inter 20. The setup with regards to the sheets and other equipment is done very well by performance catamarans and should not be changed. Mast rake: This is an area where the adjustment will be determined by the
type of sailing you are doing. When racing in a typically upwind situation a
mast rake of 3 pin holes forward is used. When mostly down wind is
experienced, no pin holes forward is used. For around the buoys, a mast rake of 1
pin hole is used. Mast rotation: Starting points for the mast rotation are very straight forward. Up wind and down wind works very well with the mast center axis pointing at the daggerboard. This is assumed that you are sailing with the spinnaker down wind. Outhaul: In medium to moderate air strengths you will want the out haul
adjusted as to allow the bottom of the sail to clear the edge of the boom by 3-4
inches. In lighter air you can apply more bag to the sail and in heavy extreme air
you will want to maximize the out haul tension as to flatten the sail. Downhaul: The square top main sail responds very well to down haul
tension. In light air to 10 mph with most conditions, you will leave the down haul
loose to just pulling the wrinkles out of the sail. From 10-20 mph you will have to
adjust down haul tension to your weight. You have too much tension in this breeze,
if in order to hike the boat you have to head down more than 50 degrees from the true wind
angle. Not enough tension will cause your boat to hike without any forward
motion. You will be sailing very close to the wind but not with any speed.
Down wind you will typically want to just take the wrinkles out of the sail. Jib leads/luff tension: Jib leads should be adjusted to the outer most holes in the beam
in all conditions except one. This one condition in which you will move the jib car
to the center adjustment hole will be in very calm seas with a very steady wind. The
reason for this is the operating band of the sails becomes very narrow as the jib becomes
closer to the main sail. Rig tension: As with most sloops you will want the rig tension snug.
Leave just enough slack to allow for the mast to rotate with out major binding. |
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