INTER 20 TUNING GUIDELINES
Written by Matt Struble



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:
Minimum mast pre-bend 1"

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.