How to Win in an Interclub
When you optimize, or tune, a strict one-design boat, it usually revolves around attempts to correct an original design flaw. With the Interclub, it is the placement of the centerboard trunk and its relationship to the mast that is the most suspect design flaw. Centerboard angle, shape and size have always been controversial, but most people seem to agree that the trunk is too far aft to keep the boat balanced properly in all conditions. As a result, the Interclub sails best with lots of rake and the centerboard canted forward.

Understanding this design flaw is the first step to optimizing you Interclub to your new Shore Sail. Your specific style of sailing may involve some minor modifications to our suggestions, but this should give you a very good starting point.

Since so much of our tuning emphasis is to try to get your boat balanced by moving the center of effort (CE) or sail area aft and the lateral resistance (LR) or centerboard forward, we should insert a warning. In very heavy air, especially during pre-start maneuvering, it is very easy to get into irons. Your CE is too far back. This is because the centerboard is all the way forward, and the rake is all the way aft. Usually the luff of the sail is being feathered, so the leech of the main puts too much pressure on the rudder. You can overcome this problem by easing the vang and setting the centerboard so the front edge is vertical. This will relieve the weather helm.

When fast paced roll-tacking is at a premium, it may also pay to have the centerboard vertical because it allows you to get the bow down after the tack. It also allows the boat to pivot on the Centerboard rather that sweeping the board through the water every time you tack.

T1 is the starting point for most of the important measurements. It is the center of the transom at deck level.

  • Make sure your partners are capable of holding the mast at the maximum aft position of 106.5" from T1. This is your normal setting. Many older boats do not have adjustable mast blocks, but, if you do, it may pay to block the mast forward about 1/4" in light air. This will bend the mast slightly and relieve the slight knuckle forward sail shape. As the sail ages the need to pre-bend declines as the draft migrates aft.

  • A good all-purpose mast butt position is 111" forward of T1. This determines your rake.

  • The chainplates should be at maximum forward, 1'5" aft of the max aft partner position. This insures that you can let your mainsail all the way out downwind.

  • Our Shore sail works best with the centerboard canted forward about 4"-7".

  • Hoist a tape measure to the top of your mast. Lock the halyard. Measure to T1. The rake should be about 18'7". The shrouds should be as tight as you can get them by hand. Keep the headstay slack. There will be about 1/2" of pre-bend. Kenyon masts will need more shroud tension to get the same bend.

  • The headstay adjuster allows you to restrict mast bend. The tighter the headstay, the stiffer the mast. The stiffer the mast, the harder you can pull the mainsheet. In moderate air, pull the mainsheet until the boom is about 4"-5" off the deck at the transom. Take the slack out of the headstay. As the wind picks up you will need more and more headstay because you will be pulling harder on the mainsheet. Keep the boom 4"-5" off the transom until you are forced to vang sheet. In very light air, you will also have to sheet out much further because the weight of the boom closes the leech.

  • Other sailing tips for the Interclub:

  • Our Shore sail's leech is sensitive to main sheet control. Be careful not to over vang in lighter air as this will reduce the sensitivity of your mainsheet. When accelerating off the line, or tacking, ease the main about 2"-3" to reattach airflow. Once the boat is up to speed the main can be trimmed fairly hard in most conditions. Vang sheeting should only be used when the boom has to be sheeted outside the quarter.

  • The Interclub sail measurement rule mandates that the lower batten project further than the batten length can support. This sometimes results in a minor wrinkle under the lower batten when the sail is sheeted hard. This does not occur in light air. We could eliminate the wrinkle by reducing the roach, or we could add so much shape to the lower section that the roach would hook to windward instead of projecting aft. Neither of these options is acceptable, so we tolerate this minor compromise.

    Contact: Bill Shore  

    Visit the Interclub Dinghy Class

    Shore Sails International 2006
    (401) 862-9608

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