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To me the C&C 99 has a 'design problem' ... the rudder when the boat is on a 'hard heel' isnt totally submerged, thus able to 'suck air' or 'cavitate' thus potentially losing its ability to steer.
To prevent the boat from losing the 'bite/control of the rudder' should be set up so that under normal conditions so that the boat has only a 'very slight' amount of (the apparent FEELING of) weather helm. All adverse helm pressure is NOT weather (or lee helm), it 'could' be a *SKID to leeward*:
1. TIGHT BACKSTAY - so that the jib luff and FORESTAY dont SAG OFF TO LEEWARD appreciably when windloaded. With a too-loose forestay any boat will begin to SKID off to leeward, will aggressively heel, will be SLOW, the wake will not be coming straight off the stern, and the boats performance will be very erratic and 'very cranky'. A boat skidding off to leeward will have a LOT of helm pressure (but it isnt 'weather helm') .... and any adverse pressure on the rudder (especially a rudder that isnt TOTALLY underwater) can create 'cavitation'.
2. Correct mainsail HALYARD/LUFF tension -
typically a mainsail with a **boltrope** needs to have the luff/boltrope additionally 'stretched out' after raising the sail. The additional 'stretch' on such a sail is usually 1" of *additional luff stretch* for every 11 ft. of mainsail luff length. Your mainsail luff dimension is approx. 35 ft. 35/11 = 3.2" that the luff needs to be stretched when sailing in ~15kt. winds (less stretch in lower v. winds). Note - when a mainsail is correctly raised and stretched, the angle that the upper surface of the boom makes with the mast is about 89-90 degrees ... if the luff is not stretched out then the aft part of the boom will be lower than the goose-neck and the draft will be aft, the leech will be 'hooked up to weather, and the draft will be 'very full'.
Note - a mainsail on a mast roller furler doent have a bolt rope, but the sail luff will/can 'stretch out' all by itself due to the windloading; so, in this situation the only way to control is to REEF.
2a. Next time out (12-15kts). Set up the boat normally to get proper trim, etc., go onto a hard beat to windward and LET GO OF THE WHEEL !!!!! If the boat wants to 'head up' then increase the MAINSAIL Halyard (and/or cunningham) tension until the boat neither heads up nor falls off !!!! This is a zero pressure helm pressure (dead fish helm). Once you 'find' the 'dead fish' helm position, then slightly release the halyard tension (an inch or so) so that the boat SLOWLY heads up when the helm is released.
If the boat has a short or 'shoal keel', these suggestions are extremely important, so that the boat doesnt skid off to leeward ... as the the next thing to happen after the rudder starts to 'suck air', the keel can also begin to 'trip' when it loses its 'bite'. When that happens .... you are soon going to get 'dunked' by either capsizing to windward or leeward when on a hard 'beat'.
Last edited by RichH; 06-20-2010 at 11:27 AM.