inarathree -
The
FIRST thing you must do when you have questions of 'helm pressure' is to verify that the *forestay* is operating at near correct tension - about 15% of ultimate stress. This is the forestay tension that almost all sailmakers
expect when cutting sails .... and so that the sag in the wire matches the curved shape they cut when the boat is closehauled/beating.
If this forestay tension is 'less than expected', what will happen is that the jib will become draft aft and the leech will hook up toward the windward side and the boat will then 'skid off to leeward' (and you will *see* that wake is
not coming off the stern in a somewhat straight line), the boat will heel aggressively (also increasing so-called weather helm), etc. The result of a 'slack' forestay is that the boat will have 'helm pressure' that
mimics so-called weather helm.
You can easily mistakenly 'balance' a misshapen jib on a 'slack' forestay with a poorly SHAPED mainsail ... sometimes even having a 'neutral helm' (while the boat skids off to leewards) and NO amount of raking the mast will correct. A skid to leeward (mimics 'weather helm') is found by looking at the wake coming off the stern. A well set up boat with sails raised with the proper tensions to arrive at the *as designed* sail shape, well trimmed sails will have that wake coming off the stern at approx.
no more than 3-4° from the centerline when sailing closehauled/beating; anything greater than this 3-4° 'off' wake denotes a 'skid to leeward' ... once the boat 'skids', the rudder develops undue 'side pressure' and the helmsman will erroneously blame 'weather helm'.
So, with ANY question of 'helm balance' the
FIRST thing you must consider is that the forestay is 'tight' (~15% tension) so that the wire does not sag off to leeward when the jib is 'windloaded'. You adjust the forestay tension by adjusting the backstay.
The
SECOND thing with respect to 'helm balance', and once the forestay is close to its normally expected 15% tension, is to be sure that the mainsail has proper LUFF tension - done with the halyard (or cunningham if you have one). Probably 95% of all cruisers (with dacron sails) never apply correct luff tension.
Incorrect luff (halyard) tension will cause the boat to develop 'weather helm'. to verify correct luff / halyard tension for a mainsail:
http://forums.sbo.sailboatowners.com/showthread.php?t=120970
If you simply raise a boltroped dacron mainsail to 'just up' and do not then apply MORE halyard tension, you WILL have 'weather helm' ... with dacron boltroped (rope inside of the luff sleeve) sails you MUST add additional 'stretch' to the luff by about 1" additional 'stretch' for each 11 ft. of luff length ... or you will get 'weather helm'. The link above describes WHAT to do about it.
.... and of course you need a FULL set of tell tales on the jib and mainsail to visually SEE what is happening.
Sail SHAPE when the sails are well trimmed have more result and influence on 'helm pressure' versus the CLR/CE relationship. .... its the 'dynamics' of sail action that truly affects 'helm balance'. You really have to 'shape' the (dacron) sails after 'raising them'. To attain good 'balance' the forestay has to be near correct tension and the sails have to have the proper tension along their luffs.
hope this helps.
