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post #11 of 17 Old 08-01-2002
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Excessive weather helm?

I must not be understanding what you are doing. As I see it, if the main is centered and fully deployed while the jib is luffing I would expect severe weather helm. Clearly in such a case the center of force is well aft of the CR.

I''ve been told to think of a boat as you would a dart. As long as the feathers of the dart are well aft of its COG (CR) the pointed end will be first to arrive at the intended target. The main (on a sloop) is very much like the feathers on a dart. Fortunately, sloops also have a headsail which when deployed help to move the ''feathers'' forward and hopefully closer to the CR. In fact, if the headsail were to be the only sail deployed, the CF could actually be forward of the CR and the boat would instead have lee-helm.

At least, that''s how I have been taught to understand it. If I''m correct, then you need to reduce the main by either moving the traveler leeward or reefing it, and setting the jib to be more effective. Both of these procedures should have the effect of reducing weather helm. BTW, as you probably know, some weather helm is desireable.

~ Happy sails to you ~ _/) ~
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post #12 of 17 Old 08-01-2002
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Excessive weather helm?

Makes sense to me Frenzy. If the Center of Effort (COE) of the sails is forward of the Center of Lateral Resistance (CLR) then the boat will weathervane by the bow requiring lee helm to hold it up. If the COE is aft of the CLR, it will blow the stern down requiring weather helm to hold the bow down. Don''t think of the boat as a dart. The feathers on the dart are for drag to hold back the back end of the dart (and cause rotation). Think of the boat as a wind vane. If the big end is forward, the forward end blows down. If the big end is back, the back is blown down. COE over CLR, of course, produces balance.
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post #13 of 17 Old 08-02-2002
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Excessive weather helm?

OOPS!

Jeff you are right. He did tighten up forestay to decrease rake. My mistake.
It did reduce weather helm.


Thanks,

Mike
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post #14 of 17 Old 08-20-2002
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Excessive weather helm?

I''m confused on one point. If you increase the backstay tension, doesn''t that increase the area in the leech of the sail? Possibly that remedied by increasing the vang tension?

And by increasing the backstay tension, how does that shape the mainsail? Does that really help flatten the main, or is there something else going on? I can see that it would help flatten the leading edge of the jib.
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post #15 of 17 Old 08-20-2002
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Excessive weather helm?

It opens the leach of the main thereby depowering it. It also takes sag out of the headstay which flattens and depowers the jib. Both of which will decrease healing which in turn decreases weather helm
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post #16 of 17 Old 08-20-2002
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Excessive weather helm?

If the rig is tuned correctly, increasing the pressure on the backstay bends the top of the mast aft, and the lower part of the mast is bowed forward. When the lower part of the mast bows forward, it pulls the pocket of the mainsail forward and flattens the mainsail. This moves the center of effort forward, which depowers the mainsail and reduces the heeling moment.
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post #17 of 17 Old 08-27-2002
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Excessive weather helm?

If any of you have windsurfed,
you know if you lean the mast foward
you will fall off the wind.
And if you pull the mast back you will head up into the wind.
This made it easier when I was tuning
my rig
PB
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