Weather Helm: Desirable or Dangerous

[jackdale]

Rich

Great discussion of sail shape. Many folks could benefit from proper sail shape and flattening their sails before they need to reef.

How much does heel contribute to weather helm? Since the theoretical hull speed is based on water line, will the leeward side (with a longer longer line) not be able to generate more speed than the windward side; ending in a round up? Shifting crew weight on a race boat is a common practice. In heavy air to windward, in lighter air to leeward. Race crew also tend to change foresails before reefing the main.

The "textbooks" use CLR and CE and tell us to reef the main first, then foresail, then main, etc.. But in my experience a foresail change will eliminate heel and reduce weather helm.

[AdamLein]

Originally Posted by jackdale

How much does heel contribute to weather helm? Since the theoretical hull speed is based on water line, will the leeward side (with a longer longer line) not be able to generate more speed than the windward side; ending in a round up?

I think not, not until you're going fast enough that the leeward side can take advantage of the longer waterline. I have experienced weather helm when my boat speed was much lower than my theoretical hull speed.

Instead I think that weather helm due to heel is primarily a result of the fact that the COE of the sails is no longer over the centerline of the boat, adding a moment to the forces on the boat. This moment will always tend to turn the boat away from the side the rig is on.

This effect will be present regardless of boat speed.

[killarney_sailor]

One nice feature with our boat is that the centerboard allows us to control the amount of weather helm (I guess technically what we can do is move the center of lateral resistance when we drop the board). Absolutely essential to get maximum performance about of the Monitor windvane. I guess w/o the c/b we would have to do the things suggested here to reduce our helm when the wind pipes up.

[smurphny]

Originally Posted by killarney_sailor

One nice feature with our boat is that the centerboard allows us to control the amount of weather helm (I guess technically what we can do is move the center of lateral resistance when we drop the board). Absolutely essential to get maximum performance about of the Monitor windvane. I guess w/o the c/b we would have to do the things suggested here to reduce our helm when the wind pipes up.

Your Bristol 45 is a nice design. It seems to be similar to the P-40 which is on my shortlist of "next boats." If I had to choose one fault in my A-35, it would be the large main which requires constant attention to keep the windvane working. Being able to adjust the center of effort would be a godsend.