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Old 11-18-2003
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cal 34 - double headsail modification

In high winds weather helm comes from a number of factors but primarily from heeling assymetry and from the dynamic balance between the mainsail and the jib, and the underwater elements generating lateral resistance. In a traditional boat designed to be a cutter, the jibstay (what you have been calling in the ''inner stay'') is tacked to the stemhead and the mast us further aft in the boat and so the center of effort is further aft as well. Similarly, the center of lateral resistance is also located further aft in order to be in balance with a center of effort located farther toward the stern than is typical for a sloop.

But also, as a traditional boat heels the underbody of a traditional hull form develops lesser assymetry when heeled. Shedding the sail on the headstay works on a traditional cutter because everything else is so far aft. The trade off is that traditional cutters were infamous for developing a lot of weather helm when sailed that way.

More modern boats like the Cal inherently develop weather helm when heeled. The key is to develop a dynamic balance and that would require keeping the center of effort pretty far forward.

The other item that you touch on is the furled up jib. In the kinds of winds where a storm jib and storm trisail make sense (or even a third reef makes sense) It is not unusual for a smallish boat (perhaps under 40 feet) to take a knock down simply under the windage of the rolled up sail. (Been there, done that, wore out the teeshirt) When you talk about those kinds of survival conditions you need to strip the roller furler or you are unable to even hove to without taking big knock downs. When you talk about a comparatively low stability boat with a comparatively tall and heavy rig like the Cal 34 this is certainly the case.

Jeff

Last edited by Jeff_H; 08-08-2011 at 08:19 AM.
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