Monday, July 11, 2011

A New Twist

I’ve been playing with sail trim trying to get to know my boat. If you read my post entitled A Lesson Learned, a Sojourn Survived and are an experienced sailor, you probably realized that part of my problem was that my sails were out of trim as evidenced by massive amounts of weather helm.  I’ve since discovered, at least with some combinations of reefing, head sail and trim, that Sojourn is well balanced, resulting in very light tiller forces.

In my experimenting, I’ve observed the phenomenon of sail twist, or more accurately induced sail twist to improve flow over my sails.  I’ve never fully appreciated until I put “tell tales” on my shrouds.  2011-07-10_16-33-07_278

What exactly is “sail twist?”  Sail twist is intentional twisting of the sail to account for the phenomenon of apparent wind direction being different at the head then at the foot of the sail. This is a result of the true wind speed being greater higher up than at the water surface.  In other words, the wind appears to be blowing in a different direction at the top of the mast than down at the boom.

Click on the picture, zoom in if you need to, to find the wind vane and compare the direction it is pointing to the direction the tell tale is blowing. If you can’t find it, the wind vane is  pointed directly abeam, precisely parallel with the spreader.

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