Submitted on August 31, 2005 by Brian Wise

Question: Hi,

I am a fairly new sailor and am concerned about the % of draft depth in my main. I can measure the % of the draft depth at the boom. Is this a number I can use to represent the percentage of draft in the whole sail?

Thanks
Brian Wise

Answer: Hi Brian,

No. The depth of the sail at the boom level is only partially related to the depth of the sail higher up. Mainsails are typically designed to be around 10% deep in the middle. Some sails are deeper and some flatter, depending on a lot of factors like the size of the rig compared to the boats displacement and the amount of control the sailor has over the shape of the sail. At the boom level you can change the depth of sail by moving the outhaul. With a good outhaul system you can make the foot almost flat or ease it way off to make the foot very round. The range of depth there might be something like 1-8% depth. That will have a smaller effect on the middle and top of the sail. Over the whole range of foot adjustment, you might influence the depth in the middle of the sail by only about 2% and in the top of the sail you might not see any change.

Regards,
Dan Neri

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