The J measurement of a sailboat is from the intersection of the forestay
and deck to the leading edge of the mast. And sailmakers ask for this
dimension. And it is used to compute LP based on the percent overlap one
desires which helps (along with many other considerations) determine the
rest of the sail dimensions
But what happens when you have a roller furler and the roller sits high on
the forestay which is nice for visibility and anchoring.
Shouldn't the "J" now be measured from the tack attachment point and
parallel to the deck to the leading edge of the mast thus influencing the
total sail dimensions?
Gordon



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