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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On Tue, 6 Sep 2005 09:44:10 -0700, "Gordon"
wrote:

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?

Usuallty, yes. But your foot could easily be cut at a different angle
than parallel to the deck. This could be to catch more wind, to make a
better angle to the genoa cars, or to increase visibility.

Many furling genoas are cut higher than parallel from the tack to the
clew relative to the deck in order to increase visibility. This is
sometimes known as a "Yankee jib" and can be used alone or with a
cutter-style staysail that comes down to the deck on an inner
forestay.

Having a higher tack does complicate matters, because the furling gear
at either end is frequently variable in length, which alters the luff
length vis a vis the headstay, which alters their sheeting angle from
the clew to the track, and so on.

This makes most attempts to get an ideal sail for a furler a fully
custom job. By contrast, sailmakers usually don't need to see the boat
to make a great hank-on sail. They have all the needed measurements at
hand. The major problem is then decent execution.

People say roller furling is more convenient, and I agree that for
some it is, but I love my hank-on sails for their simplicity, their
variety and ease of installation and repair. Also, as has been
mentioned recently, it's very cheap to get tape luff sails from racers
(slightly used but still years of life in them...unless you are a rich
racer!), and to convert them to personal use.

I was offered four composite sails yesterday for free. I can convert
them myself for about $75 or have a sailmaker do it for about $130.

A new No. 1 for me in dacron costs $2,200-2,800 CDN. My choice is
clear.

R.