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wrote:
SailCare.com says they replace the "resin" that is on new sails and
they restitch whatever needs it. I want to know how to evaluate the
shape of a sail so I can decide the most effective way to restitch to
renew the shape. I agree, older material is probably not as strong as
newer but many sails arre very lightly used. Quite frankly, I simply
do not believe what sailmakers say about sails aging just by sitting on
a shelf. I also think that a considerable part of the stretch of an
older sail is in the stitching and not in th ematerial itself. Even
sail material that has stretched probably has not gone beyond the yield
point of the material so unless it is actually worn or degraded by UV,
I think that most of any loss of strength is in the stitching.
So, how does one evaluate the shape of a sail?

I think you're correct about the way sail makers always find the best
solution is; hey guess what??.............. a new sail from them:-)

The modern sail cloth is pretty strong & it will last years & years, a
close look for abrasion etc but the panels themselves should be OK,
given that most used sails are not all that old in years anyway. It's
just the boy racers imagining they'll go lots faster with new ones, so
thankfully they're a ready source of used young sails.

Obviously the panels are stitched together & again a good close exam
will show any problems, the sail cloth is so hard & tough the stitching
stands proud so it cops most of the chafing, but most are easy to have
repaired or doubled (say batten pockets, where the spreaders rub, or
from the lowers when close hauled.)

As to the shape this is not usually a problem, the sail's shape is cut
into it & despite what the go faster brigade tell you with modern cloths
there is very little if any "stretch" in the panels themselves. It
appears there is but that's the stitching getting loose.

If you want to check it just lay it flat on a floor (assuming you have
one big enough:-)) & check to see the foot, luff & leach are a
consistent curve with the max depth about 1/3 the way up for the foot &
luff & around 1/2 for the leach. The amount of curve depends on which
sail it is; say most mainsails it's around 1" for every 5' of luff
length, 1" for every 3'6" of foot length & 1' (1 foot) per 25' of leach
length. Most headsails are 1" in 5" for the luff & 2" in 5" for the foot
the leach is usually pretty straight but big genoas may even have some
reverse roach in the leach. For non racing sails you probably don't care
much about the figures just that the curve is consistent & flows
smoothly, if it doesn't the sail may have been damaged & not properly
repaired or has been recut down from a larger size incorrectly (Believe
it of not some people just take bit off till it fits the new triangle:-))

Go for it you'll get much better miles per dollar than new & in an
accident caught on something in the middle of the night:-) you haven't
lost a hugely expensive sail.

K