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

Merry Christmas to all!

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.

2 ways sails are shaped, luff round & broadseaming. Luff
round is the easiest to change, this is just a big curve
built into the front of the sail so that when it is hoisted
on a (relatively) straight mast, there is extra material in
the middle. Broadseaming is cutting the horizontal edges of
the panels in a curve so that the sail will form a 3-D curve
when the edges are sewn (or glued) together.


.... I agree, older material is probably not as strong as
newer but many sails arre very lightly used.

Well, between flogging & UV even a "lightly used" sail can
be shot.

.... Quite frankly, I simply
do not believe what sailmakers say about sails aging just by sitting on
a shelf.

Well, I'm not a sailmaker, and I told you (or tried to).
Believe what you want, it happens to be true.

... I also think that a considerable part of the stretch of an
older sail is in the stitching and not in th ematerial itself.

Certainly the stitching can loosen and give the sail a
baggier shape, but the stitches will not stretch. It's
strictly a one-way process!

... 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?

A couple of ways. One is to lay the sail out in a loft or
yard, and fasten the tack, foot, & clew at about waist
height with a line on each that can be tightened. Tension
the luff first, then lightly haul the foot up. Another is to
watch very carefully what the sail looks like when sailing.
Looking up from the midpoint of the foot, you should see a
nice classic airfoil shape, and you should be able to see
definite & consistent change when the "sail shape
adjustments" are pulled.

A blown-out sail will have one or more-

-max draft too far aft (IMHO 55%+ is shot)
-draft too deep even when sail is adjusted for max flatness
-Lack of response to shape adjustment
-Lack or elasticity, ie sail does not return to shape
consistently when shape adjustment eased
-hard spots in camber, particularly at inner batten ends (I
have seen many sails that were described by the owner as
"old but still got a lot of life" with upper sections
forming a V)

By reducing luff round, camber can be reduced but it also
shifts aft. If a sail is going to be restitched, the
broadseams can be adjusted but most sailmakers dislike doing
this. BTW it's not just the stitching, the cloth thru which
the stitches are sewn also lose strength. I have personally
used sails that have been restitched 4 times, when I took
them in for the 5th time the sailmaker said "Y'know Doug,
there's not enough cloth here left to sew" and showed me the
close network of holes from old stitching.

Blown-out sails will affect the boat badly-
-inconsistent helm, and excessive weather helm
-excessive heeling
-little or no acceleration in gusts
-poor windward performance, especially pointing
-slower

Old sails with weakened cloth & stitching are also at much
higher risk of shredding under load. I've had this happen a
number of times, too. It's a bummer.



K. Smith wrote:
The modern sail cloth is pretty strong & it will last years & years,

Actually, if you expose it to UV all day every day, and put
it under strain 24/7 it will last surprisingly short time.


.... It's
just the boy racers imagining they'll go lots faster with new ones

Spoken like a "sailor" who as 1- never won a race and never
will, and 2- has never sailed a tuned-up boat with good sails.



As to the shape this is not usually a problem

Wrong

If you want to check it just lay it flat on a floor

wrong

How the heck are you going to examine a 3 dimensional shape
laying it flat on a floor? Oh wait, you don't think shape is
ever a problem...

Proving once again that usenet is a great source of horribly
wrong info.

Fresh Breezes- Doug King

DSK wrote:
Merry Christmas to all!

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.


2 ways sails are shaped, luff round & broadseaming. Luff round is the
easiest to change, this is just a big curve built into the front of the
sail so that when it is hoisted on a (relatively) straight mast, there
is extra material in the middle. Broadseaming is cutting the horizontal
edges of the panels in a curve so that the sail will form a 3-D curve
when the edges are sewn (or glued) together.


.... I agree, older material is probably not as strong as
newer but many sails arre very lightly used.


Well, between flogging & UV even a "lightly used" sail can be shot.

.... Quite frankly, I simply
do not believe what sailmakers say about sails aging just by sitting on
a shelf.


Well, I'm not a sailmaker, and I told you (or tried to). Believe what
you want, it happens to be true.

... I also think that a considerable part of the stretch of an
older sail is in the stitching and not in th ematerial itself.


Certainly the stitching can loosen and give the sail a baggier shape,
but the stitches will not stretch. It's strictly a one-way process!

... 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?


A couple of ways. One is to lay the sail out in a loft or yard, and
fasten the tack, foot, & clew at about waist height with a line on each
that can be tightened. Tension the luff first, then lightly haul the
foot up. Another is to watch very carefully what the sail looks like
when sailing. Looking up from the midpoint of the foot, you should see a
nice classic airfoil shape, and you should be able to see definite &
consistent change when the "sail shape adjustments" are pulled.

A blown-out sail will have one or more-

-max draft too far aft (IMHO 55%+ is shot)
-draft too deep even when sail is adjusted for max flatness
-Lack of response to shape adjustment
-Lack or elasticity, ie sail does not return to shape consistently when
shape adjustment eased
-hard spots in camber, particularly at inner batten ends (I have seen
many sails that were described by the owner as "old but still got a lot
of life" with upper sections forming a V)

By reducing luff round, camber can be reduced but it also shifts aft. If
a sail is going to be restitched, the broadseams can be adjusted but
most sailmakers dislike doing this. BTW it's not just the stitching, the
cloth thru which the stitches are sewn also lose strength. I have
personally used sails that have been restitched 4 times, when I took
them in for the 5th time the sailmaker said "Y'know Doug, there's not
enough cloth here left to sew" and showed me the close network of holes
from old stitching.

Blown-out sails will affect the boat badly-
-inconsistent helm, and excessive weather helm
-excessive heeling
-little or no acceleration in gusts
-poor windward performance, especially pointing
-slower

Old sails with weakened cloth & stitching are also at much higher risk
of shredding under load. I've had this happen a number of times, too.
It's a bummer.



K. Smith wrote:

The modern sail cloth is pretty strong & it will last years & years,


Actually, if you expose it to UV all day every day, and put it under
strain 24/7 it will last surprisingly short time.


.... It's just the boy racers imagining they'll go lots faster with
new ones


Spoken like a "sailor" who as 1- never won a race and never will, and 2-
has never sailed a tuned-up boat with good sails.



As to the shape this is not usually a problem


Wrong

If you want to check it just lay it flat on a floor


wrong

How the heck are you going to examine a 3 dimensional shape laying it
flat on a floor? Oh wait, you don't think shape is ever a problem...

Proving once again that usenet is a great source of horribly wrong info.

Fresh Breezes- Doug King


Sorry Doug like most "customers" you have bought the sail maker BS,
most sails of the type we're talking about here, are cut lying staked
"flat" on the loft floor. (save the super new high tech materials &
laminates but they effectively mould the shape into them over a jig)

It's easy enough to confirm?? just lay the sail flat on a floor; or
measure the panels you'll find most "normal" sails have parallel panels.

The shape is induced when a curved edge (the luff or combination of
luff & foot) are stretched to varying degrees, in an essentially
straight line. (often along a forestay, mast, boom etc.)


K

Sorry Doug like most "customers" you have bought the sail maker BS,
most sails of the type we're talking about here, are cut lying staked
"flat" on the loft floor. (save the super new high tech materials &
laminates but they effectively mould the shape into them over a jig)

It's easy enough to confirm?? just lay the sail flat on a floor; or
measure the panels you'll find most "normal" sails have parallel panels.

The shape is induced when a curved edge (the luff or combination of
luff & foot) are stretched to varying degrees, in an essentially
straight line. (often along a forestay, mast, boom etc.)


K
Not! Each seam is cut on a curve and when sewn creates the sail shape,
unless you are sailing a sunfish or something. The most obvious example
is a spinnaker. Try laying that flat on the floor. None of my sails
lay flat except the storm jib.

Gaz