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Evaluating old sails
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 |
#2
posted to rec.boats,rec.boats.cruising
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Evaluating old sails
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 |
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