How long should a sail last?

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How long should a sail last?

Postby GreenLake » Thu Jan 22, 2015 2:52 pm

I'm looking for a handle on the expected lifetime for a set of sails. The lifetime measure that I'm interested in is when a sail turns the corner so that it can no longer be trimmed correctly (but may still be far from "falling apart").

With a trailer-sailed boat like the DS, there isn't the same issue with UV degradation that someone would experience on a boat that is sailed on long passages, I'd imagine.

That seams to indicate that mere calendar age is a poor guide to where a sail is in its life cycle. You'd have to at least figure in the actual time sailed, and probably also the conditions.

How many hours do people put on their sails in a year? And how many years of useful life for a sail does that translate into?
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Re: How long should a sail last?

Postby K.C. Walker » Thu Jan 22, 2015 7:29 pm

Good question! You would probably want to add quality of the original sail and sailcloth quality and weight to the mix.

Top racing sailors would like to have new sails all the time as those last couple of percent of performance really matter. I hate old baggy sails, they just drive me crazy. But what is the turning point for the rest of us. I recall Phil Root in an old thread saying that he could still do pretty well against Thistle A class sailors even with his 20-year-old club sails. Some months back I watched a bunch of "Heavy Weather Sailing" videos at Yachting Magazine. The subject of the video was a guy who sailed in the southern oceans where 35 kn is sort of average wind speed. He said that well-made sails last them more than 20 years and that's a lot of hours sailing. When I first bought my boat the sails that came with it were not really crispy anymore (not soft though). I asked my local sail loft, which makes a lot of high-tech sails for Maxi boats, what sort of life they thought my sails had left. Their opinion for "cruising" was a while longer for sure.
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Re: How long should a sail last?

Postby diffusion » Thu Jan 22, 2015 8:20 pm

Well, the sails that I just replaced on my '82 (I think) DS were the 32 year-old original equipment sails. I sailed with them all last summer and while they are very soft and clearly no longer well-shaped, they were fully intact and I could still trim them well enough to get upwind fairly well. Can't wait to see how the new ones perform in comparison.
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Re: How long should a sail last?

Postby GreenLake » Fri Jan 23, 2015 3:41 am

Well, I made a similar experience with even older sails. They were usable after a fashion, but there were some conditions where they would no longer set at all, and most likely many more conditions that they were setting, but far from optimally - but not so that you'd notice without some other boat for comparison.

One example, for the jib in higher winds going upwind it was no longer possible to set it without the leech fluttering. Interestingly enough, the older sail felt like it was setting better in some very low wind conditions - it may be that it was lighter or softer so that it would require less wind pressure to fill. Hard to quantify without sailing two boats against each other so this is just my impression that I felt the new jib was a little trickier.

But going back. My impression is that I can't get my main as flat as I think it should be in some conditions and that the leech likes to develop a "hook", noticeable in light air conditions. The cloth has not softened to anywhere near what the old main had been, and I don't think the number of hours on it is all that great yet.
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Re: How long should a sail last?

Postby K.C. Walker » Fri Jan 23, 2015 4:22 pm

Mike Gillum says that he almost never uses the Cunningham and that he pulls the outhall full on at the dock and never adjusts it. Of course, he's using pricey new Skip Diebald sails which are probably cut near perfectly. He does use a powerful boomvang which helps considerably to flatten the mainsail out without putting as much leech tension on.

I don't know how much longer my sails will last. Last season I was definitely thinking they were showing their age. I don't have a hook in the leech but I do have vertical wrinkles between the battens. I find with my mainsail I can still get it reasonably flat by using the boomvang tension and also using relatively high rig tension. I do use the Cunningham to bring the draft forward and take some tension off the leech when necessary.

Some thoughts about getting the mainsail flatter. If you start out with some prebend in your rig setup this should help quite a bit. With your one-piece mast you could probably get prebend even without high rig tension by chocking the foot of your mast back before you attach your side stays. For my set up, I have to do it with high rig tension and tilted tabernacle. I go for about 1.5" at the spreaders. With prebend the mast becomes more flexible, especially under higher rig tension. It makes it much easier for boomvang tension to bend the mast further flattening the sail and opening the leech.

If your Jotz sails are still in good condition, cloth wise. It may be that they are stretched somewhat unevenly and could be adjusted at your sail loft.
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Re: How long should a sail last?

Postby GreenLake » Fri Jan 23, 2015 8:23 pm

Dieball sails are definitely a step up in price from Jotz. 8) The jib from one costs as much as the main from the other.

I don't play with the Cunningham much, tend to just tighten it enough to keep it off slack. I could see whether I can tell any draft moving forward.

Outhaul, I do play with a bit, there's a generous "shelf" sown into the sail, so even with a boltrope it has no troubles taking on a curve. We have more days at the transition between extremely light and light airs than I like, and for the very light airs, I just think the camber may be too deep. (Just my impression - perhaps I'm trying for the wrong shape).

I don't have a vang for upwind (it's on my list, but...).

What I don't understand is how a vang and a mainsheet would lead to differential tension at the leech. Is it because you are bending your boom?

As for mast bend, I don't think I get any. Will have to check next time. I have a mast jack, so moving the mast step is a bit involved.

I think a talk with the local loft is probably not a bad idea.
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Re: How long should a sail last?

Postby K.C. Walker » Fri Jan 23, 2015 9:04 pm

The difference between sheet tension and vang tension is pretty significant regarding leech tension. It's not the boom bending it's the mast bend. By pulling on the vang I can easily get 4"-5" of mast bend at the spreaders. In medium or heavy air this can really help flatten out the sail but keep the leech open. In light air it doesn't work so well. Outhaul really is the main adjustment for light air. I wonder if your foot bolt rope is shrunk somewhat? Can you pull on enough outhaul tension to get significant horizontal wrinkles along the foot above the boom? As I recall Bethwaite recommends 7% camber for light air and 10% camber for medium air and then back to 7% for heavy air. This is for the lower portion of the sail. It's definitely tricky to measure because you need to be sailing. However, you can observe what looks to be 7-8 inches of camber at the middle of the boom.

Are you using 4:1 or greater outhaul purchase?
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Re: How long should a sail last?

Postby GreenLake » Fri Jan 23, 2015 10:01 pm

Yes, after removing the single block and running the outhaul through the clew cringle I still get 4:1 purchase and I definitely can get a wrinkle in the foot of the sail. However, that wrinkle is below the "shelf" cut into the sail, so the sail itself still has a bulge. (I'll try to take some pictures next time I rig the boat, my guess is that I'm getting more than 10% camber). It looks like the boltrope alone isn't the limiting factor.

Mid girth is supposed to be 6'6" so 10" of that is indeed 7-8", but at the foot, it could be 1', (because the length of the foot is 10').

The sail did receive a repair after the clew got ripped out by a passing boat's anchor. Now I wonder it that lead to a slight and unintentional change in dimensions.

I'm taking part in a winter series, so I'll have occasion for more observations, but probably won't visit a sail maker until that is done. Would be too bad to have miss part of it while waiting for the sail :)

I was thinking I might rig a makeshift topping lift from an old halyard, just so I have a line that I can pull tight to get a straight line along the middle of the sail for comparison.
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Re: How long should a sail last?

Postby GreenLake » Mon Jan 26, 2015 4:28 pm

OK, checked it out in real conditions, in light winds, going 1.5kts boat speed and heeling the boat to leeward a bit.

One thing that I seem to notice is that the section of the sail where the battens are is flat, and it's bent as a whole further in, so there's almost like a "kink" connecting the forward end of the battens.

I get a a camber of 9", which looks large, but is about 7% of 10', and on the photos it looks like it's still forward of the mid point. So that's not as bad as I had imagined - 7% just looks deeper than it seems from the number.

The impression that the leech is hooked comes from the way the battens interact with the sail shape at the rear. Look at the top.

1960
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Re: How long should a sail last?

Postby K.C. Walker » Tue Jan 27, 2015 3:08 pm

Green Lake,

I see the "kink" along the front edge of the battens. I do wonder if the repair you had would have caused this. Because everything else is still in good shape, I think that is where I would suspect the problem came from. Hopefully when you get a chance to consult a sailmaker, especially if you show them that picture, they will be able to repair it. My guess is that although this does not look optimal, it probably doesn't have as bad an effect on laminar flow as you might think.

I had that problem with a former boat mainsail. That sail was tired, though. This is an example of where a full top batten better supports the leech and avoids this particular problem, extending the life of the sail.
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Re: How long should a sail last?

Postby GreenLake » Wed Jan 28, 2015 12:55 am

K.C., thanks for the input. 3 more weeks of the winter series to go. I also need to check that the battens aren't tapered (and if they are, that they aren't inserted the wrong way around).
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Re: How long should a sail last?

Postby K.C. Walker » Sat Jan 31, 2015 1:42 pm

Green Lake,

Un-tapered battens would explain the hard spot in the sail, as would reversed battens (might have done that myself). My previous boat that had the same symptoms in the mainsail did not have tapered battens. I bought replacement tapered battens and I especially tapered the top batten. The hard spot went away, but as I said, those sails were tired so the draft ended up too deep, especially at the head of the sail.
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Re: How long should a sail last?

Postby GreenLake » Sat Jan 31, 2015 3:14 pm

K.C., just went out to the boat to check. The battens are sown into the sail, so they are as delivered. Didn't unroll the sail to check that they are untapered, but most likely.

The repair at the clew replaced an 18"x15" piece of sail. Could the clew position have wandered a bit? It's impossible to tell. Sighting along the leech, it looks like a good continuation, and with full outhaul, I pretty much nail the class dimension of 10' from the mast.

Interestingly, the new(er) sail fabric now pretty well matches the rest of the sail, even in the number and distribution of little crinkles from handling. I had to look for extra seams to locate the repair. One of the backing pieces for the clew has a pattern of holes from unused seams. Could be that the sailmaker was able to re-use that piece, in which case, he'd effectively have a precise pattern. Overall, the cloth is still pretty stiff everywhere on the sail - it's one with the extra heavy threads every 1/4" in a rip-stop pattern.

In two weeks or so, I'll decommission the DS for the remainder of the winter season and would be able to show it to a local sail maker as planned. I'll need to troll through my photo collection to see if I have anything usable as a comparison shot, but I don't take pictures of the sails all that often.
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