Leech Flutter

Mar 10, 2015
62
Catalina 30 Moss Landing, CA
Car father forward?

But the probable cause is that the jib's luff does not have enough hollow.

Headsails are cut with negative roach (hollow) so the leach does not flutter. Jibs are allowed to have less, and often the sailmaker cuts it too flat and flutter occurs. I would ask your sailmaker to recut the leach, or add vertical battens. He knows bettter. This is a common problem.

This jib would flutter with this much roach without battens.

Beautiful sails, Jd,, that can really be flattened to "climb the wind"!

When we took off cruising on our '93 F-P Antigua 37 cat 20 years ago we had UK build a fully battened furling jib with a nice roach to replace the small, scooped-leach Solent jib. Two full length vertical battens and two partials gave us about 25% more area with same overlap, and a very nice set when reefed to either of the full battens. Over 20,000 nm's on it and no flutter with mod. L-L tension when we sold her in '01.
Pete
 

Dan_Y

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Oct 13, 2008
514
Hunter 36 Hampton
Had a dacron rf 135 made for our previous '91 h30 by a local sail maker and did not have leech flutter issue that couldn't be stopped with light leach line tension. The 135 was pretty heavy Dacron compared to the sails that came on our b36. I can't remember what ounce weight the fabric was, but I wonder if the thinner, stiffer fabrics used by racers make them more sensitive to the luff hollow cut. I occasionally had to just snug the leach line on the 135 as the wind pick up, at which point I started to furl some in since it was a fractional rig.

Is there sensitivity to the leech cut (hollow) based on fabric and weight used?
 
Jan 22, 2008
763
Hunter 340 Baytown TX
Not really a lot to update on the leech flutter on my new jib. The sailmaker installed a Kevlar leech line last week because he felt the dacron line was stretching in high winds when tightening it would not get rid of all the flutter. But I still think tightening the leech line puts way too much windward hook in the leech (see photo below) and is not the answer. He wants me to do some adjustment to the shrouds to tighten up the headstay. The rig was tuned just 3 or 4 months ago, but I'll try to put a couple turns on the outside turnbuckles. And I don't need to show this photo to the sailmaker, he took it.
IMG_9356 (2).JPG


But he did come and remove the mainsail, recut it to get it the right height, bring it back to the boat, and help put it back on. It now seems to be the correct. You can see the new panel in the photo.
20170216_173645 (2).jpg
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
And I don't need to show this photo to the sailmaker, he took it.
View attachment 132919
Glad he got you sorted on your main. But wow, I would have thought that any sailmaker would have been embarrassed to see and show this picture. What's wrong with that sail is SO obvious. Dyneema leech line? That's ridiculous. Its the fabric BEHIND the line that is vibrating, because there is too much of it. Tightening the line will not help that.
 
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Jan 22, 2008
763
Hunter 340 Baytown TX
Dyneema luff line
Now I'm a little confused, I say "leech line" and you say "luff line". Are we both talking about the trailing edge of the sail?
I always thought the "leech", or "leach" as some spell it, is the trailing edge of the sail, and the "luff" is leading edge.
And I did suggest removing some of the trailing edge, making it more "hollow", but the sailmaker dismissed that.
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Now I'm a little confused, I say "leech line" and you say "luff line". Are we both talking about the trailing edge of the sail?
I always thought the "leech", or "leach" as some spell it, is the trailing edge of the sail, and the "luff" is leading edge.
And I did suggest removing some of the trailing edge, making it more "hollow", but the sailmaker dismissed that.
You're right of course. I had a million things on my mind when I typed that!
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
And I did suggest removing some of the trailing edge, making it more "hollow", but the sailmaker dismissed that.
Really? Ask him how much hollow (as a %) de designed into the sail.
 
Jan 22, 2008
763
Hunter 340 Baytown TX
I now have another new sail with issues to work out. There's a few problems with our new code 3. But to be real about it, problems with new sails are not really "real life" problems and are a lot more fun to talk about than legal, marital, money, or health problems.
While out on the bay testing the new A-sail, I found the jib sailmaker had rigged the leech line so it can't be eased unless I cut it, so I'm stuck with the leech hook until I go another round with him about the leech flutter.
Most of the issues with the A-sail from a different loft, ended up being operator error. The sock from my old sail is too small and jams up, so I probably need to bite the bullet and buy the next size up. And the thread about whether a sock is necessary, I say yes, because you will use the sail with a sock way more and not use crew or conditions as an excuse not to fly it.
I'm unsure what to do about the sail cloth manufacturer substituting for a discontinued color cloth to the loft and they didn't catch it and made the sail anyway. It's still a beautiful sail, just the difference between blue and navy blue. But, if you ordered a new navy blue car from a dealership and went to pick it up and it was royal blue, what would you do?
A friendly power boater (is that an oxymoron?) took some photos and texted them to me from our test sail yesterday. In the very light winds, it set from 55 to 155 degrees apparent, but I need to see what it does in 12 to 15 knots.
IMG_9376.JPG
 
May 26, 2015
10
Catalina 30 & 22 Kemah
Bill,
To your first question, that leech hollow does seem a little flat to me. Is he still taking care of you under warranty? We'll help you out with it if you need it. A dyneema leech line shouldn't be a big deal. We've gone to a braided line to attach to the cleats ourselves.

The windward hook however is bad, really takes power off the exit of the sail. Its bad enough that in our sail trim class we specifically point it out as something to avoid. The amount of tension of it will change from breeze to breeze, so it's common to be out in a 15-20kt day and you've put a lot of tension on and next week its 3-0 and the tension is still there so it hooks badly. I know that's not what you were talking about, just wanted you to know.

Ok guys, sorry but I'm going to have a mini hijack on the thread here. It should be obvious Bill and I know each other. And he's a great guy. We're willing to admit when we make mistakes and try to find solutions that make everyone happy.

You have no idea how bad we feel about that blue. The second I saw your email I went on a tirade in my office on the phone with them. T thought I was going to blow a gasket so he made me go calm down before I wrote you back. T told me on Tue? Wed? Thur? we'd remake it if we could get our hands on that color, but i couldn't even find pieces. And we will admit our receiving processes and who we used to buy the cloth from was outside our norms. Even though that didn't put us in a good place to catch it, we dropped the ball there and humbly apologize.

If you want the other sock, let me know. I'll work something out for you, you won't pay retail.

K
 
May 26, 2015
10
Catalina 30 & 22 Kemah
My new jib with a sunbrella UV protector does the same thing when the wind gets to around 15k apparent and I'm only having this problem on port tack. I've tried all the setting adjustment with no effect (mast is straight). Tightening the leech line is the only solution.
To me it does look like the wind is catching the edge of the UV protector when on port tack but some of you are suggesting there may be another cause. Calling the sailmaker is on my to do list.
I reread this and ran it by the loft owner/sail designer I consult with (Yes Bill I'm technically a consultant there). This seems weird to both of us. Have you check that the car position is in the same place on either side? (Measure it from the stem fitting on the boat to make sure. Tracks often are off just a bit.)

Also, have you made sure the rig is straight and the top of the mast is in the center of the boat? Don't know if that'll help you out or not. You have a weird one.
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
My new jib with a sunbrella UV protector does the same thing when the wind gets to around 15k apparent and I'm only having this problem on port tack. I've tried all the setting adjustment with no effect (mast is straight). Tightening the leech line is the only solution.
To me it does look like the wind is catching the edge of the UV protector when on port tack but some of you are suggesting there may be another cause. Calling the sailmaker is on my to do list.
That is weird. Even if the mast was not perpendicular with respect to the deck, you would think you could trim it out on port if you could trim it out on starboard.

Assuming your cars in the same position on the track, MEASURE the straightline distance from the car to the forestay, and the straightline distance to the cenerline of the boat. Compare Port vs Starboard. Could be your tracks were installed out of alignment.
 
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meb135

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Nov 17, 2012
92
Hunter 33 Shediac Bay
Svquest & Jackdaw. thanks for the suggestions. My mast is re-stepped every spring and I make sure that the mast is straight all around. So I don't think that is the issue, but I'll recheck in the spring and I will measure the distance between the car and the forestay to see if there's a difference between the two.
The sunbrella fabric is on the windward side when on Port tack, which makes me wonder if the problem could be with the fabric, although it looks pretty stitched.
 
Jan 22, 2008
763
Hunter 340 Baytown TX
As far as the leech flutter on my jib, that started this thread goes, I have now been told that it is what is to be expected from this "high aspect" sail and if I don't want the flutter, tighten the leech line. And the big windward hook you get when you tighten the leech line enough to get rid of the flutter, is not a problem and doesn't affect sail performance, so live with it. And if I don't like that answer, then it's my boat that's the problem.
Not sure what I'll do next, but these sails were a very big purchase for me and I need them to last. The extreme flutter will eventually ruin the sail and the big windward hook ruins performance, so I'm going to do something, even if it means paying another loft to solve the issue.
If you're thinking about buying sails on the Texas Gulf Coast anytime soon and want to know more, send me a private message.
 

JRacer

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Aug 9, 2011
1,331
Beneteau 310 Cheney KS (Wichita)
Well, that's very disappointing to hear given that I know and have done business with the loft involved.
 
Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Wow. Well anyway here is an experiment you can do at home.

Spread the sail out with the corners sorta tightly pulled. You will notice the leech has a hollow, vs the straight line distance (between 12-1) this prevents unsupported sailcloth, which is what causes flutter. Measure it, it should be 6 percent? Someone one else might know, but it depends. If there is very little you have a problem.

Then go down the leech and make sure it is tight. The hollow should case that. In particular, you do not want to area were the sailcloth is pulled tight BEHIND the luff, leaving it unsupported.

hollow.png
 
Jan 22, 2008
763
Hunter 340 Baytown TX
Thanks again everyone for the advice. I've learned a lot and it will help if I ever buy sails again.
I'm actually impressed with the construction and some of the details of the jib and mainsail made in Sri Lanka. But if they weren't measured or designed right, that doesn't make them good sails for my boat. I'm sure the local rep is an accomplished sailor, but someone really messed up with my sails. As far as I can tell, the advice and excuses, I know and they know are BS. I guess they figured I wouldn't know or care because my boat is just a Hunter and they probably won't sell me a lot more sails. And it's difficult to admit screw ups, their company will continue to prosper whether or not they make my sails right.
But I'll show them, when I win the Powerball lottery and have a fleet of racing and cruising boats, I won't buy any of my sails from them!