Mainsail Leech Flutter

[Howler]

We have a three-year old Neil Pryde furling main with vertical battens. This is the standard issue for most recent Beneteau cruisers. The leech flutters more than it should. I've tried all variations of sail trim, tweaking the outhaul, the vang, the mainsheet and combinations thereof. The only thing that really works is cinching down the leech line. However this creates a sort of bow shape in the leech that can't be optimal. I believe the standing rigging is properly set up. Is the sail just poorly cut? Is there something else that can be done? Thanks!

PS - I know a furling main will never have the nice shape of a fully battened main, but it should be better than it is.

[a64pilot]

Sorry to be insulting, but if there is a topping lift be sure it’s loose.

[MicHughV]

took the words out of my mouth...

[Howler]

Originally Posted by a64pilot

Sorry to be insulting, but if there is a topping lift be sure it’s loose.

Not insulting at all. Forgetting to loosen the topping lift while vanging down has happened (in my foolish youth)! But this time, that wasn’t the culprit.

[psk125]

The sail may have stretched over the span of three years. What does your sailmaker say?
(Other than you should buy a new sail ).

[gonesail]

you could have another sail made of heavier canvas?

[wingssail]

Originally Posted by Howler

We have a three-year old Neil Pryde furling main with vertical battens. This is the standard issue for most recent Beneteau cruisers. The leech flutters more than it should. I've tried all variations of sail trim, tweaking the outhaul, the vang, the mainsheet and combinations thereof. The only thing that really works is cinching down the leech line. However this creates a sort of bow shape in the leech that can't be optimal. I believe the standing rigging is properly set up. Is the sail just poorly cut? Is there something else that can be done? Thanks!

PS - I know a furling main will never have the nice shape of a fully battened main, but it should be better than it is.

A straight exit (leech) on a main gives better power power but a leech line is required to prevent flutter between the battens. If this does not work for you my guess is that the leech area of the sail has stretched. The leech line should only make a small hook at the very edge. if you are getting a big curve at the back of the sail it is too full, too much cloth. A sailmaker can open up some of the seams and take up some cloth. This is not expensive. It may extend the life of the sail. If you have a sewing machine and a place to work on the sail you could do it. After getting an eyeball of at the sail when the leech line is tight, (and take some photos) you can guess how too deep it is. Just as a rough starting point, open up three feet at each horizontal seam and sew it back up with 1" more overlap in the middle of the seam, tapering to each end of the seam you opened up. (or take it to the loft and they will do the same thing).

[grantmc]

Originally Posted by a64pilot

Sorry to be insulting, but if there is a topping lift be sure it’s loose.

Like who's stupid enough not to remember to let the topping lift off?
I've been racing sometimes, absolutely frustrated that the boat isn't sailing as it should be and the main shape is wrong, then suddenly realisation!
So easy to miss, oh and the feeling of how stupid am I?

[Dockhead]

Originally Posted by Howler

Not insulting at all. Forgetting to loosen the topping lift while vanging down has happened (in my foolish youth)! But this time, that wasn’t the culprit.

Oh, yeah, of course, that's never happened to me!

[Howler]

Originally Posted by gonesail

you could have another sail made of heavier canvas?

Good thought, but one of the disadvantages of furling mains is they have to fit in the mast when rolled up. I don't think there's much margin for expansion due to heavier canvas.

[Howler]

Great input, all. And I appreciate the humility in this thread from all those who have also had tugs of war between vang and topping lift and were willing to admit it :-)

[Dockhead]

Originally Posted by Howler

Good thought, but one of the disadvantages of furling mains is they have to fit in the mast when rolled up. I don't think there's much margin for expansion due to heavier canvas.

Indeed. A much better plan is thinner, more flexible laminate.

[Howler]

Originally Posted by wingssail

A straight exit (leech) on a main gives better power power but a leech line is required to prevent flutter between the battens. If this does not work for you my guess is that the leech area of the sail has stretched. The leech line should only make a small hook at the very edge. if you are getting a big curve at the back of the sail it is too full, too much cloth. A sailmaker can open up some of the seams and take up some cloth. This is not expensive. It may extend the life of the sail. If you have a sewing machine and a place to work on the sail you could do it. After getting an eyeball of at the sail when the leech line is tight, (and take some photos) you can guess how too deep it is. Just as a rough starting point, open up three feet at each horizontal seam and sew it back up with 1" more overlap in the middle of the seam, tapering to each end of the seam you opened up. (or take it to the loft and they will do the same thing).

I talked to a (i.e. the only) local sailmaker. He came up with the same idea as above. We'll have it done over the winter. Thanks again.

[Montanan]

Have you adjusted the leech line?

https://www.uksailmakers.com/cruisin...ech-line-genoa

"Adjusting the leech and foot lines is easy. Just snug them enough to stop the flutter. When the wind dies, you may see a hook in the leech or foot. In that case, ease the leech or foot line until the sail flutters and then put just enough tension on the line to stop the flutter."