How to fill leech of sail

[lindabarzini]

The leech of my mainsail just doesn't seem to hold air. When close-hauled in 10-15kts of breeze, most of the mainsail holds a nice full curve, but as the sail reaches the roach area, it starts flapping.

I can't figure out if the main halyard or outhaul needs more tension (it is an in-mast furling North Sail) or if the sail itself is simply blown-out (9-years old).

What is the best method to fill the leech/roach part of the sail for maximum lift?

[barnakiel]

It is an odd question. The way you put it, there can be a number of challenges. And so a number of good solutions.

Can you take a picture of the sail showing the problem?

b.

[Jim Cate]

Since it is an in-mast furling sail, it probably does not have any roach at all (unless equipped with vertical battens, which you did not mention). That being the case, the symptoms you describe indicate that the leech area is badly stretched, and either a recut or replacement will be required to cure the ailment.

Jim

[Panope]

Does this sail have a leech string?

Steve

[Don C L]

yes, tighten the leech line.

[Training Wheels]

Originally Posted by Jim Cate

Since it is an in-mast furling sail, it probably does not have any roach at all (unless equipped with vertical battens, which you did not mention). That being the case, the symptoms you describe indicate that the leech area is badly stretched, and either a recut or replacement will be required to cure the ailment.

Jim

^^^This!

[vmattiola]

1- Tighten leech line
2 - You're overtrimming. Ease traveler & vang a bit, tighten halyard & outhaul.
3 - Vertical battens?
4 - Recut

Personally, I envision this as an outhaul problem. For going upwind, I'd crank on the outhaul and make that sucker as tight as can be. No battens means it'll be tough regardless, but not impossible. I can see your roach curling wildly if the mainsheet is super tight, traveler centered, halyard tight, but outhaul loose.

Otherwise, tell your local loft and they'll take some extra canvas out of that leech.

[Stumble]

Jim is right, but if you can tighten the leech line it will help a bit. Eventually the leech line has to be pulled so tight it starts to cup, at which point it's probably better (faster at least) to let it flutter.

[barnakiel]

Originally Posted by Stumble

Jim is right, but if you can tighten the leech line it will help a bit. Eventually the leech line has to be pulled so tight it starts to cup, at which point it's probably better (faster at least) to let it flutter.

Oooops. IMHO, do not let anything flutter. Flutter kills the leech tape area.


b.

[Panope]

Originally Posted by Panope

Does this sail have a leech string?

Steve

I hope that when I asked the above question, no one thought I was countering Jim's assessment.

I do not know anything about marconi rigs.

I am genuinely curious:

Do all modern main sails have leach strings?

Do "roachy" mains have leech strings?

Do Full batten mains have leech strings?

Steve

[Sandero]

You should have a leech line in a pocket sewn into the leech which a cleat at the bottom As yoy tension the line you introduce a "curl" or tension into the leech.

Your leech is not straight and so as you tension it... it will take a curved shape. You want the entire sail to be a smooth continuous curve (air foil) with the tell tales on the leech streaming aft not curling or drooping.

Not a great pic but you can see the leech line pocket and at least one telltale streaming properly... and of course the curve of the leech.

[UNCIVILIZED]

The guys have already nailed down many of the issues, & their possible fixes. However if you have battens, you might try increasing the tension on them via the pocket closure system, if possible. It'll stiffen up the sail's roach by a wee bit, for a time.

Plus, if you can tension your battens, then you might also look at putting a stiffer set of them into the sail. Or laminating some S-Glass or Carbon onto them to stiffen them up. In addition to trying the adding tension to them trick.

And does this problem at all get better if you ease the Traveler a bit, while taking in on the Sheet slightly. Or vise versa? It's worth a try anyway. Though yes, I know, odds are it has been.


Panope, to answer your questions. All of them are yes, for the most part.

On the leech cord tightening, for those unfamiliar with what it is, & the terms used to define it, & it's effect. Cupping is when the cord's tightened enough so that the leech line pulls the loose fabric at the sail's trailing edge into a small "cup" type hook/pocket in the sail, with the cup (pocket) facing to weather/upwind. So that there's a big air brake on the sail's trailing edge. Which kills much of the smooth flow on the aft portion of the sail, sometimes significantly reducing it's production of lift.

[Jim Cate]

The guys have already nailed down many of the issues, & their possible fixes. However if you have battens, you might try increasing the tension on them via the pocket closure system, if possible. It'll stiffen up the sail's roach by a wee bit, for a time.

Unciv, it is a in-mast furling main... hard to increase batten tension when there are no battens!

Jim

PS I dunno if such sails usually have leech cords or not. With no roach, one could cut hollow (reverse roach) into the leech, and that tends to stop flutter... possibly even as a retrofit cut in this case, and that would not be expensive to do.

[UNCIVILIZED]

Jim, there are in mast furling mains which have battens. The battens are just vertical instead of horizontal is all. Much as are found on some jibs now as well, even RF jibs. But the mains had them first.

[Stumble]

Originally Posted by Panope

I hope that when I asked the above question, no one thought I was countering Jim's assessment.

I do not know anything about marconi rigs.

I am genuinely curious:

Do all modern main sails have leach strings?

Do "roachy" mains have leech strings?

Do Full batten mains have leech strings?

Steve

About the only sail where you won't see them at all is high end racing sails because by the time you need it the sail is getting replaced. All the leech line does is trim out stretch in the sail fabric, so for cruisers and club racers they can get more time between buying new sails. Basically unless you are going to buy a new sail evey 6-12 months they are a really good thing to have.

Eventually the sail is just too stretched out and instead of preventing the sail from fluttering it pulls a hook or cup in the leech. At which point even club racers should be buying replacements.