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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Head Sails Leach Line - What is it used for??

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HeelinPatrick
Navigator

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USA
102 Posts

Initially Posted - 02/02/2009 : 12:09:41

I see new head sails (jibs) often come advertised with leech line and cleats. I have yet to use a sail with leech line. What does it do, and how useful or nice is it to have it???

Patrick Moran
1981 SR/SK w/trailer
#2303 - "Chili Mas"
Lincoln, NE

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/02/2009 : 13:19:01

If you see some fluttering at the leach, that line can be tensioned slightly and cleated off to eliminate it. That flutter is said to create turbulence that adversely affects air flow (and it can be annoying). This is more likely with an older sail than a brand new one, so it's an investment for down the road. Don't tighten it any more than the minimum needed to remove the flutter--it can potentially cause the leach to "cup", which really messes up the flow.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 02/02/2009 : 13:36:34

In addition to leech lines, headsails may also be equipped with foot lines as well.

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Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 02/02/2009 : 14:10:09

Leech lines are standard features of all the good sailmakers. Even a new sail in perfect condition needs a leech line. Jibs and mainsails alike are cut and sewn so that they have a pronounced curved shape over all of their surface except the leech. The leech of a sail is very flat. When sailing in a strong wind, the pressure of the wind that is flowing over the leech of the sail can cause the leech to bend to leeward. When it intrudes into the stream of air flowing over the leeward (convex) side of the sail, the stream of air pushes the leech of the sail back the other way. When it intrudes into the stream of air flowing over the windward (concave) side of the sail, the leech is once again pushed back the other way. When it alternately and rapidly bends back and forth, first one way and then the other, it's called a "leech flutter." A leech line provides support to the leech, to prevent it from fluttering in that manner. Leech flutter can not only damage the sail, but it also disrupts the smooth flow of air over both sides of the sail, reducing the sail's efficiency.

Leech lines are easy to adjust. All you have to do is adjust them until the sail stops fluttering, and no more.

Edited by - Steve Milby on 02/02/2009 15:10:56

HeelinPatrick
Navigator

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USA
102 Posts

Response Posted - 02/02/2009 : 16:51:51

Huh, I thought maybe that's what they were for. I know my old 110 sure could use one, close-hauled it shakes the whole rig if I don't tighten it so the leech is against the side stay (just to dampen the fluttering). I would think in that case, the sail is so stretched, a leech line wouldn't be enough to stop the fluttering.

Thanks for the info, I'll see about getting them in future sails!

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Walt Oler
1st Mate

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USA
44 Posts

Response Posted - 02/02/2009 : 17:30:46

A sail shop has quoted us $100 to add a leach line to a "middle-aged" 110 jib. Is this a fair price and is an older sail worth the investment?

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John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 02/02/2009 : 17:42:09

I wouldn't.

If you're having the kinds of problems described above AND it really is making a difference in the enjoyment of your boat, AND your don't mind spending about 20% of the cost of a new sail so that you can make a slight change in the performance of an old one, then go ahead. Personally, I can think of a lot of other things I'd spend my limited boat units on first. I'd get it on the replacement sail though.

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pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 02/02/2009 : 18:38:24

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by HeelinPatrick
 I see new head sails (jibs) often come advertised with leech line and cleats. I have yet to use a sail with leech line. What does it do, and how useful or nice is it to have it???

<hr height="1" noshade id="quote"></blockquote id="quote">
Odd, I have never seen a keel boat sail without leech lines; bet you have'm.

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