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transient View Drop Down
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    Posted: 31 Mar 15 at 2:54pm
I've noticed that on some dacron jibs the trailing edge has a folded stitched hem on others it's a plain cut edge.

Is this a class rule thingy?

A cost cutting thingy?

A performance turbulence reduction thingy?

Edited by transient - 31 Mar 15 at 2:55pm
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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 31 Mar 15 at 3:23pm
Hot cut leach its called. A tabled edge lasts longer, a hot cut leach might be microsocopically less drag. I shouldn't be at all surprised if the panel layout had an influence over how desirable the tabled edge is, but I'm not a sailmaker and don't know.
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Posts: 715 		Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 31 Mar 15 at 4:01pm
Ah.. tabled edge and hot cut. Nice to know what these things are called. Ta, I was curious.

most jibs that I've noticed the hot cut leach on are cut from one panel and I didn't think it would be much different drag wise. 

I was just cleaning my Hyde RS200 jib which is relatively new. Top 9 and bottom 18 inches or so are tabled the rest is hot cut

I suppose it saves a tiny bit of material and a bit more labour but not much of either. It must reduce the longevity of the jib a fair bit though? 
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Posts: 705 		Post Options Post Options   Quote Steve411 Quote  Post ReplyReply Direct Link To This Post Posted: 31 Mar 15 at 5:02pm
A tabled leech will no doubt last longer, but the leech will stretch less than the rest of the sail so you may end up with too tight a trailing edge. A hot cut leech will avoid this but you may end up with flutter as the leech stretches a bit with age. That's what I always understood, but probably the real reason for a hot cut leech is that it's cheaper.
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Posts: 929 		Post Options Post Options   Quote Paramedic Quote  Post ReplyReply Direct Link To This Post Posted: 31 Mar 15 at 8:03pm
when you get flutter take it back to the sailmaker. They will recut the leech and it'll be almost as good as new.
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Posts: 9 		Post Options Post Options   Quote dynamicsails Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 15 at 12:07am
a fold or tape with leech line will last and suit higher loaded leeches but there are some performance gains to be had with the difference approaches, class rules and requirements are the main reasons for the different finishes

say for a cadet or mirror jib then hot cut is fine as the spec in the fabric is high enough to cover the missing layers of tape or fold

saying than I've made Star sails with hot cut leeches but then they don't expect the sail to maintain the shape for so long before they replace with a fresh sail

the leech on some jibs are very flat exit say a 470 jib, very rounded entry and flat through the leech, I used to use a meter ruler to check they were not inverted (very tricky sail to stick well), if I put a fold or tape on this leech then you'd likely see a return on the leech so loosing the gains of the shape and clean exit

worth checking leech lines are released in light winds and tightened a little in breezy sailing
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Posts: 715 		Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 15 at 12:03pm
As I say, I was curious. Thanks for the good info folks. :-) 

Looking at a very old 200 jib the hot cut leech is fine, no apparent stretching. The area around the tack reinforcement is baggy as hell though.

I guess there's a very slight saving on materials and labour + a slight improvement in performance......It makes good sense.
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Posts: 9 		Post Options Post Options   Quote dynamicsails Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 15 at 10:57pm
I wouldn't say there is any saving in money terms as the seams need reinforcing and also time taken to heat seal the cut edge, also the seams should have some kind of extra stitching or flutter patches. A fold with no line is probably the most economical finish but would use more material making the sail so depending on the material used works out similar
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