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One for a sailmaker...radial v crosscut

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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 06 at 7:00pm
Originally posted by Ian99

On the subject of the batten pocket crease, given that it never occurred with dacron sails which are like elastic compared to Kevlar cloth



It didn't? Are you sure? I've seen planty of tired old dacron sails with batten poke, although I can't especially recall whether any of them were Fireball ones.
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Post Options Post Options   Quote a_stevo Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 06 at 10:48pm

i agree with stefan and rick on this.

in high load, big sails the of axis loads can be a major issue. in dinghys it is marginal.

best bet in my opinion is to split the difference.

-use a cloth with a diagonal warp as well as the major fibres, for stability.

-then align the back half of the sail with the leach and the front half with the luff.

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Post Options Post Options   Quote Stefan Lloyd Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 8:12am

Originally posted by Jack Sparrow

by the way Steffan kites aren't just made from Ripstop.

What are they made of? I admit it is a few decades since I bought a kite. (We are talking actual kites here, not spinnakers.)

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Paramedic View Drop Down
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Post Options Post Options   Quote Paramedic Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 8:31am

The main issue with most kevlar cloths is that the mylar laminate is too thin, it has almost no resistance to creasing and breaks down very quickly.

Even if the sails are handled with kid gloves their lastability is unacceptable for an item that costs 600+.

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Post Options Post Options   Quote Jack Sparrow Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 9:46am
Originally posted by Stefan Lloyd

Originally posted by Jack Sparrow

by the way Steffan kites
aren't just made from Ripstop.


What are they made of? I admit it is a few decades since I bought a kite.
(We are talking actual kites here, not spinnakers.)



Ripstop - many types ( Carrington K42 e.t.c )
Dacron's
Mylar laminates
Nylon mesh venting
Dyneema / Spectra (anti leech motivators e.t.c)
A myriad of carbon and fibreglass tube types

Loads of stuff in fact.

What's more when you have put all that together it needs to fly.
but not only fly, fly in a particular fashion to your design brief.
especially if you are developing stunt kites -
( competition, trick of team )

why not go here : http://www.kitebuilder.com/plans/sport.htm
and have a go yourself. It's a lot of fun and you can learn a lot.

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Post Options Post Options   Quote Isis Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 11:24am
Originally posted by Paramedic

The main issue with most kevlar cloths is that the mylar laminate is too thin, it has almost no resistance to creasing and breaks down very quickly.

Even if the sails are handled with kid gloves their lastability is unacceptable for an item that costs 600+.



Im not sure about unaccetable.. How long does a far more expensive F1 engne last? a race? but from that you get far better performace than one designed to cope with several seasons.
If you choose the grater performace of a laminate sail you accept it will tend to have a shorter lifelifespan... if you dont like it stick with dacron.
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Post Options Post Options   Quote Paramedic Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 12:40pm

Originally posted by Isis


Im not sure about unaccetable.. How long does a far more expensive F1 engne last? a race? but from that you get far better performace than one designed to cope with several seasons.
If you choose the grater performace of a laminate sail you accept it will tend to have a shorter lifelifespan... if you dont like it stick with dacron.

The far more expensive formula 1 engine is being used by professional drivers and is not paid for out of the driver's pocket.

I'm not even sure that Kevlar laminate performs any better than the older - albeit slightly heavier - polyester laminate we were using 5 years ago, but the big differance is you could get a full competetive season out of a polyester scrim sail. Some people are changing Kevlar sails after about 3 months use. (To be fair the very top sailors probably did with polyester then too).

There are many laminate alternatives to kevlar, but for some reason people seem unwilling to try them. It strikes me that as far as practicality goes the kevlar cloths on offer are unsuitable for dinghies becasue it is impossible to prevent the creasing that casues so much harm. The polyester scrim cloths seemed to have more mylar and resisted the cracking much better.

Interestingly back on topic, many classes that have tried radial cut mains have now gone back to crosscuts or hybrids.

Norths make a very odd looking radial jib for the Enterprise.



Edited by Paramedic
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 2:05pm
Originally posted by Paramedic

The far more expensive formula 1 engine is being used by professional drivers and is not paid for out of the driver's pocket.


Sure, but when I was periphally involved with bike racing a set of pistons were worth 250 miles and a crankshaft rebuild every 2000... That is not a lot of races and that was coming out of the riders pocket.

I've never use kevlar sails, but the carbon/mylar sails on my last Cherub seemed to be lasting fine no probs when I sold them after two and a half seasons. However they were full battened sails which don't suffer from the batten poke problem anyway.

Edited by JimC
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Ian99 View Drop Down
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Post Options Post Options   Quote Ian99 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 06 at 7:22pm

Dacron racing sails lasting longer than kevlar is a myth. True, the absolute "life" of the sail, (the time until it falls apart) is much longer for a dacron sail, but after a season's use a dacron sail is well past its best. You can still make it look nice for photographs by doing tricks like pulling the cunningham on, but the performance is rubbish compared to a season old kevlar sail.

The Kevlar main on my Fireball (incidentally with a radial bottom section and cross cut upper) has been used for 2 Europeans, 2 Nationals and a Worlds, loads of windy opens and quite a bit of club racing, and hasn't really changed in shape very much even though the cloth hardly looks new any more! I doubt you'd get that much out of a dacron sail.

You do have to look after them, and not do stupid things like leaving them flogging on the jetty or routinely drying them out in direct sunlight, but I'd never go and buy dacron sails if there's an option to get something better.

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