Kevlar

   Most laminate sails use Mylar but I'm not sure about Kevlar sails as I've never owned one. Mylar is another trade name I'm afraid - the stuff is actually called biaxially oriented polyethelene terephthalate and it's used because it's tough and chemically very stable.  Get in touch with North Sails - they do a lot of the hi-tech stuff. Also I see that Y&Y have a feature on sail technology in the next issue. In the UK, Hyde sails are very approachable, give them a call.
The idea behind all composite materials is that the fibres of the reinforcement material, whether it be glass, carbon or kevlar are aligned to give they greatest tensile strength in the desired direction. The matrix is the "filler" and is there to keep the fibres in the right position and transfer the load if a single fibre breaks. In the case of sails, Kevlar is the reinforcement and Mylar the matrix. For GRP the glass fibres give the strength and the resin (epoxy or polyester) fills the gap.
Because woven materials have the weft and weave at right angles, sail makers can create strength in particular directions by stitching together panels in different orientations. North's 3D technology enables the whole sail to be laid up in one go so no panels are needed. In theory. However, this is expensive to make and one tear trashes the whole sail rather than a panel so those of us without Americas Cup budgets tend to go for a compromise.
Hope this helps. If there are any mistakes in the above I'm sure someone else will correct them.

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English Dave Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 10 Aug 06 Location: Northern Ireland Online Status: Offline Posts: 682	Post Options Post Reply Quote English Dave Report Post Quote Reply Topic: Kevlar Posted: 19 Oct 06 at 10:55am
	Most laminate sails use Mylar but I'm not sure about Kevlar sails as I've never owned one. Mylar is another trade name I'm afraid - the stuff is actually called biaxially oriented polyethelene terephthalate and it's used because it's tough and chemically very stable. Get in touch with North Sails - they do a lot of the hi-tech stuff. Also I see that Y&Y have a feature on sail technology in the next issue. In the UK, Hyde sails are very approachable, give them a call. The idea behind all composite materials is that the fibres of the reinforcement material, whether it be glass, carbon or kevlar are aligned to give they greatest tensile strength in the desired direction. The matrix is the "filler" and is there to keep the fibres in the right position and transfer the load if a single fibre breaks. In the case of sails, Kevlar is the reinforcement and Mylar the matrix. For GRP the glass fibres give the strength and the resin (epoxy or polyester) fills the gap. Because woven materials have the weft and weave at right angles, sail makers can create strength in particular directions by stitching together panels in different orientations. North's 3D technology enables the whole sail to be laid up in one go so no panels are needed. In theory. However, this is expensive to make and one tear trashes the whole sail rather than a panel so those of us without Americas Cup budgets tend to go for a compromise. Hope this helps. If there are any mistakes in the above I'm sure someone else will correct them.
	English Dave Ballyholme Yacht Club (You'd think I'd be better at it by now) Hurricane 5.9 SX RS700

Harry44981! Send Private Message Find Member's Posts Really should get out more Joined: 26 Aug 04 Online Status: Offline Posts: 736	Post Options Post Reply Quote Harry44981! Report Post Quote Reply Posted: 18 Oct 06 at 4:43pm
	Another question: the Kevlar are the actuall gold thread in the sail the take the strainin the sail. What is the water-resistant laminate that goes either side of the fibres generally made from?

Harry44981! Send Private Message Find Member's Posts Really should get out more Joined: 26 Aug 04 Online Status: Offline Posts: 736	Post Options Post Reply Quote Harry44981! Report Post Quote Reply Posted: 17 Oct 06 at 9:17pm
	Cheers for the tips guys- really helped with my research

English Dave Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 10 Aug 06 Location: Northern Ireland Online Status: Offline Posts: 682	Post Options Post Reply Quote English Dave Report Post Quote Reply Posted: 17 Oct 06 at 2:03pm
	Harry Aramid is the scientific name for Kevlar, Wombat is right. It is used as the fibre matrix in laminate composite sails because it is light for its strength and does not stretch or creep. Unfortunately it is degraded massively by UV light and doesn't get on well with salt and abrasion. So it's important to encase it well and make it the middle part of the sandwich. Dacron is another trade name for a polyester cloth that is the basis for most traditional boat sails (Laser, Topper, etc). It doesn't give the same strength to weight ratio as composite but it is cheaper and less fragile. For this reason, even on high perfromance boats, it is often used for jibs which will spend more of their lives flapping than a mainsail. Kevlar ropes are a nightmare to work with as they are difficult to cut and kevlar doesn't melt so heat-sealing a line is difficult. Also, becasue they don't stretch or creep, you get no warning before they do fail. So don't use Aramid-cored ropes for climbing.
	English Dave Ballyholme Yacht Club (You'd think I'd be better at it by now) Hurricane 5.9 SX RS700

combat wombat Send Private Message Find Member's Posts Far too distracted from work Joined: 16 Jan 06 Location: United Kingdom Online Status: Offline Posts: 345	Post Options Post Reply Quote combat wombat Report Post Quote Reply Posted: 16 Oct 06 at 10:45pm
	Harry remember "Kevlar" is a registered trademark... don't get sued for trademark infringment!
	B14 GBR 772

Strawberry Send Private Message Find Member's Posts Visit Member's Homepage Really should get out more Joined: 21 Jun 05 Location: United Kingdom Online Status: Offline Posts: 1337	Post Options Post Reply Quote Strawberry Report Post Quote Reply Posted: 16 Oct 06 at 5:53pm
	Does this help: http://www.cherub.org.au/choosingrags.html
	Cherub 2649 "Dangerous Strawberry

m_liddell Send Private Message Find Member's Posts Really should get out more Joined: 27 May 05 Location: United Kingdom Online Status: Offline Posts: 583	Post Options Post Reply Quote m_liddell Report Post Quote Reply Posted: 16 Oct 06 at 5:45pm
	Carbon now seems to be getting use in sails too. I understand the properties of each but nothing about sail design. When would one would be desirable over the other in a sail?

Ian99 Send Private Message Find Member's Posts Posting king Joined: 07 Apr 05 Online Status: Offline Posts: 138	Post Options Post Reply Quote Ian99 Report Post Quote Reply Posted: 16 Oct 06 at 4:03pm
	You might find this useful... http://www.sail-making.com/dbimgs/1%20All%20About%20Sailclot h%20End%20User.pdf There are others on there as well.

Harry44981! Send Private Message Find Member's Posts Really should get out more Joined: 26 Aug 04 Online Status: Offline Posts: 736	Post Options Post Reply Quote Harry44981! Report Post Quote Reply Posted: 16 Oct 06 at 3:55pm
	Didn't know where to put this really. For my AS Physics coursework I'm doing a presentation on Kevlar, it's properties and uses (particularly for sails). I was thinking of comparing it to other materials eg: dacron. Have any of you got any information/links/contacts that could give me soem usefull info (i know the next issue of Y&Y will probably help.) Cheers harry44981@tiscali.co.uk