Kevlar vs. Carbon

[jadkkd]

I will be buyibg a J100 sailboat to do some racing next year. I'm wondering if carbon sails are a better option than kevlar sails because they last a bit longer. Any opinions on wear, performance, flaking, etc.?

[arbarnhart]

I am confused; I thought Kevlar was the original and still best known brand of carbon fiber and that they are one and the same.

[Idiens]

Carbon fibre is what it says it is - fibre made out of the element carbon. Kevlar is a Du Pont trade name for an Aramid fibre. I read Kevlar looses a bit of strength when wet. So maybe a reason to choose carbon.

[Melrna]

Both have an affinity to water if the threads are not treated. Kevlar more than carbon. Both sails are encapsulated in Mylar or other materials to keep the water out. Either sail would work on a race course. If my memory serves me correct, Carbon sails are lighter. I only know this because I worked for DuPont in composites back in the 80's. We heated both materials to over 450 degrees to get the water out of the threads before treating them with resins. Most water incursions ,if any, in these racing sails accrue in the sewing threads.

[sailingdog]

Carbon fiber is an acrylic-based material which is progressively heat treated to eliminate all but the carbon, primarily nitrogen and hydrogen. It has good strength in both compression and tension. It is very UV-resistant, but can be brittle, depending on the exact formulation of the carbon fiber. The less brittle, more flexible formulations are generally higher stretch than their more brittle counterparts. Newer carbon fiber sails pair the carbon fiber with kevlar, spectra or vectran to help reduce stretch while minimizing the sail's brittleness.

Kevlar is an aramid fiber (a chemical linkage of -CO-NH-), which is often used in bulletproof vests. It has good strength in tension, but has little strength in compression—you can't push on a rope.

Kevlar has low UV-resistance compared to Dacron sails, and is far more vulnerable to mechanical damage and fatigue from flogging, folding, and flexing. Care should be taken to minimize flogging when sailing and to roll the sails when storing.

The newer carbon fiber laminates will probably outlast the kevlar ones, with similar performance characteristics. They're gonna cost you some boat bucks though.

[Hardonwind]

Carbon threads are black and Kevlar threads are yellow. Carbon does not stretch nearly as much as Kevlar does. Typically a carbon sail will look great and sail just as fast as new over the life of the sail. Right up to the day that the sail blows up. Kevlar will stretch/creep with use and the draft on the sail will shift to the rear and the sail will not be as fast. I have a barn full of old Kevlar 3DLs that are worthless as race sails (because the max draft location has moved) but they still look pretty good to the untrained eye. With carbon sails I can race them until the day they explode. Carbon is much more sensitive to flogging because the fibers will crack and it is better in non-overlapping head sails where the tacking is easier on the sail. Because the carbon fiber doesn't stretch the individual fibers in a region of a sail do not load share very well. When a weak spot starts to let go the next closest carbon thread will take all the load and it gets little help from the next adjacent thread. The sail then rips like zipper. Because Kevlar threads stretch more, they load share with each other, within a localized area of the cloth. Many 3DL sails are built with a mix of Kevlar and Carbon to take advantage of the properties of each.

[arbarnhart]

OK, OK - I said I was confused and that has been sufficiently verified (if you don't agree, pile on; there is always room).

[jadkkd]

I got a quote from Maine Sailing Partners on some Carbon Maxx sails. North sails recommends staying with the 3DL Kevlar for my boat which is 33 ft.. They tell me Carbon is for bigger boats and the school is still out on their "brittleness". They just give at some point.

[Hartley18]

FWIW, I think North Sails are right. Carbon fibre sails would get quite a beating on a small-ish boat.

If you are really serious, I'd suggest buying a carbon-fibre mast (carbon's biggest benefit is weight-saving) and sticking with the 3DL kevlar sails.

--Cameron

[Jeff_H]

If I were equipping a J-100 for racing I would probably avoid going with a film sail such as North's 3DL. On my 38 foot fractional rigger, I have had a real nightmare with North being able to deliver a 3DL sail that matches what they measure, and with them destroying the sail shape when they tried to recut the sail to fit. I would take a close look at Quantum's panel kevlar-mylar sails. I ended up having Quantum build my lapper (113%) AP #3, and found that using panel construction Quantum was able to more precisely fit and control flying sail shape on these small, high aspect ratio sails. I have been able to test this sail across a very wide wind range and they did an exceptional job. Panelized constuction should produce a significantly longer lifespan and a much lower price (it appears to be roughly 15-20% less but its hard to say precisely since the 3DL was bought at the boatshow price and the panel sail was bought in the heart of the sailing season).

Jeff