Sail matterials

For my As level physics coursework I am doing a presentation about "designer materials" mine is about sails and my current reserch suggests that carbon fibre is totally supirior to kevlar by Youngs Modulus, Ulimate tensile strength and density, so why have I never seen any cf sails even on money no object ocean racers? or have I got the wrong information?

I think this info is actually for composites which is a ratio of strength in compression to strength under tension adjusted by a factor of the composite separation.... while saturated with sp's gunk

His ultimate tesile figures, right or wrong, do show correctly that carbon fibre has a greater tensile strength than others. In sails however this isn't the MAIN (geddit) factor. Carbon is like steel, in that, once its distorted under stress beyond its range of elasticity (which is minute) its strength drops off, alot. In sailing terms, put it in a flapping sail, and the threads can break. The solution, as north and many others will tell you is to make the threads as small as poss and then combine them...... like in steel wire...... giving better range for the same strength.

The reasons kevlar is so good is you can flex it, bend it press it....... its ability to withstand repeated flexing means you can glue a workable amount into the sail and it can flap and fold etc.

The strength to weight of a sail has never been about the re-enforcements, its about the glue that holds them in and how elastic that is. At present a glue light enough to take full advantage of Carbon fibres S/Weight  hasn't been invented so a kevlar sail can be made as light..... and for less cost. The only reason CF sells well is cos it sounds really hi tech - but time will tell - I would expect it to be the material for the future.

you need to do some serious research as your figues are way out for aramid( kevlar is duPont's tradename for aramid also try twaron which is another trade name for aramid) the figures i have are UTS=1600 MPa E(youngs modulus)=50 GPa figures for aramid are dupont's kevlar 49

also if you look at the density you have for carbon you need to add a zero so i reads 1600 kg/m3 

also many sailmakers use carbon in their sails have a look through a few websites eg norths, sobstad, quantum, uk sail