Hi Leo, i assume it is a Koncept 5.8? What year is it?
Could be a busted batten joiner between the tube and rod which lets the rod slide up inside the tube and shortens the batten.
If it is not a pain in the arse take the loose batten out and have a look at the joiner. If you are not sure send me a photograph

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Regards Martin

In addition to Martin's advice,
in short...remember that the batten tension's the pocket and surrounding skin. The cam spacer's take care of the horizontal luff/mast sleeve skin tension. Getting the spacers tuned right over time as the sail breaks in with progressive use for a given mast is the key to having as smooth as possible luff sleeve surface along with appropriate downhaul setting.

Put too much luff sleeve tension on with spacers and the sail won't rotate freely, just put enough on to remove the wrinkles if you want to have good rotation. With a new sail I check, tune and tweak it every session till it looks feels right, as the sail beds in these checks and tunes become less frequent and the sail should look and perform real sweet.

cheers

Martin Spotty
in answer to questions its both luff pocket and batten tension..i have wrinkles in batten "from bottom" 2 3 4 and a very loose luff sleeve
saying all this i am using a NP mast ? X6 430 ?
the last time i sailed it was the best it ever felt as i rigged it at 430-1 down and not what it says on the sail of 437 and it gave me more body but just didn't look taught
It did perform very well though.. and Craig Hammond said it looked great wen sailing .. i was v happy with the numbers .
i just wonder if i could get it rigged the same as Daffy s on Ka site i would get a bit more ...
thanks for the help i do love my KAs 5.8 - 7.5 - 9m i do make a good ambassador for sydney as there aren't many around

thanks mathew have not had chance to rig today ended u going for a formula
thanks for the tips