What does "positive batten rotation" mean?

Usually, it means that the batten rotate around the mast, which is the way most sails work.

IE: when you rig it the battens sit to one side of the mast usually the bottom two battens work like this, usually around half a mast of positive rotation. Then when you use it on the other tack they will rotate to the other side of the mast.

Thanks Madge, it was something I read in a sail review. I'd assume negative rotation would mean the batten has pulled away from the mast with downhaul and isn't touching.

sheddweller said..

Madge said..
Usually, it means that the batten rotate around the mast, which is the way most sails work.

IE: when you rig it the battens sit to one side of the mast usually the bottom two battens work like this, usually around half a mast of positive rotation. Then when you use it on the other tack they will rotate to the other side of the mast.

What's negative batten rotation then?

when you snap one usually.....

Madge said..

kuotadriver said..
Thanks Madge, it was something I read in a sail review. I'd assume negative rotation would mean the batten has pulled away from the mast with downhaul and isn't touching.

not really, you dont really get negative batten rotation they either rotate or if its over tensioned they are flat, its like the wind being negative knots because its blowing the wrong way.

Yea....so it's just "rotation" positive isn't a meaningful addition. But people do like to confuse things.

When a sail, especially a cammed sail, doesn't rotate smoothly it doesn't have positive rotation. Sometimes it's just under-downhauled, sometimes the sail is on the wrong mast and the batten which won't rotate is on a section of the mast which is too stiff for the design. That makes the sail too full in that section and the cam just gets knuckled out so far that the windward/leeward difference in pressure in the sail won't rotate it.

LeeD said..
Negative....batten does NOT reach mast, sail has vertical folds that fill with breeze...Ezzy Takas, Hot Superfreaks, KS-3.
Neutral...batten barely reaches mast, sail is flat in zero wind, North wave sails, Duotone Waves.
Positive....battens reach around mast with tension, sail shape has belly, sail pulls early...most fast freeride sails and power wave sails.

Actually KS3 has positive on bottom batten, neutral on batten above boom, & negative on top batten... Ezzy's have a lot of shape, but it is built in mostly using seam shaping so batten rotation is nearer to neutral except on the Taka which has negative on short batten...

There's no such thing as 'negative batten rotation'.

It's not a term used by sailmakers.

The danger in making up new terms for our sails is you confuse people about how they work, and the terms become a distraction from the important stuff for those trying to learn.


'Positive rotation' simply means the sail wants to reverse its camber positively as you tack or gybe the sail.
A sail without positive rotation is a flat sail, or one that is badly rigged - possibly on the wrong mast.


Where the battens do not rotate around the mast - usually in the upper sections of the rig - we do not describe that as negative rotation. There is just less rotation or no rotation.