Each brand of sail will be different but in most cases you shouldn't need to touch batten tension from one session to the next.

Batten tensioners are not sail tuning devices on most sails, and the key is not to over tension battens beyond their role in removing wrinkles in the batten pockets.

Any batten put under compressional load will tend to bend more easily and will therefore be less effective in its primary role of adding stability to the sail panel.
With some cam'd sails it can be different, depending on how the cam is pushed agains the mast.

What can happen with all sails is that materials can appear to stretch a bit when very wet, and it's then tempting to over tighten a batten tensioner. If that sail then dries out in a period of hot and dry weather then the effect is to reveal the overtighening as the sail shrinks a little back to its dry state. At that point, too much batten tension can lead to the batten setting in a permanent curve if stored for a while.

The answer for most people will be to not over tighten the tensioners in the first place.
But, for sure, it does no harm to take tension off the batten tensioner by half a turn if you intend to store your sails for a long period.

What I found is after 1-2 complete turns of the batten tension screw, if I tried pushing inward and the tensioner moved, it meant I had released enough tension, no need to unscrew further and risk have the batten adjusters get out of the rope tether.

Manuel7 said..
A friend of mine, by fear of breaking tensioners, doesn't even tighten his!

What sail are they using? Aerotech batten tensioners are very durable, took years of over-tensioning without a problem!

mathew said..
What problem is being solved here [ by releasing batten tension ] ?

The constant tension on the sail panels in hot humid weather causes new vertical wrinkles to form in the sail panels because the plastic panels are slowly stretching out. By releasing batten tension after use, the sail panels can relax so that the next time they are tensioned the sail has the correct shape without vertical wrinkles in the panels.

An extreme example is for an Ezzy sail I saw, they ship them with battens pretensioned, and in the early days of covid they were sitting in the hot sun for a month in steel shipping containers in the Port of Miami. I know someone who bought an Ezzy sail from a local shop who got their equipment from the Port of Miami. The guy was unrolling the sail for the first time on the beach, still had the protective paper/foam (wind caught it and I grabbed it). Then he rigged it and asked me to take a look at it, between every batten on the leech end the sail had these big stretched out scallops that he could not get rid of, and he was using a brand new correct Ezzy mast using the factory down haul setting. I think the problem was the sail got cooked in the shipping container and the plastic panels stretched out on the leech end due to the batten tension and prolonged high temperatures inside the shipping container. I contacted Ezzy sails about it and they only said they now ship their sails by plane, wonder why?

I just read that the temperature inside a steel shipping container is "double" the outside temperature! So a 90 degree day in Miami would make the inside 180 degrees!
www.shiplilly.com/blog/complete-guide-to-ocean-shipping-containers/

...and who don't sail often enough

Can we PLEASE , have your view on failing eyesight .

Sandman1221 said..

mathew said..
What problem is being solved here [ by releasing batten tension ] ?

The constant tension on the sail panels in hot humid weather causes new vertical wrinkles to form in the sail panels because the plastic panels are slowly stretching out. By releasing batten tension after use, the sail panels can relax so that the next time they are tensioned the sail has the correct shape without vertical wrinkles in the panels./

What you are suggesting is the limit for elastic-deformation (aka the ability to return to original shape) becomes plastic-deformation.
Depending on whom you talk too, either you never get plastic-deform if you stay within elastic-deform, or you do get some which tends to be seen as a memory-effect.

I personally _feel_ that some (most?) sails need to be sailed a few times before it becomes "correctly set" ... the material beds-in. Once that point is reached, the material doesn't change much. But that could be bias.

I have considered removing batten-tension, but getting the tension correct in the first place, then having to redo the same tension each time, is just time-wasting.... I'd rather go sailing, than to tweak battens for the next eternity for what I _feel_ is of no benefit.

The bottom 2 battens on every overdrive I've owned and that's quite a few has ended up being to short after a few months use so something definitely gives.
while it might not be necessary to release batten tension when your not using the sail it must be better to store stuff not under tension

mathew said..

Ben1973 said..
The bottom 2 battens on every overdrive I've owned and that's quite a few has ended up being to short after a few months use so something definitely gives.
while it might not be necessary to release batten tension when your not using the sail it must be better to store stuff not under tension

This usually a result of incorrect-original-length batten - I have had sails with this problem where one batten couldn't be adjusted any further.

Most sail brands uses n hex-key-tensioner system where the batten has a threaded-sleeve-thingy; this usually uses a 8mm rod or thereabouts. ( Other manufacturers have a different system, eg: Neil Pryde ). Just grab a bit of old batten-rod, then cut off about 1cm or 2cm of rod -> insert it into the sleeve. Tighten it back up.

Note that running-out-of-adjustment sometimes is incorrectly diagnosed... sometimes sand/salt gets into the adjustment mechanism, which causes the thread to become jammed resulting in no-more-adjustment. Cleaning the adjustment mechanism ( which means pulling completely apart ) usually solves this problem.

Yes that's the fix I came up with, had to do it on my old m2,m3 and m4's seems Severne like cutting battens to short