I had to send my Glaser main sail (circa 2008) in for some work and took out the battens. I don't recall them having much bend when I took them out. Any rule of thumb here for general conditions?
Hard to quantify. Tight, but not desperately tight.
First step is to tie the battens in correctly. When you thread the tension lines you end up with one end of the line in each hand and you push the batten in with your thumbs. If threaded correctly you can let go of both the lines and the batten without loosing the tension. I tried looking for some pictures on how to thread the lines and do this but I did not find any.
Once you have the battens tied in correctly, it is easy to set the tension you think is correct, hoist the sail and have a look with some sheet and downhaul on. I usually just put them in firmly and that does the trick for all conditions.
