Had an interesting sailing session the other day, on concrete and light winds, my big recut sail, about 5.9 kept me going but did not compare with good commercial sails. Powered up it was OK but getting going was slow. Comparing it with the commercial sails they have much lighter battens than my recut windsurf sail and seem to take on more shape when not sheeted in hard. When I tightened up my sail battens it was slightly better but with the stiffness of the battens I can only occur a very slight camber and it is symmetrical from back to front. I am considering taking a flap wheel to the battens to thin them of a little and trying to get more adjustment and a better shape. Wondering if anyone has done similar or if it is worth a try?
I have a rule of thumb method for battens and it goes as follows:
Place the mast end of the batten against the wall and push from the leech end
The batten should show maximum draft ( the point of maximum deflection ) about 25 to 30 % back from the luff )
The force to do this on our size of sails should be about 1KG ( kitchen scales are good for this )
Personal preferences will vary from these ballpark figures but if you are close to this you wont be far wrong
Be careful with the sanding as the figures can change quickly. Check often !
Hope this helps
Hiko
This is an article that I found and posted some years back, it is from the NZ sandpaper magazine, I have always followed the info with great results
Although the object of your aerofoil is a maximum camber at around 40%, because of the mast and mast pocket the battens need to be shaped slightly differently.
I recommend that the shortest top batten should have it's maximum camber at 22% back and the longest at 35% with the rest arranged logically in between.
Some people prefer 25% for all battens and the fact that both methods give good results shows that what is most important is that you have a uniform shape over the whole length of the sail.
Mixing stiff and soft battens with the max. camber at vary -ing amounts is the worst of all worlds.
There need be no magic skill to planing class 5 battens so long as you are methodical and prepared to take quite a long time about it.
Also the info by Hiko is correct on the right amount of bend and pressure, although mine are a little stiffer as I sail mainly in strong winds and I am able to point very high into the wind without my sail collapsing (or inverting)
AUS230
