I hope this will end the already long discussion and explain the reasoning behind my willingness to try something different from vertical battens on my SM.
My experience as a mechanical engineer is only 40 years but I have always evaluated critically every modification I have made to my boats. In principle, I see the vertical battens as a bad design waiting for disasters like those experienced by Michael. I do understand that sail makers are by definition conservative and thus Dave’s skepticism. Sails have been around for thousands of years and worked well with minimal changes. Adding new features always brings the risk for failures and, if I made sails for a living, I would also be skeptical and conservative.
However I am not sure these roller-battens have been used in the manner we plan to do it. I can see how the roller battens, installed as full battens and perpendicular to the mast as shown in the website, can have problems. Using them like that in addition to making wider the folded sail, they exacerbate the problem brought up by Dave : as the sail is furled, each turn will make incremental motions of the inner part of the stainless batten relative to the outer part. The more turns the more this happen and the greater the force the tip of the inner half of the batten will do against the batten cover.
By putting the roller battens perpendicular to the leach it makes them shorter than if they were placed horizontal or vertical, and thus they will have less turns and make the furled sail less wide. In addition, when placed perpendicular to the leach with a length such that only 40% of them extends over the leach, the sail damage when battens are too short will be prevented. More important, the widening of the furled sail will be reduced because the battens will roll in a corkscrew shape. I am also expecting that they may reduce the likelihood of the leach folding on itself and jamming the sail when it is furled with little wind.
In any case I am willing to take the chance, knowing that if I am wrong it is for reasons that I am still not aware of. So far Dave’s skepticisms has been very helpful to identify key potential problems and for formulating solutions. Unless he or any other person identifies additional problems with the roller-batten idea I will proceed with the project, keep an eye on the battens, and will keep you posted on my progress or failure.