[Jeff_H]

I had a friend who decribed a nightmare charter in heavier winds with an inmast furling sails. It strated me to thinking about where this technology is going. At the last boat show I spent a bunch of time talking to sailmakers from a number of name brand lofts. Universally out of this group multiple sailmakers who make and develop in mast furling sails and this group includes who build some of the newer designed newer sails, the opinion was that while there has been a lot of effort made to improve the sails being used in in-mast furlers they have not been successful improving the performance or durability fo in mast furling sails. The big issue with in-mast furlers is the problem of creep. Creep occurs because the forces of the sail, especially on the luff, cause the leech of the sail to cause the layers of rolled up sail to slide over each other so that the upper portions of the leech creep down the rolled up sail toward the foot. This does two things, it powers up the center of the sail, and enormously increases leech loadings. These high leech loadings and powered up (and low stressed center of the sail)means that there is a lot greater stetch in the leech than in the core of the sail and so means a prematurely blown out sail. The high incidence of leech flutter in comparatively new in-mast furling mainsails is but one symptom of a prematurely blown out leech. Various techniques are used to minimize this problem such as using heavier warp oriented cloths along the leech of furling sails but this carries with it a whole range of other issues.

I did discuss some of the newer ideas being tried with sailmakers and designers. There is a lot being tried, from battens that can be furled with the sail, vertical battens and battens that can be rotated from vertical to horizontal once the sail is unrolled. One of the most revealing conversations that I had was with one of the designers for the one of the companies who pushes the vertical batten solution, he says that it is true that the vertical battens allow a nearly straight leech or even some minor roach, but the vertical battens do nothing for windward performance (except the one company whose design allows the batten rotates in its pocket.) Even with vertical battens, creep is still a problem meaning extremely poor sail shape when as a cruiser you really need good sail shape, and at least according to the sail designer, no improvement in sail longevity. In fact it was felt that in some ways battens agrevated the longevity issues by concentrating the loads. All of the makers of batten systems for in-mast furling said that adding battens to an sail intended for in-mast furling greatly adds to the likelihood of a jamb. Again it is a matter of creep. When the sail creeps, the batten is now wrapped at an angle and so is in a position to create a half-in/half-out jamb which is the worst of all world.

Unless someone invents a technology that is beyond anything that I can picture, I really think we will look back on in-mast (or behind the mast for that matter) furling systems in much the way that that we look back at roller reefing systems and reel winches of the 1960''s, as a potentially interesting idea that really could be made to work in a safe and reliable manner.

I don''t know about the Yachting World review of the Jeanneau''s but the guys who sell these boats, and make the sails for these boats are quite clear that there is a substantial performance penalty with in-mast furling. One of the PHRF regions did testing to determine if there should be a rating credit for in-mast furling. Based on testing of a fairly large number of sister-ships of various models in a variety of wind ranges the results of the testing suggested a 12 to 30 seconds difference between the conventional mainsail and the furling mainsail with the conventional main doing better in all windspeed but having its biggest gains in lighter winds and in heavier air. A 12 to over 30 seconds a mile difference is a big performance difference (nearly the difference between my prior 28 footer and my current 38 footer) especially when you don''t have crack crews tweeking the in-mast furling sails to get the most of them as was done during the PHRF evaluation.

Respectfully,
Jeff