In-Mast Furling Mainsail
Cruisers should be aware that the in-mast furling system adds convenience at the cost of performance. In-mast furling mainsails will have only a fraction of the performance and life of a normal mainsail. In order to furl into the mast there will be no battens (we highly discourage vertical battens as they have had a history of hanging up on the mast slot and causing it to jam). No battens means no roach which will impact the performance and durability of the sail in a number of ways. First, the roach is the back of the mainsail that works in conjunction with the keel to provide lift. Second, without a roach there are higher loads on the leech as the load travels directly from the clew to the head of the sail without the advantage of it being disbursed over a wider area that would be provided by the roach. To further compound this, the in-mast system has limited space and therefore an under spec weight of cloth is used in order for the sail to fit inside. Finally, the sail is usually designed flatter to fit in the mast and with restrictions on desired shape, the sail is likely to be lacking in performance.