Roller Furling Mainsail
Mainsails can roll into the mast or into the boom; UK Sailmakers makes sails for each of these systems.
Batten-less In-Mast Furling Mains
The simplest cruising mainsail option is the batten-less in-mast furling mainsail. These sails can be set and unfurled from the cockpit. At the end of the day no sail cover needs to be rigged. There is a trade-off for all this simplicity though. Without battens, the sail is much smaller since the leech ends up with a concave shape. To roll well the sail has to be designed with a flat shape. Being smaller and flatter hurts the boat’s light wind performance.
Vertical Batten In-Mast Furling Mains
Adding vertical battens improves the performance of in-mast furling mains by allowing the sail to be built with roach. Having roach makes the sail not only bigger, but gives a sail a much more efficient aerodynamic profile. The sail still has to be cut relatively flat so it will roll into the mast properly. To support even a modest amount of roach, the battens have to be twice as long as standard horizontal battens.
For roller main convenience without having to change to a roller/furling mast, switching to a furling boom is a choice. Several companies make booms that allow a full-batten main to be rolled into the boom. These mains have all the benefits of a standard full-length batten main, yet they can be roller reefed or furled into a specially made boom. Furling booms offer a huge safety benefit over any in-mast furling sail, in that if the furling system jams or fails, you can always drop the sail to the deck and get it down. If an in-mast furler jams, you are stuck with some portion of the sail flapping in the wind.Furling booms work well for large boats where the boom is too high up to furl and cover the main. Furling booms can be a retro-fit to an older boat or it can be specified on a new boat.