The Mainsail

mainsail as part of the Simbo rig for downwind sailing


A short vertical battened in-mast furling mainsail which can be set, reefed and struck with impunity can give one as good a performance as any self respecting cruising sailor could wish.The battens not only provide a positive roach but avoid furling a folded leach into the mast and causing a jam.

A further advantage is found when trimming the sail as the outhaul permits one to adjust the draft with ease, to gain maximum drive in light, moderate and strong conditions.

It is also consoling with yachts of say, up to 50 feet L.O.A. with in-mast furling to be able to set and reef the mainsail on any point of the wind without having to come up hard to weather to completely feather the mainsail . This is particularly consoling when needing to reef down wind in deteriorating conditions. The sail can be reefed to suit any conditions so it arguably, enables the coastal cruising sailor to dispense with the need for a trisail.

With larger yachts I have not found it possible to furl the mainsail into the mast with any pressure on the sail. Therefore on a broad reach and of course, when running down wind I normally rig a boom preventer in preparation for the possibility of needing to reef later. This stabilizes the boom in situ and averts coming head to wind to feather the mainsail and avoids any flogging sail and rattling boom . It’s also consoling not to have to round up into a ugly sea.

Of all its many virtues this ability to reef the mainsail off the wind is in my opinion, the in-mast furling mainsail’s greatest attribute and far outweighs any perceived demerits i.e. increased weight aloft, reduced roach etc.

However, I always leave half a furled roll of mainsail in the mast rather than allow the clew to pull the sail out to its fullest extremity. The reason for this is that if the mainsail luff should slacken unnoticed, allowing the webbing at the sail’s tack to be pulled out of the mast slot and become stiff with sea water, then it can stop the sail being furled. Needless to say this is something that would probably present itself when the wind was rising and it was necessary to shorten the mainsail with a degree of urgency!

As most cruising yachts are now designed with in-mast furling mainsails in mind, one should not become concerned with any additional weight aloft.