Efficient and powerful rotating mast control on a Corsair

The correct rotation of a rotating mast will give a much more efficient and powerful mainsail. It is thus important that the rig not be set up too tight as this can prevent full rotation.

There are many opinions on what the correct amount of rotation should be but a general guideline is to keep the mast rotated enough to give a smooth, even, transition from the mast to the mainsail on the leeward side.

Achieving the right amount of rotation will improve your speed and mainsail shape by pulling the apparent breeze through the slot efficiently. The amount of rotation will vary between 35° to 90° degrees.


Avoid allowing the mast to rotate or swing back and forth, which can happen in light winds combined with waves or when sailing off the wind with less sail pressure. This is usually prevented by having the mainsheet angled forward from the boom, which forces the boom forward to keep the mast rotated when pulled tight.

The amount of mast rotation is controlled by a line to the rotation arm on the mast from either the boom or the deck. This acts as more of a preventer than a positive control. The mast will naturally rotate in s position generally in line with the apparent breeze. The control line will prevent the mast from over rotating. A line from the boom has the advantage of being self-tacking by maintaining the mast at a constant rotation angle relative to the boom on all points of sail. However, the control line will have to be detached from a roller furling boom and transferred to an eye on the deck when furling the main.

A control line from the deck is also self-tacking, but it does not automatically adjust for different angles of sail. It will thus need to be let out when bearing off. Some racers like to fit two lines to the deck, one from each side for absolute control, but this can also be just another complication and is not necessary for general sailing.

Looking for an answer for your Corsair trimaran? Ask your question on our FAQ! Submit your question now or see what others have asked! >>

Comments for Efficient and powerful rotating mast control on a Corsair

Name: John S
Time: Thursday, August 21, 2014

I am not sure what "general sailing" is, but if you have a rotating mast, 2 lines with small block and tackles attached to the mast rotator with cleats are necessary to take full advantage of the mast rotating system.

Name: Steve Bogert
Time: Friday, January 9, 2015

In response to John, Corsairs and many other boats with rotating masts have the mast pushed into rotation by tension on the mainsheet which goes up at an angle to the rear end of the boom-tightening the main sheet pushes the boom forward, the boom attaches to the rear edge of the mast so the mast is pushed into rotation. Either of the 2 rotation controls described in the article can only limit rotation from the center position to prevent over-rotation. Over rotation might occur sailing upwind with the mainsheet in tight. Off wind the mainsheet is not as centered on the traveller and so has less of an angle to push the mast into rotation with, so under-rotation may occur. This is where one might use John's suggested system of a small block arrangement to pull the mast into rotation on one side. Another block set on the other side will be needed for the same control on the opposite tack. Boat builders do not like to encourage this installation though because if you forget to release the control on one tack and then steer over to the other tack the mast is being held out of rotation and may be BROKEN. Boom- day over- just because someone forgot to release a line! So for most (general) sailing those type of controls are skipped. If one is determined to have that last bit of control he will have to install the hardware himself an assume the responsibility to use it correctly or suffer the consequences with no possible recourse to the manufacturers warranty. I hope this better explains what John added.

Leave a comment