Mainsail reefing

There are many varieties of mainsail reefing. The purpose of this article is to help you choose which is the best for you

To some extent, mainsail reefing has turned full circle. First there were simple reef points – short rope pennants that could be used to gather up parts of a sail to reduce its area. Then there were rotating booms, around which a sail could be wound to achieve the same effect – roller reefing, in fact. It was slow, particularly when ‘shaking out’ the reef. But it was simple and reliable.

Perhaps the method gathering the most favour these days is known as in-mast reefing and describes a system where the mainsail is drawn into a hollow mast by a rotating spar. The drawing above shows a typical installation. Unfortunately, with mechanised reefing come fallibility and a host of other problems, so many offshore sailors have turned their backs on such fancy gadgetry and returned to more traditional forms of reefing. We’ll deal with the in-mast variety in another article. For now let’s stick with more conventional methods.

In olden days the first reef was known as the ‘slab’ and this term has rattled down over the years to describe the various methods of slab reefing. Actually the terminology surrounding this whole subject is vague, with different definitions describing different methods in different parts of the world. Usually, the words ‘line’, ‘pennant’ or ‘pendant’ are interchangeable and describe the various ropes used in lowering and securing the sail.

None of which is important, of course, so long as the principles are understood.

Get ready to reef

Reefing can be a struggle, but that’s not inevitable. The wise skipper will make life easy as possible for the crew. Done properly, it only takes thirty seconds or so to put in a reef.

  • First sail close-hauled or on a very close reach. The helm’s attention should be focused entirely on maintaining the course.
  • Tighten the topping lift to support the weight of the boom – unnecessary on boats with rod kickers (vangs).
  • Ease the kicker to allow the boom to lift.
  • Ease the mainsheet to depower the sail which should now be flapping.
  • Lower the sail. Some skippers mark the halyard to indicate how much it should be eased.

From here on the procedure depends upon the reefing system you have

Single line and hook

This is the most common method, involving a single reefing line through each reef clew point (only the first reefs are shown in this diagrams). Although the line can be led back to the cockpit, it’s usual for this to be done singlehanded by the crew member at the mast, since there has to be someone up there to deal with the cowhorn.


  • With the sail partially lowered, hook the reef tack cringle over the ‘cowhorn’.
  • Re-tension halyard to prevent the reef clew from unhooking itself.
  • Next, pull the reef clew down to the boom. If the sail is flogging heavily, this can be difficult and it may be easier to use the topping lift to raise the end of the boom up to the reef clew. It’s important to ensure you have plenty of tension along the foot of the reefed sail.

Double line reefing

This is a great system –  we use it ourselves on Shindig. It’s particularly suitable if the main halyard goes back to the cockpit but if you’re content to employ two crew members that’s not essential. The clew line is used as before but this time the tack has its own line to pull the luff of the sail down. With the halyard led aft, everything can be done from the cockpit. Otherwise this is a two-handed job.

Get ready as before then:

  •  Pull the reef tack line down and secure it.
  • Once the tack is secured re-tension the halyard.
  • Next, attend to the reef clew, again making sure you have plenty of foot tension.

A neat variation on this system is to have a reef tack line on both sides – one primarily for the cunningham and the next attached to the first reef. When you take in the first reef, the cunningham’s line is moved up to the second reef just in case you need it. The process can them be repeated for the third reef and so on. Clearly, this arrangement needs someone at the mast to switch the lines over.

Jiffy reefing

Here a single line is reeved as shown in the drawing below. This is a simple and inexpensive arrangement, making it a predictable favourite among boat manufacturers and sailmakers looking for an easy option. Unfortunately, the cumulative friction can make for heavy going – firstly in taking in the reef and later when it comes to shaking it out again. It looks like an attractive arrangement and might serve acceptably on the smallest boats or those which only expect to take a very occasional reef;


  • After proceeding as before, the reef is taken by simply by pulling on the single line – usually from the cockpit. Almost invariably you will find the reef tack pulls down easily, leaving the clew still slack.

Not recommended for serious sailing.

Twin lines and ‘balance block’

This ingenious arrangement was developed as an improvement to jiffy reefing. Both tack and clew pull down evenly and there’s considerably less friction. Again it has the potential to be worked entirely from the cockpit, so it’s popular among shorthanded crews.

  • In operation, the reef is taken in exactly the same way as for jiffy reefing.

Since the balance blocks must be allowed to move fore and aft inside the boom, the depth (meaning the height up the sail) of any reef is limited by the boom’s length. Typically, only two reefs are possible, which means an alternative must be found for a third reef. However, it’s arguable that if conditions deteriorate to the point where you need a third reef, it’s time to rig a storm trysail.


Finally, remember the old saying:  ‘Don’t delay. The time to reef is when you first think of it.’






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