If you have spent any amount of time around sailboats and sailors, you will have heard the term “reefing.”
So just what does it mean?
Here’s What the Term “Reefing” Means:
“Reefing” is a term that refers to reducing the sail area of your mainsail and sometimes your headsail. The sailboat will heel and become increasingly difficult to handle as winds increase. In this situation, you reef your mainsail, reducing the sails’ sail area and pressure.
What Does it Mean When You’re “Reefing a Sail”?
“Reefing a sail” means reducing the sail area.
With the mainsail, this is usually accomplished by dropping it and securing it at areas of additional reinforcement along the luff and leech. These areas of reinforcement are known as “reef points” or “cringles” and are made specifically to take the load of being a new tack (the forward corner along the foot of the main) and a new clew (the back corner of the foot).
The reinforcing patches (layers of cloth that the rings are set into) at these reef points are usually identical to the patches at the normal tack and clew, as they will be under the same stress.
In addition, there are usually a series of small patches between the fore and aft reef points, set with grommets and thin “lace” lines pulled through the sail here. These lace lines are used to draw in the loose cloth now below the new foot of the sail. Securing that cloth to the boom prevents it from fluttering in the breeze.
The usual process is to drop the main and secure the new tack location first; this is either done with a metal horn or hook at the front of the boom or with the cunningham hook.
Then the reef line is hauled in, which runs through the new clew ring, raising the boom and bringing it flush with the new clew. Then the halyard is re-tensioned, if necessary (it usually isn’t).
The reef lines along the new foot are tied down now to gather in the extra cloth from the collapsed portion of the sail.
These are tied loosely to avoid undue strain on these smaller reef points, which are not nearly as large as the reinforcing patches at the new tack and clew. If they fall under tension, they can rip the grommet out of the sail and cause it to tear.
Some rigs have rotating booms. These mains are reefed by rotating the boom and drawing the sail down the mast.
This is an older style of reefing and much more time-consuming to do, and very few boats are set up for this now.
Genoas may also be reefed. The most common way is if the sail is on a roller furling system.
In this case, you furl the sail up until you reach a certain point of sail reduction. Many furling genoas will have visual references along their foot, like colored dots, to indicate a certain size (i.e., a 150% genoa might have two reference dots to indicate a 133% size and a 110% size).
Some headsails have reef points similar to a main. They must be lowered to the new tack and the sheets tied to the new clew. Then reefing lace lines are used to draw in the extra cloth at the bottom of the sail to keep it from flapping.
This last is uncommon these days; usually, a sailor will put up a smaller headsail that reef a deployed sail, even if it has reef points, as it creates a lot of extra windage with the excess sail below the reefs, and these folds of cloth can also catch water.
How Hard is it to Do?
Reefing your sails may be difficult or easy, depending on your setup and the conditions you are reefing in.
You always want to reef before you have to, as it becomes more difficult as the wind strengthens. Being prepared for the worsening weather (as it is in most cases) is half of the battle.
In general, it is not too difficult of an operation. You release the halyard to a certain point and secure the new tack, and then pull in your reef line to draw the new clew to the boom. Then the lace lines are tightened along the boom to contain the excess sail.
This can be done with by single crew member, as most reef lines are taken forward and handled as the halyard is being used. However, it is easier with two people operating, which is much faster.
If you wait to do this until bad weather is upon you, there will be a lot more pressure on the sails even as you lower it, and the boat will, of course, be heeling and rocking in the waves. This does make the operation more difficult.
Roller reefing your headsail is easy; ease your sheets, release the pressure on the sail, and take in your furling line until you reach the desired size. Then bring the sheet back in.
You never want to roller reef with pressure on your headsail; this puts a lot of stress on the bearings and also the joints in the furler’s extrusions. This kind of torque has damaged many units and extrusions. So always ease your sheets when roller reefing (and furling in general).
How Do Reefing lines Work?
The reefing line on your main is usually an easy setup.
It is anchored at the back end of the boom. From here, it runs up and through the ring at the clew reefing patch.
Then it comes back down to the back end of the boom, where it goes through a block and is then led forward to a cleat.
When the line comes back down from the reefing point, it may be led through an internal block to the boom or external. Most larger boats have internal lines in their booms, and some of these work on internal purchase systems to make the job easier and reduce the number of lines outside of the boom.
So the layout and operation are very simple. When the line is run as indicated above, all you have to do is pull it in after the main has been dropped.
How long Should Reefing Lines Be?
Usually, a mainsail will have two sets of reef points to allow flexibility in reefing and safety. Most sailmakers will put these at 12% and 28% of the luff length in designing a cruising sail. This gives good options to reduce the sail area and dodges the battens nicely. There will be a third reef for serious offshore sails, as well.
The length that a reef line needs to be can be precisely calculated by measuring the sail and rig, but a good rule of thumb is that the first reef should have a line that is 2.5 times the length of the boom.
This gives plenty of lengths to run up from the boom end to the reef point, back down, and then run forward to the reefing cleat while allowing the extra line to get plenty of purchase in a blow.
The second reef line should be 3 times the length of the boom, as it has more distance to travel up the leech of the sail.
For sails with a third reef they are usually not run while sailing. There is most often a thin line like a flag halyard looped between the clew reef points of the second and third reef. When the second reef is taken in, the line for the third reef is then run up that point and back down using the flag halyard.
This is done usually to reduce the number of lines aloft while sailing, but sometimes out of necessity as not all booms have three reefing lines, and the first is then reused for the third.
What is “Slap Reefing”?
“Slab reefing” is the term to describe the method of reefing your main that we have primarily discussed in this article.
That is, lowering the halyard first to the new tack and then pulling your reefing line to raise the boom again and make the new clew flush with it.
The overwhelming majority of boats with conventional mains use slab reefing, as it is easy and reliable.
The term “slab” comes from the slabs of the mainsail that is left along with the boom after reefing.
The single-line system is how most other boats with conventional mainsails are set up.
The other primary system used for reefing is for mains that are roller furling, like many of the large cruising boats. These usually feature sails that furl into a mast.
In this case, it is done similar to roller furling genoas; the sheet is eased so that there is no pressure on the main, and the furling line is pulled until the desired amount of sail remains outside the mast. Then the sheet is tensioned again.
The difficulty here is making sure the boom is at the right angle, usually about 85 degrees. If it is too high, the leech will be loose as you furl; too low, the foot is loose.
This can cause the sail to bunch in those areas and jam in the mast.
Other systems, like roller booms, as very rare these days.
What is Single-Line Reefing?
Single-line reefing is a variation on the slab reef in that the clew and tack are pulled in with a single line.
Your reefing line is secured at the clew and run up through the reefing ring and down and then forward, just as slab reefing is done.
The line runs from the inboard end of the boom up through the reefing tack cringle and back down again. It can either be terminated at the gooseneck or led aft.
The idea here is that when you release the halyard to the reef, you pull on one line to haul down both ends of the sail to the boom.
The main problem encountered here is the drag that the line has to go through. It is now working twice as hard, pulling down the outboard and the inboard portions of the sail, and even with large blocks to aid the line, it still meets a lot of resistance.
This system works better on smaller boats, but many larger boats employ it as well, as they often lead all of their lines aft to the cockpit.
The single-line system is not as popular because of this drag, and thus, it is usually slow to perform. While it does have its advocates because it uses only a single line in conjunction with the halyard, most prefer the cleaner simplicity and speed of slab reefing.
Tips for reefing sails – North Sails
Conventional Mainsail Reefing – The Rigging Company