SJ23 Tech Tip F05, (Updated 2022-09-20) B. Schimmel


Mainsail Reefing Systems - Dual Line, Reef Procedure and Single Line, Reef Procedure.

Most sailors will stay in protected water or at the dock during lousy weather claiming they don't have decent reefing on the mainsail.  Staying put is OK until you get caught out there having to deal with what Mother nature hands out to you.  Being able to reef the mainsail quickly is sort of important when the weather turns nasty!  This is a time for acting, not thinking.  Reef early and reef often is a fundamental safety procedure.  I'm always impressed that Panache goes just as fast reefed and with more control.

The factory reefing arrangement works OK but a crew has to go to the mast to set the first reef tack cringle on the ram's horn hook and then pull the clew line in.  The problem with this system is that the mainsail has to be dropped out of its track.  The trip to the mast must be coordinated with the helmsman.  Reefing is usually easier with crew on board but I wouldn't count on them if they are green horns.  You can only watch anxious crew dance around on the coach roof for so long, entertaining as they may be, before you have to do something and quick!  Sailing in heavy weather can humble a crew and sailing solo usually adds a few twists that you may not have thought of.  Staying within the safety of the cockpit helps to avoid risks, which means the reefing lines must be extended to the cockpit.  This demands that the system be well engineered and the process well thought through, unless you enjoy entertaining as well!   To determine which reefing system you want on your boat you have to decide where you want to control the lines lead to; cockpit, mid boom or mast.

Described here are two typical cockpit lead mainsail reefing systems that can be installed on an SJ23.  There are variations of these that tend to be complicated but I prefer a simple and functional system.  If you are unsure which one to choose, try using the system on a similar boat.  That way you can experience the pros and cons before you spend your hard earned cash or perforate your boom with unnecessary holes.  The biggest hurdle to overcome is not pulling in the reef, but releasing it.  That is why some people opt to keep the free ends of the reefing lines on the boom.   It has the least internal resistance, is the cheapest to install but requires you to crawl to the mast to adjust the lines.  I prefer to stay in the cockpit when I'm sailing solo which is why I lead the lines to the cockpit.  Having installed and used the single line system I can tell you that the dual line system works way better, which is why I mention it first.

DUAL LINE REEFING SYSTEM, (Separate Tack and Clew Lines) - The biggest advantages of a dual line system is that it has the least internal friction and the tack and clew lines can be controlled independently, making it easier to use than the single line system.  The dual line system is depicted below, mainsail hoisted on the left and reefed on the right.  For the sake of simplicity the lines for the second reef are not shown but they are shown in bottom of the table below.  The clew block (marked A on the boom) is positioned so the reef line intersects the strain (reefed sail) at about 450.  If the position of the SJ23 boom on the mast is fixed then the tack eyelet should be positioned on the mast, a bit below the bottom of the boom.  This intersects the strain at about 600 (reefed sail) with most of the force being upward along the luff.  The tack cringle will slide across the tack reef line when the boom swings, therefore it is OK to leave a bit of slack when the tack line is set.  A perfectly packed, efficient sail isn't required for a reef since there is too much wind anyway.  However, you should flatten the sail with foot tension as much as possible to reduce lift.

If you want to slide the SJ23 boom down the mast in heavy weather then the tack line fairleads must be installed on the boom instead of the mast.  In this case you will have to mount the fairleads as far forward on the boom as possible.  This configuration isn't that conducive to efficient reefing.  I far prefer the boom to be fixed with the fairleads mounted on the mast.  Your choice.












The lines of each reef should be colour coded to differentiate between reef 1 & 2.  Its a "good" thing to pull the correct one, the first!  For the same reason the rope clutches or cleats should be labeled (tack 1 / clew 1).  Of less significance is the colour of the mid tie down lines on the mainsail. 

HISTORY - In 2014 I replaced my single line reef system with a dual line system experimenting with some old 1/4" polyester line.  My single line system didn't work.  Once the tack cringle was down to the boom I couldn't pull the clew down due to too much friction in the system.

An SJ23 has very little deck space to install reefing lines lead back to the cockpit so one has to be careful with the design.  I did a trial installation using the single line blocks and discovered it worked way better.  The first time I tried the trial system I set and released both reefs in five minutes; quicker if I didn't have to explain it to the dock watchers!  Click here for a description of how the system works.  Later I installed more blocks and rope clutches for each line as shown in the photos below.  Line length is described in Tech Tip F03.

By 2019 my polyester reefing lines were getting old and difficult to release.  Ironically releasing a reef quickly is the test of a good system so it was time to replace the lines.  This time I chose 6MM (1/4") green line for reef 1 & red line for reef 2 to match the green and red rope clutches.  While it is tempting to use 1/8" slippery single braid Dyneema line, it would just be my luck that I would slice my wet hands open when pulling it.  So I installed 6MM (1/4") line which is the minimum size a person should handle without wearing sail gloves.  See Tech Tip F03 Dyneema doesn't exhibit torque loading, making it perfect for all the right angle turns it has to go through.  When shaking out a reef I usually hoist the mainsail with the winch to pull the Dyneema lines through the deck hardware.  Sometimes the load is too much and have to feed the lines at the mast.  

Unfortunately the 6MM Dyneema line with the slippery jacket creeps slightly through Panache's rope clutches so I thickened the line where it is gripped.  Where to bulk the line up and for how long was determined with the mast standing to make accurate measurements.  Splicing a piece of 1/8" line inside another line is a clever technique that creates tapered ends that easily slide through a block.  I spliced it using a 1' length of coat hanger wire, a wrap of fibreglass tape, some coconut oil for a washable lubricant, and then zigzag stitched through both to make them as "one."  The advantage is smooth operation, minimal wear and when the thick portion is in the line clutch you know the sail cringle is down correctly.  There are two alternatives:

  • Slip a braided jacket (sleeve) over the line and whip the ends to create a smooth transition for sliding through the blocks.  Then zigzag stitch through it to make it as "one" with the core.

  • Replace the cam in the rope clutch to handle a thinner line.

NOTE - In my tests of 1/8" Dyneema line I determined that it grips well in a dual or single cam cleat and around a rough finished deck cleat.  What a surprise since this small size is the most difficult to grip.  It failed miserably over a polished cleat as I could easily pull 3 wraps of line off that cleat. 


2019 - Below are the photos of Panache's deck mounted reefing system using 6MM Dyneema line e/w a polyester jacket so they can be gripped by the Easylock rope clutches at the cockpit.  In 2022 I moved the boom vang line to the starboard rope clutch.  These photos reflect that move.
NOTE - By convention port should be mainsail and starboard should be jibs.  The lines were installed by the previous owner and it was too difficult to relocate them.  I've gotten used to it.

* For the best visual perspective view these photos from the bottom to top of this table as if looking forward while standing in the cockpit. *

Overall view of port lines.

Overall view of starboard lines.

Port clew fittings.

Starboard clew fittings.



The tack lines through cringles are tucked in just behind the mast so they are pretty well out of the air flow.

These port eye straps organize the tack lines and set the correct angle when the tack cringles are down on the boom.

The starboard eye strap.  Tack lines can be quickly released from the mast and stored on the boom when mast is stepped.



The tack and clew reefing lines run over separate sheaves at the mast base to minimize friction.  All blocks are spring loaded to keep them aligned with the lines for minimal friction.  The foot of the mast is labelled to identify which line goes through each block.  Convenient when the mast is stepped. 



Each mounting hole for deck hardware is sealed with epoxy and the foot print under each is sealed with butyl rubber.




Deck fairleads to organize lines on both sides of hand rail & to protect the gel coat from abrasion.


Rope clutches are bolted together as a unit to make for a neat installation.  The cross pins are secured with a 3/16" E-clip at each end.  The mounting holes are sealed with epoxy and the foot is sealed to the deck with butyl rubber.  Gotta love those Lewmar winches with dual pawls.

The black Easylock rope clutch is for the main halyard and divides the tack lines on the left from the clew lines on the right.  To make sense of this arrangement, the green clutches are for reef 1 & the red clutches are for reef 2.  With this configuration I simultaneously pull both tack lines and then both clew lines so reef 1 comes down while keeping reef 2 lines snug.  It is important to pull the clew 2 line with clew 1 so it doesn't snarl around the end of the boom.  However, it is usually easy to pull clew 2 in later when pointed upwind. 

HINT - A really easy way to "push" a line through a rope clutch is to use a fid.

- The boom vang line is located in the cockpit where it is convenient to control and easy to see the effect it has on the mainsail shape.  Far superior than reaching forward under the vang where the mainsail is out of sight.
- The red halyard for the storm sail is coiled at the top of the halyard bag for quick deployment.
- The green halyard for the roller furler is normally tensioned at ~50 pounds and the free end is coiled at the bottom of the halyard bag.

- The halyard bag is oh so comfortable to lean against.

This is a sketch of how reef 1 (lower) and reef 2 (upper) lines should be run on a SJ23 using separate tack and clew lines.  In Panache's installation each reef point is 3' deep and parallel to the boom.  The reef 2 line is usually omitted from many diagrams but for the sake of clarity I've shown both here.  Somehow the gurus expect you to figure this out!  Having said that, the lines on the port side of the sails are omitted since including them challenges the drawing ability of my software.  However, it is shown in the Harken diagrams above.  So there you go, guess I'm just as guilty.

NOTE - Tack and clew lines are shown above deck for the ease of drawing.

What a sweet shape to the mainsail.  It shows how the reef lines stay close to the sail cloth for minimal drag.  There is a bit of slack in the reefing lines so they don't pull on the cringles to affect the sail shape.

CUNNINGHAM LINE - This mainsail flattening line is not shown in the drawing above because the drawing would become too cluttered.  The cunningham cringle is about 6" above the tack.  Look closely and you'll see it.  There are several ways to pull this cringle down to flatten the mainsail.  You could run a permanent line through it similar to a tack reefing line.  I prefer to slip a stainless tack hook (with line attached) through the cunningham cringle then pull it down and secure it around a cleat on the mast.  This extra tension flattens (depowers) the mainsail to match higher wind speed.  It is a useful technique for racing where a tenths of a knot may allow you to sail faster.  When cruising I seldom bother with the cunningham unless the wind blows not quite hard enough to reef.  The cunningham should be used in conjunction with matching outhaul tension to depower the main.  I do like to sail as fast as possible.

TACK LINES - As mentioned above you have to determine if the tack lines on your boat are to be attached to the mast (shown on diagram) or to the boom.  Regardless of which location, the dead end of a tack line is tied to an eye strap on one side, passes up through its respective cringle and down the opposite side through an eye strap and finally down to the turning blocks at the base of the mast if you want to terminate the line in the cockpit.  Since the majority of the sail cloth is bundled on top of the boom it is important to keep the lines away from the cloth so they slide freely.  This is why many people prefer to install the tack lines on the mast instead of the boom.  I transferred Panache's lines from the boom to the mast for the same reason.  Line length Tech Tip F03.

CLEW LINES - The dead end of each clew line is tied to the pin on the turning block installed on the boom.  From there it goes under the boom and up to its respective clew cringle, then back down through the same turning block on the boom.  This balances the load on this turning block and creates a 2:1 mechanical advantage for pulling sail cloth.  With the reefing line under the boom it also transfers some of the load to the boom.  Since there is limited space to install two turning blocks on the same side of the boom, the block for the second reef is installed on the opposite side.  The clew lines then go forward to turning blocks mounted on the front of the boom at the goose neck.  This greatly reduces the internal friction of the clew line since it can align with the direction of the pull to the deck block as the boom swings.  Line length Tech Tip F03.

I hope this explains the rational behind the dual line reefing system.  Each tack and clew line terminates in its respective rope clutch installed back at the cockpit.  The alternative is to install it on the boom.  Your choice.

REEFING PROCEDURE - Usual reefing procedure for Panache's 2 lines system is as follows: 

  1. Snug up the boom topping lift, having previously attached it due to worsening weather.  (You do check the horizon every now and then don't you?).  If you trust your mechanical boom vang you may dispense with the topping lift but it is a good backup.
  2. Release the mainsheet to let the boom feather in the wind.  This relieves the stress on the cloth, slugs and lines.  Maintain speed with the jib.
  3. Lower the mainsail with the tack reefing lines while letting the main halyard slide through your hand, working one against the other to maintain a bit of luff tension.  Stop when the tack cringle reaches the boom or the mark on the halyard reaches the rope clutches. 
    - Pull the second reef line along with the first to minimize the chance of a snag!
  4. When the tack cringle is just above the boom, cleat the reefing line and tension the halyard to flatten the mainsail.
  5. Pull the clew reefing line till the cringle is lowered to the boom and adjust the tension along the foot to flatten the sail for the wind speed then lock the line.
    - Pull the second reef line along with the first to minimize the chance of a snag!
  6. If you expect to sail for a long time in heavy weather, roll up the loose cloth and tie the intermediate lines to gather the cloth.  If you tie around the boom, leave the lines slightly loose so as not to strain the cringles.  This may flatten the foot a bit which should create an easier motion through the water with more speed.  Not all mainsails are equipped with these lines or require them.  If you expect to sail reefed for a long time you could tie short lines through the tack and clew cringles and around the boom to remove some strain from the reefing lines.
  7. If you haven't done so, pull in the second reef lines before they snag.
  8. If the weather worsens set the second reef on top of the first, repeating steps 2 to 6.
  9. If you want to set a third reef on your SJ23 (I don't envy your weather situation) use loose lines with reefing hooks on the end to pull down the third set of tack and clew cringles.  Best to set these in place right after you set the second reef.
    - Very few SJ23s have a third set of cringles.  While reefing hooks may be difficult to set on a rolling deck, installing a third set of permanent reefing lines will clutter up the mainsail for the majority of use during lighter winds.  Trade offs again.
  10. As the weather improves, shake each reef out by releasing the reefing lines and pulling the halyard up to tension the luff.  Maintain headway with the jib to keep the boat moving in a comfortable motion through the lumpy water. 

Here are some extra tips you might find useful.

  • Support the boom with the topping lift to prevent stretching the leech or to support it if the mainsail should tear.  This is something I usually do with the first reef and always do with the second reef due to the 8x1 mechanical advantage of my mainsheet. 
  • Keep a reefing hook handy in case a line wears through.  I keep 2 reefing hooks with a 4' long 1/4" line spliced to each, hanging in the companionway so they are ready for use. 
  • I abandoned the single line system described below because it has too much internal friction with lines through the cringles.  I was never been able to set a reef properly and always had to hike to the mast to pull the reefing lines.  I averaged 15 minutes to set a reef, a bit less to release one.  Enough said, I think the single line system sucks!

SEASON START - Each clew line is tied to the block pin at the end of the end of boom.  From there the lines go under the boom, up to the cringle, down to the block and forward to the blocks at the end of the boom, down to the deck turning blocks, to end at the rope clutches on the deck. 
Each tack line has a loop spliced at the mast end and secured at the eye strap on the mast with a shackle.  It then goes through the mainsail cringles to end at the rope clutches on deck. 

WINTER STORAGE - At haul out time I will pull the clew and tack reef lines out of the deck blocks and bundle them under the mainsail straps on the boom.  The intention is to keep the reef lines with the boom during winter.  I store my full batten mainsail on the boom over winter, wrapped in the mainsail cover with straps relaxed.  The load is spread over several cushions to make it easy on things.  At launch time I unbundle the reef lines from the boom and run them through the deck blocks to the rope clutches.  Straight forward organization.


SINGLE LINE REEFING SYSTEM, (One loooooong tack to clew line) - A single reefing line is simpler to install but more difficult to operate on a pocket cruiser due to lots of internal friction if the line is lead back to the cockpit.  It is likely OK if the line is lead to the mast.  When a reef is set you end up with lots of line in the cockpit, which can be a nuisance but doable if you stuff it in a bag.  The first reef should be a different colour than the second reef and the rope clutch should be labeled to eliminate confusion when the hull is heeling too much.  The problem with this system is the internal friction through the cringles, blocks, and against the sail cloth bundled on the boom.  I was never able to pull all the reef line to fully lower the sail to the boom.  It always required a trip to the mast to fiddle with the lines or tuck cloth in.  Just the trip I was trying to avoid. 
If setting a reef line is difficult then releasing a reef is even more difficult, to the point of being dangerous because it takes so long.  Usually I climbed to the boom to pull the reef line out through the cringles and free up the line jammed against the cloth and inside the blocks.  There was a better than excellent chance that the loose line has snagged on something which is really frustrating.
On some boats it is impossible to achieve proper luff and foot tension using a single line.  I think a single line reefing system will work OK on a smaller sail or one with lighter cloth but not on an SJ23.  I wouldn't recommend it.

The usual reefing procedure for a single line system is as follows: 

  1. Release the mainsheet and let it feather in the wind to relieve the stress on the cloth and lines.  Maintain some speed with the jib.
  2. Snug up the boom topping lift, having previously attached it with the worsening weather.  (You do check the horizon every now and then?).  If you trust your mechanical boom vang you may dispense with this step.
  3. Pull the mainsail down with the reefing line while letting the halyard slide through your hand.
    Work one line against the other to maintain some luff tension.  It really helps to mark the lines so you know where to stop.  
  4. When the tack cringle is pulled down to the boom, cleat the reefing line.
  5. To lower the clew to the boom you will have to pull the reef line by hand and pull the extra line through the tack cringle and cleat the line. I find that I can seldom flatten the sail sufficiently for the higher wind speed.
  6. Tension the halyard to flatten the luff.
  7. If you expect to sail for a long time in heavy weather, tie the intermediate lines around the boom to flatten the foot and distribute the strain.  It also helps to pack in the excess cloth.  Not all mainsails are equipped with these lines or require them.  This is one job that you have to climb on the cabin roof for.  It cannot be done from the cockpit but the boat will have easier motion with a reef set in.
  8. Pull in the second reef lines to remove the slack and eliminate the possibility of a snag.
  9. If the weather worsens further set the second reef on top of the first.  Repeat steps 2 to 7.  This time it will be next to impossible to pull the line past the bundled first reef.  I have always had to do this in the marina before I set out into rough weather. 
  10. As the weather improves, shake each reef out by pulling the halyard against the reef lines to maintain luff tension.  Maintain headway to keep the boat moving in a comfortable motion through the lumpy water.  (This is when you have to watch for motion sickness).


There are many variations of these two systems.  Some sailors will dispense with leading the lines to the cockpit, preferring to terminate them on the front of the boom or on the mast.  While this system works very well, it necessitates going to the mast which may be difficult if you sail solo.  In this case you better have a tiller tamer, auto pilot or be very quick!  Years ago I used this technique on my previous boat but usually delayed the trip to the mast hoping that the wind would subside.  It almost never did!  
Yet another system involves terminating the tack and clew lines at the center of the boom.  Positioned here it is possible to reef the mainsail while standing in the relative safety of the companionway or sitting on the coach roof.  As appealing as this may seem, the boom must be hauled inboard over the cabin to reach it which could create excess heeling when sailing upwind.  If you have an Olympic gymnast on board this is merely a challenge! 
If you want to add a second "set of hands" for reefing, install some lazy jacks.  See Tech Tip F22 for Lazy Jacks. 

NOTE: I borrowed the diagrams from the nice folks at Harken.

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