SJ23 Tech Tip F05, (Updated 2014-06-21, B. Schimmel)

Mainsail Reefing Systems - Dual and Single Line Jiffy Reefing.

Most sailors will stay in protected water during lousy weather claiming they don't have decent reefing on the mainsail.  This is OK until Mother nature gets angry and you have to deal with what she hands out.  Being able to reef the mainsail quickly is sort of important when the weather turns nasty!  This is a time for acting, not thinking.  The factory reefing arrangement works OK but a crew has to go to the mast to set the first reef tack cringle on the rams horn hook and then pull the clew line in.  The Problem with this system is that the sail 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.   This system 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 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 my drawing further 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, about even with 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 it with foot tension as much as possible to reduce lift.

If you want the SJ23 boom to slide 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 fairleads to be mounted on the mast.  Your choice.









The reef lines (tack/clew) should be colour coded so you pull the correct line.  The rope clutches or cleats (first reef/second reef) should be labelled so you release the correct one.  Of less significance is the colour of the mid tie down lines.  Don't use red line as it becomes black at night and therefore difficult for most elderly gentlemen to see.  Personally I like the "hot" lime and green colours because I find them easy to see at night. 
TIP - One way to simplify pulling the correct lines is to tie the free ends of a reef (tack and clew lines) together like a Venetian blind.  Grab a set and the both move in unison. This technique works only if both tack and clew lines have to be pulled the same length. 

2014-06-21 Update - I've had it with a single line reefing system.  Both systems I've installed don't work due to too much internal friction.  I was hopeful though.  So I tore it out and installed a dual line reefing system using 1/4" polyester lines. 

An SJ23 has very little deck space to run these lines back to the cockpit so one has to be careful with the design.  To determine if it can fit and work effectively on the tight deck space I did a trial installation by doubling up the lines through the existing single mast base blocks, deck turning blocks and rope clutches.  It fit, it worked and I learned a few things in the process: 

  • Two lines through the same rope clutches must be the same diameter.
  • Two lines running through a common block or rope clutches have a tendency to twist around each other and snag.

These two facts meant that I have to install separate blocks for each line.  The slightly higher internal friction of the doubled up lines was acceptable as an experiment.  The first time I used this system I set and released two 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.  The system worked well enough that it can only improve by installing individual blocks and rope clutches.  The real test of a reefing system is to set and release a reef quickly.  These photos of my final installation say it all.

At the deck turning blocks I ran the two blue tack lines under the hand grip to turn aft to the rope clutches since there is not enough space to run all lines inside the hand grip.  The mounting holes through the deck for these turning blocks were epoxied and sealed with butyl rubber.  Similarly the foot print under each block was sealed to the deck with butyl rubber.


The reefing lines on the port side of the mast run through individual blocks to minimize internal friction.  The blocks are labelled on the mast to identify which line goes through which block on launch day.  The front double block is for the two blue tack lines and the aft double block is for the two white clew lines.  It is the natural way they run.


Below are the photos of the port and starboard decks incorporating aluminum fairleads between the deck turning blocks and the Easylock I rope clutches.  They keep the lines from rubbing the gel coat off the pods that support the hand grips.  The screw holes are epoxy saturated and sealed with butyl rubber.


The center black rope clutch is for the main halyard and divides the tack lines on the left from the clew lines on the right.  To create some logic with this arrangement, the red lockers are for reef 1 and the green lockers are for reef 2.  It is quite easy to pull the tack and clew of reef 1 lines at the same time so this reef comes down real quick.  Then pull in the slack of reef 2 lines.  This was a pleasant surprise to me.  It is important to pull in the slack so the clew line doesn't get snarled up on the end of the boom.  Shaking out a reef is not quite as easy but a quick way out for now is to pull the lines forward at the mast.  I still have a few bugs to iron out.


Below is a sketch of how the first (lower) and second (upper) reefing lines should be installed on a SJ23 using the two line reefing system, tack and clew.  Each reef point is about two feet deep and parallel to the boom.  The second reef line is usually omitted from many reefing 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.


CUNNINGHAM - This line is not shown because the drawing would become too cluttered.  However, the cunningham cringle is shown, being the cringle just above the goose neck.  There are several ways to pull this cringle down.  You can run a line through this cringle similar to a tack reefing line described above.  Alternatively you can slip a stainless tack hook (with line attached) in the cringle and pull the line down to tighten the luff.  The purpose of this tension is to flatten the mainsail to match higher wind speeds.  It is a useful technique for racing where tenths of a knot may allow you to win.  In cruising I seldom bother with the Cunningham.

TACK LINE DEAD END - 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 a strap eye on one side, passes up through its respective cringle and down the opposite side through a fairlead and finally down to the turning block 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 have transferred Panache's lines from the boom to the mast for the same reason. 

CLEW LINE - The dead end of each clew line is tied to the pin of the turning block installed on the end of the boom.  From there it goes under the boom and up to its respective clew cringle, then 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 around the boom it also transfers the 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 usually installed on the opposite side.  The clew line then goes forward to a turning block hung from the bottom 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.

Hope this explains the rational behind the 2 line reefing system.  The tack and clew lines terminate in their respective rope clutches installed on the cabin roof back at the cockpit. 

The usual reefing procedure for a 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 safety feature.
  2. Release the mainsheet to let the boom feather in the wind.  This relieves the stress on the cloth, slugs and lines.  Maintain as much speed as possible 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 some luff tension.  It helps to mark the halyard so you know where to stop.  Pulling the second reef lines along with the first automatically removes the potential for a snag!
  4. When the tack cringle is just above the boom, cleat the reefing line and tension the halyard to flatten the luff.  Pull it hard 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 and cleat the line. Pulling the second reef lines along with the first automatically removes the potential for 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 around the boom to further distribute the strain.  This will likely flatten the foot some more which creates an easier motion through the water with more speed.  Not all mainsails are equipped with these lines or require them.  You could also tie short lines through the tack and clew lines to back up the reefing lines.
  7. If you haven't done so already, pull in the second reef lines to remove the slack and the possibility of a 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.  (Ironically releasing a reef is the real test of a good reefing system.  It is also the time to watch for motion sickness).

Here are some extra tips you will find useful.

  • Pull up on the boom topping lift slightly to prevent stretching the leech or to hold it if the mainsail should tear.  This is something I usually do with the first reef and always do with the second reef. 
  • Keep a reefing hook handy in case a line wears through.  I keep 2 reefing hooks (equipped 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.  I have 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!  


SINGLE LINE REEFING SYSTEM, (One loooooong tack and 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.  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 cam cleat should be labelled 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 have never been able to pull the reef line to fully lower the sail to the boom.  It always requires a trip to the mast to fiddle with the lines or tuck cloth in.  Just the trip I'm trying to avoid. 
If setting a reef line is difficult then releasing a reef is really difficult, to the point of being dangerous because it takes so long.  Usually I have to climb 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 is 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.  (Ironically 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 helm 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.

Return to Tech Tip Index. . . . . . . . . . . . . . . Have a Question?