Index

SJ23 Standing Rig Tuning and Sail Setting Guide.

INDEX - Rig Preparation, Mark Turnbuckles, Rig Tension, Loos Gauge, Sail Trim,

"The sails for the San Juan 23 have been developed using primarily our proven designs from the San Juan 24.  Although many San Juan 23 sailors are not interested in racing, most of you would still like to get maximum performance while cruising and the occasional race that many are likely to enter.  Here are some ideas (rig preparation) that will help you get the maximum performance from your boat and sails."  Don Clark.

STATIC RIG PREPARATION

MAST RAKE - The San Juan 23 is designed to have up to 12" of rake in the mast when floating level on her waterline.  This is an approximate measurement and you will be in the ballpark by tightening the factory backstay so 1/2" of thread is showing on the top of the turnbuckle barrel.  Then adjust the forestay turnbuckle for the proper head-stay sag, ~(5-6)" when sailing to weather in a medium breeze. 
- You can also determine the mast rake by lowering the main halyard to the deck with a heavy weight on the end.  Measure how far aft the weight is from the mast base.  Subtract 2" to allow for the mast head sticking out.  The mast on Panache is raked at ~8".
- If a bucket full of water is placed at the base of the mast and the weight hangs in the water, the water dampens the movement of the line due to windage. 
- You could also use a thin line on the end of the hoisted halyard to further reduce the effects of the wind.

MAST PERPENDICULAR - The most accurate method to ensure the mast is perpendicular (lateral) to the hull is to hoist a light steel wire, Dyneema line or measuring tape from a secured main halyard.  Hoist the halyard and extend the wire so it just touches the starboard toe rail, adjacent to the chain plate.  Then touch the wire to the port toe rail, adjacent to the chain plate.  If the wire just touches either toe rail with the same pull, the mast is perpendicular to the hull.  If you want to get real picky, allow for the main halyard being on port or starboard masthead block.  Light wire is superior for this than anything else.  To correct a lean, adjust the upper turnbuckles with the lower turnbuckles loosened. 
- If you are not ultra concerned about precise rig tuning, its OK to use the main halyard.  It stretches very little but you should account for sag. 

SHROUD TENSION - After the mast is perpendicular adjust port and starboard turnbuckles the SAME amount to adjust the tension, +1/2 turn or -1/2 turn.  Hold the wire from twisting while turning the turnbuckle barrel.  Final adjustments can be made while under sail which is most easily done by adjusting the leeward shrouds, tacking, looking up at the mast, tacking, etc. 
- The upper shrouds support most of the weight and tension of the mast.  The lower shrouds keep the mast straight when the boat is heeled and have less tension.
- When heeled 20 degrees, take note of the leeward shrouds.  Are they slack, just loose, almost loose or still snug?  You want the "still snug" setting to prevent shock loading while the mast is transitioning during a tack.

The shrouds should be fairly tight to the point where the leeward shrouds are still snug when the boat heels 20⁰.  (This is approximately 10% of breaking strength or 350-400 lbs as measured with a Loos tension gauge).  Sight up the mast and adjust the lower shrouds to straighten a bowed mast.  A slight amount of sideways bend to leeward at the top is OK while sailing.  Keep in mind that 1x19 SS wire or the fittings do not like to be shock loaded which is why it is so important to tension the shrouds correctly.  The leeward shrouds MUST NEVER go completely loose to minimize shock loads or fatigue when they tighten on the next tack. 
- The final tension adjustments should be preceded with static tuning of the mast.  Also see Tech Tip F24, Rig Tuning.

MARK THE TURNBUCKLES FOR STEPPING MAST - The spreaders and chain plates of an SJ23 are installed in-line with the mast.  As such, they MUST be loosened to step the mast. 

With the rigging tension set correctly the turnbuckle threads should be marked (top & bottom) so you can quickly restore the settings the next time you step the mast.  It also a great way to see if you have loosened the barrels 1/4" to lower the mast.  Marking the turnbuckles is a real time saver to those of you who trailer launch your boat. 

For all of you sailors who seasonally launch and retrieve your boat, don't consider yourself done after the initial mast tuning.  Since 1x19 SS wire stretches after the first outing you should repeat this procedure in about a week or after a few more outings.  Once you have tuned the rigging to perfection, mark the turnbuckles with tape (top & bottom) around the exposed threads to mark the position of the nut against the barrel. 

The alternative to using electrical or rigging tape is to set a tie wrap around the thread, really tight.  I use synthetic grease on Panache's turnbuckles and have discovered it eventually dissolves the tape adhesive.  This loosens the tape, rendering it useless.

Another technique to quickly restore the rig tension of an open turnbuckle is to use a calliper, dial or digital, to measure the distance between the ends of the threaded studs.  This can get the tension in the ball park very quickly and is actually quite accurate.  This visual feedback is confirmation to a force that can be fine tuned with a Loos tension gauge. 

Ever since I learned how critical rig tension is to sailing performance, I finish setting the tension with a Loos PT-1 gauge on Panache.  It really pays in the performance department.

RIG TENSION - The SJ23 is e/w closed barrel turnbuckles from the factory.  A closed style turnbuckle must be loosened initially to confirm how much thread is screwed into the barrel.  Maximum strength is achieved when all the barrel thread is screwed over the toggle thread.  An equal amount must be screwed over the top and bottom toggles. 
Consider the following when tensioning standing rigging.  In general, wire is tensioned to about 5% of it's breaking strength when most of the sag is removed.  It is tensioned to 10% when it first produces a low frequency musical note when struck with a metal object like a wrench.  This is close to the desired tension.  CLARK SAILS.  TOP

Set Rig Tension With a Loos Gauge - "I have used a Loos strain gauge for all our sailboats.  There are several models so use the gauge that matches the wire size on your boat.  All Loos gauges measure strain to +5% accuracy.  The PT-1 Professional gauge fits 3/32", 1/8" or 5/32" wire, which is suitable for the 1/8" wire on a MKI SJ23 or 5/32" wire on a MKII.  The PT-1 Professional gauge can be used to continually measure the tension as you adjust a turnbuckle, making it much superior to the older A-91 gauge.

• If you have the correct model Loos gauge for the wire size on your boat then the shrouds and stays will fit in the measurement slot on the side.  Read tension in the corresponding wire size column.

• The pointer at the top of the instrument translates to the scale number in the left column, indicating which row to read.  The wire size tension ratings and % breaking strength are shown to the right.  Read the tension corresponding to your wire size. 

• Set the tension to ~10% breaking strength of the wire.

• Now that we have covered most of the technical BS here are the settings that work on my 1982 SJ23 e/w 1/8" wire.

  RIGGING	(1982 SJ23 e/w 1/8" 302SS wire) Loos Scale / Tension lbs	(1977 SJ23 e/w 5/32" 316SS wire) Loos Scale / Tension lbs
  Upper Shrouds	28 / ~390 lbs	31 / ~360 lbs
  Lower Shrouds	26 / ~345 lbs	30 / ~335 lbs
  Forestay	24 / ~300 lbs	(Can't measure tension inside foil. It's a bit more than the backstay)
  Split Backstay,   5/32" upper wire.	22 / ~260 lbs	22 / ~160 lbs (rest) 29 / ~320 lbs (tightened)
  Split Backstay,   1/8" lower wire.	?	8 / <110 lbs (rest) 18 / ~180 lbs (tightened)
  NOTE - For comparison I show Panache's tension for consideration of the Mk II SJ23, both of which are equipped with 5/32" wire.  The difference may be due to instrument calibration, wire size or the different types of stainless steel wire, 302 versus 316.

• Before adjusting anything you should lightly tension all wires, center the mast side to side, set the mast rake and then slightly tension the forestay/backstay to the point of about 3" of deflection in the forestay with slight hand pressure.  When you tension the shrouds always sight up the mast kerf (mainsail slot) to ensure the mast is straight.  Sometimes you can turn one of the upper turnbuckles too much and you create a sideways bend above the spreaders.  Similarly if you turn one of the lower turnbuckles too much you create a sideways bow in the middle of the mast.

• I find I can adjust one full turn on each turnbuckle until I achieve about 3/4 of the tension I want and then 1/2 turn until done.  After the shrouds are done, turn the the forestay and backstay turnbuckles equally to maintain mast rake until the forestay is about 300 lbs and you have ~3" of deflection with moderate hand pressure.  I have a split backstay so I can run a little less tension in the forestay when the boat is at rest and then tighten it up when the boat is sailing, especially for stronger winds.

Now, all this may seem to be a lot of technical mumbo jumbo but the boat really responds MUCH better if you take the time to do this.  The first time is a PITA but subsequently it takes less time to keep it in tune.
I set the mast rake with the boat in the water at the dock loaded with gear for sailing.  After the first setting the tension will change very quickly with a strong blow so you should redo the tension to your initial settings.  After the second setting the tension will hold nicely for the remainder of the season.  If you find a wire has changed a lot the next time you check it then look for a broken strand in that wire or a loose lock nut.  Pin all turnbuckles when done and sleeve or tape the pins.  I use 3/4" schedule 20 PVC tubing over my turnbuckles to protect the sails.  You can buy it at a hardware store.  The tubes are 2' tall and vent nicely to maintain SS finish. 

There are as many methods of setting wire tension as there are sailors.  I have found this works very well for me over 6 different boats.  Good luck and email me if you have a question or problems."  Ray Bowles  TOP

A Lesson Learned Setting Rig Tension Under Sail - "Panache in cruising mode has 70 lbs of ground tackle in the anchor locker plus a 5 Kg anchor on the bow roller, 10 gallons of drinking water under the V-berth tank, 2.5 gallons of flush water in the head, some stuff is lying on the V-berth, a 50 lb battery under the starboard settee, 2.5 US gallons of gas in the port cockpit locker and a 70 lb outboard on the transom.  She floats level on her lines but heels ever so slightly to starboard in the slip.  The turn of the transom is about 2" above the surface.  The mast has ~8" of rake, is equipped with roller furling on 5/32" rigging tensioned with a split back stay adjuster, the center board usually hangs just aft of vertical resulting in a light feel at the helm.  If the Tiller Tamer is locked she can maintain her heading and follow wind shifts provided I don't move around too much in the cockpit. 

A sail and tune session with some buddies in 2018 demonstrated something I could never learn when sailing solo.  The three of us purposely went out in a breeze that would heel the hull to 20⁰ to tune the rigging.  The boat sailed well but the 1/8" shrouds were a tad loose.  After the shroud tension was tightened as per Clark's recommendation, Panache could point 5⁰ higher and sailed livelier when the turnbuckles were tightened only one more turn.  This was reported by an experienced sailor on the helm who had never sailed an SJ23.  It demonstrates how effective correct tension is, which was also reported by Ray.  Later I used the Loos gauge to fine tune the tension, equalizing port & starboard.  Panache's settings for 5/32" wire are shown in the table above."  Bob Schimmel  TOP
 

Mainsail Trim - Since it is possible to induce only a small amount of mast bend in a mast head rig, the luff is cut fairly flat and shape is produced by broad seaming the Dacron cloth.  As the wind increases, pull the Cunningham down to move the max draft forward to 35-40 % back from the mast.  You'll find that by removing the horizontal wrinkles in the mainsail luff you'll be very close.  The outhaul should be adjusted so the sail has 6" or so of belly in light air while sailing upwind and downwind in most airs, and pulled all the way aft as the wind increases and the boat heel approaches 20⁰.  Trim the mainsheet so that the uppermost batten is almost parallel to the boom or slightly falling off to leeward.  A tell tale at the leech of the top batten can tell you whether the sail is sheeted too tightly and stalled up there.

Jib and Genoa Trim - The 110% jib should be used in a breeze that produces 20⁰ or more of heel.  The mainsail may be reefed according to the wind strength, however the SJ23 should always be sailed with <25⁰ of heel (when the pulpit inside leg is vertical).  The genoa will be happy if the leech is sheeted to 3-4" outside the spreader and the foot is just inside the lifeline on a beat, being careful not to pinch high, which keeps the boat driving hard.
- One method of depowering the jib is to move the sheet lead farther aft to let the top of the jib twist off, and/or release the mainsheet a bit, even to the point of luffing.
- If you have a split backstay, this is another tool for affecting the jib/main relationship.  Starting in a lighter breeze with the backstay fairly loose, halyard fairly loose, the first trim increase with wind increase would be a little more halyard tension .  Look at the jib/spreader relationship that changes with only slightly more halyard tension: the slot closes up.  Get a little puff, and the slot opens up.  More backstay: slot opens up.  More halyard, slot closes.

Sheet Tension - Sheet tension and the angle of the sheet leads should be adjusted so the sail luffs evenly top to bottom when sheeted in for windward sailing.  Generally the genoa should be sheeted so the leech is 2" or 3" off the spreader and the body of the sail should parallel the outer shroud from the spreader to the chain plate.  It may be sheeted more tightly for flat water.

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