SJ23 Tech Tip F34b, (Created 2021-09-20) Greg Overton, Bob Schimmel.


Dyneema Standing Rigging for Goodpain
Specs, Mast Connection, Technora Sleeve, Construction Stretch, Lashing Line, Mast Step, Spreader Ends.

Hey there SJ23 crew!  I finally got around to taking photos of our new standing rigging after we got the mast up on Goodpain.  This is our progress at this point in time.

When we took stewardship of Goodpain on May, 2021 we knew the ageing rigging was high on our list for replacement.  She hadnít had sails hoisted in 3 years or more.  We sailed the snot out of her for the first few weeks and the rigging complained.  I donít have a pictures of this, but in late June I was on a beat to weather in ~25 knots of true when the forestay wires started twanging like a guitar string.  The strands of the 1x19 wire started letting go, one at a time!  We immediately put her in irons and doused the headsail to discover that four of the strands had broken at the turnbuckle and we had a veritable birdís nest of strands 10' above the deck.  We instituted a moratorium on sailing until we could replace the standing rigging.

I spend a lot of time around the racing community here and have some friends who work for North Sails, plus others who helped to build America Cup boats.  Iíve long been convinced that Dyneema was the way to go for SJ23 rigging.  I contacted John Franta, the owner of Colligo Marine, who helped me spec out rigging for Goodpain.

We used 5MM Dyneema Dux (heat-stretched) covered with a Technora chafe sleeve from Premium Ropes.  Covering the Dyneema is not normal practice.  I have not found anyone who has fully covered Dyneema rigging with a chafe sleeve, although Iím sure itís been done.  The reason that itís not necessary and difficult to do, is because of how compressed Dux already is.  We decided to do it because we wanted graphite blue rigging.  I mean,Ö come on,Ö it has to LOOK GOOD!  In reality, Technora protects against UV damage and sail/sheet chafe.  It could also be used to cover a length of Dyneema so a line locker can grip it.  It should extend the life of the Dyneema shrouds.  By the way, bare Dyneema is good for ~7-10 years according to John.  Covered, as Iíve done, they should last as long or longer than the SS wire they replaced.

DYNEEMA SPECIFICATIONS - In terms of sizing the Dyneema, you actually size it for the STRETCH, not the breaking strength.  I noted from Tech Tip F34a that Bob chose to upgrade from 1/8Ē wire to 5/32Ē wire, so I chose to spec the Dyneema against 5/32Ē wire for comparison.  5mm Dux will stretch approximately 50% less under load than 5/32Ē (4mm) 1x19 SS wire, and has an ultimate breaking strength roughly 4 times higher (2,822 lb for SS, 10,472 lb for Dux)!  The following 3 charts are from the Colligo Marine website.

Dyneema Stretch Chart
(John had info for 5mm Dux that he provided over the phone)

Breaking strength of 5mm Dux:

Breaking strength of 4mm 1x19 wire:

CHEEKY TANGS to CONNECT SHROUDS to MAST - Of course we had to convert all of our terminations from wire to Dyneema.  For the mast connections that meant using their ďcheeky tangsĒ and for the chain plates using their knot-stopper terminators.  Pictures below.  By looking at their drawings online, I noticed that the cheeky tangs should be able to fit over the spreader mount bolt and that the spreaders should be able to butt up against the cheeky tangs!

I removed the spreader mount bolt and compression sleeve and replaced the bolt with a longer one to accommodate the new length.  And tested it out.  Starting to feel hopeful!  Itís gonna work!  I straightened one end of the old bolt to remove the sleeve, wrapped the new bolt in electrical tape to electrically isolate the aluminum and stainless and then bent the new bolt to match the old one.  As a side note, my original bolt was not symmetrical.  I measured the angle with a digital gauge and the two sides differed by ~5 degrees.  The new one is much better.

At left spreader compression bolt straightened.
Below is longer bolt with cheeky tang connectors installed for shrouds.


TECHNORA SLEEVE to PROTECT DYNEEMA - To use the Technora chafe sleeve I had to use a covered eye splice instead of the standard locking splice recommended by Colligo Marine.  Getting the Technora sleeve over the eye splice was a bear.  The first prototype took me 3-4 hours of swearing and sweating to complete.  I thought of abandoning my plan to cover the new rigging, but then it occurred to me that some tension might help.  I built a tensioning rig between my workbench and the tie down in my van (because I could move the van to accommodate the different lengths) and it worked like a charm.  Now I was down to about 30 minutes per termination (with 12 total to do, two per length of rigging).

Comparing length of old wire and new Dyneema shrouds.

First shroud covered with Technora sleeve to cover eye splices.

Bottom of shroud on a Line Terminator.

Top of shroud on a Cheeky Tang.


REMOVE CONSTRUCTION STRETCH - Once all six were complete there was one final step.  Dux is pre-stretched at the factory and when it is spliced the fibres loosen and they must be tensioned again to restore the stretch.  John said that for a SJ23, based on its displacement and righting moment, the 5mm Dux was overkill.  I shouldnít have to pretension these again.  ButÖ ďanything worth doing is worth over-doingĒ so we hitched them up between our 4Runner and some bollards at the end of our alley.  We had one spare piece that I wanted to use as a proof test, so I hooked that one up first and pulled it.  We ended up breaking the tire loose on the vehicle!

This is a screen grab from the video showing the setup.

All the shrouds stretched and ready to go on the boat.

TENSION SHROUDS with LASHING LINE - A lashing of light Dyneema is used on the deck end of the shrouds, forestay and backstay to tension the standing rigging.  Some people still use a turnbuckle for this application but for an SJ23, and because I wanted to be able to loosen the shrouds quickly to unstep the mast, I used their stopper knot lower chain plate adapter (typically used for beach cats) and 4mm Dyneema lashing line.

Hereís one of the cool parts.  The length of the replacement rigging is very flexible.  Because youíre going to make up the length with a lashing, your tolerance on shroud length is pretty large.  I ended up using very long shroud lashings because Iím planning to move the chain plates to the cabin roof in the spring, as well as converting to integral composite chain plates instead of stainless steel.  That will reduce the length of my lashings by ~12-14Ē, so I made them about 28Ē long this time.  In the spring, when I move the chain plates, I wonít have to make new shrouds.

  • Initially I tied bowlines where there should be an eye splice.  I did that to prove this conversion wasnít all folly.  Now that I know it works all the lashing eye splices are done.

  • Left - Dyneema lashing line.

  • Below - New rope clutches.

Deck views


Back stay lashing.  (the vice grips don't stay!)


I tensioned the rigging using a Loos gauge with a conversion table from Colligo Marine:  Colligo did their homework to convert a gauge calibrated for steel.

MAST HINGE PLATE - While I was at it, I replaced the mast step plate with one I machined a few months ago.  I also fabricated a new gooseneck with a spare.  To avoid pulling tension on bolts through the deck and to use the compression strength of the mast itself, I wanted a mast step with integral attachments for halyard fairleads.  I found a piece of standard aluminum C-channel that is the perfect size.  Holes were drilled through each side, and I did some end milling for sex appeal, flats for the spacers, then followed with sanding and polishing and it was ready to rock. 
NOTE - I machined a slot instead of a hole for the hinge pin because it it allows the mast about 100 of athwartship movement without torquing on the plate when raising and lowering the mast.  The sloped insides also allow athwartship movement.  The slots do not alter the function of the step plate when the mast is in its sailing position.  When I loosen the shrouds to step/unstep the mast, I won't have to be quite as careful to keep it perfectly centered for fear of damaging the deck.

New mast hinge plate and goose neck U-joints, plus a spare.

Static lashing blocks at base of mast.

I routed the halyards to the cockpit and secured them with Spinlock XTX rope clutches.  So far Iím pleased with how they work!


Synthetic rigging demands smooth curves over the spreader ends.  That is what this section is about.

SPREADER ENDS to SUPPORT SHROUDS - I replaced the spreader ends with new ones drawn in CAD and printed out of carbon fiber-reinforced nylon and then filled with West resin.  The spreader end is drawn to be perfectly vertical on the bottom and ~150 inward at the top, with the fairest curve possible in the ~32mm outside diameter of the spreader end. 

They are designed to remain attached to the shroud instead of the spreader, so I didn't use a bolt to hold it to the spreader.  I whipped the each end straight through the center of the shroud, which means I should be able to adjust, inspect, replace it easily.  When I unstep the mast, I simply unplug the end from the spreader and it stays attached to the shroud in the correct place.  When I step the mast, I plug the spreader onto the mast fitting and the spreader end into the spreader and hoist away! 

(pictured in CAD without the whipping holes drawn)


Goodpain is now equipped with Dyneema shrouds, backstay and forestay.  She has several hanked on headsails using brass hanks, albeit highly polished with a Dremel Tool to eliminate burrs that can damage the Dyneema forestay.  In the future the brass hanks may be replaced with soft shackles.  They are a little slower to install but will yield other benefits.

To douse a jib, we install a dousing line (Tech Tip F11) to the sail when itís rigged.  Itís a 5mm covered line with a small stainless steel carabineer spliced to the end.  The carabineer hooks onto the halyard shackle.  From there, the line goes through a block on the foreword most hole of the toe rail, then aft through some fairleads to a cam cleat in the cockpit.  It is left loose for hoisting, then snugged up to remove most of the slack.  The line just sits up along the forestay while sailing.  When itís time to douse, especially single handed, you release the jib halyard and pull in on the dousing line.  The dousing line hauls down on the head of the jib and accordions the sail straight down to the deck.  If you leave the jib sheeted in for this, then it makes a nice, neat stack pack on the side deck.
Bonus: we can leave the dousing line cleated at this point while weíre doing other things and thereís no risk of the jib launching itself or dipping into the water. 

The all in cost for the Dyneema rigging was about $1,200.00 US (2021).  Most of that was for the special new hardware required for the Dyneema.  If I were to replace the Dyneema it would cost only $250.00 US.

Overall Iím exceptionally pleased.  The rigging has this crazy space-age-yet-traditional feel to it when youíre standing in the cockpit.  Not to mention Iíve load-tested each piece well beyond any force they could experience aboard the boat.  I went for a sail in moderate wind on Tuesday evening and I must say the rigging is STUNNING under sail.  It already out performs my old rigging without any tuning.  Granted, Iím pretty sure my old rigging was factory original vintage and was also not tuned to within a mile of spec. 

If anyone has any questions about this process or is interested in converting their SJ23 rigging to Dyneema, please email me.  Iím happy to put you in touch with John at Colligo Marine

Fair winds, my friends.

Greg Overton
SV Goodpain
Tacoma, WA

Go to Tech Tip P07 to see the rest of the modifications.

See Tech Tip F34 - Standing Rig Maintenance & Replace.
See Tech Tip F34a - 5/32" SS Rigging for Panache.

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