Clutch Testing, engagement and load slip for 10mm line

Sails and cordage keep evolving with every new fiber, construction and treatment.  With each generation sailors get a stronger lower stretch product that performs better than the last version.  For riggers, we’ve got ultra low stretch rope cores, and incredibly touch and sticky covers that can handle the increased loads. This is key to handling new sails that have high carbon contents and other low stretch adaptations.  With low stretch sails, the dynamic loads of sailing get transferred into the lines. If your core is stretching, the lowest stretch sail in the world won’t hold it’s shape. If your core is low stretch but your covers can’t handle the increased load, the results are either cover failure or slip.  We’ve got some great solutions for problems like that, but one of the hardest areas to get good performance out of is the rope holding clutch.  To see what the best solution would be for the typical Chicago Yacht Rigging customer, I set up a simple test on the rigging bench and tried out a variety of common clutches.  To paraphrase the great Mr. Fry: I’m shocked, well, not that shocked.

The baseline for most of the testing I do is aimed at my most common type of customer’s boat; racing boat, 35-40′ long.  I wanted to use rope that represented what I’m likely to see when I visit a boat that needs clutch help, so selected 10mm V100, a fairly common vectran cored, polyester covered double braid.  After that test was done, I also tried an upgraded cover with 10mm New England Poly Tec.  The Poly Tec cover is often specified where the line sees either high abrasion or needs to be high grip, so it made a lot of sense to try here in a clutch.

The testing method was a bit tricky to decide on. In a perfect world, I’d have a large static load like a weight providing constant pressure on the rope. This would best represent tensioning a halyard, with a loaded sail on the other end.  Our test equipment instead has a winch on one end of the bench and a hydraulic cylinder on the other,  with the clutch in between.  To do our test I anchored one end of a line to the cylinder, ran it through the clutch, and then tensioned the other end on the winch.  Each line was knotted in place, so that I could move the knot and therefore move the point on the rope where each clutch was used.

What I wanted to get out of the test was how much slip there would be  when the winch side load was released (initial slip) and how much slip  it would take to then reach the target load. In any clutch there is always going to be a certain amount of slip as the cam, teeth, jaws or rope sleeve engages, but less is definitely better than more here! The process was easy: first stretch the rope and engage and disengage the clutch several times to remove the stretch and set the knots. Then load the line to 1000lbs. Following that I’d release the line from the winch to see how much of the load was lost, and how much the line would slip while that happened. Then I would tension the cylinder to simulate the load continuing to be present on a halyard.  The test would be repeated for a several cycles, and then I’d take the average number for three different values:  how much load remained when the winch was eased, how much the line moved as the winch was eased, and then how much slip through the clutch it would take to get the load back to 1000lbs.  It’s a hard test on clutches as the load behind the clutch would not be constant, as I only had about 4′ of rope between the clutch and the cylinder. This meant the load would drop considertably with the smallest amount of slip, leading to big drops in tension.  The measurement of slip to get the tension back to 1000lbs was going to be the more important number here, as it would measure the transition from near zero load to 1000lbs, so we could see how much rope had to pass through the clutch to engage to our target.

The other part of the clutch was full load releasing, to see how much the line was worn. If you’ve ever read your clutch instructions, you’ve probably noted that every line is supposed to be winch tensioned before the clutch is released.  This is ideal, however it has very little in common with how crews actually treat the clutch during racing.  In our projected 35-40′ boat racing around the buoys, you can imagine that the genoa halyard clutch would get dumped at least twice in your typical buoy race, after the spinnaker set. Lastly the top two, middle two and bottom two clutches were tested head-to-head for a video that provided a visual example of how they compared.

For products to test, I wanted to be as comprehensive as I could so had every brand and type of clutch I’d sold that would be appropriate for our imaginary mid size racer cruiser with 1000lbs on the halyard.  I started with the venerable Spinlock XTS/XCS.  This is by far the most common clutch we encounter as it’s been standard equipment for years from the J Boats, Beneteau and other factories.  All of the XTS and XCS clutches function the same: a stationary base plate, opposed by a rotating cam above. As the rope slides through the clutch, the cam rotates down to the baseplate, and the gap between the base and cam get’s smaller and tighter until the rope stops moving.  However, all XTS/XCS are not created equal. The model numbers always end with one of two numbers: 0610, or 0814.  The 0610 indicates that the clutch is sized for 6-10mm line, and the 0814 is for 8-14mm line.

Web XTS_1


What this means in practice is that best rope holding for the smaller cam is going to be with 10mm line, and for the larger cam with 14mm line. It’s incredibly common both for OEM and customer purchases to get the 8-14mm model, with the thought that the bigger range will be more versatile. This is a mistake, as the typical 10mm halyard on our fictional boat will be quite small relative to the cam on the 8-14mm clutch, and so we’d expect a lot of slip. To that end, we tested the 0610 cams, the 0814 cams, and the 0610 ceramic cams. Wait, the what? Spinlock has also started making a ceramic coated cam for these clutches, with the goal of improving initial slip, ultimate slip and rope wear, optimized for blended cover lines like our 10mm Poly Tec sample. We tested the Spinlock XTS with the 6-10mm cams, and the XCS with 8-14mm cams, and then the XCS with the 6-10mm ceramic cams. The XTS and XCS use the same cams, baseplates, handles, just with different fasteners and metal side plates (XCS) vs plastic (XTS). For the purposes of our test they’re the same, but it did save me some time swapping cams out! The XTS0610 usually sells for around $130, with the ceramic version usually being around $175 (although you can purchase the bases and ceramic cams separately to upgrade your existing XTS or XCS) and the XCS is around $215. In terms of load capacity, the metal sided XCS has a higher working load, 2640 vs 2200lbs for the plastic sides on the XTS.

Also from Spinlock was their XX clutch. This was an unfair test in some ways, as the XX is a far higher specced clutch for this test, with a load capacity significantly higher (3970lbs vs the 2000~lbs for the others) and a much higher cost (usually around $450 although there are other variants like side mount, lock-open, ceramic and carbon versions that are all higher priced) so it’s a bit overkill for our pretend boat (which needs a name… Clutchy McClutchtest?) as this clutch is found on lots of 40-50′ boats. However, this clutch is really designed for larger lines than our target 10mm line, so would it actually be at as disadvantage? To find out, we took it to our test, bench. The XX uses textured jaws that slide on roller bearings to hold the rope, so there are two gripping surfaces in motion, with a larger contact surface.


Becoming more common on production boats are the clutches from Antal. Their V Cam clutches are a cam style clutch, but instead of the flat grooved cam as found on the Spinlock cams, the V Cam is-surprise!-V shaped. They’re also stainless steel instead of aluminum.  Loads of newer J Boats have these from the factory, so we wanted to see how it would handle our lines. The working load was lower than the others at 1874lbs,  as was the cost at around $115 each.



Less common on race boats, but often specced on cruisers are the Lewmar D2 clutches. Instead of a moving cam as on the Spinlock and Antal clutches, these use a series of hinged plates, that tilt forward with the line and apply tension over many different points.  The advantage here is that the multiple points of contact reduces the point load on the rope cover. The cost on these is around $120, and the working load is the lowest of the test at 1102lbs. The typcial assumption is that the Lewmars are kinder to line, but slip a bit more than the Spinlocks.  The other differentiating feature on the Lewmars is that the handle is hinged at the aft end of the clutch, not the front as all of the others.  This can lead to hilarious installation mistakes, so do be advised that the clutches have an embossed picture of a winch, with an arrow, so there really is no excuse!

Finally from the “now for something completely different” department, we have the Constrictor. This has no cams, plates or jaws, but instead uses a long sleeve of hollow rope which constricts-ha-on the rope and holds it in place by the same principle as a single braid splice. The clutch is also unusual in that it takes quite a bit more space than the others; the spec sheet says 25”, but I found better results with the bungee stretched out so that the whole clutch took up closer to 30”  The bungee  cord tension is key: if the tension is too low, the clutch will slip more before engaging. Too high, and the clutch won’t release. I have some concerns over how the sleeves will hold up over time, but haven’t modeled that.  We also had a bungee hog ring fail during testing, which in the real world would make the clutch unable to re-engage.  What’s really slick about these is the forward mounting hole is actually a slot, so you could use these with fastener spacings from 70-90mm. The cost on these is usually around $175. They don’t list a working load, but do list a break load at 4920lbs.   These have been used on many offshore boats as the rope sleeve puts less wear on rope covers, but how would it hold?




So here are the numbers for the 10mm V100 tests:

Clutch Remain after release (kg) Release Loss    (mm) Return to 1000lb in mm
XX 31.3 7.6 11.3
XCS0610C 72 8.6 14.3
XTS0610 33.6 12 16.3
Constrictor 10mm 39 18.3 18.3
Antal VCam-0814 (10mm) 23.3 34 20
Lewmar D2 10mm 22.3 17 21.3
XCS0814 5 50 33.6


And here with 10mm Poly Tec



Clutch Remain after release (kg) Release Loss (mm) Return to 500kg in mm
XX 102 5.33 8
XTS0610C 76 6 12
Constrictor 66.33 8 14.66
XTS0610 36.33 7.33 15
Lewmar D2 10mm 44.33 16 17.33
Antal V Cam 0814 37 22 18.66



Phew, lots of numbers, which one matters?  Good question.  The release loss number was surprising at first; this number was what load remained on our load cell when the line-at 1000lbs-was released from the winch. The numbers are all in the double digits except for the Poly Tec in the XX which frankly seems like a huge loss. However when you consider that the loaded portion of the line was only several feet, and there was nothing keeping constant tension on it, it makes sense. The “release loss” column is how much line slipped through the clutch as the winch was unloaded. Given how little load remained, this number should be considered in context, and I don’t think it’s very useful. The most useful number was how much slip it took to bring the load back to 1000lbs on the cylinder. This number was corroborated when we did the head-to-head videos, as the slip numbers were similar.


So, what are our conclusions? Let’s start with the obvious: the wrong size clutch did the wrong thing. The 8-14mm cams slipped the most, which is not a surprise. The 0814 cams simply have to move more to catch 10mm rope than they would for 14mm. The rope when removed looked flattened out.

The next up was the Lewmar D2, which slid the 6th best with V100, and 5th best with Poly Tec, although it did better than it’s slippy reputation would suggest. The impression left on the rope was wavy, as opposed to flattened like the Spinlock. What was really shocking was the wear from the D2.  I saw the most wear of any clutch with the D2, which could have been because we were using it quite close to it’s working load.

The Antal’s were next up, coming up in the middle of the test. The triangular profile of the grippy surfaces did not seem to make much difference here, although it was neat to pull the line out and see it be triangular. This was 5th best with the V100, and 6th best with the Poly Tec.


The Constrictor performed next best (4th best with V100, 3rd best with Poly Tec), although there are some asterisks present on this test. The Constrictor’s rope holding is all done with the rope sleeve, which is tensioned forward by way of a bungee. I tried quite a few bungee tensions to see which was best; the higher the tension on the bungee cord, the lower the slip, but the harder it was to release the clutch.  The testing was done with the bungee as taught as it could be while still being releasable.  Incidentally, one of the frequent questions on this piece of gear is “will it release under load” the answer is yes, as at 1000lbs, this was actually easier to release than the other clutches excepting the XX. The other asterisk, was that this number was obtained without a “cheat code”, Say what? You can cheat the Constrictor tighter if you manually “milk” the rope sleeve forward until it’s tight on the rope.  In our tests, this reduced the slip-to number down to 14mm average.  As a sidenote, you can also cheat the Spinlock XTS/XCS as well, by partially opening the clutch after closing it, and manually pushing the cam down onto the rope (doing this netted the following numbers in slip-to: XTS0610C 13.6mm, XTS0610 12.3mm)


Then cam in the standard Spinlock 0610 cam at 16.3mm, then the ceramic 0610 at 14.3mm for V100, and 0610/15mm and 0610C/12mm.  Since these are pretty much the default for rope holding, it wasn’t too surprising.  These were quite hard to release at 1000lbs, as was the Antal and the Lewmar. The release felt harder to me than doing it on an actual boat like a 36.7 does, although it’s clearly not a back to back test. This does make me think that the typical genoa halyard load is probably less than 1000lbs, especially after a mark rounding where the rig is being pushed forward, the apparent wind is lower and the sheet is (better be!) eased.


The double-edged sword of the XX performed best, with the least slip to at 11.3mm with V100, and 8mm with Poly Tec, and an easy release.  One one hand, it’s clearly the most expensive clutch so perhaps should be best, but on the other, it really should hold best with 12mm line, not the 10mm used here.  To see how it would do, I also tried only this clutch with a 12mm chunk of line, and got averages of 150lb remaining load, 4.3mm initial slip, and 7.6mm slip to, which was pretty impressive.  I can’t say this is the most cost effective solution for our imagined boat, but it certainly would be the best in terms of slip, especially if you were to bulk the line to 12mm at the clutch.



Suggested Retail Fasteners and hole spacing Max Working load lbs Slip to 1000lbs V100 Slip to 1000lbs Poly Tec 10mm
Spinlock XX0812 $523.49 140mm 3970 11.3 8
Spinlock XCS0610C $157.04 70mm 2640 14.3 12
Spinlock XTS0610C $206.36 70mm 2200 14.3(projected) 12(projected)
Ronstan Constrictor 10mm $189.54 70-90mm 4920(break) 18.3 14.6
Spinlock XTS0610 $262.34 70mm 2200 16.2 15
Lewmar D2 10mm $130.71 70mm or 107mm 1102 21.3 17.33
Antal VCam814 8-10mm $119 105mm 1874 20 18.6
Spinlock XCS0814 $262.34 70mm 2640 33.7 27



For those of you that prefer a visual comparison, here are some head to head clutch testing videos



Here was our top performing clutch, up against our best performing cam in an XCS clutch. As you can see the differences weren’t great, but there was a little more movement with the XCS0610C than the XX0812.


Here were the middle ground clutches, with the Constrictor vs the XTS0610 with the standard cam. The different angle from the other videos is due to the ginormous length of the Constrictor existing right where I had shot the previous videos.

Here are the stragglers in the test, as you can see it’s really very close between the Lewmar and the Antal.


For a comparison on what the clutches did to the rope, here are the Poly Tec samples, immediately after the head-to-head videos.

Top is the Spinlock XTS0610. It’s clearly flattened out the line, which makes sense as the cam is flat/toothed, pressing on a flat toothed baseplate.  The Constrictor shows no deformation or wear, which is one of the reasons I would think this unit is going to do very very well if rope longevity is your concern.

Top in the above image is the line after the XCS0610C was done with it, as you can see  the line gets flattened quite a bit. One of the treatments we do to improve rope holding, is to bulk the line internally, which adds both size and stiffness to the rope. The stiffness keeps the rope rounded under load. The XX flattened the rope as well, but not as extremely, likely do to the increased area.

Wow. The Lewmar really did a number on the Poly Tec, which is an extremely tough rope.  This is probably because we were using it at the upper end of it’s working range but it’s still surprising as this clutch is commonly regarded as being gentle on line.  The photos don’t show it well, but the Antal compressed the rope into a triangle shape which was kinda neat.


Here are some other pics of the rope wear, shown next to the clutch.  This is after several cycles to stretch the rope and set the knots, then 3 tests of taking the clutch to 1000lbs with the winch, easing the winch, then using the hydro to bring the load back to 1000lbs, then dumping the clutch. Generally, the XX and the Constrictor showed no wear that I could detect, the Spinlock 0610 regular showed some, then the


The Spinlock XX was easy to release, and didn’t show any wear on the line with the standard jaws.

The Ronstan Constrictor is really kind to line, and CAN be released under load which may surprise some

The Spinlock XTS0610 showed some wear, a lot more than I was expecting but I believe that the load and releasing were probably a little more extreme than the usual boat experiences in 3 cycles.

The Antal V Cam wore on the line pretty similarly to the Spinlock 0610, but was very very hard to release so I only did it once instead of 3 cycles.

The Spinlock 0610 ceramic cams did wear the line a lot more on the V100 than it did on the Poly Tec. The ceramic cams are explicitly designed for blended covers like Poly Tec, so this is not surprising.

The Lewmar was surprising in how much wear it did to the rope. It was the only one to do significant damage to the Poly Tec.  If I were to do the test at lower loads, say 500lbs, I would imagine this would not be the case. 

1/8″ Dyneema Break Test Final: Bury Splice vs Brummel Splice

For the final it was no surprise to see the bury splice and the brummel splice.  The previous rounds saw knots, specialty splices and things done purposefully wrong, so these should be the top end.

The bury splice, again, is the tapered tail of 72x rope diameter, inserted into the rope to form an eye, and stitched to keep the splice intact under no/low loads. The brummel is the same, but with an interlocking weave instead of the stitch.

Well, as you can see it was the bury splice that walked away the winner, besting the brummel which lost at 2958lbs. This is 134% of rated strength for 1/8″ Endura 12, so pretty happy with the result. If you read the semi finals, you’ll get some explanation of why it’s so far above rated, but it’s nice to know CYR splicing is beating the numbers we use for specifying rope.

Based on the result,  you might ask why we don’t use the bury splice as standard, instead the brummel is the default for sheets and halyards.  The reason is the brummel is faster, and has a locking mechanism which can be verified and can’t possible wear out or be removed.  At the numbers seen in this and other tests, it’s always broken above rated for good quality lines, so I can use rated strength when speccing with no concerns about strength.

For the full series of tests:

1/8″ Dyneema Break Test Bracket: Quarterfinal Rd 1 Skiff Knot vs Bury Splice

1/8″ Dyneema Break Test Bracket: Quarterfinal Rd 2: Loop vs Short Bury Splice

1/8″ Dyneema Break Test Bracket: Quarterfinal Rd 3: Bowline vs Sliding Sling Splice

1/8″ Dyneema Break Test Bracket: Quarterfinal Rd 4 Soft Shackle vs Brummel Splice

1/8″ Dyneema Break Test Bracket: Semi Final 1 Full Bury Splice vs Short Bury

1/8″ Dyneema break test bracket Semi Final 2: Brummel Splice vs Sliding Splice

That concludes the break testing for now, if you have suggestions or requests for similar tests feel free to get in touch with me at

1/8″ Dyneema Break Test Bracket: Quarterfinal Rd 4 Soft Shackle vs Brummel Splice

Here’s the last result from the quarter finals.  That’s an 1/8″ soft shackle with diamond knot on the left, and a pair of brummel splices with full buries on the right. They are in basket configuration to even things up with the soft shackle.

3718lbs break, and it was the soft shackle that failed.


Testing: Clutch Slip Solutions 1

Spinlock clutches are the de facto choice for halyard holding in racing boats. For holding and releasing lines at deck level theres nothing that comes close in holding power, controllability and the durability of the gear.  That said, it’s a pretty common job for a rigger to try to eliminate the slipping that occurs as the line slides through the cam.  Much of this is due to the way clutches and cam cleats work; the cams move out of the way in the direction of the winch when the line is being tensioned, and then when the tensioning is complete, the line moves back towards the sail, taking the cam with it until the cam is completely engaged and the line held fast.

Spinlock XCS with 8mm Crystalyne

Above, we have a Spinlock XCS clutch with the test rope, a piece of 5/16″ Crystalyne.  The cam is the toothed gray metal piece just above the line. It’s hinged where it meets the cam arm, which is again hinged where it meets the base plate.  When the clutch handle is open, the line can move in either direction since the cam is lifted away from the rope.  When the clutch handle is closed, the cam presses against the rope, which in turns presses against the base plate. When this happens, the line can only be pulled “with” the cam, away from the load (to the right in this photo)  This means that when loaded (moving to the left) the line jams between the teeth on the cam and the baseplate and is held in place.   In order for the holding of the line to occur, the line has to move towards the load a little bit, which engages the cam.  This is where we get our initial clutch slip;  it’s an inescapable part of how the clutch works, but it can be limited.

Here is a quick look at clutch slip: the lines loaded to ~470lbs, then released.  There are two things to note here: if you look at the cam under the clutch handle you can see it drop as it grabs the line, and also, thats a LOT of slip! Video: Clutch Slip

Another thing to note in the cutaway view of the clutch is that the line is flattened a bit where it is held by the cam.  Since rope is just a round braid of fibers, when it’s loaded from the side it will deform, getting flatter and wider.  This is an important bit of data to use when trying to minimize clutch slip.

The tests are being done with clutches provided by Spinlock.  In talking to them about the test, their expectations mostly revolved around proper sizing, as well as quality of the line.  Spinlock has done their own testing and wasn’t surprised when the best performance came from better quality lines using higher tech materials.  Even among similar constructions,  you can tell a higher quality line as it’s generally firmer, with less slop between cover and core. The size helps in that the gap between the clutches baseplate and cam can be greater before the line is captured, and the firmness helps in that the line will flatten out less, and therefore accomplish the same thing.

The problem of slip has paradoxically increased as cordage has gotten higher tech.  As we’ve gotten stronger fibers and treatments, downsizing line has become common so as to reduce weight and windage.  There are 35′ boats using 8mm line, where as a few years ago they may have used 12mm.  This means that the same load (or higher as sail technology improves alongside cordage) on a much smaller cross section.  Those same higher tech sails are also far more sensitive to losses in tension caused by slipping, so solving slip is all the more important.

This first test concerned a very common line, 5/16″ Yale Crystalyne. I consider this to be lower/middle of the road for a vectran cored line.  It generally works fine, and is quite easy to splice. That ease of splicing does indicate that the cover is relatively loose to the core.  It’s the cheapest vectran cored line commonly used in the US, and you can find it at just about every regatta.   The 5/16″ sample I have actually measured 7.1mm under load, a bit under spec.  It’s the smallest line that’s going to to be tested, and in addition to trying it “bare” it was tested with two sizes of core bulking, as well as a cover addition. The clutch is a Spinlock XCS fitted with the smaller of 2 cam sizes, the 0610 (6mm-10mm)

Core bulking is the addition of extra material inside the core (duh) which yields and increase in the overall diameter of the line, as well as a firmer line.  If done properly, the core insertion is tapered at both ends to prevent a hard point in the line and to eliminate any potential snag points.  The line for this test was bulked with a 1′ section of it’s own core, which increased the diameter to 8.5mm.  After the initial rough draft of this test, I was curious as to how a max diameter core bulk would work, and added a piece of 5mm dynex dux to another section of the same rope, which brought the finished diameter to a very firm 10.2mm.

Cover addition is taking a piece of cover and sliding it over the halyard, and splicing it into the halyards cover in the area of a clutch.  If done properly (the extra cover must be tight to the existing cover) , it firms the line, as well as increasing the diameter. It’s a bit more time consuming than the core insertion, and does result in a stiffer line with 2 hard spots where the extra cover tapers into the core.  I have seen past  failures of this type of treatment (in the cover) on older halyards with lower quality splices, so I do think of this as less reliable than core additions.  I used a piece of small New England ARC cover here, which brought the diameter up to 9.3mm.

Plain Crystalyne (top), bulked to 8,5mm, ARC covered to 9.5mm, bulked to 10.2mm

The test was conducted on the prestretching bench, which had a Spinlock XCS clutch mounted in the middle.  Tensioning was performed with a winch on one end of the bench, from there the line ran through a snatch block at the other end of the bench, then through the clutch in the middle where it was tied to a piece of 3/4″ nylon on the “load” side of the clutch.  The nylon line was used so it would stretch, and provide some pull on the Crystalyne as the clutch slipped.  After being tied to the test rope, the nylon line ran through _another_ snatch block on the other end of the bench, then back to the opposite end, where it was tied to a hydraulic cylinder on a load cell.  All this mess was there in order to provide a long run of line to tension against, as the first time I tried the test the clutch the tension on the line would drop dramatically after the winch was released. This was because there was only a few feet of line on the load side of the clutch before it was dead ended to the bench. Without load behind the clutch, the cams won’t engage.

To test the line, each section was brought up to 1000lbs or so and left to sit for around 5 minutes.  This should remove constructional and bending stretch, as well as make sure any stretch was pulled from the other components in the system.  For the test numbers, I took the line up to 600lbs, about appropriate for  a 10m boats jib.  Once it was there, I released the line from the winch, and measured how much the line moved, as well as how much the line had compressed under the clutches cam.

First the stock Crystalyne.  The actual size of the line under load was around 7.1mm, and in three tests is averaged 26mm, or just over 1″, of slip.  The pressure was dropping quite a bit, going from around 600 to the high 300lb range.  If this were on a boat,  I think the result would be quite a lot of change in the draft of the sail, and scallops off the hanks and/or wrinkles.  Really interesting was how much the line flattened out where the cams held it; down to under 1/4″! 

The next test was with the core bulked by adding a cut piece of the Crystalynes core.  This made the line firmer and larger, to around 8.5mm under load.  This is a pretty typical change CYR would make to a line thats been slipping, and I’ve had good results and reports from customers.  The slip was reduced around 40%, at 16mm or ~5/8″.  This would be a big improvement over stock, but would still show up in the sail. In three tests the pressure dropped from 600 to between 430 and 480lbs, and the line under the cam shrank to 8.1mm. Better, but not perfect by any means.

With an extra cover of New England ARC (great product!) the line was firmer yet, and measured at 9.3mm, or just under 3/8″  This is a pretty big increase, and I was expecting this to be our top performer, as in addition to the size we had the extra grip of the ARC.  It did improve, to around 11mm or 7/16″.  The line barely deformed under load, being 9.2mm where the cam gripped it.  Pressure dropped to an average of 510 lbs over 3 tests.

I’d done the initial test with those three lines, but wanted to try again with a more extreme treatment, and used a piece of 5mm Dynex Dux inside the line for a bonus test.  This is NOT something I would recommend actually doing, as the line is incredibly stiff, and I think theres a good likelihood of it jamming over a sheave or through a turning block.  Additionally, when bulked it was over 10mm, which is the max line in the clutch. This meant that even when the handle was open, the line still dragged over the cams a bit.  Oddly, using an actual 10mm line didn’t result in this, which makes me think that the incredible stiffness of this bulk was keeping the line from moving properly through the clutch. This would slow releasing the line, as well as wearing more quickly over the bulked portion. I believe the braid of the core was distorted a bit as well, so there may be a commensurate loss of strength with this goofy bulk.  It did perform well though, as it saw just over 6mm (1/4″) of slip, and the pressure only dropped to 565lbs. The line didn’t shrink at all where it was in the cams. Again,  I wouldn’t actually recommend this bulk, but it does illustrate the core (heh) result of this test.

The takeaway here is that the more material you have in the line, the better.  Bigger helps, but firmer is just as important.  The negative effects of the cams action are minimized with a good core bulk or cover addition, and getting as close to the max size the cam allows is key.

Based on this, I’ve modified the specs I’ll use at CYR for bulking halyards.  Typically, I’ve used the same size core for core additions.  In the future it’s going to be larger sizes of core, as well as prestretched pieces to make for a firmer core addition.  The goal I think, should be to get to just below max cam size for best performance, but not to make the line so stiff or large that it impedes the release through the clutch.  It’s been quite helpful to learn what the targets should be for this sort of work, and it’s going to improve the quality of the product I turn out.  Coupled with CYRs extensive database of boat measurements, we can now provide halyards that outperform bare lines and other treatments.  Contact me at today to discuss this and other ways to get the most out of your rigging.

While doing the first draft of the test,  I also encountered a few tricks that can help you on your boat while racing.  Both involve getting cam to grab the line more efficiently as the line is released from the winch. First, once you’ve tensioned the halyard, but before releasing from the winch, open and close the clutch handle, then open again and physically push down on the top of the cam. This will better seat the cam against the line.  Then, when releasing the line, let it off the winch smoothly and slowly. This keeps the relatively slick cover of the line from sliding over the teeth of the cam.  These techniques helped most with the untreated line, although they were still nowhere near the performance of the core and cover treatments.

The first test generated a ton of interest, as well as “you shoulda”s, so feel free to keep them coming, as well as any ideas for other tests on stretch or break testing.  The rigging season has started in earnest with the warm weather, but I’ll take the best ideas and give them a try on slow days and get the results up here. Thanks for reading!



Big boat backstay strop destructive test: ~2300lbs

Backstay Webbing Strop

1″ spectra webbing, believed to be originally rated at 5000lbs, used in vertical configuration for break load of 10000lbs.  Age max is 7yrs,  only know for sure that it’s older than 3yrs. If you’re using a safety factor of 5, which is more conservative than most GP boats seem to use,  you’re at a 2000lb working load.  Headstay pin max load on this boat is reported at 13000lbs,  guessing probably 7k max on backstay?  This strop was seeing 1/4 total backstay load. Broke at around 2340 lbs,  at the point where the overlap of stitched webbing began.

All that taken into account this is still pretty low break for this.  Guessing the age+original saltwater environment+load wore it out.