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 track..er, 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. 

Studio Gang exhibit at the Art Institute of Chicago

In the middle of CYR’s busiest season ever, an opportunity came along that was just too cool to pass up!  

Chicago-based architecture firm Studio Gang was presenting an exhibition of their work at Chicago’s Art Institute, and they came to CYR for a very rigging themed part of the project.  They’d created four “rope rooms” made from steel rings and rope. The designs were taking cues from past designs and buildings, and needed to be secured to the ceiling of the gallery.  Initially they wanted to go with steel cables, as was traditional for this sort of thing.  We had a meeting to sort out costs and dimensions of turnbuckles and cable, and I happened to bring a piece of New England STS-75, just to provide an alternative.  Once they saw the dyneema sling next to the clunky swaged cable (or-gasp-rope clips per the drawing) their eyes lit up!  The dyneema was lighter, easier to install and cheaper. Most importantly the slim white rope would be far lower profile compared to steel cable and turnbuckle, and where it was visible it would blend in with the rope rooms themselves.

Once we’d decided on going with cordage, CYR had to find a way to make the assemblies to a tight length tolerance, ensure no stretch and still provide a way for the architects to level the rooms to the floor once installed.  Enter the lashing thimble!

CYR has been using thimbles for adjusting fixed assemblies and low travel/high load purchases for years.  Initially it was custom machined and anodized rings, and now Antal and Tylaska are making these in volume for great prices.  So long as these are applied properly (please no more spin sheet turning blocks!) they’re fantastic products.  The right length was critical, as well as having zero movement once installed, so they were made and prestretched on CYR’s testing bench.  Each sling was taken to 1500lbs to remove the initial stretch. As part of the package we prooftested one assembly, and provided an install demo and photo instructions.  The installers loved it, and were blown away at how fast and easy it was to work with, getting our parts in took less than a full day!405418_10151187498952502_1706797292_n.jpg (720×960)

After a quick inspection during installation, it took a few weeks before I was able to see the finished product.  It’s a real pleasure to see CYR rigging in such a unique location, and the rooms look great and fit with the rest of the exhibit well.  The architects seemed very interested in the capabilities of Chicago Yacht Rigging, and are going to visit the shop and North Sails loft soon, hopefully we get more exciting projects from outside the the boating world!  Here are a few more images, and be sure to check out the greater exhibit now through February! 


Architectural Exhibit: video

Here’s a link to a video of the Studio Gang exhibit at the Art Institute of Chicago. CYR supplied the suspension system that hangs the 4 rope rooms from the ceiling.

The client originally wanted stainless cable and turnbuckles, for load capacity and adjustment, however after seeing their drawings I had my fingers crossed that they would be open to using high tech line, as it would share the look of the project, as well as being cheaper, easier to assemble and most importantly far lower visibility.

They were crazy about the concept, and I think it turned out looking really nice.

The specifics are New England STS 75 Dyneema, spliced to Antal thimbles and lashed in place using smaller dyneema line.  The key was to prestretch the lines to 2x working load so there would be no movement once the exhibit was installed.  The installers really enjoyed working with the dyneema slings, and said it was much easier than wire.

Antal

A pair of Antal Mini snatch blocks, and a bare loop with carbon dogbone. Sky’s the limit of attachment options with these, and theres loads of uses for these-and Antal’s larger-snatch blocks.