Stretch Test!

On my “Good Ideas To Do At Some Point In The Future Maybe When Things Quiet Down” (GITDASPITFMWTQ) list there has been an item that’s been hovering near the top of the list (above “Right grate American novel” but below “Close the door you’re letting all the heat out” ) has been a bench test to see how the different materials, treatments and brands of rope we use here at CYR perform in one of the most important metrics we have: stretch.

As cordage evolves, it almost always trends in 2 positive directions: lower stretch and higher strength.  In the last couple years strength has become less relevant as the finished size of the rope becomes the limiting factor.  If we really wanted to, we could have 4mm cores on 35′ racing boats and not be worried about it blowing up.  Stretch has become more important. If you look at the “flavors” that Dyneema generations come in,  the most recent iterations have become more and more stretch focused.

Dyneema SK60 (most similar to Spectra 750) was strong and light, but stretched, crept and wasn’t significantly stronger than the aramid fibers it was compared to. SK75  (Spectra 1000) was lower creep and much stronger. SK78 was lower creep, but not stronger (this is now the “standard” Dyneema from most marques). SK90 was stronger but no better on creep than 75, so has been supplanted by SK99 (better in creep and stronger).  DM20 is… weird and I’ve never used it.

In the past year,  I’ve made halyards with each of the ropes shown below.  All of these are 3/16 or 5mm so comparable in size and would yield a ~5/16″ halyard.  From the top:

MARLOW SK78 MAX The MAX line of Marlows Dyneema cores is their version of heat setting.

Defining characteristics: It’s black!  The black comes off on your hands. Second stiffest rope in test.  Looks cool. The braid angle is exactly average in this sample set.

Sizing:  The 5mm core measured 4.4mm after being loaded.  Round? Not really,  unloaded it measures 5.3 one way and 3.69mm the other

Dumb observation:  If this were a car, it would be an Audi A3.


Defining characteristics: Silver. Not as stiff as HSR or Max, but stiffer than STS78.  Longest braid angle.  Smells nice.

Sizing:  The 5mm measures 4.6mm loaded. Round? Meh.  It measures 4.73mm one way and 4.2 the other.

Dumb observation: If this were a football player, it would be Odell Beckham Jr.  Never heard of XTM either, but it’s good.


Defining Characteristics It’s white (comes in 7 colors too) it’s floppy compared to the Vectran and the Heat Sets. Very shallow braid angle. Gets super stiff once loaded.

Sizing 4.9mm under load Round? Round!

Dumb Oberservation While typing this up, I dropped all the samples on the floor. I could tell the STS78 just by feel. I bet if I were to total up all the STS78 (aka STS75 aka Endura 12) I’ve spliced, it could go to Belmont harbor from the shop and back.  Lets put that on the GITDASPITFMWTQ list!


Defining characteristics Gold! Much more abrasive than any of the Dyneemas.

Sizing 4.2 under load. Round? NO.  2.9mm one way, 4.6 the other.

Dumb Observation I totally forgot I had any Vectran in stock.  It’s gone from about 40% of my high tech cordage to exactly .8% ( I have sold one Vectran rope all year) If this were a car it would be a Pontiac, because in a few years people will be all “Pon-Tee-Yak? What’s that?”


Defining Characteristics It’s stiff! Really stiff. When you put a cover on it properly the crew all hates you for the first race because it only gets stiffer when covered.

Sizing: 5.1mm under load Round WOAH, they make round rope! 5.2mm one way, 5.3 the other. About as round as it gets.

Dumb Observation If this were a car it would be a WRX.  Not exactly pretty, some people don’t like how they feel but does everything really well. And I sometimes cover it with orange cover, and WRX’s are often covered in tacky aftermarket gear as well.


So how did they do?  Well, nothing broke and no one got hurt, which is good.  Before I share any results though, lets talk methodology.  Before we talk methodology, lets make a bunch of disclaimers for how rudimentary my testing methods are. Before we do that,  have you listened to Astronautalis? He’s great, and I think it’s a damn shame that the yanswer to the previous question is always “who?”

METHODOLOGY I spliced all the samples into 10′ lengths. Then loaded everything to 1000lbs with a dwell of 30 seconds.  The samples were length checked, and respliced to 10′.  Why respliced?  The construction stretch on new rope is huge.  Even heat set ropes lose some of their “set” when coiled and handled.  Splicing takes up a long length of rope, but then releases some of that once it’s under tension. Everything was loaded again and checked again.

To test stretch,  I loaded all the samples to 200lbs, did the CYR Load Distribution Procedure (hit rope with mallet, kick hydraulic cylinder) then then loaded everything to 100lbs.  A clamp was made off at the dogbone holding one end of the sample. Then the tension was added slowly until 1000lbs was reached and stable. The distance between the clamp and dogbone was then measured using a digital mic. The samples were then tested in reverse order after being left flat on the bench to minimize bending the rope.  After that test, all the samples were taken to 2000lbs with a dwell of 1 minute, then retensioned to 1000lbs.

ROPE Stretch @1000lb Stretch @ 1000lb 2 Stretch @ 1000lb after 2000lb load
Yale Vectrus 55.25 31.37 26.99
Marlow MAX SK78 21.64 19.52 11.64
Alpha Ropes D Core XTM 78 24.32 17.53 9.78
New England STS78 29.9 22.93 14.33
New England HSR 20.35 14.42 8.84

There is lots of interesting information here.  All the ropes developed less stretch after being loaded, with the benefits increasing with the amount of load applied.  This fits with what conventional but often ignored wisdom, as most riggers recommend preloading your halyards before use.  For mains I like to load the main halyard around the boom at the mainsheet strop, then tension the mainsheet as hard as possible. For genoas, jibs and code sails I use the tack fitting, tension with a winch, then “banjo” the halyard from the foredeck by pulling aft on the line.  For spinnakers I go get coffee and think about the weather.

The vectran stretched more, significantly more, than all the flavors of Dyneema.  This is not a surprise, but keep in mind that Vectran should in theory have less creep than Dyneema SK75 and below over time, although SK78 and Vectran are supposed to be comparable.  I will be modeling this, but since creep takes a long time to develop, I’ll be loaded the samples over a weekend and checking on Mondays.

The non heat set STS78 showed the next most stretch, but comes with a caveat.  When setting the lengths to 10′ on the samples, I took nearly 100mm  of initial set out of the STS78, whereas every other sample was more like 5-60mm after the splices were set.  This means that if using regular Dyneema for length critical applications like strops or pennants, it needs to be set under tension. For best results I usually exceed the working load by 3x and have had good results with regular Dyneema after that.

The Heat Set Dyneemas all performed very well.  The Alpha XTM stretch a lot initially but settled down after hitting our target load, and did particularly well after getting tensioned to 2x the test load. The Marlow MAX started better than the XTM but was overtaken after it was tensioned to 2000lbs.  If you’ve got lots of experience with rope, this is very intuitive after handling the lines; the XTM starts out being much less stiff so it stands to reason that it would stretch more initially. The XTM braid angle however, is much more parallel to the rope, so once all the stretch is removed, it makes sense that it would show less load stretch.

The New England HSR did the best, especially once tensioned.  This again fits with the “feel” one gets from the rope, as the HSR is the stiffest running rope I have ever used.

This was a fun test and will be updated as the creep results come in.  The good news is that all the Dyneema lines performed really well compared to the state-of-the-art-circa-2005 Vectran.  If we accept these numbers, and assume a boat like a T10 has these ropes on the main halyard.  The T10 sailors, being good preppers and not tired from the party, preload their halyards before sailing.  It’s windy out, but the ropes only stretch: Vectrus 130mm,  MAX78 56mm, XTM78 47mm, STS78 69mm, and HSR 42mm.

As always, let me know if you have any rigging related bits for the GITDASPITFMWTQ list.


The overnight time on the bench has been surprisingly tied up, first with a steering cable and now with loops over the weekend, so I’ve decided to do some shorter term testing.  Figuring that on a bad day, a windward leg of a race takes 30 minutes,  I let each sample dwell on the bench for 45 minutes at 1000lbs after a 1500lb set.  As it turns out, not much at all happens in 45 minutes.

Yale Vectrus 0 978
Marlow MAX SK78 0 982
Alpha Ropes D Core XTM 78 0 982
New England STS78 0 980
New England HSR 0 986

The ropes didn’t move. Even a little. Testing was done with a metal square clamped to the bench even with the dogbone, and after the first sample I kind of knew the score, and that this  test wouldn’t be very exciting.  The most interesting thing is that the load numbers at 45minutes were down off of 1000lbs, but I’m willing to chalk this up to the bench itself, as there is always some movement and it’s not particularly exact as a dedicated testing rig would be.  An interesting proof to this is that once the ropes were taken to 1500lbs, and then tension released to below 1000, then brought back up to 1000lbs, the numbers actually went UP before they went down.  Could be the load cell itself, the loops, the winch, the tensioning rope (1/2″ vectran)

Here are some videos of the best and worst stretch from the test.  This was done after the actual testing, so the clamp zero is a bit off, and the camera isn’t in line, but even so you can see the huge difference in stretch

With no change in dimension and negligible change in load, it seems like creep in the context of something like a windward/leeward race is not a significant factor. My understanding on creep is that it takes a combination of load/time and temperature to occur, and that it happens on the order of days and not minutes or hours. If I ever end up going upwind with the same tension on a halyard for days, please send help, as not only MIGHT creep be a factor but that sounds like an absolutely boring race and I don’t want to do it.

The interesting observation from the setup for this test was how much all the ropes initially moved when being spliced and set to 10′ lengths. So, for kicks,  I also took a 6′ piece of STS78 and did the same test. This piece of rope only had a quick 1500 set, then was taken to 1000lbs.  This one did grow, by about 28mm, and dropped tension to 658lbs.  This fits my own experience in that prestretching any halyard on the bench makes it perform better once on the bench.  Heat Set Dyneemas only really needs the ends stretched after splicing, and Vectran doesn’t seem to either (Dr. Bam Miller of Oyster Bay Boat shop thinks this is due to the higher coefficient of friction with vectran, but he’s not a real doctor and I don’t think Bam is even his real name.) Regular Dyneema does grow by quite a lot,  the splices set as well as the rope itself elongating with load. The good news is that this settles down with a decent prestretch or lots of use.

My news for customers is this:  get a Dyneema halyard. If you want more performance get a Heat Set Dyneema halyard.  If you really want to come in and talk about creep for a boat that does buoy racing, please excuse me while I bang my head on the test bench.

Creep Update 1 HSR heat set Dyneema

The HSR sample was left on the bench at 1000lbs from Friday afternoon through Monday morning,  the length was unchanged and the load was at 960lbs.  Over 60hrs with no dimension change is pretty good!  Assuming you were on a J105, and this was your main halyard, and the ENTIRE Mac race was upwind on the same tack in the same amount of breeze, you still don’t have to worry about creep in a halyard.  So far this testing just reinforces my recommendation for heat set Dyneema halyards, aft standing rigging and critical control lines.

Creep Update 2 STS78 Dyneema

On Monday I loaded the STS78 sample to 1000lbs and planned to leave it there through Wednesday. As it turned out,  it was left until this morning, so about 60 hours just like the HSR.  In theory, this would be the most creep prone sample.  Heat setting as a process removes the constructional stretch, but in theory also reduces creep since it accelerates it during production and aligns both the fibers and the molecuslar structure of the rope.  Regular Dyneema should show considerably more constructional stretch, as well as more dynamic strech and definitely more creep.  The constructional stretch on this sample should have been mitigated by all the cycling (multiple times to 1000, 1500lbs, once to 2000lbs) but I was still expecting to see some creep as compared to the Heat Set.

Instead,  the sample is exactly where it was left on Monday, showing no dimension change.  We’re at about 16% of break load.  Although normal working loads for racing/cruising running rigging are about 20%, I feel that 1000lbs in this case is pretty indicative of a typical max-normal halyard load on a boat that would use 5mm Dyneema core.


Over the weekend (OH THE BEARS…) I decided to continue the creep testing by going with a higher-than-recommended working load on the STS78 sample.  So far, the loads  tested for creep have been loads you would likely see on the water with a 5mm piece of rope. No creep has been observed in any of the Dyneema lines, even in STS78 which is non heat set Dyneema and should in theory show creep.  The fact that this piece has been prestretched by being cycled to 1000 (many times with long dwell), 1500 and 2000lbs has made stretch pretty minimal, but I was a bit surprised we couldn’t generate any creep (OR ANY PASS RUSH, BEARS).

To try and generate creep, I loaded the line to 40% of the breaking load (2440lbs). This is well above any SWL for running rigging, and would not likely be encountered on the water. After round 55 hrs the rope had elongated by just under 1mm (UNLIKE THE BEARS SECONDARY WHICH ELONGATED ENOUGH FOR 48 POINTS).

This is still really good!  There was no prestretch beyond getting the rope to tension, so you’re likely seeing construction stretch as much as anything.  Getting <1mm over 3048mm at this % of break load is incredible. You could debate whether we’re seeing construction stretch (probably) or creep (unlikely) but it’s nice to have this data (AND THE INEVITABLE TOP FIVE DRAFT PICK IN 2016).

If you’re curious about the angry parentheses…. 

Recovery Mode

If the picture above looks familiar, you’ve probably experienced the upper limit of a rope covers durability before!

This is an asymmetric spinnaker sheet made from New England Endura Braid Euro.  It’s a great line, very tough cover, but it still failed after just 2 seasons.  What gives?

Asymmetric sheets are very tough on covers.  They tend to have higher loads than a symmetrical spinnaker sheet, and are also trimmed more actively.  Things really get interesting in a gybe, when the line speed is MUCH higher.  In a gybe on a boat this size, you’re moving around 65′ of line every time you gybe, and the faster the better. On a boat like this with a pedestal grinder, you can pull the sheet around quite quickly, so it makes for snappy maneuvers.

What this means for the rope cover is lots of heat and abrasion.  Most assym  sheets start to feel a bit crispy in the middle, and that’s because the friction over the drums is generating enough heat to melt the cover.  The bigger the boat, the higher the loads and the more line to move, so the covers get abused more.

The solution is better covers,  specifically using heat and abrasion resistant fibers.  At the very top end we have PBO covers, which handle the highest head and load, but can retail for over $40/meter for the 10mm size. No, I’m serious, stop laughing! It gets better too, since they’ll break down in the sun and wear out quickly. Oh, and it leaves gold dust all over your boat and crew.  Anyway, the good news is there are lots of better-than-polyester covers that will cost less than a used car.  There are kevlar blends like Yaletail, and Runnertail (technically Twaron but who’s counting) but in the last couple years the default go-to special cover has been Technora blended with polyester. New England makes a rope called Poly Tec which is available as a cover or a built rope with Dyneema core.  I’ve been using this for the last 4 seasons and have been very happy with it, and have never heard a complaint about it from owners.  Marlow Ropes makes a full suite of specialty covers, but their version is Tech 50. The 2 covers are quite similar, so it usually comes down to which is available in what color first.  In addition to durability, you’re going to find that the grip on winches is more consistent, and they handle great!

So, let’s pretend your boat has taken your nice Dyneema double braid sheets and turned them into the mess you saw in the first picture. The cores are ok, but the cover looks like a shriveled churro.  We can take the cores out of the old line, and put a Technora blend cover over the top for less money than new sheets.  The cores still have a few years of life, so this is a great way to keep them going while get a nicer hand to the line and better grip on winches.

For the above sheet, the owner opted to swap both covers for Poly Tec, and gave them distinct colors while we were at it. The sheets were end-for-ended as well so the old loaded end of the sheet is now the tail and vice versa. The sheets look new, and should perform that way for many seasons.  Win!

It was a good idea in this case for a few reasons: the sheets were relatively new, the cores were in good shape and the core material was Dyneema.  If you have a damaged cover with similar parameters we can save it!  CYR also stocks regular polyester covers for a repair at considerably lower price point, although it’s worth considering why the cover failed in the first place (*usually T10 halyard with XAS clutch) It doesn’t make sense for every line though.  If the line is particularly short, the cost of labor doesn’t usually add up to less than a new line, and if the core is damaged, or Vectran/Poly/PBO it’s not usually a good idea to recover it.  If you’re in doubt, drop by the shop and we’ll look it over.  Plenty of samples to look at, and the odds are very good I’ll have rope in for the same repair to show you!


Dux all in a row

Dynex Dux was the first mainstream heat set Dyneema to arrive in the yachting world, and  had a huge effect on rope selection on racing boats.  Using heat and tension, it gave us higher strengths and lower stretch in a smaller package, and quickly stole ground from not just regular Dyneema, but has replaced Vectran and Zylon as well.

These days, there are quite a few varieties available in heat set prestretched rope. Stopping by this week is the most recent version, and likely the strongest,  from New England Ropes.  I thought it might be interesting to compare the available options, so below are some notes.

On the left is Gleistein’s Dyne One HS.  This is by far the easiest heat set product to work with, as it has a pretty wide angle, and is soft compared to Dux.  It’s also the roundest option, and tends not to flatten out over sheaves.  The downside is the high angle between braids should theoretically make it stretchier.  The other drawback is that it doesn’t seem to be much stronger than regular Dyneema, at least in the small sizes.  Last summer when doing some break testing I found that the 4mm Dyna One HS broke at ~3800lbs, where as plain old New England STS75 breaks well over 4000lbs.  The 9mm shown is supposed to be approx 18000lbs, which is again in line with regular Dyneema.

Second from left is Maffioli Ultra 75, actually the core from 11mm double braid. This is probably the least stretched product, and rated at 17000lbs it’s the weakest as well. It’s kind of an odd duck(x) here as it’s not targeted or made like the others, and I believe it’s just a quick prestretch to take out some of the constructional stretch.

Middle line, in dark gray, is Marlow’s D12 Max 78 product. Rated at ~23000lbs, this is much stronger than the first 2.  It has quite a long angle, partly from construction and partly from stretching.  This is the only SK78 product here, but they also offer an SK90 heatset, for max (ha) tensile.  Marlow has the widest range of fiber choices, and more importantly sizes, going all the way down to 3mm which is unique for a heat set dyneema.  The downside to Marlow is the stretching process makes for a rope that isn’t very round,  as it’s flattened out over whatever bobbin they use to stretch the product.  The Dyneema is a bit fuzzy when new, due to the fibers that fail during prestretching.  This is the choice of high tech dinghy and small cats, as the range of sizes makes for lots of options.

At the far right (I’m skipping the second right for the moment) is a piece of Dynex Dux in 7mm, as I was out of the 9.  The original, and still very good, it has a rated break of ~26000lbs, and is quite round and very stiff with less popped strands than the Marlow. The amount of prestretch is very high, which makes it a good choice for running rigging where stretch is key, as well as some standing rigging and slings.  I really like this material for backstays as it’s so light and strong you can be quite aggressive in downsizing.  Most people call any prestretch Dux, but that can be troublesome as some of the other heatset products aren’t exactly interchangeable as far as strength and stretch.

Second from the right is the newest arrival, an as-yet-unnamed product from New England Ropes.  Pretty excited about it, as it seems to have taken all the best attributes from the other brands and improved on them.  The construction is very similar to Dynex Dux, but lacks the flyaway/popped strands. The roundness of the rope is closest to Gleisteins product, and the smoothness is better than any of them.  NER hasn’t released final break numbers, but the initial tests had it all comparing very favorably with Dynex Dux, which is really saying something.  This particular spool is destined for the VO70 Il Mostro, replacing the Gleistein rope is arrived with.  I’ve got more spools arriving soon and am going to have more info soon!

Big Boat check stay upgrade

There are tons of great old IOR boats out there that can benefit from more recent technology.  The old wire check stays and blocks in the picture above were heavy and a bear to use.  We were able to match working loads with much lighter gear and still keep the traditional look favored by the owner. 

The Harken runner block shown (4″ stainless runner) isn’t in the Harken catalog anymore, but is still available on a special order basis, which is great as they’re excellent blocks with a traditional appearance. These weight less than a third of what the old mammoth blocks weighed, and still deliver much less friction.  We replaced the wire-to-rope (yuck!) tails with simple New England STS 75 covered with a Marlow MGP cover.

Always nice to get kind feedback, and one of the funniest of the season Iv’e gotten was from this boat: “I know I’ll get whacked in the head by the checks at least once, so I’d much rather have it be the new runners than the old runners!”

T10 Backstay: Cascade

Here are a few pics of the T10 fiber backstay with cascades

Above is the tackle, composed of Antal thimbles for the first few high load and low speed cascades, then Harken ball bearing blocks for the faster cascade and control.  Total power  is 32:1.  The control lines ease much more quickly, and the trimming is easier.  Total weight for the backstay is less than 2 lbs.

Here is the transom attachment.  The first cascade goes to port, everything else to starboard to keep the standing stay centered. Important with shackles-especially as part of a boats standing rigging-are plastic ties to hold the shackle pin closed.  Alternatively, the shackle could be drilled to remove the threads, and a clevis pin and cotter used.  

Here is a photo of the flicker on the masthead before taping. On this boat there was a windex mounted on centerline near the aft end of the crane, so I reused that hole with a 1/4″ machine screw and nut.  The windex was moved slightly off center and retapped.  If theres no hardware at the top of the mast, drilled and tapped 10-24 machine screws are sufficient. Very important: use washers as large as the batten under the screw heads, and use plenty of loctite on the fasteners: there is a lot of load on the aft screw, and the screws will see thousands of cycles in a season, so if they’re not really secure it will loosen and break.

Long view of the flicker installed on the mast.

T10 Cascading Backstay

Updating the popular T10 fiber backstay,  we now offer a cascading purchase to replace the “pinch” style with 2 legs and a lashing.  When the fiber backstay rule was legalized in 2007, the hope was that cascades would be legal, but according to the measurer only 2 leg deflection systems were ok.  A couple years have gone by and now the cascading system has been ok’d and is on several boats.  Our system is incredibly light, works great with the flicker and pins right into place, needing only your boats original control line and blocks.

The standing backstay weighs .6lbs (vs over 3 for the wire standing portion) and total weight including cascades/less control lines is 1.2lbs (vs over 9 for a typical wire system with link plates, toggles etc).  Pretty nice weight savings, but just as important is how effective this makes the backstay flickers.  Dyneema cover where the flicker and battens hit the stay makes the sail cross easily in tacks, and the light weight means the flicker can lift the stay out of the way with little pressure.

Total power is 32:1, for plenty of adjustment of mast bend and forestay tension. The standing stay is heat set SK78, and the legs are prestretched SK75.  The SK78 is the lowest creep grade Dyneema available, and the heat setting improves the strength, stretch and makes the stay fit perfectly the first time out. Hardware is all captive spliced for safety, and uses Antal thimbles and your choice of Karver or Harken for the final cascade. Shackles for the transom chainplates.

Cost for the system is $445, and with the flicker is $580, send me any questions you may have at