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!