The Daisy Chain:
For years, there has existed two distinct types of loops sewn into daisy chains made by various manufacturers around the world. In theory it seemed to me that one was decisively superior in design as it would pull on the sewn stitches in shear while the other design, when loaded, would pry the stitches apart. Designs that depend entirely on stitch strength routinely fail first. Good designs use the strength of the webbing coupled with the sewn elements to achieve high strength. To hang only on stitches is a recipe
for failure, injury and possibly death.
Design # 1 pulls on the stitches and Design # 2 pulls the stitches in shear
pulls each loop apart when clipped into. and utilizes the webbing strength
along with stitch strength.
This wouldn’t even be an issue if people would just use them for what they were designed for—holding gear. But, it has been my observation that rescuers and recreationalists alike, use daisy chains as human daisies, not gear daisies, disregarding the warnings supplied by the manufacturer.
Catalogs and product descriptions can be misleading. CMC uses Design #1 and makes claims of 5350 lbf in the loop. Ah! “loop” must really refer to the big loop in the end of
the daisy chain. So CMC is really only explaining the strength of a looped piece of webbing. They give no reference as to the strength of each individual loop’s strength. Blue Water also advertises Design #1 in their Titan Daisy Chain. They give no loop strength. While the product is made of Spectra, the loops are sewn with nylon while the final loop closure is sewn with Spectra thread. Using nylon is a great option when using patterns or stitches that need to work together to form a unified holding force. Nylon stretches and adjusts until all the stitches feel the same tension, then break in one violent moment when pulled to destruction. Spectra does not! Spectra does not stretch nor does it adjust, nor do all the stitches work together to provide a unified force. In tests initiated by On Rope 1, Spectra stitching proves to be about 1/3 weaker than the same Nylon stitching when sewn with similar sized thread. As each individual Spectra stitch feels tension it feels the force and breaks. Then the next stitch feels the force and does the same thing and so on! Listening to Spectra break sounds like someone picking
PMI, CMI, and Rescue Tech all profess to Design # 2 with directional gear loops. PMI’s catalog gives no loop strength nor overall end-to-end breaking strength, but advertises that it is intended for gear attachment not life attachment—thus the name “Gear Daisy.” The attached product tag claims the product is tested to 2 kN (450 lbf). CMI advertises their daisy chain’s loop strength at 2900 lbf (12.9 kN) and an over all end-to-end strength of 6800 lbf (30.2 kN). Rescue Tech advertises loop strength of 1500 lbf (6.7 kN) and and end-to-end strength of 6800 lbf (30.2 kN).
On Rope 1 decided to sort out all these claims and inconsistent numbers in an attempt to answer the question, “Which was stronger?” and “If my life ended up hanging from a daisy chain which design would be safest?”
Testing Design # 1. Our testing method was crude but telling. We attached a wrap 3-pull 2 to a tree. We then attached a Dillon Dynamometer to the anchor--then the daisy chain and then ran a tripled 11.1 mm static rope to the bumper hitch of a big car. We
put the car in 4-wheel low and slowly began pulling.
Notice the carabiner pulling the threads rather than being supported by webbing.
The first bar tack popped at 9.1 kN (2050 lbf).
Picture of the first popped bar track.
Driving a few more inches caused all the loops to catastrophically fail all around 9 kN. We were surprised that three bar tacks actually held that much. This almost provides a 10:1 safety factor for an average person of 190 lbs (including gear and clothing). It would, in actuality, be the weak link in most instances. If used in a rescue scenario, it would fall significantly short in meeting the requirements of elements used to lift, haul or support life loads.
Testing Design # 2. The entire set-up remained the same in an effort to insure consistency. Notice the pulling direction and the shear force on the stitches.
Picture: Loading characteristics of the directional gear loop design
This time when the force tightened up the system the
large SUV couldn’t even pop the first bar tack. The Dynamometer maxed out and started to circle the dial for a second time achieving 13-15 kN before all 4 wheels began to spin on the concrete. Finally the first set of three bar tacks broke in one loud pop.
The Dynamometer was reset and again the 4-wheel vehicle began to spin its tires. The vehicle was backed off and then, getting a running start, the vehicle lurched forward affectively breaking several sets of bar tacks before the webbing itself broke. Interestingly, the webbing broke before the bar-tacks zippered apart.
Picture: Final pulled apart Daisy Chain. Design # 2
Conclusions In our crude way, it became pretty evident that Design # 2 was substantially stronger than Design # 1. It came to my attention that PMI low balled their mbs at 2 kN in an effort to remind people that their daisy chain was rated for gear usage not human suspension, yet their Gear Daisy rated as high or higher than any of the other’s that also used Design # 2. Taking into consideration that the webbing broke before the bar-tacks
is very telling. Doubled webbing typically breaks between 5000-6000 lbs. Did the directional gear loops (Design # 2) test higher than the strength of webbing? This needs to be answered by folks with more sophisticated testing equipment.
I should expect, however, that Design #1 will average around 9 kN while Design # 2 should provide an average breaking strength of 13 kN or more. It appears Design # 2 seems to be the best answer for both our original questions: “Which was stronger?”
and “If my life ended up hanging from a daisy chain which design would be safest?”