Ins & Outs, Ups & Downs of Rigging Rope

Rope may seem simple, but close inspection reveals it is complex in its construction as well as in its application and use. This is especially true with ropes for climbing and rigging in tree work. This article will look at the selection and use of rigging rope.

Universally, manufacturers say that selection of a rigging rope depends on the job at hand.

Adam Moser, arborist sales representative for Yale Cordage, a 27-year TCIA Corporate Member company based in Saco, Maine, says his company, in its arborist guide, warns, “Choosing the correct rigging line is vital for safety and longevity of your rigging system.”

It also advises the following for selecting a rigging line:

• Dynamic-Rigging Configurations: If you anticipate “dropping” a limb or trunk segment and relying on the rigging line to “catch” the load, this is a classic dynamic-rigging scenario. The forces exerted on the system by the log can be as much as 10 times the weight of the log. Select rigging ropes with more stretch, such as high-elongation polyester or nylon products, as they are better suited to absorb the energy of a falling object.
  
• Static-Rigging Configurations: For rigging arrangements where load is applied in a constant and controlled manner, a low-stretch, high-tensile-strength rigging rope will provide more control of the payload. Low-stretch ropes have the additional benefit of reduced recoil hazards in the event of rigging failures. Crane removals and pick-off rigging arrangements are examples of static-rigging configurations.
  
• Natural-Crotch or Block Rigging: When block rigging is impractical, use hollow-braid products or products with thick, braided jackets to protect against abrasion. Hollow braids are easier to inspect and present more material on the surface to uniformly “distribute” wear and tear. Conversely, when friction is being managed, double braids can offer performance benefits over hollow braids, with desired stretch characteristics for more precise load control.

“I do training events, and rigging rope is a common topic,” Moser says. “Students fixate on numbers, especially with rigging rope, and think they simply need the strongest for their money. That may be one of the least important things for you to consider.

“First, we ask what they are doing, dynamic or static rigging. Second is whether they will be using blocks for managing friction or using a natural crotch,” Moser says. “Those are the two biggest things.

“For dynamic rigging, you want something that will take a lot of shock from a large load repeatedly without becoming damaged, usually something made with nylon or polyester,” he says, stressing, “Higher elongation is a function of how the rope is made, not the type of poly that’s used. Manufacturers have learned how to tweak rope for higher levels of elongation.”

In Moser’s opinion, “Nylon will generally offer greater elongation (stretch) than the highest-performing polyester, but there is some overlap.

“Static rigging is about predictability in loads, usually with a winch or GRCS (Good Rigging Control System) to lift a log,” Moser continues. “Here you want lower elongation, the reason being that the rope behaves more predictably. That way you do not have to adjust for elongation.”

The next important consideration, according to Moser, is construction, including double or hollow braid. “Again, it’s about how you intend to use the rope. If you’re rigging a natural crotch, you’re probably better off running hollow braid. When subject to abrasion, you have a lot of material to work through before the rope’s retirement,” he says. “Another thing, hollow braids are less-expensive ropes. When used in an abrasive crotch setup over a limb, you do not want to risk damaging your more expensive, double-braid rope.

“However, if you’re going to be setting up rigging that is more engineered with blocks and other components, relying on something other than the tree for friction, I think you’re better off using double braid,” he states.

Building on that, Mark Chisholm, CTSP, director of operations with Aspen Tree Expert Co., Inc., in Jackson, New Jersey, states, “When selecting the right rope for a job, the two main points to consider are construction and material.” Chisholm, who also is a consultant for Teufelberger, a 28-year TCIA Corporate Member company based in Fall River, Massachusetts, adds, “These two factors will change the effectiveness of a given rope for a given situation.” According to Chisholm, construction and material will determine things such as:

• Tensile strength – the amount of weight the rope holds just before it breaks;
  
• Elongation – how much the rope stretches at different loads;
  
• Abrasion resistance – how well the construction holds up against wear and tear;
  
• “Hand” – how the rope feels (12 strand is rougher than 48-strand carrier);
  
• Spliceability – some ropes are spliceable and some are not;
  
• Use in devices – more or less friction, holding power;
  
• Linear density – weight of the rope;
  
• Water absorption – does the rope absorb or repel water; and
  
• Heat resistance – the temperature before it melts.

“Understanding the differences between rope designs is paramount in finding the right solution. Choosing the wrong rope could be catastrophic,” Chisholm states. “A good example would be using a Dyneema (a polyethylene fiber) rope for rigging applications. This rope, in ½-inch diameter, seems like a great choice if we look at tensile strength alone (30,000 pounds). However, with an elongation of about 5%, it gives little chance of being able to absorb any dynamic loading, and will part at much lower loads than a polyester double braid of the same size. Another weakness is the low melting point – using this fiber to make a friction hitch would be extremely dangerous.”

According to Chisholm, “One common rope construction we see in tree care is single-braid hollow construction. It tends to be very strong, lightweight and easy to splice. One of the best options for this style of rope is creating dead-eye slings for rigging gear. A poor option would be to use it as a rigging line, because the fibers are loose and would pull and pick when running along rough bark, and untying loaded knots would be challenging due to flattening from the lack of a core.”

Tom Daly is president of All Gear, Inc., an 18-year TCIA Corporate Member company that sells to distributors and original equipment manufacturers (OEMs), but not to end users. Daly says that while his company serves markets such as marine and construction, “the arborist is our mainstay.

“When it comes to rigging ropes, we talk about categories,” he says. “For a worker doing natural-crotch rigging in the ‘Y’ of a tree, they likely will use several items. That could be a 3-strand or sometimes a 12-strand. The braided is stiffer, with a straight core and jacket that stay together and work together when pulled through a rigging point.

“A second category may be someone working with rings, not using a block and pulley, who would go to a double-braid Husky Bull Rope, but some may still rely on a 12-strand Forestry Pro, kind of a basic.

“Then,” he adds, “for more advanced setups with multiple rig points, for example, one or two rings for lowering points and a block, the worker would get into a Husky Bull Rope or a specialist rope over a low-stretch fiber. That would work near or over a greenhouse or architecturally sensitive area where one needs to be very precise.”

Daly boils it down to essentially a case of good-better-best, and adds that what one needs to look for is dependent on the nature of one’s business. Another way to look at it, as Daly explains, is one might think “lower stretch as you go up in functions. On the lower end, you get thicker jackets and thinner core, and vice versa on the higher end.”

With respect to safety, Daly warns, “As you climb from job to job or rigging to rigging, you should have a sense of where your ropes have been and gone and the weights they have taken.” In respect to a rope’s history, “You need to keep track,” he states, echoing comments of other suppliers suggesting that an activity log for each rope should be kept, which will become a factor in determining when it is time to retire that rope.

“A lot of people keep books or a log in their bag of rope, along with their safety-warning sheets. I highly recommend this. Logs like these are underused,” Daly maintains, “and are critical to this industry.”

In addition to keeping a log of use, there are other clues or indications as to when it is time to replace a rigging rope. “One thing to look for is obvious abrasion, and for some, rope strands that are broken or torn are sufficient to remove them from service. Rope coverings are made to wear, but they need to be monitored,” Daly stresses.

Chrissy McGillveary, commercial sales representative with Marlow Ropes, a seven-year TCIA Corporate Member company based in Plymouth, Massachusetts, focuses on the importance of long-wearing rope. “Because choosing a durable rigging rope is highly important, there are a few key properties to look for,” she says.

Acknowledging that every job is different and that the approach varies from company to company, she says factors or characteristics to explore when looking to buy rope will also vary based on need. But, McGillveary advises addressing what she says are the basics: strength, elongation, firmness and construction.

She refers us to the company’s website, which, for example, outlines the benefits of “super-strong and lightweight Dyneema rigging slings and throwlines or heat-resistant accessory cords for Prusik loops and friction hitches.”

McGillveary mentions a new rope in Marlow’s rigging line, Blue Ocean Raptor. “Marlow Ropes’ new, eco-conscious Blue Ocean Raptor is made from polyester using 100% recycled bottles and provides the characteristics required in a high-quality rigging line.” The benefits of the rope include abrasion, ultra-violet-light (UV) and chemical resistance, a coating to improve grip, ease of splicing, high strength, low water uptake and zero shrinkage.

Samson Rope, a 27-year TCIA Corporate Member company based in Ferndale, Washington, deferred to Lawrence Schultz, a Certified Arborist and an ISA Certified Municipal Specialist working as a California-based contractor specializing in climbing and rigging, to talk about the qualities and characteristics to look for in rigging rope.

“Depending on the job, if you are in very close quarters, you’d likely want a strong, quality rope with not a lot of stretch, perhaps a double braid, depending on the hardware you’ll be using,” Schultz explains, and goes on to mention high-modulus, synthetic-fiber ropes. “These are tempting because they are so light and strong, but primarily they are meant for static operations such as lifting, towing and pulling, not dynamic operations such as negative rigging.

“Some people still do natural-crotch rigging, and will stick to a 3-, 12- or 16-strand rope. In these, strength is dependent on the rope cover. If there is a core, it is just for shape. The cover is the main load-
bearing part of the rope,” Schultz explains. “It can be easily inspected.” He says heat from a difficult drop can “fry” the rope. “If you’ve done damage, that would warrant replacement.”

Ropes where the cover and core share the load are better suited for block-and-pulley hardware, he says. “You could damage the core and not know it,” says Schultz.

“One important thing people often overlook or don’t think about is the maximum force you put on the rope.” He cites lowering situations, blocking down wood, which can result in shock loading – where the weight of the drop exceeds the actual weight of the piece being lowered – potentially loading the rope past its rated maximum breaking point. “If I have to figure that 10 times the force is generated, that is the rating you will need for the rope,” Schultz maintains.

“Any time you’re rigging or climbing, plan that your system will be strong enough to take the maximum force and not break,” he warns. “Your plan needs to handle the worst-case scenario. For example, if you are working with 20-inch trees in the Northeast, you probably do not need 3/4 – to 1-inch-diameter rope. But out West, where tree diameters are larger, you will definitely want to consider larger rope,” Schultz explains.

“It is time to change rigging rope when you start to notice flat spots, hard spots or inconsistencies in the rope diameter,” he advises. “In some cases, if you can bend a rope and it bends sharply, you may have core damage.”

He concludes with one big warning about retiring damaged rope. “If you have ever broken a rope, it’s likely it has damage all through the rope, and it will be easier to break the second time.”

Mike Ziecik, director of product management for Vertical Supply Group, parent company of the Sterling and Notch rope brands, sums up rope construction this way. “Think of rigging construction as solid and single versus double braid/single braid. “Within single braid, for example 3-, 12- and 16-strand, the application is usually with friction, such as with
natural-crotch rigging. Three-strand is common in natural-crotch rigging and does not work well in mechanical rigging because of the diameter,” he adds, “so it’s important to know the final application.”

Ziecik continues, “When we deal with double-braid ropes, which have higher tensile strength than single, these are a lot better for pulley-and-block use, because they stay firm under load and tension. Double-braid is our number-one seller because of that construction. Predominantly, all feature a ply jacket, the reason being for low-elongation tendency and higher abrasion resistance.

“One of the major improvements in the last 10 years for double-braid construction was the introduction of a nylon core, allowing us to attain better energy absorption. Physics show elasticity is better. Shock absorption and energy absorption lower peak forces, particularly in negative-
rigging applications,” he explains.

In addressing when it is time to replace a rigging rope, Ziecik says, “That depends on its frequency of use and if you run the rope through a pulley versus tree crotch. Natural-crotch rigging can have a big impact. It can need to be replaced in a month or a year. A rope with a tighter jacket will live longer,” he maintains. “Generally, with a pulley you extend the life versus with a natural-crotch application.”

Lifespan also depends on how you store the rope, according to Ziecik. “Use a bag to keep the rope away from dirt, moisture and UV, all of which have a huge effect on your rope’s longevity. We recommend storing your rope in a dedicated rope bag with its description and length.”

He says manufacturers also have added urethane coatings to rigging rope to aid in abrasion resistance.

There’s more to the world of ropes and rigging than it might appear. You can learn as little or as much as you wish about their construction and composition, but the most important thing to know is that rigging rope can make you or break you, literally, so it is up to you to do as much homework as you can before taking to the trees.