Cordage and Paracord

Natural or synthetic

Rope is made either from plant fibres, such as manila, sisal, hemp, jute and cotton, or from plastics, mainly nylon, polyester and polypropylene. For most outdoor jobs here, synthetic rope is the better choice. The NSW Government’s rigging guide says synthetic ropes are preferred because they resist moisture and UV damage.

Nylon, polyester and polypropylene

All three are common in hardware stores. They look similar on the spool, but behave very differently.

Why stretch matters

A stretchy rope absorbs a sudden jerk, which is useful for a tarp in gusts. For pulling a vehicle, use a rated tow strap and follow its instructions: a stretched rope that breaks can snap back with dangerous force. But stretch is the enemy of a tight line. A nylon guy line that’s tight at supper can sag by morning, especially after rain. That’s why adjustable knots such as the taut-line hitch and Prusik matter, and why low-stretch polyester is a good choice for a ridgeline.

Twisted and braided rope

• Twisted (laid) rope, usually three strands, is easy to splice and to inspect, but can kink and untwist if it’s handled badly.
• Single braid is flexible and doesn’t kink, but can snag.
• Double braid and core-and-sheath rope have an outer braided sheath around an inner core. Paracord and climbing rope are built this way. The sheath protects the core, which carries most of the load.

When you take rope off a new spool, pull it off the top while the spool turns. From a coil, pull it from the centre, never the outside. The NSW rigging guide notes that unreeling it any other way can cause kinks or distort the strands.

Paracord and what “550” means

Paracord started as parachute suspension line. It’s a nylon cord with a braided outer sheath and several inner core yarns. It’s light, strong for its size, stretchy, and comes in endless colours, which is why so many people carry it.

What “550” means

The number comes from an old United States military specification for parachute cord, MIL-C-5040H. Its “Type III” cord is nylon with a minimum breaking strength of 550 pounds, about 250 kg. That’s where the names “550 cord” and “Type III” come from.

Two things to keep in mind:

• 550 is a breaking strength, not a safe load. It’s the force at which new, dry, straight cord breaks in a test. Knots, wet cord, sharp edges, wear and sudden jerks all lower that. See the next section.
• Not all “550” or “Type III” cord meets the specification. Cord made to the military specification is usually sold as “MIL-SPEC” or with the specification number. Much of the paracord sold for crafts and camping is commercial cord labelled “550” or “Type III” to describe its general style. It may have fewer core yarns, a different material or a lower real strength. The label alone doesn’t tell you it was made or tested to the specification.

Paracord’s quirks

• It stretches (it’s nylon), so guy lines need retightening.
• It’s slippery. Some knots creep in paracord; add an extra wrap or a stopper knot.
• The inner yarns can be pulled out as thin thread for repairs, but then the sheath alone is much weaker.

Breaking strength versus working load

Two numbers can appear on rope packaging, and they mean very different things.

The NSW Government’s rigging guide puts it as a formula: the working load limit equals the minimum breaking strength divided by the factor of safety. It adds that safety factors don’t account for dynamic forces such as shock loads. The safety factor depends on the use and the rope, so if a package gives only a breaking strength, your safe load is a small fraction of that number. For example, dividing paracord’s 250 kg by a safety factor of 10 gives 25 kg, and a knot lowers that again.

What lowers a rope’s real strength

• Knots. A rope is weakest at its knots. Tests published by the U.S. Army Mountain Warfare School put a figure eight at about 75 to 80% of the rope’s unknotted strength, a bowline at 70 to 75%, and an overhand knot or clove hitch at 60 to 65%.
• Sharp edges and rough surfaces, such as a truck box edge, a trailer frame or rock.
• Sudden jerks and shock loads, such as a load bouncing on a rough road.
• Water, in the case of nylon.
• Sunlight, age, heat and chemicals.
• Wear, including dirt worked into the fibres.

Not climbing or rescue rope

Rope made for climbing and rescue is designed and tested for that purpose, comes with its own markings and instructions, and is used with matching equipment and training. Even then, it’s retired after a fall, damage or a set age. If you or your kids want to climb, learn from a qualified instructor at a climbing gym, school program or club, using their rope and gear.

This also applies to swings and backyard play. A homemade swing on paracord or old rope can fail without warning.

Cutting and sealing the ends

A cut end that isn’t finished starts to fray and unravel straight away. How you finish it depends on the fibre.

Synthetic rope and paracord: heat-sealing

1. Wrap first. Wrap a few turns of tape tightly around the rope where you’ll cut. This stops it splaying out.
2. Cut through the middle of the tape with a sharp knife or scissors on a cutting board, cutting away from your hand.
3. Melt the end outdoors or somewhere well ventilated. Hold the very end near a lighter flame (in the hot air just above it, not in it) and turn the rope until the fibres melt together. A hot knife made for cutting rope cuts and seals in one step.
4. Let it cool. Don’t touch the melted end until it’s hard. Molten nylon sticks to skin and causes nasty burns.
5. Check it. The end should be smooth and firm, with no loose fibres. Trim any sharp beads of plastic.

Natural-fibre rope: whipping or tape

Natural fibres don’t melt; they burn. Finish the end by whipping it (binding it tightly with several turns of thin twine), or with tape as a quick fix. For three-strand rope, a back splice is a neat, permanent finish. Ask someone experienced to show you.

Care, inspection and storage

Care

• Keep it clean. Don’t drag rope over the ground. The NSW rigging guide notes that grit works into the strands and cuts the inner fibres.
• Protect it from sharp edges with a scrap of hose, cloth or a rag wrapped around the rope where it runs over an edge.
• Dry it before you put it away. Hang wet rope loosely out of direct sun.
• Undo knots after use. A knot left in for months can be very hard to untie and leaves a weak spot.
• Keep it away from fuel, oil, battery acid and solvents.

Inspect before you trust it

The NSW rigging guide lists signs of a rope that should be retired:

• Bleached or faded colour from sun and age.
• Worn, frayed or broken fibres and strands.
• Powder or fibre fragments falling out when you gently open the strands.
• Any change from the rope’s original thickness, such as flat, thin or lumpy spots.
• For paracord: a cut or worn sheath with the core showing, glazed or melted spots, or a stiff, crunchy feel.

Its rule is simple: if in doubt, destroy the used rope. Cut a worn piece into short lengths for garden ties, so nobody mistakes it for good rope.

Storage

The NSW guide says to keep fibre ropes clean and dry, away from heat sources, chemicals and direct sunlight, on a rack that lets air move and makes inspection easy. At home that can be a hook in the garage or shed, out of the sun.

• Coil or hank rope loosely so it doesn’t tangle, and tie the coil off with its own end.
• Label lengths, for example with a piece of tape, so you grab the right one.
• Don’t leave rope on the truck or the trailer all summer. Our strong sun breaks down synthetic rope, polypropylene especially.

What to keep on hand

For pitching tarps in prairie wind, see our Bushcraft page and Tent camping. For other camp gear, see Camp gear.

Sources

• NSW Government, Dogging and rigging guide, Construction of fibre rope (synthetic preferred; nylon and polypropylene stretch, wet strength, UV and melting): nsw.gov.au
• NSW Government, Dogging and rigging guide, Rope handling and maintenance (unreeling, abrasion, grit, storage): nsw.gov.au
• NSW Government, Dogging and rigging guide, Fibre rope inspection (signs of damage; “if in doubt, destroy the used rope”): nsw.gov.au
• NSW Government, Dogging and rigging guide, Lifting slings and winch lines (working load limit equals minimum breaking strength divided by factor of safety; shock loads): nsw.gov.au
• U.S. Army Mountain Warfare School, Knot Guide (strength of knots): army.mil
• United States military specification MIL-C-5040H, Cord, nylon (Type III, 550 pounds minimum breaking strength). The specification is no longer active; its text was not available to check directly, and these details are as widely described.
• Polyester properties, heat-sealing and whipping follow general rope-handling practice; check the maker’s instructions for any specific rope.