of the following rope types, whom amung us have used and will review a rope type ?
Note that between breaking and not breaking under load, rope exhibits various qualities mostly undesirable.
Neither a climber nor a large hull sailor, I’m not aware of how rope is graded for use near the breaking limits area.
So far, a 3/8ths nylon diamond rope is a hawser while a 3/16ths cord ties a canoe down on the roof with a .25 Walmart cord bow to bumper. Walmart floating ropes as end lines…no problem.
am I missing the point with the low quality rope I’m using
of the following rope types, whom amung us have used and will review a rope type ?
Never in my life
of boating have I ever seen a rope fail except where it has been abused and abraded or kept in service too long. I think we tend to get a bit obsessed about breaking strength statistics. For 99% of the things we do with rope any old hardware store rope will do so long as you don’t abuse it and so long as you replace it every now and then if it has been exposed to the elements too long. Just one mans opinion.
I have seen them fail
Quality ropes seldom fail when subjected to normal usage. I have seen ropes (and carabiners) break when attempts are made to free pinned boats using drag systems with high mechanical advantage. The effective mass of a fully swamped canoe pinned in current may exceed a ton. Using a mechanical drag system with 3:1 or 5:1 mechanical advantage will easily allow a single individual to exert a force on a rope exceeding several hundred pounds. Any knots or bends in a rope (such as where a rope runs through a pulley) reduces the effective breaking strength of a rope.
As to how the strength of ropes (and other devices) is assessed, they are given a minimum breaking strength rating in units of lbft or kN. This is the force (not weight) at which a new rope without knots will break when subjected to a straight line static load. Bends in the line, knots, or jerking on the rope under load will all reduce the force at which the rope separates.
Manufacturers will also list a safe working load, or working load limit. This is much less than the minimum breaking strength. The ratio between the minimum breaking strength and the working load limit varies from manufacturer to manufacturer. The ratio is referred to as the safety factor.
The safety factor may be as little as 4 or 5. Or it may be as great as 15. Makers of quality climbing and rescue gear tend to use very high safety factors, no doubt for liability reasons.
A few examples: a good quality nylon rope 3/8" in diameter will typically have a minimum breaking strength of 3240 lb/ft (14.4 kN). If the safety factor is 12 the working load limit will be 270 ft/lb (1.20 kN). This equates to a static load of 122 kg (268 lbs).
Nylon is the strongest synthetic fiber. The values for a 3/8" polyester rope would be mbs 2700 lbft, wll 225 lbft, static mass 224 lbs. Polypropylene is a bit weaker still and the corresponding values for a 3/8" rope are 2430lbft, 203 lbft, and 202 lbs.
Because of the safety factor it will usually require significantly greater loads than these to break the rope and these loads will not usually be seen in typical use, unless a very heavy individual, or multiple individuals attempt to climb a fixed rope. But a typical Z drag with 3:1 mechanical advantage can allow a single individual to subject a rope to loads exceeding the working load limit.
‘A few examples: a good quality nylon rope 3/8" in diameter will typically have a minimum breaking strength of 3240 lb/ft (14.4 kN). If the safety factor is 12 the working load limit will be 270 ft/lb (1.20 kN). This equates to a static load of 122 kg (268 lbs).
Nylon is the strongest synthetic fiber. The values for a 3/8" polyester rope would be mbs 2700 lbft, wll 225 lbft, static mass 224 lbs. Polypropylene is a bit weaker still and the corresponding values for a 3/8" rope are 2430lbft, 203 lbft, and 202 lbs.’
Reread then check your rope supply…
I’m using Wal’s poly cord on the black holder….AAA so far…no failures here either but infrequently nylon will stretch further than acceptable usually on site in Gaboon or Nillysville Forest
On the way to the Rio in Fort Stockton found Wal’s large hank of dayglo orange paracord…a last minute trip saver. Neither Grain nor MacCarr were around.
Using the Blanc quote for the cordage used here for roof racked bowlines…if the hull came loose then the current cordage would not hold that yank pressure at 70 mph…once the hull caught air
awwww WEST say it aint so…no specs ? West sez Wal’s rope has poor quality control ?
callum for me wudja
West dingy rope from New England Rope at -1/2" will dangle your VW from the ceiling.
I can imagine the legal problems for your dingy floating away…
Rescue and climbing rope (and even marine rigging cordage, aka Plymouth Goldline, which is used for both ships and mountaineering) is designed with a stretch capability which gives it a higher strength and safety factor under abrupt loading. I’s stopping power, so to speak, is dampened by the friction gradually tightening up. This protects the fibers from snapping and also dampens the shock and stress on any human attached to the line. If one was to take a climbing leader fall on, say, polypropolene yellow tow rope, it would cut you in half.
My outdoors club used to retire the Goldline rock climbing school ropes after a certain amount of use and abuse and cut them into short pieces for members to use for various utility functions like towing, stump-pulling and boat tethering. have never known the stuff to break, but it is bulky for tying knots.
The problem with cordage that does not have stretch built in is that it can fail under a heavy enough load applied abruptly.
off we go to West for a Wal/West floating rope test…
maybe borrow Flakey’s tractor ?
dynamic versus static ropes
The best rope to use for climbing or vertical rescue situations is dynamic rope because the rope will better withstand the dynamic load applied by the body weight of a climber falling.
Static ropes are defined as ropes that have less than 10% stretch at breaking strength.
Dynamic ropes are not the best for throw rope or mechanical haul situations. If you are throwing a rescue line to a swimmer who is about to go over a waterfall or enter a lethal strainer, you don’t want a lot of stretch in it. Dynamic ropes with a lot of stretch are also not very efficient for mechanical haul systems since the traveling prusiks have to be reset more frequently.
In a pinch either type of rope can be pressed into duty for any of the above scenarios if there is no alternative.
old climbing rope, pulling with the flow
I’ve got an old climbing kern/mantle style rope that I’ve kept around to unpin boats. Never had to use it. Meaning I haven’t had to go back and retrieve a boat after getting the rope. good to know about the stretching, and the need to reconfigure prussics more often.
The only time I’ve actually used z drags is in a learning situation- like a clinic, or just practicing. The big thing in my book is to pull with the flow. Also helps to elevate an end of the boat. Too many times people set up z drags based on convenient anchor points rather than working with the direction of the flow.
Sometimes its best to leave pins and stranded boats that are jammed up under undercuts until the water drops- usually personal safety is an issue in these situations.
Static waterproof kernmantel rope designed for spelunking is probably the best for any kind of water use or hauling. We used to buy spools of it for deep vertical cave exploration expeditions and the leftover bits were highly prized for everything from large dog leads to slacklines.
McMaster-Carr has a ton of stuff in their catalog, some very hard to find items, but it’s VERY expensive. Try West Marine or BoatUS for top quality rope at reasonable prices.
I don’t know about you, but I’d never even give a thought to using 3/16" cord to tie the boat to a roof rack. Your insurance company might not be amused if the boat comes off the roof and injures someone else because you cheaped out on the tie downs.
Yes, stretch in a rope reduces the effective load placed on the fibers during a sudden arrest, but it isn’t friction.
It’s a simple effect - a stretching rope takes longer to stop a falling weight, so the deceleration on the body is lessened, i.e. a = (delta V)/(delta t) is less with greater time. Lower deceleration means the force provided by the rope is lessened, because F = ma.
In the situation of arresting a vertically falling body, the rope force will be: F = ma + mg. The first term comes from dynamically arresting the body, the second is the static weight of the body. So if the peak deceleration on a person is two g’s during arrest, the peak force on the rope will be three times the static weight of the body. Clearly reducing deceleration is beneficial.
In a physics class I teach occasionally, there is a homework problem involving designing a bungee jump cord. Unfortunately the solution in the book results in a maximum of 35 g’s on the jumper! This would be fatal, obviously, but it gives an opportunity to talk about the consequences of careless design and to have them redo the problem with a reasonable solution.
A few years ago I got involved in z dragging a pretty badly pinned boat. As luck would have it we had a z drag kit along that had been put together by the boat's owner. It worked but I was darned nervous during the pull - Guideboatguy and I were in the water and the stretch of that rope was not inconsiderable.
Like anyone who has worked pulling stuff (tree stumps for instance) with a tractor and knows of the danger of snapping steel cables (and therefore prefers chains for such uses), I was thinking about what might happen if that big ole' rubber band snapped. Heads might not roll, but I could see how it might cause pretty serious injury.
So I looked into (~3/8 if I recall) Bluewater haul rope for my own kit. It was strong, expensive, and available from climbing sources but nobody I spoke with knew if it floated or not.
I bought a small sample and threw it in a bucket of water. It doesn't even come close to floating. It sank like steel cable would. That looks like a problem to me. In any scenario involving swimming a rope out to a pinned boat or wading through a boulder garden with the possibility of slack rope drifting around your feet... well, you can see why something that floats and floats well would be far preferable.
Perhaps larger diameters of the spectra rope as is used in throw bags would be a better solution for that particular use. I'm thinking you'd want at least 2000 lb. tensile strength for Z drag use.
For painters or tie downs I don't think stretch is as worrisome and a little might even be a good thing. You certainly don't need anything that strong.