From what I understand they are designed to give a bit of cushion to short falls.
Should I climb on this rope?
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From what I understand they are designed to give a bit of cushion to short falls.
Ghillie
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Static ropes are more accurately described as low-stretch ropes.
According to the Cordage Institute, a "static' rope can stretch up to 6% of it's length at 10% of it's minimum breaking strength.
A "dynamic" rope will stretch more than 6% but not more than 10% at 10% of it's minimum breaking strength.
A fall factor is described as how far the fall was divided by what the length of rope the load fell onto. If you are below your anchor point and you fall 5 feet but you have ten feet of rope between you and your anchor, that is a fall factor of .5 and is easlily managed by "static" rope.
If you have ten feet of rope out and fall from the exact height of your anchor point, that would be a fall factor of 1 (10 foot fall divided by 10 foot of rope = 1) and you should consider using a higher stretch "dynamic" rope if you are going to put yourself in those kind of positions.
But generally when I climb trees I keep as much slack out of the rope as possible to keep the fall factor low.
I hope that helps clear up the descriptions a little bit, without getting into dealing with kilonewton's and other force factors.
Another piece of trivia by the way, a 8mm prussik on 1/2" static line will slip at around 1500 lbs of force while a mechanical ascender (such as a Gibbs) will desheath the rope at 2000 lbs with out slipping any. Translation: a friction hitch will act as a shock absorber if you "shock load" the rope where a mechanical climbing device is more unforgiving and will compromise your ropes integrity.
Good luck and be safe,
Fred
According to the Cordage Institute, a "static' rope can stretch up to 6% of it's length at 10% of it's minimum breaking strength.
A "dynamic" rope will stretch more than 6% but not more than 10% at 10% of it's minimum breaking strength.
A fall factor is described as how far the fall was divided by what the length of rope the load fell onto. If you are below your anchor point and you fall 5 feet but you have ten feet of rope between you and your anchor, that is a fall factor of .5 and is easlily managed by "static" rope.
If you have ten feet of rope out and fall from the exact height of your anchor point, that would be a fall factor of 1 (10 foot fall divided by 10 foot of rope = 1) and you should consider using a higher stretch "dynamic" rope if you are going to put yourself in those kind of positions.
But generally when I climb trees I keep as much slack out of the rope as possible to keep the fall factor low.
I hope that helps clear up the descriptions a little bit, without getting into dealing with kilonewton's and other force factors.
Another piece of trivia by the way, a 8mm prussik on 1/2" static line will slip at around 1500 lbs of force while a mechanical ascender (such as a Gibbs) will desheath the rope at 2000 lbs with out slipping any. Translation: a friction hitch will act as a shock absorber if you "shock load" the rope where a mechanical climbing device is more unforgiving and will compromise your ropes integrity.
Good luck and be safe,
Fred
livinalaska
ArboristSite Lurker
Those ropes will perfectly fine for climbing trees as it's not lead climbing such as being belayed while climbing rock. You'll want the static line and if you're in a tree and subject to a fall, look for a high redirect to minimize impact to you and you're equipment. Some of the properties I don't like in a nylon kernmantle line is the reduced strength when wet, the UV resistance, the water absorption and lesser heat resistance than polyester. That said, don't look a gift horse in the mouth. A three year old rope thats in brand new condition will last you for several years.
I agree 100% with Fred in that a three-wrap prusik will slip at 8-12 kN which isn't a force you will generate in a tree unless you're dropping yourself a serious distance. Also, if you are using SRT and using a cammed ascender as your attachment point, you will die if you drop. They are notorious for desheathing ropes.
Lastly, someone mentioned the 15:1 NFPA safety factor. The safety factor is set for a three kN rescue load and a 12.5mm rope with a 40kN strength. When you tie a knot in said rope you lose 1/3 your strength which brings you down to 27.7 kN that equates to a 10:1 safety factor where your rope is the weakest link in NFPA. A 15:1 SF is a misnomer that causes several people to overengineer their systems in hopes of achieving this SF when it's unnecessary considering that NFPA doesn't spell out a 15:1 SF. They call for 40kN ropes and call a rescue load 3kN. There is also some science behind it in that they take into account that a firefighter may be responding in their turnouts and are generally larger than the 2 kN rescue load that backcountry practitioner using 11.1 mm rope consider.
Anyway, you caught me monologueing. That rope is perfect and stretches more than most when dropped on a rescue load so you'll be fine. As far as climbing, remember that the polyester arborist lines have a 12-15% elongation at failure and nylon lines have a 15-28% elongation at failure, which means that polyester stretches even less. If you still don't want to use them, send them to me (I'll pay postage) and I'll be more than happy to post pictures of me using them...in a tree...with a smile on my face.
Peace
I agree 100% with Fred in that a three-wrap prusik will slip at 8-12 kN which isn't a force you will generate in a tree unless you're dropping yourself a serious distance. Also, if you are using SRT and using a cammed ascender as your attachment point, you will die if you drop. They are notorious for desheathing ropes.
Lastly, someone mentioned the 15:1 NFPA safety factor. The safety factor is set for a three kN rescue load and a 12.5mm rope with a 40kN strength. When you tie a knot in said rope you lose 1/3 your strength which brings you down to 27.7 kN that equates to a 10:1 safety factor where your rope is the weakest link in NFPA. A 15:1 SF is a misnomer that causes several people to overengineer their systems in hopes of achieving this SF when it's unnecessary considering that NFPA doesn't spell out a 15:1 SF. They call for 40kN ropes and call a rescue load 3kN. There is also some science behind it in that they take into account that a firefighter may be responding in their turnouts and are generally larger than the 2 kN rescue load that backcountry practitioner using 11.1 mm rope consider.
Anyway, you caught me monologueing. That rope is perfect and stretches more than most when dropped on a rescue load so you'll be fine. As far as climbing, remember that the polyester arborist lines have a 12-15% elongation at failure and nylon lines have a 15-28% elongation at failure, which means that polyester stretches even less. If you still don't want to use them, send them to me (I'll pay postage) and I'll be more than happy to post pictures of me using them...in a tree...with a smile on my face.
Peace
