so i have to ask if my fears about a prussik knot are warranted. i use a 8 mm loop of sterling brand cord, its what the rock climbing shop local carries, and while it seems to grab very well with no slippage in climbing or holding position i have to wonder if it would slip under a slight shock load and send me slipping on down at a fast rate? or do they usualy slip and then grab in such an event? does bee line or icetail or the other brands they carry in the catalogs have any gripping advantage or just wear better over continued use? myself those little spliced eyes look like the weak point and i dont like how splices are hard to see if they are coming apart etc whereas a knot is pretty positive and easy to inspect. also, how is it that the prussik loop isnt the weak point in the system since its usualy smaller than the main rope? i guess its only got half your weight on it since the tree limb above acts as a pulley effect but still something to think about. just thoughts that bounce thru my mind and figured i would put out there for disscussion, tree climber companion is a great book that shows alot but still leaves me wondering about some of these little curiosities!
prussik knot security and holding
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canopyboy
ArboristSite Operative
I think there will be more experienced people to come along and give further advice (and hopefully correct any bad advice I'm putting out there), but I'll start.
In my experience, the only time I've had a prussik not hold is when it wouldn't really set in the first place. The prussik cord was too stiff and big compared to the line it was trying to grip. If your prussik is grabbing like it's supposed to, a shock load will only pull it tighter. If something bumps your prussik and starts it sliding, it should grab again as soon as that point of contact stops pushing down on the prussik. Remember, prussiks are what you use to back up mechanical ascenders sometimes. They're about as reliable as they get (in my humble opinion).
As for being the weak point in the system, there are two things to consider. First, I think most (at least some) of the prussik cords are rated for a maximum load that is near, at, or even more than the climbing line. Second, your prussik loop or eye-to-eye is doubled, with each side theoretically carrying about half the load.
The little spliced eyes in some of the prussik cords are plenty strong. In these cords the core is carrying the load, and the outer braid isn't needed for strength. I can see your point about being able to inspect the splices, but if they were done professionally you should be fine. That said, I'm still using knots as it's cheaper and allows me to continually mess around with the length.
I think there is some difference between how different brands grip, and definitely in their longevity. But I think you just have to play with it a bit and see what works best for you.
Oh, and I'm talking as if prussiks are any friction hitch tied with prussik cord. I believe a true prussik is one of these hitches tied with a loop, usually either 4 wraps or 6. Although there is a 5 wrap version that requires the loop to be finished after the hitch is tied.
In my experience, the only time I've had a prussik not hold is when it wouldn't really set in the first place. The prussik cord was too stiff and big compared to the line it was trying to grip. If your prussik is grabbing like it's supposed to, a shock load will only pull it tighter. If something bumps your prussik and starts it sliding, it should grab again as soon as that point of contact stops pushing down on the prussik. Remember, prussiks are what you use to back up mechanical ascenders sometimes. They're about as reliable as they get (in my humble opinion).
As for being the weak point in the system, there are two things to consider. First, I think most (at least some) of the prussik cords are rated for a maximum load that is near, at, or even more than the climbing line. Second, your prussik loop or eye-to-eye is doubled, with each side theoretically carrying about half the load.
The little spliced eyes in some of the prussik cords are plenty strong. In these cords the core is carrying the load, and the outer braid isn't needed for strength. I can see your point about being able to inspect the splices, but if they were done professionally you should be fine. That said, I'm still using knots as it's cheaper and allows me to continually mess around with the length.
I think there is some difference between how different brands grip, and definitely in their longevity. But I think you just have to play with it a bit and see what works best for you.
Oh, and I'm talking as if prussiks are any friction hitch tied with prussik cord. I believe a true prussik is one of these hitches tied with a loop, usually either 4 wraps or 6. Although there is a 5 wrap version that requires the loop to be finished after the hitch is tied.
tree md
Addicted to ArboristSite
As long as the prussic is well dressed it shouldn't slip on you. Ease your weight onto it while your still attached with a lanyard and it well dress up and hold fine. If you slightly shock it it will tighten up and you will have to work it loose a little bit to be able to descend on it. I have been climbing on one for 18 years and have had zero instances of it not gripping when set and dressed properly. The smaller diameter cords grip even better.
As far as spliced eyes go, there is a reason that it is recommended to set the bite of your timber hitch around the eye of the sling with a block. It is the strongest point. It is considered improper to set the bite below the eye. That should give you an idea of how sound the eye is.
As far as spliced eyes go, there is a reason that it is recommended to set the bite of your timber hitch around the eye of the sling with a block. It is the strongest point. It is considered improper to set the bite below the eye. That should give you an idea of how sound the eye is.
tree md
Addicted to ArboristSite
Almost forgot. You need to make sure you are climbing on a prussic well suited for your size. When I first started climbing I was 165 pounds and climbed on a 2 over 2 prussic. When I got bigger that knot started running on me a little more than I liked and I went to a 3 over 2 (5 coil) prussic. You might need to experiment and see which is right for you. I am climbing on a french prussic now (VT) it it runs well and grips well but it takes a little tweaking to get it where you want it.
clearance
Addicted to ArboristSite
I have a double ended 5/8" 18' steelcore with a smaller diameter steelcore prussic. I am over 200 lbs. with all my stuff. It has never slipped at all, ever. tree md is right about the turns though.
tree md
Addicted to ArboristSite
Yeah but I meant 2 over 3 on the 5 coil. I use 3 on the bottom 2 on top, running end and working end exiting the coils in the same direction with a stopper knot in the end. Or I should say used to use that, how soon we forget. No looking back since I went to the VT.
ok well thats relieving to know, i havent had it slip i just sorta had this mental image of one slipping from shock and just keeping on sliding. someone mentioned that they used just tied loops for prussic, what cord do you use for that? can you get the material they use in the eye to eye ones by the foot or whatever? in baileys i only see the eye to eye ones, altho i guess maybe i will just go with one of them since the eyes dont seem to be a danger point that i feared they might, and the strenth rating is much higher than simular sized other rope and cord
Metals406
Granfodder Runningsaw
If you tie your own, you might try a Blake's hitch? A 4-2 or 6-3 would work good from what I've seen. Just another type of friction hitch to try.
tree md
Addicted to ArboristSite
An open prussic is far superior to a Blake's hitch in my opinion. Runs a lot smoother and doesn't bind as much. I think you would do well to just buy a prussic cord or use the one you have if you currently have one. I use a scaffold knot to tie my eyes. Makes it adjustable so I can shorten or lengthen the cord as needed. You can by cordage by the foot and make your own.
Metals406
Granfodder Runningsaw
I'm sure you're very correct, as I am a noob to this hitch thing... Thought I'd throw the Blake's out there though.
Now I'm going to have to look up this 'scaffold knot'.
Metals406
Granfodder Runningsaw
Just tried the scaffold knot, pretty cool and simple slip knot! So you use the scaffold for the prussic loop? How is it adjustable without undoing the prussic, adjusting, and redoing it?
tree md
Addicted to ArboristSite
I don't climb on a prussic loop just a cord. I do have a prussic loop though that I use for other applications. You can loosen it and slid the knots up to adjust it or just retie them. When you tie a double fisherman to form a loop, I believe that is also called a grapevine knot as well. As if the knot didn't already have enough monikers...
Metals406
Granfodder Runningsaw
I didn't know there was such a thing as a steelcore prussic. Where do you get them?
hmm this steelcore prussic does sound interesting, altho its less likely to get cut anyhow being right at your hip. i just ordered some prussic cord from blue ridge arborist supplies, i like the 7200 lbs break strength a bit better than the sterling cords 4500lbs, altho its realy double that using it as a loop either way makes me feel better! that little prussik loop just looks so thin when your hanging there 50ft up!
outofmytree
Addicted to ArboristSite
I learned old school and still climb on an english prusik using a loop created by joining the ends with a double fishermans bend.
All you need to do is buy prusik cord cut to length, I use beeline for its heat resistance, tie the two knots simultaneously and you have a continuous loop. This is wrapped either twice or three times around your lifeline then you secure the loose end to your karabiner with a girth hitch.
What I like about this set up is that it is cheap to buy, with nothing needed other than a length of appropriate rope. It is simple to learn and done properly cannot come undone. There is the added advantage that it is possible to nick one side of the loop and still not fall.
What I dislike about this set up is that, unlike a french prusik with microsender, you cannot work the knot one handed when coming in towards the trunk. Branch walking is definately better with a self tending hitch.
There is a picture of the English prusik on page 86 of Jeff Jepsons "The Tree Climbers Companion" or you can go here http://www.animatedknots.com/prusik/index.php?LogoImage=LogoGrog.jpg&Website=www.animatedknots.com and search english prusik and girth hitch.
I am in the process of switching to a VT myself and just need a little spare time to set it up and practise with it. It seems that most climbers end up with some form of self tending friction hitch in the end but I think it is better starting on the simplest and safest to begin with.
All you need to do is buy prusik cord cut to length, I use beeline for its heat resistance, tie the two knots simultaneously and you have a continuous loop. This is wrapped either twice or three times around your lifeline then you secure the loose end to your karabiner with a girth hitch.
What I like about this set up is that it is cheap to buy, with nothing needed other than a length of appropriate rope. It is simple to learn and done properly cannot come undone. There is the added advantage that it is possible to nick one side of the loop and still not fall.
What I dislike about this set up is that, unlike a french prusik with microsender, you cannot work the knot one handed when coming in towards the trunk. Branch walking is definately better with a self tending hitch.
There is a picture of the English prusik on page 86 of Jeff Jepsons "The Tree Climbers Companion" or you can go here http://www.animatedknots.com/prusik/index.php?LogoImage=LogoGrog.jpg&Website=www.animatedknots.com and search english prusik and girth hitch.
I am in the process of switching to a VT myself and just need a little spare time to set it up and practise with it. It seems that most climbers end up with some form of self tending friction hitch in the end but I think it is better starting on the simplest and safest to begin with.
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