Loop vs prussic

#1
I often use a maasdam rope puller to help with back leaners and side leaners and wherever else I need a mechanical advantage. I have my rope puller set up with 30' of rope rather than using it directly on the rigging lines. When setting up a pull line or a safety line with tension I sometimes use a farmers loop on the pull line to hook into the rope puller and sometimes use a 1/2 rigging prussic with 6-8 wraps. The prussic makes it super easy to adjust the location of the anchor on the pull line to get maximum pull length. I've watched a bunch of Richards videos of him breaking gear and it got me wondering, which is stronger, the prussic or the farmers loop? I realize that the rope puller is the weakest link in the system with only a 1500# rating, and there is no way me just cranking on the handle can overload anypart of the system. So I'm pretty confident neither the loop or prussic will fail, but am still kinda curious which would fail first when put to the test?
 
#2
prussiks tend to slip around 1000-1500 pounds (though more wraps on the rigging prussik probably increases that some) But your loop would definitely be stronger as far as being unable to slip. That being said, you can double up prussiks for extra holding ability (run them in tandem) with the rigging prussik left with long legs so it balances with another prussik.
 

Stephen Moore

Well-Known Member
#3
What would concern me is a 1500 pound rating. In any system there must be a safety margin that exceeds the maximum load that may be present by a pre determined factor. 1500 pounds is not really very much in the grand scheme of things but adequate for smallish trees. Most knots that have a loop or bite will reduce the strength by 50 percent there about. The prussik is not a part of the rope and as such can move without warning, whereas a knot such as a figure 8 or butterfly is part of the rope and as such cannot inadvertently slip. I personally would only use a prussik as a backup for a direct connection in a critical pulling scenario. Ill assume you are capturing the tail in a permanent way in the event that either the puller fails or the prussik slips?
 

flyingsquirrel25

Well-Known Member
#5
The puller is rated for 1500 pounds of pull at a 10:1 mechanical advantage. What the manufacturer safety factor is I’m not sure but it is rated to 1500 # of use. I would be interested to put a load cell in on some of the trees we fell with it to see how much pull we put into a rope anchored up high in a tree to over come a lean. Would be an interesting number.
Our puller is set up very similar to yours but we always use but we don’t use a prussic connection because of the slipping possibly. As a climber I trust prussic’s Because I only weigh 10% of what we could potentially be putting on pull ropes with the Maasdam. Out knot of choice is the bowline on a bite or double bowline. This gives better a bend radius due to more sections of rope being included in the knot. It also gives us 2 or 3 loops to hook our puller into spreading the load throughout the knot.

*We don’t use our puller very often and normally only in a backup or additional pull situations, only because our mini is easier and quicker to set up*
 

Jehinten

Well-Known Member
#6
I agree that the prussic may slip before the other loop fails, however a stopper knot behind the prussic would prevent that. Then there are the variables on which prussic cord and the actual hitch that is tied. I do not have any numbers on any of that, but I am leaning towards the loop failing first.

This assumes that it is a 1/2" rope that the loop is tied into. A large enough pull rope, and the de-rating due to the knot, may surpass the prussic.
 

Stephen Moore

Well-Known Member
#7
Curious as to why you wouldn’t rely on the prussic, climbers have use prussic’s for a long time as a solo piece of life support,
Well for one thing Prussik cord is typically of a smaller diameter than the rope it’s used on and normally not as strong. While it will easily take the strain of a climber, it is not really intended for use in pulling due to the potential for slippage and breakage. The prussik is a constricting hitch, you might as well use a rope grab behind it or even ahead of it for back up. In either case a second short length of rope can be attached to the anchor point or a separate anchor point inline with the haul system. On that second rope is a rope grab or second prussik that captures your progress and backs up the pulling device. Not unlike your climbing system being backed up by a prussik. Sudden loss of tension in a pulling system can have really bad consequences!
 

Jehinten

Well-Known Member
#8
And not that it answers the question of this thread, but I use the ropejack and not the masdam. Having a midline attachable, endless pull is great and it loves pulling 1/2" Stable braid. It eliminates the need for moving an attachment point while pulling
 

Stephen Moore

Well-Known Member
#12
I use what we call block and tackle. Just a pair of double pulleys with a mechanical brake built in one end. Quick to set up. Definitely not heavy like the GRCS.

@Stephen Moore, I don't use a truck .... well, next to never. You can't feel the load as you can when you pull by hand. I've seen a rope or two overloaded and snap.
Blocks work good but it's not as convenient as a clove hitch around my pintle on my truck. As for snapping a rope... Ain't goona happen, I use way bigger rope than I need for job. I can do a burn out with my 5 ton with a 1" bull rope. But even if I use lighter tackle, the procedure to prevent rope failure is simple. Set the rope in tree, connect to truck, snug up so that top is showing some movement, do undercut, start back cut til room for wedge is available, hand set wedge, continue progressing back cut, watch top for movement and wedge for dipping, once wedge and top show movement you are good to cut up or pull with truck. Easy as pie with no need for rope failure. Plus blocks are slow to take up, 3 to 1 means 3 times slower etc. More rope is required also, and to get the needed force for really big trees you will need to incorporate a winch or puller anyway. Not saying I don't do it... we do use blocks in the trucker's hitch for hand jobs regularly, but a heel block and truck is super fast and easy. Bigger tree = bigger rope and heel block.
 

KevinS

Well-Known Member
#13
On a heavy pull using a Prussic do you guys chase the friction hitch with a slip knot as insurance to avoid slippage. I find the weakness of it being it slips under load so it fixes everything.

Anyone else?
 

96coal449

Well-Known Member
#15
Blocks work good but it's not as convenient as a clove hitch around my pintle on my truck. As for snapping a rope... Ain't goona happen, I use way bigger rope than I need for job. I can do a burn out with my 5 ton with a 1" bull rope. But even if I use lighter tackle, the procedure to prevent rope failure is simple. Set the rope in tree, connect to truck, snug up so that top is showing some movement, do undercut, start back cut til room for wedge is available, hand set wedge, continue progressing back cut, watch top for movement and wedge for dipping, once wedge and top show movement you are good to cut up or pull with truck. Easy as pie with no need for rope failure. Plus blocks are slow to take up, 3 to 1 means 3 times slower etc. More rope is required also, and to get the needed force for really big trees you will need to incorporate a winch or puller anyway. Not saying I don't do it... we do use blocks in the trucker's hitch for hand jobs regularly, but a heel block and truck is super fast and easy. Bigger tree = bigger rope and heel block.
I hear where your coming from. You, well as I, have been in the field long enough to know how to pull with a truck or machinery. When I'm doing the cutting, I prefer the guys doing the pulling are doing it manually, Steady pressure with minimal pulling usually does the trick. Also block and tackle can go places where machinery can't. I do like the ease and speed of hitching up to a truck but a friend of mine put his voice in my head some time ago. "Practice safe driving habits."
I do believe the block and tackle to be somewhat safer. Especially if your relying on a greenie to do the pulling.
 

Stephen Moore

Well-Known Member
#16
I hear where your coming from. You, well as I, have been in the field long enough to know how to pull with a truck or machinery. When I'm doing the cutting, I prefer the guys doing the pulling are doing it manually, Steady pressure with minimal pulling usually does the trick. Also block and tackle can go places where machinery can't. I do like the ease and speed of hitching up to a truck but a friend of mine put his voice in my head some time ago. "Practice safe driving habits."
I do believe the block and tackle to be somewhat safer. Especially if your relying on a greenie to do the pulling.
Many times I setup my own pull- no one else doing anything. I install my bull rope, rappel off it using rescue 8, install on pointless hitch, place undercut, pre tension TIL top dances, do back cut leaving modest amounts of holding wood and walk calmly to my truck. Put the truck in gear, then remove air brakes- 1” bull rope always wins!
 

flyingsquirrel25

Well-Known Member
#17
Many times I setup my own pull- no one else doing anything. I install my bull rope, rappel off it using rescue 8, install on pointless hitch, place undercut, pre tension TIL top dances, do back cut leaving modest amounts of holding wood and walk calmly to my truck. Put the truck in gear, then remove air brakes- 1” bull rope always wins!
I know 2 guys that used this practice, they are in wheel chairs now! I’m not saying you dont take the long way to the truck and I’m not saying I haven’t used the practice. You must be 100% focused and be watching all around when you do.
 

KevinS

Well-Known Member
#18
Blocks work good but it's not as convenient as a clove hitch around my pintle on my truck. As for snapping a rope... Ain't goona happen, I use way bigger rope than I need for job. I can do a burn out with my 5 ton with a 1" bull rope. But even if I use lighter tackle, the procedure to prevent rope failure is simple. Set the rope in tree, connect to truck, snug up so that top is showing some movement, do undercut, start back cut til room for wedge is available, hand set wedge, continue progressing back cut, watch top for movement and wedge for dipping, once wedge and top show movement you are good to cut up or pull with truck. Easy as pie with no need for rope failure. Plus blocks are slow to take up, 3 to 1 means 3 times slower etc. More rope is required also, and to get the needed force for really big trees you will need to incorporate a winch or puller anyway. Not saying I don't do it... we do use blocks in the trucker's hitch for hand jobs regularly, but a heel block and truck is super fast and easy. Bigger tree = bigger rope and heel block.
Plus blocks are slow to take up, 3 to 1 means 3 times slower etc. More rope is required also, and to get the needed force for really big trees you will need to incorporate a winch or puller anyway.

You make ma sound like a nuisance
 

Tony

Well-Known Member
#19
You are all overstating the amount of slip a prussic will have in an overlaoded situation. In my expereince at heavy loads (4000-6000 measured) the slip was quick and a few inches max. ( These were pretensioned side guy lines on large trees) This was easily absorbed into the system and managed by tailing the rope through a port a wrap. In fact the cord will melt or bind itself to the pull line in extreme loads during the slip. Instead of a total “fail” as some of you are envisioning it served as more of a wake up call. The only true failures we had were due to low melting point hitch cords. ( These were post fell, i.e. after the tree hit the ground. They were unmeasured).

Use high temp cords, rated for the system. Knots work as you expect, but lack adjustability when you 2 block.

Any rope grab in a rgging system is an excesssively poor idea. Those won’t slip, but part the rope when overloaded.

Tony
 

96coal449

Well-Known Member
#20
More rope is required also,
I get around the rope shortage by having 3 dedicated ropes in the block and tackle setups.
1 set has a 150'x 5/8'' Wall Braid in it, which stays incredibly round for running through the pulleys,
and the other 2 have 100'ers. The shorter 2 give me 25' of pull and I've never run out. Not even on hard leaners. I use, (what we call a rope block), to hook the block n tackle set up to the pull rope.
It's an exhilarating feeling when you manually pull over a biggie with a couple of guys, and maybe a wedge or 2 in the back cut.
 
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