Rigging question

[tophopper]

The only thing I generally use a timber hitch for is for hanging a porty or hanging a block. And I will always try to tie a cow hitch first, but if my sling is too short I will use the TH. For terminating rigging lines to the piece being cut.....99% of the time I will use a running bowline. I will add the half hitch or marl above or below only when Im worried about the rope slipping off the end. Never do I use it thinking its needed to reduce stress at the termination knot.

 

[squisher]

Interesting, I've always kind of considered that it(a half or marl) helps share the load as I'm under the impression that a running bowline is not really that strong of a termination? It's how I always rig when negative blocking and for the rigging point above I generally only use it if I'm worried about slippage as there's so little shockloading I'm never usually concerned about strength if the rigging is above.

Skool me up!

 

[FJR]

I have always done like John does, only use the marl when needed with the running bowline. I use to use the clove hitch a lot, until I had a little mishap a few years ago. No mas.

 

[tophopper]

To clarify, when negative blocking I use the half hitch often, especially when getting into straight heavy pieces. I do it because I like more rope surface area on the piece being rigged, hence giving more grippage. If there is a prominent collar or protrusion in the log that Im sure a bowline wouldn't slip over I will consider not using a half hitch.

If a running bowline is only 60% efficient, you should still be plenty safe using one at any time, if you are staying withing your 10% safe working load limit of the rope. My thinking anyway. Anyone disagree?

 

[SkwerI]

Exactly, John. If knot strength is an issue then you need a bigger rope.

 

[brendonv]

Straight or slippery stems will get a half hitch or marl. Also to make the distance closer between the block and piece as to not worry about the bowline slipping off so close. Limbs I'll just throw the bowline in a crotch or around a stub or something. Every branch is different.

Running bowline is used most of the time, rarely a clove hitch (almost bad experience), and I even sometimes tie an over hand knot in the end of the line and timber hitch limbs with three wraps. Easy and quick untie for stupid ground crew.

 

[squisher]

I hear what you're saying. I guess in the back of my mind on bigger pieces I'm considering that the end of the line is the weaker point. And yes 60% puts you well within safety when running a 10 to 1 safety factor. I guess in my mind I've always thought that the marl or half takes some of the load off of the knot and that this is a good thing.

To me I wouldn't say, "oh we don't have to worry about the knot strength loss because the rope should be plenty strong enough."

I would say, "a marl or half hitch helps take some of the load off the termination knot and this combined with a proper size(rated) rope, rigging so as to reduce the length of drop or shock, cuttng appropriate sized pieces, allowing pieces to run as much as they can, and so on and so forth. All work together to keep rigging as safe as possible."

My real question would be, does a half hitch or marl reduce the load on the termination knot? Not do we need to worry about reducing the load on the termination knot.

Cycles to failure and things like this all come in to play with rope strength than imo. If your rope is plenty strong enough to handle the load that is one thing, but if you can reduce that load at the termination knot than your rope should be good for more cycles before needing to cut it back. No?

 

[SkwerI]

My understanding is that the marl becomes the weakest spot in the rope and if a rope failure were to occur, it would likely be at the marl. I think it has to do with shock loading and the tight bend radius of the rope crossed over itself.

 

[tophopper]

I cant disagree Justin, adding the half or marl definitely helps distribute the load out over the piece and along more rope area.

Cut it back? What about the rest of the rope that has the same cycle to failure history?

 

[rskybiz]

Sorry to have left this for a few but estimate called a little hanger fixed. The "marl" Skwerl and South Sound have what I was speaking of. Above the block proudly represented on the http://gypoclimber.com/showthread.ph...pur-s-Coverboy Now to answer the other, termination=end hitch, Knot.

 

[squisher]

My understanding is that the marl becomes the weakest spot in the rope and if a rope failure were to occur, it would likely be at the marl. I think it has to do with shock loading and the tight bend radius of the rope crossed over itself.

So as you see it a marl with a running bowline would be weaker at the marl than just a running bowline would be by itself?

I'm not trying to be a dick here but I would like to know all y'alls opinion. These are details I'd like to really know about

 

[squisher]

Cut it back? What about the rest of the rope that has the same cycle to failure history?

I end up cutting my rigging lines back a few times before retiring the whole rope. Again based on my own fingering, in my mind the end of the line takes the worst beating/loading/unfavorable bend radius/and what not. So after some severe abuse but usually long before I'm considering retiring the whole line I'll cut back to a 'fresh' end. Am I mental in this thought pattern?

 

[Burnham]

Straight or slippery stems will get a half hitch or marl. Also to make the distance closer between the block and piece as to not worry about the bowline slipping off so close. Limbs I'll just throw the bowline in a crotch or around a stub or something. Every branch is different.

Running bowline is used most of the time, rarely a clove hitch (almost bad experience), and I even sometimes tie an over hand knot in the end of the line and timber hitch limbs with three wraps. Easy and quick untie for stupid ground crew.

Regarding the part of your post I bolded above, Bren...I want to make sure you're not under the impression that moving the marl/half hitch closer to the end of the piece towards the block is changing the distance the piece falls before being arrested/controlled. The center of gravity of the piece is the point from which that distance is measured, and so long as the attachment point is anywhere below the COG (so the piece cannot flip) the distance of freefall (that one would consider when calculating the dynamic load on the rigging system) is the same no matter where the rope is attached.

 

[Burnham]

I think that makes some sense, Squish. But like Top infers, it's not an "as new" rope, I don't think.

 

[rskybiz]

My understanding is that the marl becomes the weakest spot in the rope and if a rope failure were to occur, it would likely be at the marl. I think it has to do with shock loading and the tight bend radius of the rope crossed over itself.

This covered the basis of my question And want more on the very heart of this. I sense it as the spot to fail also, is there hard fact research for say "same wood piece same hitch and marl same drop where is failure?" and I know each rope is different.

 

[Burnham]

I'm not so sure the marl/half hitch is the weakest point due to the fact that the rope can move a bit though that bend as the load comes on...but that's just speculation.

 

[squisher]

Man I bet Kenny(TreeSpyder) knows the answer to that question.

 

[tophopper]

I only cut it back if it is visibly damaged, which in most cases can be the end 3-4 feet. But I dont make a point to cut it back because of beating/loading/unfavorable bend radius/and what not.

At my current gig, on average I go through 2 or 3 5/8's and 3/4" bull ropes per year. They are then downgraded to a less critical job. But i do so much negative blocking, after a year or so they are pretty well used, and I begin to question their integrity, so they are replaced. A minor cost considering the jobs they do and the income they (and I) produce.

I carry more rigging than any other thing on my truck. 2 people could easily fit inside my rigging box, and its usually close to full. I have specific rope for specific tasks. Heavy bull ropes for negative blocking, bull ropes for use with the GRCS, and rigging blocks, ropes for use in blocks only, ropes for natural crotching ( burn ropes)

 

[squisher]

I think that makes some sense, Squish. But like Top infers, it's not an "as new" rope, I don't think.

Oh I don't for a minute think it re-sets the cycles to failure or anything like that. I just think that the end sees alot of abuse and like to see it lopped off occassionally.

 

[Burnham]

That's the way to roll, John.

Justin, I agree re what Kenny probably knows...but about 7 out of 10 posts of his I wasn't able to decipher what that actually was . But I miss the lil' bugger...wish he still hung out with us.

 

[squisher]

Interesting John, on the cutting back. I don't cut it back just because but I guess I do it because on inspection it always seems like the working end is a bit more 'trashed' than the rest of the rope so I end up lopping it.

I too, basically run a lowering line for a year, then it becomes a pull line, than it becomes a dirty pull a truck out if need be line the year after that. And separate ropes for natural vs block rigging.

This thread is making me feel like ordering some new rigging lines. Lol.

I do make a point of thinking about what I'm rigging and what forces are involved vs just doing it with what I have.

 

[tophopper]

On some jobs it can be a real pain packing up all the rigging at the end of the day.

 

[MasterBlaster]

But is there a choice?

 

[squisher]

You could leave it behind. Like my new guy did with his saddle last Friday. Sucked for him, job was over an hour away.

 

[Burnham]

Ouch...successful retreival I hope?