Rigging Study

[treelooker]

http://www.tree-consult.org/html/eng/indexeng.htm

Winter reading

[Mr. Sir]

Is there an abridged version? :P

[MasterBlaster]

That's a lotta wurdz for "Rope it out!"

[Wagnaw]

I really appreciate how on the ball the Euros seem to be when it comes to safety, and it was really cool to get to talk to some of them about the study they're doing on tie-in point strength, bending, etc... I remember using a lot of the tools they use, but it all gets way more interesting when it actually pertains to what I'm doing. :|:

I wish the U.S. would sponsor that much research to keep workers safe. ...granted they may also start trying harder to make people wear chaps if they do. :P

[Wagnaw]

My bad for double posting... but an interesting thing that the Treemagineers guys found with the "Worst Case Senario" rigging study was that putting a half hitch below your running bowline when rigging from above ends up putting way more stress on the tree than just a running bowline. It was all in that the slack in the half hitch added so much rope that the increase in the distance of fall greatly increase the shock load at the rigging point.

[PCTREE]

the US has no reason to do these studies to keep workers safe. We dont have socialized health care. Plain and simple thats why our safety regs arent as strict, dont wear chaps, cut yourself, then go pay for it.:roll:

[PCTREE]

My bad for double posting... but an interesting thing that the Treemagineers guys found with the "Worst Case Senario" rigging study was that putting a half hitch below your running bowline when rigging from above ends up putting way more stress on the tree than just a running bowline. It was all in that the slack in the half hitch added so much rope that the increase in the distance of fall greatly increase the shock load at the rigging point.

You were typing as I was you sneek. Now that is interesting, if I used a half hitch I would have to think about changing......

[CurSedVoyce]

I down loaded it and I am definitely reading it over this winter... Should be some cold snowy days I will have nuttin else better to do. :D Thanks for the post treelooker. Now I need some more toner and a ream of paper to make another book for the library :D

[stig]

the US has no reason to do these studies to keep workers safe. We dont have socialized health care. Plain and simple thats why our safety regs arent as strict, dont wear chaps, cut yourself, then go pay for it.:roll:

When helmet and seatbelt laws were implemented here, the reasoning was that when stupid people get hurt, it costs society too much via socialised medicine to heal them again.

Well, it wasn't put quite like that, but the meaning was the same:)

[MasterBlaster]

the US has no reason to do these studies to keep workers safe. We dont have socialized health care. Plain and simple thats why our safety regs arent as strict, dont wear chaps, cut yourself, then go pay for it.:roll:


I've never thought about it like that - it makes sense.

[Old Monkey]

When people get hurt without insurance all our medical costs go up.

[top hopper]

the Treemagineers guys found with the "Worst Case Senario" rigging study was that putting a half hitch below your running bowline when rigging from above ends up putting way more stress on the tree than just a running bowline. It was all in that the slack in the half hitch added so much rope that the increase in the distance of fall greatly increase the shock load at the rigging point.

Really depends where the bowline and half hitch are placed doesnt it? If the half hitch adds say an additional foot of rope and fall, couldnt the bowline / half hitch combo simpy be moved up to compensate? Anytime you increase the distance of fall loads will be greater, but to say its because of the half hitch would be false in my opinion. A more accurate statement would be -that adding a half hitch and placing it so the increase in fall is greater would put more stress / greater loads into the tree and / or rigging system. Simple physics really.

[top hopper]

When people get hurt without insurance all our medical costs go up.

But arent all of our medical insurance costs going to go down now with our new president? :roll::/:

[rbtree]

Really depends where the bowline and half hitch are placed doesnt it? If the half hitch adds say an additional foot of rope and fall, couldnt the bowline / half hitch combo simpy be moved up to compensate? Anytime you increase the distance of fall loads will be greater, but to say its because of the half hitch would be false in my opinion. A more accurate statement would be -that adding a half hitch and placing it so the increase in fall is greater would put more stress / greater loads into the tree and / or rigging system. Simple physics really.

Did you read the study? I read that part, briefly. I think your supposition is not what they found. I think the reason the line failed at the half hitch was due to friction from rope stretch and slippage.

Also, as far as butt hitch rigging is concerned, one should always place the lowering block as close to the top as possible. But, if the load is tied down a ways, all that means is more rope is out. The center of mass of the load still falls the same distance, assuming the load is snubbed off.

Main reason i see for a half hitch/marl before the bowline is to spread out the tie point to make it more secure, and lessen the chance of the rope coming off.

[Nails]

Putting the half hitch on also decreases the preasure on the final bowline knot.

[Stumper]

Putting the half hitch on also decreases the preasure on the final bowline knot.

,....but a half hitch is a much weaker connection so that reason becomes somewhat apparently foolish.

[MasterBlaster]

HuH? :?

[Stumper]

Half hitching in addition to choking a piece with a running bowline may serve a function in stabilizing the way a piece will hang but a half hitch is more prone to the liine damaging/cutting itself when shock loaded than is a running Bowline. Thus "taking part of the load off the running bowline" is a stupid reason to go to the trouble of working a wrap with half hitch into the rig. Mear as clud?

[MasterBlaster]

But doing that on a heavy load allows easier untieing, eh? It does for me.

[Stumper]

I suppose....I don't usually have any difficulty untying bowlines.

[MasterBlaster]

Me either! ;)

Know what I mean?

[gf beranek]

I've never been a fan of drop loading standing vertical work, because I have seldom work with a ground person that could fully understand the intricacies of letting the work run. Which invariably resulted in me getting a fantastic ride or getting hit by the work when it's caught and spins around.

During the drop load tests we did it was assumed that the failure point in the line would be at the marl/half hitch. And in one drop it was. Other line failures occurred at the capstan and in the line other than a knot. The line used in the test was well used and so any conclusions couldn't really be based on one specific cause of failure.

[Mr. Sir]

Me either! ;)

Know what I mean?

Ha! Same here! 8)

[Stumper]

:D Point taken Butch. However, I'm the weird exception one man show so I wind up untying most of my own knots. I also have a lot of experience working the ground-for my dad and for my own subs. In some lines a bowline can get sucked down to where it is moderately difficult to untie. mostly if the loads are not excessive for the rope the bowline unties readily. Of course you are also aware of my longstanding advocacy of taking smaller pieces compared to many aerial loggers.

[Old Monkey]

The last climbing class I attended they recommended tying what I think is a marl but I am not certain instead of a half hitch. It looks like the first part of a simple square knot or the first wrap of your shoe laces before you ad the bow. The reasoning the teacher used was to not put a hard bend in the line. I have to say that I haven't really tried it yet and keep tying half hitches above my running bowline.

[TC3]

When people get hurt without insurance all our medical costs go up.

Blah blah blah blah blah blah blah

[Old Monkey]

Don't make me come out there and...

[TC3]

Rephrase :
O'Blahma, O'Blahma, O'Blahma

[DMc]

Interesting study. It shows how difficult it is to put mathematical formulations on a biological.

Not discussed on the half hitch/marl backup of the primary knot, strength loss issue was one of the primary reasons for using that setup to begin with.
When lowering a limb, you are often able to use a primary knot by itself tied within a crotch or behind a stub. On a heavy, slippery log, such as eucalyptus, especially when lowering off the stem itself, no matter how much slack is taken up on the line, when the log starts to tip over the rigging goes slack. At that point, the running bowline eye becomes loose on the log. The log will then, very often, slip right through without even slowing down. The marl or half hitch were used to prevent this loosening of the eye on the primary knot, which they do very well.

I also wished they had done some off-angle oscillation studies. It would have been nice to add a few more pages to this study. :O We found in the interest of reducing the yo-yo effect in the slack/tension combination and to avoid bashing your lowering line that sending the butt-hitched log off a few degrees to the side would accomplish this. The resulting vibrations felt odd but were manageable. Just would have liked to have known what types of stress that scenario produces.

Dave

[TheTreeSpyder]

The running bowline gets pulled at an angle and the marl or half hitch gets pulled inline (correcting the angled pull on running bowline by full loading, and giving buffered pull to it instead) i believe securtiy rather than strength is the issue hear(arguing in favour of marl/hitch. If there is a branching that can dawg Bowline, can go without Half/Marl, have more strength, and more elastic line in formulae, with less Turns that might turn that factor against us.

i think block should be as close to CG as possible, hitchings should be b4 CG. First hitching/catch farther from block gives potential for more elastic buffering(because more line b4 frictions); but also can allow slack to give impacting(unless 'tuned' out).

Best is not shock loading, snubbing when it does shockload, including pulling over to travel farther on hinge b4 release to linewith line pull or bar/wedge push), and even retightening out slack on support line during hinging over. And that hinging being slower/ mopre controlled (as long as the slow leveraged length doesn't then cause problems by going too slow givng more problems than more impacting.