Large Pine Rigging

Bixler

Bixler

Participating member
Location
Nevada City, CA
http://youtu.be/34RtA8m120o

No crane access and a steep driveway made for an interesting job in Nevada City, here's some footage from the job.

A big thanks for BOTS to come up and help out with the speed line the first day, ground support and photos.

Joe 'Madman' Madrigali rigged the wood the second day.

Tree fit into dump truck in two loads. Loaded with 8,000 lb. excavator.

Clients are happy.
 
You've got the magic touch Bix... one suggestion would be to snug those blocks/slings up right below the notch.. I always tie my sling on first, then cut the notch within a few inches.. obviously, the lanyard then has to then go under the sling.. doing the math is a real eye opener... No need to re-hash it here other than to point out that the piece is going to free fall 2x the distance from notch to block, making the height of the block the most important factor (in the climber's control) in determining the amount of shock load.

With a good ground man running the ropes, its a lot less important... However we should develop and hone our skills and techniques for worst case scenarios, so we're prepared for a bad situation. AND there can be hidden defects in the tree, which could kill the climber in the even of stem failure. So why put any more stress on the tree or the rigging system than absolutely necessary.
 
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Good job Bryan. How long to get the tree down ?

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Thanks Reg, I was in the tree for a good six hours the first day. Had a nice lunch up there too.

The second day the climber was in the tree by 9am, wood all rigged by noon, after lunch he spent another couple hours in the tree slicing small pieces.

12 Hours total to get the tree down.
 
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BixVid for life.

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You two get a room?
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Thanks guys, Murphy that's some good info.

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Yes, it was good advice, Bix.... I always do the same..

Also, if using the GRCS/Hobbs, employ "rapid slack removal" as the piece tips into the rigging, during that brief moment with no tension on the rigging. Takes a good rigger, to immediately then be able to let the load run as needed, which sometimes isn't much, or at all, when low down and with little clearance. In such cases, if the center of mass of the load has only fallen, say, 6 feet, then the peak forces, even if the load were snubbed off, would only be 6x its weight, minus system friction.... (or is that 7x??)

Superb vid, by the way!!
 
Thanks Rog, glad you enjoyed it. Rigging large wood is pretty intense. I'd like to gain a better understanding of the forces generated.

It would be nice we had a block hooked up to a ratchet strap to get that sucker really tight, but I've never seen one.



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BixVid for life.

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You two get a room?
grin.gif


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We can't, you and Oxman took the last one!
 
Wait Roger, if the ground guy is letting the piece run smoothly and consistently, what is the benefit of trying to add the step of 'rapid slack removal' which I'm assuming you mean to take up slack in the line as the piece is tipping over and before the rope has caught the piece?

This seems an unnecessary step if the groundie is reliable and consistent in letting the piece run? So what is the benefit? Maybe there is one, I just can't picture it?

jp
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The strapped on block would probably be hinged on a plate. Interesting idea it would tighten the free fall but that bit of flex in the system from a tied sling seems like a nice shock absorber. Once the sling gets used once the slack is gone so it may not be as flexy as I was thinking. Hmm have to think about that some more.

The plate could put some leverage on the stem and cause a break. Forget the plate. Hmm ratchet strap. Not built for shock loading as well as a tied sling.
 
John, the idea is simply to limit the slight bit of slack in the system that will occur as the load tips into the rigging. This is especially important for those times when there's little room to let the load run. If its, say, only 500 lb, and the center of mass only drops 6-7 feet, that would apply about 35,000 lbs of force to the line, well within a 5/1 safety margin.

And, if the load is let run, the goal is to start braking it's movement right away. True it will still accelerate for a few feet, but the starting movement will only be maybe 5-8 feet per second, if the braking is initiated within about 0.25-.35 seconds...

(In free fall, a load drops 16 feet in the first second, and is traveling at 32 fps after one second...for reference..)
 
it might not seem like much of a benefit in theory, but in real life the climber can notice a BIG difference.

I have always trained my good ground guys to be "clicking" out those inches on the hobbs as the piece hinges over. I want to hear those clicks!

If you lessen that free fall just 8 inches, it seems to make a big difference.

pull out slack as the piece is hinging over, then go into a run with progressive braking from the VERY top down.

OR... if the groundperson is not good at this switching up, then pre-tension the line a bit and let the rigging rope stretch take care of this slack that would happen as the piece hinges over.
 
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