8 tonne rope failure, shock loading

[TimberMcPherson]

We have been removing some big montery cypress (macs) and pine on a steep hillside development. Its all been ugly stuff, the whole area is sand with a little topsoil. Trees have been between 50 to 80inch DBH. When you have to be roped just to get to the base of the tree you know its steep. (but some have been on flatter ground).

Yesterday one of the ugliest of the bunch we had to get down, it was about 120 feet high, probably 70dbh. It was on a STEEP incline (like the lowest part of the back of the tree was about 10 foot higher than the lowest part of the front of the tree. In the attempt by the developer to cut a track below the tree the ground had slumped about 14 feet below the tree, a few roots exposed, we have been getting alot of rain so time was crucial.
We had spent 2 days taking off its lower 70 feet of limbs (some overhanging house but much higher) but been rained off a week prior.
Tree had a strong lean downhill, right at a house at the bottom which was about 50 feet away as the crow flys. Dismantling would have taken time we didnt have with wood to big to rig safely, to close to the house to just block and I really didnt know just how stable it was going to stay in the near future.
No chance of crane or anything this side of a 4wd getting there. Helicopter would have been an option but this place is right on the coast under a ridge in which we have seen the wind direction change from calm to 3 directions of gusts and then still again in 15 minutes. Really nerve racking with big flops.

Just to get in the cuts we had scaffolding put around the tree (and we totalled most of it). I put a scarf in that started out really small aimed at the house and its lean which opened up as it moved to about 10 o'clock of its lean direction (which is at 12). At 9.30 oclock we had a tirfor set up.

About 2/3 up the tree we set up my big line, 4 inches of mooring line set up to a BIG fresh stump at about 8 oclock up on the hill. the line was horizontal and we did all we could to pretension it (but a line that heavy is hard to work with). The idea was that the tree would move slightly towards the house, the line would take the load and help with the tirfor to direct the tree to swing and fall into the bank. A couple of city arborists had been watching the set up, experienced guys. They pretty much said they were very glad they werent doing it and couldnt see a better way of doing it.

Put in the backcut, left alot of holding wood on the LHS. I REALLY didnt want that side to fail and send the tree right at the house and needed it to hold so if the tree did a violent swing the butt wasnt going to end up heading towards the house to fast (although it was butt roped/cabled) , I had alot of trust in that line but wasnt willing to aim at the house when it came down to it. The tree was VERY stubborn, I cut and wedged hell out of it, and then after alot of work and sweat the tirfor pulled it over. When the tree came over it didnt follow the lean at all, so didnt pre tension the big line. About a third of its way the it found tension, of course to late. It gave that gut thumping gunshot sound as the 4 inch line snapped. The tree fell in line with the scarf at 10 o'clock.

The tree didnt fall exactly where I ideally wanted, but did fall within what I had considered a safety zone. Nothing of value or consequence broken. Developer was stoked. Owner of house was VERY happy (although I did break a few branched of her lemon tree.) She had been living in fear under that tree for years and when the ground slipped a couple of days ago, she stopped sleeping at night.

I have run the whole thing through a hundred times, and aside from coming up with a way of pretensioning a 4 inch line set horizontally 50 feet away or just having a bigger line, I dont think I could have done much different aside from aiming the tree more at the house, but even that make me worry about how things could have been much, much, much worse.

I dont think Im being to pedantic. I take my very clean record for breakage very seriously. Big tree, bad ground, target rich environment with a tight timeframe and limited options. I am confident in my ability and track record but I am simply not happy with how it went, do I just need to harden up?

 

[clearance]

Glad it all worked out. Last month we cut down a dead, heavy leaner Doug fir, about 4' dbh and about 100' to where the top had broken off at about 6". It leaned heavily downhill, directly towards the three phase powerline across the road and the guywire pole that supported the guywire that ran above the road across to the power pole. I climbed it and took off lots of branches, then tied on two bull ropes at about 60'. We made a clearing for it to go into and set two medium sized Tirfors uphill and out of the bight. We had radios and flaggers, shut the road down, had a faller at the tree, two guys on the Tirfors, me standing on the road, running the show. The tree was guyed directly in the path we wanted it to go, everything worked out just fine and she thumped down nice. But still, you are always thinking, what if? I like the direct pull, maybe you could try that, I have hung blocks on the end of a choker to put them in the right spot.

 

[Magnum783]

Glad it all worked out. Last month we cut down a dead, heavy leaner Doug fir, about 4' dbh and about 100' to where the top had broken off at about 6". It leaned heavily downhill, directly towards the three phase powerline across the road and the guywire pole that supported the guywire that ran above the road across to the power pole. I climbed it and took off lots of branches, then tied on two bull ropes at about 60'. We made a clearing for it to go into and set two medium sized Tirfors uphill and out of the bight. We had radios and flaggers, shut the road down, had a faller at the tree, two guys on the Tirfors, me standing on the road, running the show. The tree was guyed directly in the path we wanted it to go, everything worked out just fine and she thumped down nice. But still, you are always thinking, what if? I like the direct pull, maybe you could try that, I have hung blocks on the end of a choker to put them in the right spot.

What are Tirfors?
Jared

 

[clearance]

A line pulling machine that unlike a come-a-long does not wind the cable around a drum. It pulls it sort of like you pull a rope hand over hand. They pull or back off under load in a very controlled manner. Pretty expensive, made by differnt manufactures, varying quality as well. 3/8" to 5/8" line is common.

 

[TaoTreeClimber]

That sounded like some sketchy stuff. Glad everything worked out for you and no one got injured or property damaged. I would have loved to see some pics or video of that big Muldoon.

Kenn

 

[TimberMcPherson]

I did get some pic on my phone, I have to get a cable to download stuff of it onto the comp.

I just put a file on youtube. A large pine done a few years back that wanted to go all by itself, thankfully the lean was right. Bet you havent seen many go over like this one! No backcut. I just ran for the camera when the ground started shaking.

http://www.youtube.com/watch?v=1XozZhBeCnU

 

[Ekka]

Fundamental errors made.

The "big line" was not pretensioned and not set at 90 degrees to the scarf (notch).

Trees follow scarfs, leans give weight, providing hinge wood never breaks then trees are delivered on scarf.

However gunning adjustments need to be made for lean.

All of this explained and showed in real life on this video. By the way, this is the most heavily viewed video in my collection, I suppose that is because fallers/forestry and arborists watch it.

http://www.arboristsite.com/showthread.php?t=34252

Diagram attached showing angles pertaining to your words.

Also, in support of my video I made these diagrams so people get a better understanding.

 

[TimberMcPherson]

Great diagrams Ekka, although I cant get the video to work.

Your right Ekka, and your ideas are bang on. I did consider sloping the scarf, seriously considered it. I understand the benefits of them and used them on smaller trees, but I have also had trouble getting them right in larger diameter trees. Especially with macs being so knotty and unpredicatble. Even with a horizontal setting the scarf was at least 50 inches (about 1.3m) across.

I wish I could have pretensioned the line, but it was just to heavy and reaching to far and I was stuck with the anchors i had to get a better angle. And I wasnt keen to direct the tree closer to the house! If the same situation comes up again, I will come up with a system to pretension using a tirfor (without the tirfor staying in the system of course). I thought the tree would lean enough towards the house to tension the line early on and was wrong, I also didnt think it would go so far over before loading.

Im going to do more work with sloping scarfs, but I have to say I very very very rarely get trees with enough safety margins to experiment with! I wonder how hard it would be to make a tree cutting simulator? Or a computer program where you put in the landing zone, danger zone, height, species, DBH, wind, lean, anchor points, available winches, bar length, canopy bias etc etc and it would tell you just were to scarf, at what angle etc etc.

Ah what where would be the fun in that?

 

[Ekka]

Finding a suitable anchor for a side rope with nothing in the way is always a challenge.

Rather than a sloping scarf use the horizontal scarf with adjusted gun. You'll have more hinge wood across it.

 

[masiman]

Great diagrams Ekka, although I cant get the video to work.

Timber,

If I remember, I could not get the videos to play in Windows media player either. Technically, I almost certain it was a coded problem.

Try downloading and installing VLC player. I prefer it to not be my default player, but I have found it to be able to play alot videos that other players have problems with.

 

[Ekka]

Timber, what sort of knots did you have in the rope too?

 

[TimberMcPherson]

No knots. the line had big splices in both ends. I had two 5 tonne strops around the tree that were shackled to the line, and the other end (anchor) was wrapped 4 times around a 40 inch stump and locked off. I learned some time ago not to put knots in lines that size as they can be near impossible to undo.

 

[Ekka]

That's good, no knots.

I was thinking today about it, the angled scarf, that'd suck lining it up right ... I'll stick with the horizontal and adjusted gun.

 

[John Ellison]

I bet that four inch line is a bear to wrestle around. Did the line recoil much when it broke?
I know its not the only way, but,
Got to say that I am for keeping the felling cuts at right angles to the stem. Its the way I was taught, and how the fallers that I respected in Alaska and talked to about it would do it. Depending.... you can gun it dead on, just have to sight in the same plane as the leaning tree.
Horizontal cuts on a leaning tree get more screwy the farther it leans.

 

[TimberMcPherson]

It is a pain to work with, you have to work with it feeding it in and out of a large sack the whole time, I found it was the best way to handle it especially where its sandy or muddy.
It weighs less than 40kgs dry though and would have been about 100 foot long I guess (never measured it). Yeah it did recoil, ended up draped over the house! My next line will be bigger and stronger! (and always pre tensioned.)

its been gold over the years, we do alot of steep work ugly work and it was good insurance,m although I was always careful not to shock load it (much). Will be suprised if its less than a grand to replace it. At least I know have a couple of good butt ropes!

 

[John Paul Sanborn]

Instead of a huge standard fiber like look into the exotic fiber, super low stretch, high tensile stuff..

You will have a smaller diameter line for the SWL and less stretch to take up on pretensioning.

This is out of the the SeaMar catalog
Spectron 12™ Single Braid

A unique combination of 100% SPECTRA®12 strand braided Parallay® construction with a proprietary Samthane™ coating. This rope yields the highest strength to weight ratio available, fast/easy splicing of a single braid and low elongation with a firm/durable Urethane standard gray coating. Also available in standard commercial and bulk put-ups in a variety of solid colors. Uncoated product available for low snag applications. Specific gravity: .98.

Stock # - Dia. - App. Tensile - Apx. Wt/CFT
SAM81501100 - 1" 80,000 23.43


These are used for tug and mooring applications, Roger in Seattle uses these types of rope for speedlines and I know people who use it for specialty slings. One thing I've heard that they are higher wear then poly or nylon

 

[joesawer]

To the best of my understanding, you faced the tree somewhat in the direction of the lean and then opened the face/scarf in the direction of the fall and intended to swing the tree into the intended lay/dropzone.
I have never cut this species, but have cut a lot of big trees in North America. Swinging big trees is a lot different than smaller younger trees. The younger trees have much more resilient fiber, the older trees are usually much more brittle. The large diameter and hight equals huge weight that really compresses the opening cut and puts a lot of lift on the holding wood.
Wedges don't work well on large hinges, for them to really shine you need just enough hinge. Really hard to do around high value hazards. Pulling will work much better on a thick hinge. I think this is why pulling is so much more common in the arbor world.
You might consider using smaller rigging and a false anchor to properly position and tension your side rope. If you can stop it from moving in the wrong direction, it is much better than trying to catch it and change its direction.
Without seeing your tree, it is hard to say what I would have done differently. From your description, I would normally face the tree in the desired direction with a very straight and clean hinge, probably with a small gap in the back to give the fiber a little radius as it bends. The hinge would go all the way across the stump, tapered, smaller on the compression side, but thick enough to hold the weight up. I would not want it to lean any more than it already does. Then I would pull and wedge it into the direction off the lay.
As others said, allow for the lean while gunning the face. Remember that the tree can drift to the lean when the hinge breaks.
Don't feel to bad about not hitting a bullseye with this tree. You didn't hurt anyone or tear anything up. You are doing the right thing, learning from it.

 

[woodchux]

Glad to hear no damage was done.
IMO i would get rid of that big unmanageable rope and get something more user friendly.
My 5/8 double braid is rated at 18,000 lbs. and you can carry it with one hand.

 

[John Paul Sanborn]

My 5/8 double braid is rated at 18,000 lbs. and you can carry it with one hand.

It is nice for rigging, but with WL ratio of 5 you have a SWL of 3600 LBS. Also it is rather dynamic so you need to work the streach out of it for heavy pulls, the stretch is a factor in the tensile, so you reduce your SWL by preloading it.

A short ton is 2000# which is what we use as a standard, he is talking metric tonne which is almost 205# more.

With a 4 inch mooring line I figured he was either using his SWL or dropped a decimal point in the thread title, 8 tonne is only 17640#

 

[lees trees]

turfor? is that wire or sinthetic line? thanks