Plunge Cut On A Set Back Tree?

[GIZROID]

I Was Working With An Arborist On An 70' Tall Black Oak That Was Dead. The Tree Was Leaning 5 Deg. In The Opposite Direction Of The Fall. We Rigged A 7:1 Mechanical Advantage And Pretensioned The Tree. He Did A Plunge Cut And Then Released The Back Strap And The Tree Didn't Fall. We Had To Pull The Tree Over. Was This The Best Approach Or Should We Have Done A Traditional Back Cut? If The Back Strap Wood Will Hold A Heavy Head Leaner Will It Nullify The Pretensioning From The Pulley Rig? This Guy Uses The Plunge Cut For Every Cutting Scenario Except For Very Small Trees. I Also Want To Mention That I Bought Some Chain From Bailey's And Feel That It Is The Best Value Chain That I Have Ever Used. I Cut Up This Oak Plus 4 Other Hardwoods The Day Before And It Didn't Even Need Touching Up.

 

[clearance]

An Arborist, They Are Not Fallers But Many Of Them Think They Are, Sounds Bogus To Me, Tension After The Undercut And Then Make The Backcut, Sounds Like You Guys Didn't Put Enough Pull On It To Begin With. This Whole Plunge Cut Thing Seems Overrated To Me, A Plunge Cut In A Real Heavy Leaner Will Pinch Your Saw.

 

[Dadatwins]

I Was Working With An Arborist On An 70' Tall Black Oak That Was Dead. The Tree Was Leaning 5 Deg. In The Opposite Direction Of The Fall. We Rigged A 7:1 Mechanical Advantage And Pretensioned The Tree. He Did A Plunge Cut And Then Released The Back Strap And The Tree Didn't Fall. We Had To Pull The Tree Over. Was This The Best Approach Or Should We Have Done A Traditional Back Cut? If The Back Strap Wood Will Hold A Heavy Head Leaner Will It Nullify The Pretensioning From The Pulley Rig? This Guy Uses The Plunge Cut For Every Cutting Scenario Except For Very Small Trees.

Hard to say what happened with out seeing the whole picture, lot of variables, how high was the pull rope? angle of pull? how far away was the anchor point? I have never been a big fan of strap cuts, and think some folks use them exclusivly for a false sense of security, thinking it is the safest method for all falling. Watched a guy crush his new 044 with a strap cut that went bad and he was smart enough to haul a$$ without the saw. I think a big mistake many folks make in this biz is not recognizing different trees and different scenarios require different methods. Not a good idea to ALWAYS do anything. JMHO.

 

[GIZROID]

The Rope Was Set At 50 Feet And The Angle Was Approx. 45 Deg. Three Of Us Tensioned The Rope. It Seems More Logical To Have Started The Back Cut And Then Applied More Tension.

 

[clearance]

The Rope Was Set At 50 Feet And The Angle Was Approx. 45 Deg. Three Of Us Tensioned The Rope. It Seems More Logical To Have Started The Back Cut And Then Applied More Tension.

7 to 1 advantage with 3 guys pulling, rope at 50'. So lets say 100lbs. each x 3 x 7 =2100 lbs, rope at 50' means thousands of lbs. pull, something does not make sense here. I have being part of pulling over many trees with manpower and a bowline on the bight, bull ropes hooked to a boom truck or excavator, bull rope hooked to a pto winch on a Blazer, tirfor hooked to the front of my pickup and so on. I put in the undercut, yard the snot outta the rope, backcut and she usually goes over like nothing with only a slight backwards lean. On heavy leaners it is best to wrap a chain above the cuts, put in the undercut, tension, and then put in the backcut, backed up with wedges, as you slowly pull it over straight back from the lean. When it starts to fall, pull fast to make sure it is committed.

 

[Dadatwins]

The Rope Was Set At 50 Feet And The Angle Was Approx. 45 Deg. Three Of Us Tensioned The Rope. It Seems More Logical To Have Started The Back Cut And Then Applied More Tension.

How far away was the anchor point?

 

[GIZROID]

The Anchor Point Was 60-70 ' Away.

 

[Dadatwins]

Still hard to say without seeing the tree, but assuming the tree was balanced the pretension only held the tree in position, since the saw did not pinch. Given the distance of the rope and the height placed I would still think you would have to pull the tree over by hand and that the pretension only held the tree from pinching the saw. Even with a pretension rope someone should be pulling the tree over at least until it was past its back lean and on the way toward the notch. Not a strap cut scenario in my opinion.

 

[smokechase II]

serious stuff

If the rope was set at 50 feet and at a 45 degree angle and the tree was 70 feet tall. Whoa. First of all, I hope you had some length of rope and pulley set-up that put you at least 1.5 tree lengths away from this pull point under the trees fall.

The key to this event is not the plunge cut. It is the amount of force applied to counter the lean and the other techniques needed. If the final product, the back-cut, is the same.
Once either the strap is severed or the standard back-cut is finished. No difference should be encountered with either technique if it is the same cut and an appropriate tool such as rope pull or wedges was used to prevent pinching.

The method(s) and other techniques that allow you to conquer the back lean are the keys.

I think you might want to look at what you did as being actually correct. Too much force, in this case pulling too hard on the rope, is an error that could cause a barber chair. Perhaps you should view the release of the strap, a stable tree, then applying the necessary pull, as exactly what you should have done.

(Caveat: dead wood, if fairly dry, is much less likely to barber chair than green wood.)

Items that may have affected this fall:
1) Hinge wood width, too much could have been a problem, especially in a strong wood like oak.
2) A back-cut too high in relation to the apex or corner of the face.
3) A face that was very shallow, i.e. it only went into the tree 1/5th of the way.

I suspect that with a plunge cut advocate as you appear to be describing, that #3 above would be the most common error in those cutters. If there was an error at all. Remember that the face cut needs to be not just adequately high and open, but also adequately deep to provide a release to allow the tree to fall. A face cut that is too shallow can create unnecessary resistance.

An alternate method that loggers could use is applying the force called wedges.

May I suggest a detente' between loggers and arborists. A more perfect world where the arborists can use both ropes, wedges, tapered hinges and massive insurance policies.

By the way:
What was the trees diameter?
Just how dead was it? Was the wood at the stump dry too?
Did the arborists state any concerns or look sheepish?

 

[P_woozel]

I wasnt there, but from what you described, I would have started with a back cut, set wedges redistibuted some wood, then finsished with a little deeper face. try that next time you'll like it.:yoyo:

 

[notahacker]

I wasnt there, but from what you described, I would have started with a back cut, set wedges redistibuted some wood, then finsished with a little deeper face. try that next time you'll like it.:yoyo:

I agree 100%

And this situation also leads me to asking; what was that guy thinking?:bang:

 

[clearance]

I wasnt there, but from what you described, I would have started with a back cut, set wedges redistibuted some wood, then finsished with a little deeper face. try that next time you'll like it.:yoyo:

On real small trees I have put in the backcut first and set a wedge, put in the undercut next and pounded it over. If you make the undercut after the backcut you have to be carefull not to cut off too much holding wood, it is harder to make a good undercut this way.

 

[Kneejerk Bombas]

I Was Working With An Arborist On An 70' Tall Black Oak That Was Dead. The Tree Was Leaning 5 Deg. In The Opposite Direction Of The Fall. We Rigged A 7:1 Mechanical Advantage And Pretensioned The Tree. He Did A Plunge Cut And Then Released The Back Strap And The Tree Didn't Fall. We Had To Pull The Tree Over. Was This The Best Approach Or Should We Have Done A Traditional Back Cut? If The Back Strap Wood Will Hold A Heavy Head Leaner Will It Nullify The Pretensioning From The Pulley Rig? This Guy Uses The Plunge Cut For Every Cutting Scenario Except For Very Small Trees.

It sounds like everything went perfectly.
If you pretension a dead tree too much, it can break off at the ground before you start cutting, then fall the wrong way!
It sounds like he was putting just enough tension on the tree to hold it up until the hinge was properly set up, then pulled the tree over. The fact that the tree didn't fall when he cut the back-strap is irrelevant. He knew it could fall back, it had the rope holding it, and wouldn't fall to the side, the hinge wood was holding it.
By leaving the back-strap (plunge cutting), it allows him to take his time and make the the hinge perfect, it allows him time to reposition for an easier escape, it holds the tree up so he can take one last look at both sides for mistakes, it lets him stop and make sure the fall zone hasn't changed (like a dog run into it or something), and there are lots of other advantages to this method.
For a dead tree, I feel this is an excellent felling method.

 

[TheTreeSpyder]

Ummmmmmmm in that position the release trigger of plunge behind hinge is not tensioned, but is rather compressed. So, that it is like a wedge you can't lift, just placed there to hold tree up.

i'd rather use conventional, give more lift with wedge to help rigging for same compressed position, not have to cut compressed rather than tensioned trigger, then walk and have pulled over.

But, that is just from the cheap seats opcorn:

 

[John Ellison]

I think that if the pull line was tensioned perfectly that it would not matter if you bore cut/strap or used a conventional back cut because the tree would not move until you pulled it over. Since the tree is dead I would want to pull it over as gently as possible. I would not use the strap cut release because if there is too much tension it would be a sudden shake.
If the line is tensioned and the backcut is made in the conventional manner, you can tell almost immediatly what you have, if you need more tension or less.

 

[rbtree]

Good subject, and replies as well. Only two small corrections for me to add:

Based on facts given, the angle of pull would have been about 60 degrees, not 45.. And, clearance guessed at 2100 pounds of pull was applied to the rope, which would equate to many thousands at the tree top. Not right. The pull at the treetop would be less than 2100 pounds due to the line angle.....I'm not good at trig...but this reminds me of the old ISA webboard where we used to have lots of great discussions. A few guys would supply accurate math. Sure learned at lot back then! Still don't know the math though.

I, too, don't like plunge cutting for back leaners, but can see that if properly setup and wedged, that the method should work...but why? Only reason I can see is it allows you to set up what you think is the proper size hinge.

i agree with wiley that a few wedges might have been enough, as a 5 degree back lean isn't much. But in residential tree work, there's usually a target, so we set lines 90% of the time as well. Of course, 80% of our work requires that the tree be climbed and pieced out.

Great post, smokechaser!

 

[smokechase II]

Plunging into cutting

Yea, I'm goona agree with Mr. Ellison:
He states:
"If the line is tensioned and the back-cut is made in the conventional manner, you can tell almost immediately what you have, if you need more tension or less."
The advantage with the old school back-cut is that the tree will tell you, by its movement - opening or closing of the back-cut kerf - if you have the appropriate tension. That is a definite plus and he is correct.

Mr. rbtree states:
"Only reason I can see is it, (plunge back-cut), allows you to set up what you think is the proper size hinge."
That is a real advantage to the plunge back-cut normally but does not offer an advantage here. With an intelligent team working together, applying just enough pull/wedges to prevent a set-back, the tree will move in slow motion or only as directed, allowing for a uniform quality hinge.

I see the logic and I stand corrected.

 

[clearance]

Good subject, and replies as well. Only two small corrections for me to add:

Based on facts given, the angle of pull would have been about 60 degrees, not 45.. And, clearance guessed at 2100 pounds of pull was applied to the rope, which would equate to many thousands at the tree top. Not right. The pull at the treetop would be less than 2100 pounds due to the line angle.....I'm not good at trig...but this reminds me of the old ISA webboard where we used to have lots of great discussions. A few guys would supply accurate math. Sure learned at lot back then! Still don't know the math though.

I, too, don't like plunge cutting for back leaners, but can see that if properly setup and wedged, that the method should work...but why? Only reason I can see is it allows you to set up what you think is the proper size hinge.

i agree with wiley that a few wedges might have been enough, as a 5 degree back lean isn't much. But in residential tree work, there's usually a target, so we set lines 90% of the time as well. Of course, 80% of our work requires that the tree be climbed and pieced out.

Great post, smokechaser!

OK, point taken, maybe I just expressed myself not well. What I mean is that if you have pull on a rope that is set at 20' and the same rope set at 60' the higher the rope the more pulling power you have. This is what I mean, the hieght of the rope from the ground multiplies power a lot, does it not?

 

[TheTreeSpyder]

Those numbers show angle to spar, not ground. so we have already lost 5 degrees or so here. 5 isn't very much as said, going by 11o'clcok being 30 degrees backwards. Degree back wards should be calcualted from hinge as pivot.

i think the missing piece here is the differance between hitchpoint and Center of Gravity, then assessing flexability in hinge for this exagerated range of movement before correctly commited. If i though the outside was good and flexible and inner was drier/stiffer, might plunge thru face, to only have flexible fiber and at the outside positions.

If line was set with all that tension from inline pulley pulls, might jsut lock off purchase amd jump on line to hang as perpendicular as possible to leverage all that tension higher to make tree move without further line compressions.

 

[Rigger]

O'h dear,
In some way's I wish I had not found this site, on this rainy day my saws would all have been sharpened and all gear ready for tomorrow.....But this is all so bloody interesting I am addicted.

First I must drift from the main topic and find a major fault in a previous post stateing that "~arborists are not fallers~" I agree SOME are Not but many Arborists/Tree Surgeons are mighty fine Fallers and could show many a logger the way just as many loggers could show some "arborists" the way!!

OK... with that said: The plunge-cut is a technique that is available and appropriate in certain situations just like the dutchman (swing or step), conventional OR humbolt face-cuts etc.

I remove heavy duty trees nearly everday, NO I am not a logger, right now I'm an arborist if I were in Aussie Land or Europe I might be considered a Tree Surgeon, I consider myself as a fully qualified 42year veteran "Tree Specialist".

Yes it does bother me when the original posting stated that this particular "arborist" nearly allway's uses this technique. It is VERY rare that a circumstance warrents such a technique or offers anything beneficial. Dead tree leaning 5deg. with correct bull-rope and pull, cut a little tension up, cut a little tension up, should get it back up and commited with no problem. By watching the kerf slowly open up you can determin pull allready asserted and pull required verses hinge wood left to cut, back up with a wedge or two if dia. allows and you ain't felling no matchstick.
This way you can retain maximum hinge wood untill the tree starts to fall, with a strap on the back you are pretensioning the tree for a sudden uncontrolled release when that strap is cut, IF the tension in the rope is lost befor that tree reaches the upright position you could be in trouble.

Plunge cuts are used to avoid Barberchairs (waste Timber) in heavy leaners especially if being pulled with extreme tension, but if you bind up a couple of wraps with chain & chain tensioners just above your cut and you know & understand the characterisics of the species all should be well.

I am curious, does this guy use plunge cuts on heavy limbs too?