thoughts on the tapered hinge...

[utlarb4trees]

I attended a seminar today, and there was a discussion about the tapered hinge. I know we have discussed this on TB before, but I believe the consensus was all over the board. I'm on the fence myself.
The speaker was an Arbormaster trainer, and one with credibility! and he said one gains nothing by using a tapered hinge. 10 percent hinge thickness across the stump is the way to go. It is understood that wood is stronger in the tension plane(around 2x I think), so is there reason to leave more hingewood on the tension side? With a thicker hinge the hinge fibers pull out rather than hinging and breaking. However, at what point in the fell do the thicker fibers pull out? We all know a hinge that is too thick is not good, and the 10 percent rule is a standard guideline. I was at a loss for words when I heard this today because I have trained my guys to recognize tension wood and compression wood. I know there is alot of literature out there supporting the tapered hinge and combating side lean---what are your thoughts..

 

[Jamin_Mayer]

I use a taper on side leaners all of the time. I have noticed that if I didn't taper my hinge (even though I was trying to) that a equally thick hinge held just fine.

From those observations, I wonder if there is a threshold of when we need one and when it is not needed at all.

For example, if the tree had a 10° lean, then it may not be necessary to have a tapered hinge, rather a slightly thicker hinge (of equal thickness). However, if a tree had a 35° side lean, then would it hold without a tapered hinge, or not? I would personally put a tapered hinge on something with that much of a side lean.

 

[utlarb4trees]

" I wonder if there is a threshold of when we need one and when it is not needed at all."

I agree, species will usually dictate my inclination to use it or not, and of course the amount of lean.

The speaker demonstrated that the thicker hinge fibers left in the tapered hinge, on the tension side, pull out, instead of hinging--and it's at this point the hinge loses its capacity to function. We understand that the hingewood breaks from the back to the front, yet at what point do these thicker hinge fibers pull out, instead of breaking. They must bend to some degree and then pull out?

 

[Gord]

A tapered hinge is often the most effective one, if you don't agree you haven't cut enough trees. There shouldn't be any debate. Saying a even 10 percent hinge is always best isn't constructive teaching, it's a gross generalization that'll only get students in trouble.

 

[cashmoneytreeboy]

stop reading and start cutting,,

 

[utlarb4trees]

[ QUOTE ]
stop reading and start cutting,,

[/ QUOTE ]

Good advice, the fact is there were 160 people in this seminar and I'm sure that almost everyone in there use the tapered hinge to some degree. As a foreman and as a trainer for my company, there will be guys confronting me on this after I have trained them in different tapered hinge applications--just looking for opinions.

 

[Tony]

Here is a PDF of the only Scientific Study I know of conducted to answer this question. It was conducted by Laurie Newsham and Jean-Mathieu Daoust.

I offer it not as an end-all-be-all conclusion, but in the spirit of adding info to the discussion.

Tony

 

[southsoundtree]

My use of the tapered hinge is not for directional swing, but to resist side-lean wanting to rip the hinge on the tension side.

 

[tarzanstree]

Really hard to put those mechanical parameters on every tree, as every tree is different. I used to make a living falling timber and I learned this fact over a long career of doing it every day. The only way to know how much hinge wood to leave on a tree is experience with a huge variety of trees in a huge variety of environments. I am always hesitant to give any timber falling advice on here as it can be interpreted wrong, and like I said, when it comes to falling trees proficiently, considerable experience helps a ton. Usually with heavy side leaners I will almost always leave a fatter hinge on the pull side. Another little trick that helps a lot is a sizwheel. Very difficult to explain so I will attach a couple of pics. Basically you get more out of your hinge wood on the high or pulling side, and a tree will usually pull around better to the lay...not always though. Something to ponder

First pic I have the undercut out. Rotten old Cottonwood that had some heavy leaders leaning the opposite way of where my chainsaw is and I wanted it to pull around to my gun and knew that I was working with some punky holding wood.

This pic, I took out the sizwheel piece, and you can see all the holding wood there. Really important to follow the grain of the wood...Don't want to sever any wood fibers cross grain.

You can see in this pic that I followed the grain of the wood...notice how the cut curves towards the bottom...

After the tree went where I wanted it. You can see how much more I was able to utilize the hinge wood on this rotten tree. I also used what I call the ugly stump. Angled my back cut so that it matched up with the first cut on the far side, but was high on the pull side. Just imagine a steak that is cut with the grain...tougher to chew...same principle with this.

You can see how far down the wood pulled into the stump. Works really well with sounder wood. I have had trees pull roots out of the ground it works so good sometimes, but that is in a forest environment with big trees. Don't take any of this as gospel, just something to ponder

 

[jmcscrap]

Great pics Tarzan. A very interesting approach that I have not seen before, definitely something to ponder.

 

[Fernhorn]

Woulda loved to see one more pic from the top of the tree back to the stump or one of the tree standing.

 

[Treezybreez]

x2

 

[tarzanstree]

Mostly did it to show some other guys on a different forum what it was about. Tree was not much to be seen...had been topped years prior and had a couple of big topped leaders. I will try to scrounge up some more pics.

 

[theXman]

Tarzan, I like the pictures and thought in it. I will pull this up again and think on it some more. I think I like it though.

I taper the hinge thickness on sideleaners too, when I'm afraid the lean could prematurely snap off the hinge on the opposite side of the lean. As some of you said.

they can't say this doesn't help, because it does.

Another thing, for sure: If a tree i am felling ever slightly starts to fall a little off course (likely from notch being a little off or heavy crown on one side), IF I quickly cut to thin down the hinge on the side it is falling wrong towards, I definitely often see the tree change direction and go more towards the location I wanted. You can clearly see it change direction.

although i don't think anyone should stick around the trunk while it's going over..... On touchy ones where the impact location has to be perfect, I stay until the tree is half way over sometimes and adjust hinge if the tree started a little off course in the beginning.

You can definitely change the course a little.

And I agree, if someone is stating that a tapered hinge doesn't do anything, they haven't cut enough trees.

I read that report. The test method was okay, but not great. Get a timber feller with lots of experience that knows the tapper can change location of fall and let him in on the test to show them.

 

[zebhaney]

Since I wasn't there, I don't know what was said exactly, but the curriculum from Arbormaster is all about having control. The tapered hinge works, sometimes. Basically it a rule of thumb thing. It is generally accepted but not scientifically proven. If you have a tapered hinge, the tree will have to twist and pull and break fibers until a straight hinge is created. During the twisting and pulling and breaking, a whole lot of heavy wood is being controlled by gravity and some unknown fibers. What we do know for sure is that hinges work best if they are straight and level. In the urban setting there is often a very small margin for error when felling trees. So Arbormaster, NATS, ACT&E, and other training companies do not advocate the tapered hinge.

Second reason is that to control the trees twisting the faller has to be actively cutting the hinge while the tree is in motion. This is dangerous. You probably heard the trainer talk about the 5-15-90 rule about that point in the demonstration as well.

If I want a leaning tree to go exactly in a certain spot, I use a guy line. If I have some room for error, I aim the notch 1.5 x the amount of side lean, or if the tree has 1 foot of side lean, I aim 1.5 feet the other way from where I want it to land. This works (rule of thumb here.) up to about 4 feet of side lean, depending on species.

 

[Tony]

All good points!

Tarzantree I like the pix and the explanation. Interesting technique. From your experience are you actually changing direction from hinge thickness or gravity? Would your cut work the same (most things being equal) if the hinge went without a taper?

I think what the study show us is that hinge thickness alone in straight up trees with an open face notch is unlikely to change direction of fall. That being said the study was good, but limited in scope compared to real world experience. As with all science it needs repeated. However, an excellent starting point.

X, I agree with most of your observations. I also think you are an experienced enough arborist to "know when to walk away and know when to run" (yes, an obscure Kenny Rodgers quote!) So aside from the 90-15-5 rule I ask: Do you think it is possible other forces acting to change direction of fall other than altered hinge thickness played a role in your experiences?

I'll look forward to all your responses.

Tony

 

[Blinky]

If you've cut many trees, you know tapering a hinge (live wood) will alter the way the tree falls. How and how much varies but you develop a feel for it over time. It's not scientific, closer to Zen than science. That makes it impossible to teach in a workshop so it's better off not taught that way.

I also agree that to make it work well you generally have to be cutting and tapering as the tree is committing to the fall.

 

[southsoundtree]

Why set a tapered hinge instead of facing to the lay?



I liked Tarzantree's technique. It looks to be designed to break the compression side hinge after falling about 30 degrees, with the tension side still holding until its closer to the ground.

I wonder about the line formed by the sizwheel piece and the humboldt facecut that the trunk would rock of off. What happens if that line is changed in relation to the lay?

Sounds like what Willie from SOTC described as a whizzy. Maybe the sizwheel and whizzy are cousins.

 

[Daniel]

Tony,
That is an extremely flawed report, and calling it a "scientific study" is a stretch. I have excahnged emials with Newsham about it, and produced a short video response to the report, which could also be seen as "flawed" science. My video did however show that a tree can fall perpendicular to the back cut, rather than the front of the hinge. Most experienced fallers will tell you that a tree will often go with the back cut, rather than the front of the hinge. That is one of the reasons why I always check the gun on the backcut as it is approaching the desired hinge thickness.

In watching a lot of my falls on video, I noticed that the tree will often shift direction slightly as it starts to go, its a little jiggling motion, hard to pick up with the bare eye, but unmistakable on the screen. I AM 95% sure that this results from a slight taper to the hinge, when the tree, at some point in the fall, switches from falling "with" the front of the hinge to falling "with" the back of the hinge (or vice-versa). On straight trees it appears to me that the tree will either fall with the front of the hinge or with the backcut, BUT not somewhere in the middle. I still have to play with it a little more, but it seems that that could be influenced by the direction of pull. In any case on tight falls, its very important to check the gun of the backcut. That is the most practical application of this knowledge.

When the taperd hinge article was published in 2004, it caused quite a stir in the industry. Ken Palmer told me to my face, that the TH does not work, as per the OP's mention of Arbormaster's perspective, while others said this was such a basic and simple concept, that I might as well write an article on "where to put the gas and oil".

I had a 90 minute conversation with Sharon Lilly about the technique and why the decision was made not to include it in the "art and science of practical rigging". She suggested 7 scientists/teachers (Gilman etc..) that might be interested in doing follow up research on the subject. They all expressed an interest in helping out with research, and getting grants. I have yet to follow up.

I AM with Tarzan in thinking that rules themsleves are very flawed, a necessary evil in this industry.. There are so many variables in this work that are not taken into account when some trainer make some blanket statement like 10%, or 1/3 deep, or always use the adjusted gun, etc etc. Or even that someone with three decades of saw handling expereiecne should follow the same rules as a rookie (not cutting above shoulder height etc..) These rules are like paint by numbers, when a good west coast faller is like Picasso.

So yes, we need rules to guide and give some direction to newbies, yet to criticize someone who's knowledge and skill level far exceeds those who always stay within the rules, is a shame. And the rule followers often have a fundamentalists zeal and passion, so sure that there is only one "RIGHT" way.. They have a child-like morality of right and wrong, black and white, when in thruth, there is a rainbow of possabilities.

That said, it is my firm conviction that any organization that teaches NOT to use the tapered hinge is doing a dis-service to the students and the industry. It is certainly one of the most controversial subjects in the industry.

And thank you Tarzan for that teaching on the sizwheel.. I had heard it described, but could never get a clear picture in my mind. That is a good piece, should be publised..

 

[Daniel]

[ QUOTE ]
What we do know for sure is that hinges work best if they are straight and level. In the urban setting there is often a very small margin for error when felling trees. So Arbormaster, NATS, ACT&E, and other training companies do not advocate the tapered hinge.

You probably heard the trainer talk about the 5-15-90 rule about that point in the demonstration as well.


[/ QUOTE ]

Zeb,
What does "works best" mean?.. Works best for what? There are a lot of different outcomes that a faller may want to get out of his hinge. I think you mean holds best.. Even that is questionable.. you make a blanket statement.. is there some science behind that??? Casue last I heard, there wasn't.. It irks me a little that you make this statement, like it is an established fact, when there is obviously a lot of debate on the subject.

I personally cut about half my hinges with some sort of taper, for a variety of reasons.

Is Arbormaster really teaching the 5-15-90 rule for suburban arboriculture. That rule was developed from studies of timber falling accidents. Falling timeber in the woods has a whole set of dangers involved that are rarely, if ever, faced by the suburban arborist, making the 5-15-90 nearly completely irrelivant in my work.

Those that have been hanging here a while know that I have been criticized for "running" from my trees... You all should have seen me the other day, dropping a big monster sugar maple that had been dead 5+ years, and falling apart upstairs. I ran like the cops were after me as soon as it started to move. That said, I have no hesitation at staying at the stump and steering a tree or spar all the way to the ground when necessary and safe, though as my falling has become more accurate, that is rarely needed these days.

Anyhow, if its true that these training organizations are teaching the 5-15-90 rule, its just more fuel for their critics' fire. Between that and not teaching the tapered hinge, one has to wonder how in touch with reality they are. Bunch o' boy scouts if you ask me.. LOL (just kidding)