I don't understand why the face cut is only 1/3 on a straight tree if you are not using wedges. If the tree is perfectly vertical, healthy and balanced it seems to me the tree would fall backwards and pinch the blade. Or is this only done when the tree is leaning in the direction of the face cut? What's up?
why is face only 1/3?
- Thread starter cmossol
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If the tree were perfectly balanced you would have a point. Few are. An error of judgement leaves the feller without enough wood to use wedges.
Look at it this way, a tree is a column of wood that is under compression because of the weight. If you remove a piece of the trunk, that part of the trunk no longer gives support and biases the tree to lean in that direction. If the centre of mass was directly over the centre of the trunk, it will now move slightly to the side where the support is missing and the back cut should finish the job smoothly. Usual screw-ups are because of judgement errors in where the centre of mass actually is due to lean, distribution of limbs, wind, etc.
Straight trees may be the hardest ones to predict which direction they will fall. These are the ones that most require felling wedges to drop them and anything else that you can use to steer the direction of the fall. Heck, if the tree is already leaning, you can almost forget about felling wedges to steer it down. The drop cut just above the wedge cut will produce a hinge and the tree's weight will take it down.
Thanks, I like your details. The mass of the wedge removed is minuscule compared to mass of the tree, so the the center of mass is still pretty much dead center. Once the back cut passes through the center, isn't the support more towards the front? If the force is still in the center, shouldn't the tree fall away from the support and pinch the blade? Sort of like Jenga, where you remove one from the front, and 2 for the back cut
I know somehow you are right, but I still don't get it. So far I drop trees in the direction of the lean, until I understand better.
outdoortype
ArboristSite Guru
Yep, the straight ones scare me the most
Yup, I trust gravity. So far I only drop them if it has a good lean.
An extreme example of this would be if you did a 1% face cut, and started on a 99% back cut, I think you would pinch the blade. I'm not suggesting to do it, just taking the problem to an extreme.
Yes, that's the guideline for a forward leaning tree with top weigh to pull it down. Too deep can cause excessive tension in the back cut, there causing it to go prematurely and devalue timber, barber chair the tree or possibly pop the root system.
If you are not sure on the lean then B.C. fallers guidelines call for 25% undercut for trees to be wedged.
(It will make It easier to wedge than a deep undercut)
If you have a stubby tree. Just a shorter stub with no top weight when a deeper undercut will help.
OK, that makes sense. I'm still looking for a perfectly balanced tree, and how to understand women.
Aren’t we all
It might actually be much easier to understand the balanced tree than to understand women. I've been trying hard to understand them both for six decades. It could be an impossible mission.
So...
There is no such thing as a perfect tree, there are many that are close, but every tree has some sort of favor to one side or another
the 1/3 rule is like piracy laws, just a guideline, sometimes you wan't less then a 1/3 sometimes closer to 40% or even damned near 1/2.
the assumption is that you will use a wedge, even if the tree is perfect, the weather isn't, the wedge prevents the tree from sitting back, even if its just palmed in, then once you cross centerline or even not quite centerline, gravity from the face cut takes over, pulling the tree to the desired direction, but without that wedge, it more then likely will set back
I'm guessing this is another one of those instances where some grandpa somewhere made some **** up and since grandpa was old, everyone believed him, and didn't bother to look for their own answers, the theory more then likely being reaffirmed by dumb luck or subconsciously falling timber with the lean, and never needing to fight the lean
Now having said all that, a relatively straight tree, with a deep face cut more then likely will go where you want it, in fact as a rule I tend to make faces way deeper then 1/3, especially on timber big enough to sink a wedge to the hilt, any extra weight I can get on the face side is less work to lift over.
This may help some understand. I am a big believer in wedges to move trees the way I want. Some times wedges and a tag line are necessary. My expertise and job in many cases is to put trees where they are desired regardless of the lean. Wedges are just one tool to make that happen. I use mostly Oak limb wedges as they are plentiful and inexpensive. If one cuts in the middle of a very obviously leaning tree it will not fall or move. The tree is being held up by the remaining 50% of the trunk. If calculations were made as an example a tree has 2,000 lbs more on one side than the other this can be made up easily with wedges. It is not uncommon for me to use five or more wedges. I will make a back cut just deep enough to get wedges behind the bar and tap them in tight. As I continue cutting I drive five wedges in the back cut as far as possible lifting that side of tree up. The hinge is not often going break if there are still several inches holding. The hinge is holding the tree down while the wedges are lifting up the very out side of the trunk. Each wedge can lift 500 lbs so I have exerted 2,500 lbs of lifting on the out side edge of the tree. With this being said the tree will start to tilt to the direction I want it to go. I often allow for a healthy amount of the hinge to remain intact until I see the tree moving then proceed to continue cutting until it is laying down. Thanks
A lot of good comments about 'perfectly straight trees' (telephone poles), wedges, etc. Also good that you are trying to understand what is going on.
I was taught to get a wedge in the back cut as soon as possible to prevent the tree from pinching the bar. Essentially, you want all of the weight left on that 'hinge' / 'holding wood', with the tree balanced on it, so that you can wedge the top over toward the face cut side, and let the weight of the tree do the rest. If you cut the face too deep, the weight of the tree might pinch the bar in the face, or pull the tree over in a less controlled manner.
This method works well with a chainsaw or crosscut saw. I am really interested in understanding more about how trees are felled using just axes, where wedging a back cut is not an option.
https://www.arboristsite.com/community/threads/how-were-trees-cut-before-saws.264420/
Philbert
I was taught to get a wedge in the back cut as soon as possible to prevent the tree from pinching the bar. Essentially, you want all of the weight left on that 'hinge' / 'holding wood', with the tree balanced on it, so that you can wedge the top over toward the face cut side, and let the weight of the tree do the rest. If you cut the face too deep, the weight of the tree might pinch the bar in the face, or pull the tree over in a less controlled manner.
This method works well with a chainsaw or crosscut saw. I am really interested in understanding more about how trees are felled using just axes, where wedging a back cut is not an option.
https://www.arboristsite.com/community/threads/how-were-trees-cut-before-saws.264420/
Philbert
InfiniteJest
ArboristSite Operative
1/3 because OSHA knows best.
I'll go 1/2+ on a tree that looks sky bound. I want the weight to shift. You'll see it shift in the top, or feel it through the saw. Wedges are a last resort.
Not that I'd listen to me...I'm not endorsing short cuts if you're not in a production setting. I just like to keep the yarder socially distanced.
I'll go 1/2+ on a tree that looks sky bound. I want the weight to shift. You'll see it shift in the top, or feel it through the saw. Wedges are a last resort.
Not that I'd listen to me...I'm not endorsing short cuts if you're not in a production setting. I just like to keep the yarder socially distanced.
Jhenderson
Addicted to ArboristSite
1/3 because there’s no need to cut extra wood. The face takes 2 cuts. The back cut takes 1. 1/3 will generally give you 80% of the diameter . Plenty of hinge.
Because it works, and it gives you enough to set wedges even on a small tree. Your wedges prevent your *bar* (unless you’re cutting trees with a quickie saw, circ saw or sawzall) from having the tree sit back on it and pinching it.
Big trees allow bigger faces, and yes, in theory just over 1/2 would cause a perfectly balanced tree to go right where you want it to go. That said, you’re crippling the tree with the undercut, placing the back of the tree in tension, and wedges then continue to hold it in such a way that the back cut does not cause it to sit back. From there, the back cut releases the tension side until the stress in the wood exceeds the capacity of the wood and the hinge fails. This is, of course, assuming perfect balance, which is pretty much nonexistent anywhere.
Big trees allow bigger faces, and yes, in theory just over 1/2 would cause a perfectly balanced tree to go right where you want it to go. That said, you’re crippling the tree with the undercut, placing the back of the tree in tension, and wedges then continue to hold it in such a way that the back cut does not cause it to sit back. From there, the back cut releases the tension side until the stress in the wood exceeds the capacity of the wood and the hinge fails. This is, of course, assuming perfect balance, which is pretty much nonexistent anywhere.
Pictures?
