Why 1/3?

Broncman

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I have been searching and see plenty of directions but no reasons? Why make the face cut 1/3 diameter? On a perfectly balanced tree so to speak, a face cut of 1/3 and then a back cut, seems like it would not fall, or once the face cut is removed, does the tree lean over some before the back cut is made?
 
It's enough under mined to convince most fairly plumb trees to go over easy, enough wood in back to give wedges some leverage, puts the hinge in a place where it has the most width etc
 
Indeed a straight up and down tree might just sit there, until a wind gust comes along...that's why it's important to assess lean before you cut and plan the cut accordingly.
It's also why you should always have at least a couple wedges with you when felling, they can get you out of a lot of trouble!
 
As far as I'm concerned, this is the bible on the subject:
https://www.treestuff.com/store/catalog.asp?item=1260

Starting on page 59, Jepson talks about how using an "80% of diameter" rule has advantages over the traditional 1/3 rule on certain trees.

If you've got access to professional training, that's ALWAYS preferable, but if you're trying to learn on your own 1) To Fell A Tree 2) asking the Treehouse experts and 3) knowing your limits & when to walk away SHOULD keep you off this list...
 
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Thanks for the replies. I get the Drip line on my FB. Some scary stuff! Went through some of the OSHA stuff last night. I will get that book. Got some more stuff I need from treestuff so I will throw that in the cart.
 
The 1/3 or 80% rule shouldn't be a "rule".. more a guidline for rookies..

VERY FEW arbs or even arb intructors, I would guess, can explain in accurate detail the "why" of it.. If you don't know the why then you alos don't know the "why not" and there are plenty of situations where its better to go deeper or more shallow...
one reason that is fairly well known is the tree will tend to Barber cahir more easily when the notch is less than 1/3... Not every tree is at risk of BBC so most times (around here in east coast suburbia) that's not an issue..
On e reason to go deeper as was stated already is to cut a lean into it.. a deep notch will tend to undermine the center of gravity on a straight stick, so it is especially helpful when working down a spar... climber or buckewt op cuts a deep notch, past 1/2, and the piece falls right into the notch with the backcut... no pull line, no pushing one handed etc.. And there are plenty of other reasons to go deep or shallow...
I believe the 1/3 rule ws developed at a time whent he notch was cut with an ax.. making it a lot harder to go deeper.. now that we have chainsaws its long over due to re-examine that "rule"...
 
The 1/3 rule is so that when the tree starts to fall the face does not close prematurely.
No, this particular point is only related to the face cut's angle.
A narrow face cut closes soon, breaks the hinge and lets free fall the tree early. Short control but good to drive the tree throw many limbs.
A wide open face cut can even not close at all until the tree is on the ground, allowing the longest control for precision felling.

It's enough under mined to convince most fairly plumb trees to go over easy, enough wood in back to give wedges some leverage, puts the hinge in a place where it has the most width etc
What Sotc said.

Actually, the 1/3 or 80% rules (not really far apart) are for generic use. It works well most of the time. But if needed, you can adjust it in a way that your felling cut would perform better, either easier or less tricky in some hairy cases.
For example for a side leaner, I'd cut almost at 1/2 deep (or 100% diameter) to get the widest hinge and then the strongest hold.
For a heavy back leaner, it's only 1/4 or so to give a bigger leverage for the wedges. It's at the cost of a smaller control sideway, but it can just make the wedge's work doable.
 
Actually, the 1/3 or 80% rules (not really far apart) are for generic use. It works well most of the time. But if needed, you can adjust it in a way that your felling cut would perform better, either easier or less tricky in some hairy cases.

Excellent points, Marc-Antoine. Jepson maintains that the 80% approach works for MORE trees than the 1/3, but completely concedes that nothing works all the time. He uses some of the same examples you do as evidence.
 
80% refers to the hinge being 80% the length of the diameter of the tree. Though its not clear is that the widest point of the hinge, the narrowest, or the average...
most trees are not round, they may be more oval or irregular, so the 80% rule superceeds the 1/3 diameter rule by saying as long as teh hinge is 80% as long as the diameter of the tree, its OK to be less than 1/3 the depth..
 
Bronc, Daniel is right on both counts.

The formula is that face cut width (or hinge) = 80% of the tree's diameter. The easiest way I think of it is that 10% of the diameter should be visible on each side of the face cut.

Jepson argues that the 80% rule takes oval/oblong trunk shape into account better than the 1/3rd rule, keeping more of the hinge in the live tissue of the sapwood where it can better control the tree.
 
I think some of that is throwback to the olden days.

A longer back cut gives you more leverage to wedge with. It's a longer lever at the bottom.

I routinely go over 1/3.
 
General rules are damn good, as they are meant to get the beginner / novice started in the right direction. For most in the industry, the more we learn the more we advance beyond the general rules. Haphazardly for fools, unfortunately.

I have to say, though, for the proactive tradesman in the Tree Care Industry the level of professionalism I see just continues to get better. I see it every day in this forum.

Thank you!
 
General rule is the key... I cut down a severely declining water oak the other day, with my notch probably more like 1/8 of the tree's diameter. Even that shallow, the entire center of my notch was a void, as the tree, though ~40"-45" diameter, had only 3" of green wood around its circumference. Had I gone to 1/3, there would have been precious little for it to lever over on. Not only that, with some trees holding power is in the heart, others, more in the outer wood. By sticking to the 1/3 rule, nearly all trees will have sufficient stump hold, regardless of which is applicable.
 
In my imagery;
1/3rd fair starting point to evaluate hinge placement mechnaix allowed.
>>not so much about face you are taking, but positions you leave behind to focus on.
.
Less than 1/3rd can push loading to outer rings only and peel down side towards more of barberchair as Daniel says;
We want the 'whole welded mass' of tree (or close to/not just outer rings) supporting our hinging;
we want a wider / less loaded per inch support base of hinge/ not focusing all loading to more of a high pressure point like faceless fall.
.
In many trees, 1/3rd back for facecut would place hinge at or right before tree center/widest positions;
this would allow tapered hinge most leveraged 'backfield fibers' to extend from about widest part of tree for most side to side control.
.
On the other side of project, 1/3rd face helps to maintain fair face slap deck;
less face might eliminate this effect, clean tearoff etc.
.
Hard forward leaners, might come forward with hinge, to move pivot of compressed part of hinge closer for some less lean angle to this pivot.
Shallow lean might come back more to undermine center of gravity more/ give more lean angle to compressed part of hinge as pivot.
Back leaners, would come back even further, but lots less side to side control
.
In standard mechanix of movement, the saying 'a pivotal change' is very apt.
For pivot position change is compound action in 1 move,
can take leverage away form load and give more leverage to support side at same time (or vice/reversa).
>>returning high impacting immediate changes in mechanix.
.
1/3rd back would tend to not allow/cast hinge center into center of tree;
avoiding any heartwood less flex-ability concerns.
.
Evaluating of hinge fibers AND face slaps positions verifying good wood for mechanix is essential.
i think it is also logical and witnessed/tho hard to sift out;
That colder or deader wood can give good face slap mechanix, but less flexability on hinge.
Greener, outer wood, perhaps opposite...
.
From 1/3rd face position, if not hard forward lean/list ;
would generally not want to go less facecut;
but ; have left room to go for deeper face, and might want to..
>> after re-evaluating what fibers are asking to do what function, after tree 'cracked open' w/facecut
 
I have to say, though, for the proactive tradesman in the Tree Care Industry the level of professionalism I see just continues to get better. I see it every day in this forum.

That's a great observation and pretty cool! Between youtube and these forums there has been a huge amount of collective knowledge shared making it MUCH easier to learn from the experience of others.... I;ve been on these forums for near 15 years and learned A HUG AMOUNT from them.... MUCH more than I learned in 20 years of working with the same old crown here on the east coast... part of that was meeting John Grier. I met him on treebuzz and we worked together from time to time, on and off for 10 years or so...

Even with all the differences of opinions and personality conflicts / arguments and all its been a huge learning experience for all of us. Not always pretty, but maybe that is helpful in spurring thoughtfulness.

Particularly appreciate your input Jerry... your words carry some weight
 
Good observations, Daniel...on the wisdom of Jerry Beranek's comment and on the description of MB's terse posts...I always appreciate the Boss's succinct, short and to the point words (or dearth of).
 
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