1/3 Diameter Notch Rule

Rugged made
Wesspur
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RES said:
I have always wondered why the manuals tell you to make the felling notch 1/3 the diameter of the tree and not more. When you make the notch the weight of tree above the notch is supported by the uncut lower portion. Therefore an overturning moment is created to cause the tree to fall towards the notch. When you begin cutting the opposite side and reach 1/3 that overturning moment no longer exists. From that point on the moment begins to turn the tree back towards the cutting side. It would seem to me that it would be better to make the notch 1/2 the diameter to avoid this from happening. The 1/3 notch seems to work. The only explanation that I would have is that when you make the notch, the overturning moment causes the flexible tree to shift its weight towards the notch. This is enough to cause the tree to fall towards the notch, even though the back cut is bigger.
Click to expand...

If everyone is done beating down a new guy and posturing, I will try to answer his questions.
As mentioned earlier a 1/3 notch is a good safe place to start. It gets you into good diameter for hinge wood (unlike the 1/5-1/6 notch) but leaves you some wood to work with to adjust your gunn, or line up your cuts before you get to the 1/2 mark that you should only go past in advanced felling techniques.
The tree should not move very much at all towards the notch when it is being cut. If it does it will try to pinch your saw as you make the notch and also will try to barber chair as the fall will almost certainly out run your back cut.
The weight will rarely shift towards the face cut on its own. Either the center of gravity is already on the notch side of the hinge or something will have to move it to that side in order for it to fall forward. The center of gravity would have to be between the outside edge of the stump and the hinge for the depth of the notch to come into play. Then you would have to cut the hinge up so small,l for the tree to start moving, that it would make me nervous.
Even though the back cut is about 2/3 it will only let the tree move backwards a small amount before it closes. If your hinge holds it will stay there until you move it forward. Ideally you should already have a wedge in the back cut or another method already in place to help move the tree forward.
If the tree moves backwards and closes the kerf (the thickness of the saw cut) the farther from the hinge the kerf closes the less the tree can move back. The open face (notch) gives the tree room to fall and build momentum to break the fiber in the hinge before it closes.
 
Thanks for all the good advice. For all those years that I have cut down trees, I have always assumed that for a fairly straight tree, that all you had to do was cut the notch and then make your back cut. The tree would then fall in the direction of the notch. From this thread I have learned that this is certainly not true. You need to provide some means of directing the tree towards the notch, most easily done with wedges.
 
My father was a carpenter. He make me wedges of red oak that always worked very well. The price was right too.
 
Alot of times a person that has an abrasive personality really comes across as offensize when you are just reading words, however if you were with the person I'm sure it would just be "all in fun" I'm sure if we were all together that same person would keep us laff'n till our sides hurt.

Doug, I don't think that post had anything to do with it.
 
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Variables in notch depth

Perhaps the depth of the undercut should be on a tree by tree basis.

If you hear of a formula where "one size fits all" maybe your personal life experience will guide you.

********************

"The main purpose of the notch is not to influence the balance of the tree; it's to create the front side of the hinge with which to control the direction of the fall. There are many variations of how to make the notch depending on the type and size of the tree and the lay of the land. The idea is to control the fall through the hinge and wedges or ropes."

The above quote from this thread sounds typical of smaller tree (Scandinavian influenced) methodology. A smaller notch can work just fine when the forces aren't all that great to conquer. In fact, a shallower undercut is desirable as it provides more space to place wedges in certain diameters.

***********************

Where this fails is in larger diameters. Same physics, just more of 'em. The face cut also should be viewed as providing the initial 'release'. It is not just there to control the size of the hinge. Using the face depth to create a hinge dimension fails to take advantage of placing the fulcrum in an optimum location to lever. This becomes clear as one moves from smaller diameter shorter trees in northern latitudes, Sweden for instance, to larger diameter taller trees in the Western US and Canada.

An instance of where this very obvious is on a 'short stubby' or 'fat staub.' Picture a balanced 30 foot tall 5+ feet in diameter staub. If one were to place a small undercut in one of these guys you would fail. Too much weight to lift and no tall tree lever to assist. Those guys need face cuts 1/2th or even deeper. Physics. Take that knowledge and vary it back to the small diameter falling and then an understanding can become available as to the need/preference to do a deeper face on a tree by tree basis.
Why, because it can make for less wedging needed.
 
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RES said:
Thanks for all the good advice. For all those years that I have cut down trees, I have always assumed that for a fairly straight tree, that all you had to do was cut the notch and then make your back cut. The tree would then fall in the direction of the notch. From this thread I have learned that this is certainly not true. You need to provide some means of directing the tree towards the notch, most easily done with wedges.
Click to expand...

One of the scariest situations that can occur is facing and backcutting a tree and not having it fall. Generally it is because the limbs of the tree to be felled are locked with one or more other trees. If the tree to be felled is dead and the sap is longer high in the trunk then the weight distribution is fouled up. Wedges or a jack is needed to make the tree commit to a lean. A throw bag and rope are good to have along also. If the tree is dead widowmakers are another problem, simlimb training can help keep you alive here. A wider maybe deeper face cut can help too. Each tree has to be looked at separately.
 
A lot of times it's not a single comment that gets an AS member in trouble, it's their history of similar comments that does it. Kind of a 'last straw that breaks the camels back' thing. Also consider that some folks have been allowed back on AS (several times in some cases) with the understanding that they would be under closer scrutiny, & on a shorter leash.
 
smokechase II said:
Perhaps the depth of the undercut should be on a tree by tree basis.

If you hear of a formula where "one size fits all" maybe your personal life experience will guide you.

********************

"The main purpose of the notch is not to influence the balance of the tree; it's to create the front side of the hinge with which to control the direction of the fall. There are many variations of how to make the notch depending on the type and size of the tree and the lay of the land. The idea is to control the fall through the hinge and wedges or ropes."

The above quote from this thread sounds typical of smaller tree (Scandinavian influenced) methodology. A smaller notch can work just fine when the forces aren't all that great to conquer. In fact, a shallower undercut is desirable as it provides more space to place wedges in certain diameters.

*********************** .....
Click to expand...


I believe that is true - good point about making room for the wedge in smaller trees.....
 
From my experience and observations, several factors influence face cut depth. One is that is has to be deep enough so that you get a good width of hinge. Smaller face cuts leave smaller length hinges for the tree to tip over on, leaving you with less hinge control. So you want at least 25% depth for longer hinges.

If you go the other way, like as far as suggested in the original post on this thread with a 50% face cut, that gives you a longer hinge, but that also places the hinge on the back cut side of the tree. That tends to want to casue the tree to flip over the back cut, or even a bore cut, because the holding wood is all on the back side of the tree. The forces also tend to want to pinch your saw, and leave no room for wedges behind it. So a 40% face cut is about as far in as you want to go for a long hinge and placing the holding wood to the face cut side of the tree.

Another factor that has not been mentioned is the leverage of the wedges when you pound them in. Basic lever physics is that the farther you are from the fulcrom (or hinge, in this case) the more mechanical leverage you will have with the wedge. Meaning the wedge will have more lifting force with a smaller face cut. So a smaller face cut favors both more leverage and more room for wedges behind the saw.

In all, the 1/3 of the diameter is pretty much a compromise for having good holding hinge wood on the falling side of the tree, a good lever length on the backcut side of the tree and room for wedges behind the saw in a backcut. All things cosidered, I typically fall using somwhere between a 25% and 40% face cut. After doing a lot of screwup cuts, like Dutchman's and overcutting hinges, and cutting too big and too small a face cut, and too low and too high a back cut, and cutting at angles, and in the wind and rain and with dull chains, and at the end of the day, or well, screwing around, it all comes down to some average width of face cut. After a few barberchairs and back flippers, I started to pay more attention to details in face and back cuts and cutting depths.
 
smokechase II said:
Perhaps the depth of the undercut should be on a tree by tree basis.

If you hear of a formula where "one size fits all" maybe your personal life experience will guide you.

********************

"The main purpose of the notch is not to influence the balance of the tree; it's to create the front side of the hinge with which to control the direction of the fall. There are many variations of how to make the notch depending on the type and size of the tree and the lay of the land. The idea is to control the fall through the hinge and wedges or ropes."

The above quote from this thread sounds typical of smaller tree (Scandinavian influenced) methodology. A smaller notch can work just fine when the forces aren't all that great to conquer. In fact, a shallower undercut is desirable as it provides more space to place wedges in certain diameters.

***********************

Where this fails is in larger diameters. Same physics, just more of 'em. The face cut also should be viewed as providing the initial 'release'. It is not just there to control the size of the hinge. Using the face depth to create a hinge dimension fails to take advantage of placing the fulcrum in an optimum location to lever. This becomes clear as one moves from smaller diameter shorter trees in northern latitudes, Sweden for instance, to larger diameter taller trees in the Western US and Canada.

An instance of where this very obvious is on a 'short stubby' or 'fat staub.' Picture a balanced 30 foot tall 5+ feet in diameter staub. If one were to place a small undercut in one of these guys you would fail. Too much weight to lift and no tall tree lever to assist. Those guys need face cuts 1/2th or even deeper. Physics. Take that knowledge and vary it back to the small diameter falling and then an understanding can become available as to the need/preference to do a deeper face on a tree by tree basis.
Why, because it can make for less wedging needed.
Click to expand...

Agree in essense Smokechase, good post, another consideration with the deeper face is that it could leave little or no room for wedging should it be necessary, and loss of effectiveness of the hinge when the tree is halfway down and the mouth closes before the hinge breaks, decreasing directional stability, just a thought on a cloudy day, don't know if its been mentioned yet as I haven't read the whole thread yet (catching up), :D

:cheers:

Serge
 
Lots of good input on this thread, despite how it started. :) It appears (to me at least) that Smokechase and Windthown have different opinons as to depth of face.

Windthrown says that the shallower the face, the more leverage the wedge has for moving the tree to the face side and Smokechase gave the example of a short fat heavy staub needing a deeper face because of the weight factor.

Now drawing on memories of my geometry teacher (Mrs Foxx) that I must have frustrated to the point of husband abuse each night, my understanding of these angles are as follows.

A shallow face cut moves the fulcrum (hinge) away from the wedge so it's easier for the wedge to lift the tree... but

with a deeper face cut, a 1" tall wedge inserted, altho harder to get in, moves the tree further toward the face cut.

The same amount of work is being done to move the tree a given distance. Drive the entire wedge in easily (shallow face) Vs drive the wedge in partially but with more difficulty (deep face cut)

It's a trade off and the biggest tree I've felled is 18". That should put some perspective on my opinions... LOL

Ian
 
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smokechase II said:
********************

"The main purpose of the notch is not to influence the balance of the tree; it's to create the front side of the hinge with which to control the direction of the fall. There are many variations of how to make the notch depending on the type and size of the tree and the lay of the land. The idea is to control the fall through the hinge and wedges or ropes."

The above quote from this thread sounds typical of smaller tree (Scandinavian influenced) methodology. A smaller notch can work just fine when the forces aren't all that great to conquer. In fact, a shallower undercut is desirable as it provides more space to place wedges in certain diameters.
Click to expand...

You're 100% on the mark Smoke, I rarely get into anything over 30" and my comments were based on some skills I learned at a certain Scandinavian chainsaw falling demo - techniques that I have since used many times with great success.
 

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