Technical Felling

Technical felling is an “umbrella” term that covers a whole lot of ground, encompassing a variety of techniques and methods that professional fellers, loggers and arborists use to get wood on the ground safely and efficiently. While many of these techniques and methods have been discussed in previous columns, technical felling is where they all come together, from the five-step felling plan through the right PPE all the way to influencing the lean of the tree that’s the target to be felled. In a way, it could be considered similar to the way the overall descriptive term baseball is actually made up of the individual skills and techniques of hitting, fielding, pitching, running the bases, etc., with the additional and quite important factor of large pieces of woody debris traveling at high rates of speed from above and the use of extremely sharp cutting implements.

In any case, regardless of similarities or dissimilarities, technical felling is about getting wood on the ground where it was intended without breaking any man-made objects, and the crew going home with all the pieces and parts they started the day with. Having knowledge of the principles and techniques of technical felling is, as is often the case, just the beginning of the journey. A great deal of practice, training and repetition are necessary to make these individual components part of muscle memory and the mental toolbox. Once that has been achieved, the result is safer and more effective felling operations.

With a 70-degree notch, the hinge breaks as the tree reaches the ground. Photo: Michael Tain

Pie, chunks and notches

The purpose of technical felling is to get the tree, or section of the tree, to fall where the operator wants it when they want it, not much more and certainly not any less. If an operator’s technical felling skills and plans work about 50 percent of the time, or even 80 percent of the time, those ain’t skills, those are the whims of fate. The goal of technical felling is 100 percent reliability, certainly not always possible when working with large organic matter, but if used correctly and all the variables considered, properly carried out technical felling should have a much greater success rate than 80 percent.

While the whole process starts with the five-step felling plan, the key to getting the tree on the ground is the notch, piece of pie, chunk, or whatever else it may be called in the operator’s particular geographic location.

The face notch, when placed correctly with all the other factors taken into consideration, is what makes the tree go where the operator wishes. Traditionally and on many work sites today, a piece of pie of 45 degrees about a third of the way into the trunk is used. These dimensions were developed and learned in the “school of hard knocks” by contemporary tree crews’ logger ancestors and the tools they had to work with: axes and crosscut saws. The bottom cut was done with the crosscut saw, and since they don’t cut well at an angle, the top would be done with an axe. An axe cuts best at 45 degrees, thus the angle of the top cut was 45 degrees. This traditional or 45 notch worked very well for those old-timers, especially seeing as they didn’t have a whole lot of other choices; and it can still be quite effective in some situations, but it does lack some degree of precision and control that is available to operators in the age of chain saws.

Two things about the 45 lessen its precision and control. One, with any notch once it’s closed the hinge breaks and all control is lost, therefore any tree that is perpendicular to the ground, or straight up and down, is only in a controlled arc for about half of its fall, which can make it prone to twisting or going “sidewinder” if any side lean or other unnoticed factors are present. Two, the point of maximum “push back” in a tree’s fall is at about a 45-degree angle, right when the notch closes with this notch, thus there’s an alarming tendency for the butt of the tree to come backward at a high rate of speed towards the unsuspecting operator. Experienced users of the 45 know to combat this push back by elevating their back-cut, thus providing a step or ledge that prevents this “hop back,” thus adding another degree of complication to setting up and carrying out the cut.

A chain saw, if it’s well maintained and cared for, will cut at any angle or orientation, much like the honey badger, it just don’t care. Given this advantage, a face notch choice that offers much more precision and control is the open-face notch. The open-face is usually 70 degrees or more; and this larger opening helps the tree get all the way to the ground without the notch closing, keeping the hinge and its attendant control intact. An open-face notch will also take the tree through and past that dangerous 45-degree angle of “push back,” so the back cut doesn’t need to be high, and, in fact, it can be dead level with the bottom of the face notch or back of the hinge. If there’s back lean present, the notch can be opened even more into a “bird mouth” to help the operator get it all the way to the ground before the notch closes.

A word of caution when using the open-face notch: If using it aloft, the climber should not open it too greatly, as the hinge wood holding on after the piece has reached parallel can lead to a “ride” of exciting and memorable dimensions.

This example of “barber chair” shows how the wood splits vertically. Photo: H. Neustaeter

Plunging, boring and settin’ up the hinge

Being able to effectively use the tip of the bar of the saw allows contemporary operators to bore into wood and can be particularly valuable in technical felling. A skilled operator can not only set up their hinge just right, usually 5 to 10 percent of the diameter depending on species, but also eliminate the possibility of that nasty surprise called “barber chair.”

In a barber chair, the tension and compression forces within the wood split vertically, both upwards and downwards, often resulting in somebody or something getting hurt. The bore cut severs these fibers before any movement takes place, thus eliminating the surprise. As has been discussed before, operators should be quite comfortable and practiced with the plunge cut before using it in the real world — after all that’s what all those chunks of wood sitting around the yard are for — but as always it begins with the lower quadrant or “go” corner of the tip of the bar. Using the top or “no” corner is an excellent way to experience the force of a kickback.

Plunge cutting will also allow an operator to fell a tree much larger than the length of the bar, as they can bore in from both sides to set up the back cut; and with practice and skill even from the front center if necessary. This makes it possible — though a larger saw would be more pleasant — to fell a tree with a diameter that is roughly three times the length of the available bar. The plunge cuts in this scenario do not need to match up perfectly, just overlap to sever the necessary wood fiber. Once fully understood and practiced, the bore cut is a valuable technique not only for felling on the ground and aloft, but also in bucking and limbing operations.

Trigger, strap and back strap

Setting up the hinge with a bore or plunge cut allows an operator to leave a section of wood at the rear or side of the tree and check out the whole scene and situation before letting it go. This section is often called the strap or trigger, and it should be at least 10 percent of the diameter of the tree. Trees with severe forward leans or compromised wood fiber should have even larger straps to ensure the control the operator has worked so hard to establish.

The stability and time provided by the use of a back strap can be used to make sure the landing zone is clear, the operator’s escape route still looks good, that the pull line or wedges are set, and that the most basic item, enough gas in the saw, is present.

The tree is still quite high in the air when the hinge of a 45-degree notch breaks. Photo: Michael Tain

Straps should be cut either on level with the hinge or below hinge level. Cutting above hinge level means the saw is in the wood that will soon be going away, and can carry both saw and operator along for the trip. Typically, the further below hinge level that the back strap is severed, the longer it will take for the tree to start its fall, thus providing additional time for the operator to get off the dance floor.

Influencing the lean

Making trees go against their existing lean is going to call for pull lines or the use of wedges. Though pull lines are used most of the time in the arborist industry, knowledge of felling wedges can be helpful for tree crews, particularly when the pull line was forgotten or just went through the chipper. Felling wedges have bumps on them, often called dogs, which help them stay in the cut or kerf, unlike bucking wedges, which are smooth as butter to enable easier removal from the cut.

Stacking wedges is an art in itself, but once understood and employed can eliminate the nerve-racking process of wedges spitting out of the severed back cut. Pull lines should not have any pressure put on them, just held taut; and the crew providing the momentum should wait until the chain saw operator signals before inputting any force. Early vigorous pulling has caused many a felling operation to go south.

There is obviously a great deal more to the topic of technical felling than is described here, but some knowledge of these basic principles and ideas, coupled with training and practice in controlled situations, will go a long way toward making crews better and safer fellers, ones that though they may not have to fell a tree in a precise location every day, will be up for the challenge when confronted with it.

Editor’s note: This story was originally published in May 2012 and has been updated.

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