Posts Tagged ‘Tree Felling’

Back-Cuts, Hinges & Control (Article 6)

Monday, August 2nd, 2010
 

This is the last in a series where I have been discussing a sequenced planning method to tree felling.  When read in sequence, the articles combine to describe an effective tree felling planning process. It has been my intention to encourage readers to think about many aspects when felling trees – with the focus being on tree faller safety.

It is important to remember that some tree felling techniques developed from years of trial and error and in field practice and in all cases deserve our respect and acknowledgement. It is difficult to produce conclusive scientific data that verifies certain aspects of tree felling techniques, due to the many variables that are at work when dealing with living organisms such as trees.

Remember that new tools cannot get into a toolbox when the lid is closed.  An open mind is like an open toolbox and new tools when tried and proven are a wise addition.

In most cases, the back-cut is the final step when felling a tree.  The back-cut removes the wood left preventing the notch from closing, it also forms the hinge wood. The hinge wood is the wood left uncut behind the notch and is what provides control and guidance to a felled tree. It is important to understand that the hinge can only offer control as long as it can work; when the hinge fails, control is lost.

Cutting & Forming the Hinge
 

Traditional Back Cuts

A crosscut saw was the tool of choice and for generations back-cuts were cut by hand with a crosscut saw, cutting from the back of the tree towards the notch.  The modern chainsaw and tooth design offers us alternatives to this traditional method. The notch selected should be considered when deciding where to place the back-cut. Traditionally it has been recommended to raise back-cuts above the apex of the notch.  This technique (called the stepped back-cut) forms a step or back stop and minimizes a tree from sliding backwards off the stump causing great risk to the faller. It is important to raise back-cuts whenever felling a tree with a small notch opening such as 45 degrees or less. In these cases, the hinge will have to break when the face notch closes. After all a notch with a 45 degree or less notch aperture will have to break the hinge and as a result will lose control when the tree in most cases is only half way to the ground. A limitation of a small notch aperture is that it forces hinge failure before the tree reaches the ground, thus causing loss of control and gravity takes over before the tree is on the ground. If limb tying or felling obstacles are present that could snag the falling tree a stepped back-cut is also advisable regardless of notch opening.

Open Face Notch

Technical Tree Falling – Faller Escape Routes, Understanding the 5-15-90 Rule (Article 4)

Monday, May 3rd, 2010

By Dwayne Neustaeter

Having a clearly identified and prepared escape route is one of the most important parts of any felling plan. Statistics show that a well-planned and utilized escape plan has a significant impact on your personal safety. Accident and fatality reports also reveal some useful information regarding workers injured when falling trees.

People falling trees have learned over the years that the area directly on either side or directly behind the tree is very dangerous. This is because branches, tops and trunk sections often fall near the base of a falling tree.

One type of falling mishap, know as a barber chair, is particularly dangerous. A barber chair occurs when a tree being felled delaminates vertically before the hinge is cut thin enough to bend. The term refers to the sliding action of the old style barber chair that positioned patrons in a head down, feet up position so the barber could more easily shave with the straight razor.

In falling, a barber chair occurs when using conventional back-cuts where the hinge is formed by cutting the wood from the back of the tree towards the hinge. As the saw severs the more resilient sapwood fibres typically found in the outer rings of a tree, the more brittle heartwood must resist the bending load. In cases of heavy forward lean and in older trees, this can result in the hinge wood splitting upwards as the tree falls. When the tree top contacts the ground the section of tree that has split upwards crushes either the remaining wood column straight backwards or the split standing section tears and rolls off to either side. In either case, the best place to be is away and at an angle.

Another compelling justification for the escape route is that while a tree is being cut, vibrations sent up through the entire tree can cause branches and tops to loosen. This vibration dislodges branches, where the sway from wind will not. As a tree begins to fall the force of gravity acting on it changes as well and a branch or dead top that is hung up for many years will suddenly dislodge during the first several seconds the tree is falling. These loosened limbs and tops fall generally within a few feet of the base. Trees that have dead tops or dead branches often referred to as widow makers for this very reason, because many a tree faller has been struck or killed.

The 5-15-90 rule is a concept we can use to emphasize the importance of using an escape route. Review of where tree falling accidents and fatalities occurred revealed that 90% of all accidents and fatalities happen within the first 15 seconds of the tree falling and within 5 feet of the base of the felled tree. Therefore, if you identify, plan and use an escape route you can increase your chance of survival or escaping injury by 90% and that the best escape route is at an angle away from the falling tree.

The most advisable angle of escape is away from the direction of the falling tree at an angle approximately 135 degrees from the direction of fall or 45 degrees from the opposite of the direction of fall.  (see diagram)

Many times obstacles or terrain influence the escape route plan, therefore it is not an exact science but rather the escape zone is at an angle diagonally away from the direction of fall, as illustrated in the diagram.

Remember:  Identify, Prepare and Use an Escape whenever you fall a tree.

Both of the escape routes shown here are 135 degrees from the direction of fall. It is also 45 degrees from the opposite of the direction of fall.

Technical Tree Felling – Assessing Lean (Article 3)

Monday, May 3rd, 2010

 

 By Dwayne Neustaeter

An important step of any falling plan (and one I believe that is often the most overlooked) is assessing the lean. In almost all cases whenever possible it is best to fell a tree in the direction it is naturally leaning. That is to say that if all of the strength of the wood fibres holding the tree up against gravity were to be severed or be instantly released then the tree would fall exactly where gravity is taking it. Therefore, if you can fell a tree in the direction of its natural lean gravity will ensure it falls that direction.

In my last article, I touched on height measure and how, if you have determined how tall the tree is and accurately assess the lean, then there is little that can cause the tree to fall anywhere other than planned.

 Assessing lean is much more than the angle of the trunk.  Other factors must be considered.  I tell my students to consider the entire ‘bio-mass’ of the tree as this is what truly creates bendin gon the trunk.  The ‘bio-mass’ is all of the parts of the tree combined – every branch and trunk.  This is best assessed as part of your outer perimeter survey s described in the previous article.

 The bio-mass and lean is best assessed from a distance from the tree.  In your mind’s eye, draw a line around the entire tree, being sure it touches the tips of every branch, start at the base of the trunk and then proceed left or right around the entire canopy or bio-mass of the tree.  Once you have this visualized, split that shape in half (it usually is an oval or egg shape) and imagine a line plumb down the center.  The distance this line is in relation to the notching area of the trunk tells you how much lean you are dealing with.

This tree shows about 5 - 7 feet of lean.

This tree shows approximately 1 foot of lean

 It is important to look at the tree from all sides and assess lean as you go because the lean will change from different viewing locations.  Using this method the natural lean may be determined and the fell should proceed in that direction.  If there are obstacles in the way of this natural lean, then other technical felling or rigging techniques are needed and worked into the plan.

 What I have just described is how to calculate ‘forward lean’.  There is another aspect of lean that is also important to evaluate.  Once the ‘forward lean’ is established, it is important to eliminate any side lean in relation to your direction of fall.  Often side lean is not considered.  The problem is when obstacles are in the way of the ‘natural-lean’, the faller must obviously choose to fell the tree away from the obstacle.  In doing this – side lean becomes a factor.

 Side lean is lean that is perpendicular to the felling notch and hinge.  This is important because wood is much weaker in the vertical plane than the horizontal (imagine trying to split a log by hitting along the side, yet when you hit it from an end, it splits relatively easily).

 Gravity acts on the hinge much the same way; as the tree falls it can cause the hinge to break prematurely, sending the tree once again in the direction of the ‘natural lean’.  Therefore, once natural forward lean is determined, be sure that there is no side lean acting on your hinge 90 degrees to your direction of fall.

 Mastering how to perform a lean assessment will ensure all of your trees fall exactly where you want them to.  By using the outer and inner perimeter survey and height measure you can predict accurately and confidently where the top of the tree will land.

 There are more factors to consider in your felling plan and in my next article I will discuss establishing and using an escape route.

Technical Tree Felling – Evaluating Site, Height and Hazard (Article 2)

Tuesday, April 27th, 2010

By Dwayne Neustaeter

The first step in any work plan and especially a felling plan is evaluating site hazards, tree risk indicators and tree placement considerations such as tree height and felling site location and placement. When evaluating a site and tree, I like to look at it from two viewpoints – one from a distance back and another up close. This two-stepped process I like to call my outer perimeter and inner perimeter surveys. The word ‘perimeter’ is key in that it indicates a circular or all encompassing look.

Perform the outer perimeter survey from a distant back, preferably about the distance back as the height of the tree. View the site and tree from all sides by simply walking around the tree. During the outer perimeter survey, some site considerations you are looking for are obstacles or hazards such as power lines, other trees, buildings, fences etc. Tree considerations include the size of the tree, dead limbs or tops, decay and prominent lean. It is always best to choose to fell your tree with the natural lean so gravity can work for you. I will expand on lean assessment in the next article of this series.

During the outer perimeter survey, site considerations you are looking for are obstacles or hazards such as power lines, other trees, buildings and fences. Tree considerations include the size of the tree, dead limbs or tops, decay and prominent lean.

One final step I recommend performing as part of the outer perimeter survey is to determine the trees height as this often dictates if a tree can fit in the desired drop zone. A simple field method for determining the height of a tree can be done using a straight stick roughly the length of your leg.

1.  Cradle the stick in your hand and hold it up to your eye, (be sure you have safety glasses on) by aiming down along the stick line it up with the base of the tree.

2.  Next, hold the stick upright so the stick and your arm form a 90-degree angle.

3.  Sight along the top of the stick and walk forward or backward until the top of the stick is in line with the top of the tree and the bottom of the stick where you are holding it is lining up with base of the tree. When this lines up, the spot where you are standing is very close to the height of the tree.

Estimating a Tree's Height. The worker on the left is sighting along the stick to the bottom of the tree while the worker on the right is lining up the top of the tree with the top of the stick. Though simple, the method is quite accurate.

The more you practice this technique, the more accurate you will become. This technique is difficult to explain in words, but is quickly learned with some hands on training. By determining the height of a tree, it becomes easier to decide where to fell the tree and ensure it is free and clear of contacting any obstacles during the felling process.

The inner perimeter survey is done up close and focuses specifically on the tree, the placement of your notch and establishing your escape route. Once again, make a complete circle around the base of your tree in close proximity to the tree, and look for additional indication of wood decay and cavities. Mushrooms or conks can be indications of internal wood decay and should be seriously considered as decayed wood affects the performance of your hinge.  Additionally, the desired direction of fall may change due to the presence of a cavity or wound where your hinge wood needs to be. Your inner perimeter survey also involves clearing brush, debris or anything that could impede your cutting of the notch, back-cut and escape route.

The inner perimeter survey should include watching for root decay & structural damages.

An inner perimeter survey also involves clearing brush, debris or anything that could impede your cutting of the notch, back-cut and escape route.

This survey process is the beginning of your plan and is very important. It is step one of a five step planning process for felling trees and integrates into all of the other steps in this plan.  I will be referring back to the outer and inner perimeter surveys as I continue this series.

Remember accidents are unplanned events and an excellent way to avoid an accident is to plan your work and work your plan. We use a planning process and explain it in series of steps to help us remember and follow a system. When felling a tree these steps are blended and integrated in our mind as we formulate our felling plan. 

Thank-you for taking time to read this article and sharing some of your valuable time with me by being willing to think and consider adding some tools or techniques to your tree felling toolbox.

Technical Tree Felling – A Historical Perspective (Article 1)

Tuesday, April 27th, 2010

In the first of a six-part series on felling, Dwayne discusses how the legacy from the days of the axe & crosscut still influences modern techniques

Tree felling has been taking place for thousands of years because trees have provided resources necessary for the survival of humankind. This is the very reason why it is such a controversial and varying subject. In the past trees were in some cases burned to the ground.  This required a lot of time and tending and when it was finally weakened enough by the flames, the tree would fall in any direction. This method gave way to chopping at trees with stone implements, like tomahawks. In the not-so-distant past, felling accuracy, tree placement and landing improved with the use of a crosscut saw and axe.

Burning as a way of felling trees gave way to chopping at trees with stone implements, like tomahawks.

Tree felling techniques date back beyond the advent of the modern day chainsaw.  Unfortunately some techniques and practices used to fell trees have not kept up with the technology of the chainsaw itself. For example, it is often thought that there is a safety or wood quality reason for the common 45 degree notch opening. But the fact is that this notching technique originates back to the crosscut saw and axe. In order to notch in a tree with a cross cut saw and an axe you have to make the under cut first and then chop out the wood above the cut. It is easiest for an axe to remove wood in this situation at a 45-degree angle and that is the very reason why a 45-degree face notch is so common. In other words, it is a legacy from long-ago.

The wood left uncut during the felling process is called; “hinge wood”.  It is formed by cutting a notch and using a back cut to release the wood behind the notch. The purpose of the hinge wood is to provide control during the arc of the fall.  This control is only available as long as the hinge is intact and working. Many things can work against the hinge wood and cause it to break prematurely resulting in a loss of control of a falling tree. Some other things that cause hinge failure are side lean, hinge too thick, wood fiber decay, by-pass and uneven hinge wood, all of which I will discuss later in the series. I have not met anyone that fells trees that wants to lose control of a tree.

The most common method of notching trees today is the 45-degree face notch.  The flaw in this is that it only allows your hinge to work for about half of the arc of the fall of the tree. A tree generally grows 90 degrees to the ground with the exception of slopes and uneven terrain and even then the trunk is parallel or in line with the force of gravity acting downward along its length. When a tree begins to fall, the angle of the trunk to the ground closes and in order for the hinge to bend from start to finish, the tree must have gone from standing to laying on the ground. The hinge can only provide this control if it can remain intact through the entire arc of the fall. And the only way to maintain control of the tree being felled using a hinge is to allow the hinge to work or hinge through the entire arc of the fall. Control of the tree can only be achieved if the hinge is allowed work through the entire arc of the fall, and this requires a notch opening of 70 degrees.

Control of the tree can only be achieved if the hinge is allowed to work through the entire arc of the fall, and this requires a notch opening of 70 degrees.

In this series I will expand on a five-step tree felling planning process that allows anyone felling trees to remain in control of trees they are felling and also be as safe as possible during any tree felling process. If you are interested in learning about control and accuracy when it comes to tree felling then look for my next article where I will touch on the first step in the plan which is evaluating site hazards, tree risk indicators and tree placement considerations such as tree height, felling site location and placement.