Archive for April, 2010

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.