Natural forrest area in the Southpansburg Area

Figure 1: The danger of felling a crooked tree.

Figure 2: The danger of felling a tree on a steep slope.

Figure 3: The danger of felling a tree on uneven or rocky terrain.

Figure 4: Determining the lean and lay of a tree to be felled.

By Cleve Cheney

Felling trees is a risky and dangerous business which can result in serious injury or death. Without experience it may be prudent to fell only straight trees smaller than 30 centimetres in diameter and on level ground. A quick way to estimate a diameter of 30 centimetres or less is to reach around the tree and touch your left shoulder. If you cannot do this then the tree is too big to take on without experience. If you do not know what you are doing, avoid trees that grow on slopes, lean to one side or are located on uneven ground.

Crooked trees can kick up when they fall and cause the woodsman serious injury (see Figure 1).

When felling a tree on a steep hillside, the tree can slip back over the stump and slide downhill onto the woodsman (see Figure 2).
It is also dangerous to fell trees on rocky or uneven terrain, as the falling tree may flail from side to side or kick up if it impacts with a hump on the ground or a rock. This can result in serious injury to the woodsman (see Figure 3).

Before you attempt to fell a tree, take the time to carefully assess the situation. You must have a clear work area, a sure footing and a readily available avenue of escape. Low branches, which may trip you up if you have to move quickly or which may catch the axe, should be cut or cleared away. Pay special attention to overhead branches or wires as the axe may rebound off them during a swing and cause you serious injury.

The direction in which a tree will fall, is determined by many factors. Unless there is a pronounced lean to one side, a tree will generally fall in the direction that the wind is blowing, especially if it has many leafy branches. Before attempting to fell a tree, check from at least two or three positions if it has any lean and try to estimate where it will fall. Lean is the deviation in any direction from the vertical and lay is the position in which the tree will come to rest when it falls (see Figure 4).

An experienced woodsman can make a tree with a lean of less than four degrees fall in any direction he desires by placing the undercut and back cut in the appropriate position (see Figure 5).
Careless estimation of the amount of lean is the main reason for a tree falling in an unexpected direction. Another potential hazard is attempting to fell a leaning tree with little or no undercut. The tree breaks and falls while still attached at a point acting as a fulcrum, which pivots the tree in an arc around the point. The lower end of the stump can hit the woodsman, resulting in serious trauma or even a fatality. When the top end of the tree hits the ground, it can also rotate backwards in the opposite direction around the same fulcrum, which is also extremely dangerous (see Figure 6).

Remember, trees weigh hundreds, and in some cases, thousands of kilograms. Great caution should be exercised when felling trees leaning to one side. The correct cuts to be made with the axe are shown in Figure 7.

In the next article we will look at the hazards involved in felling trees with an axe.

Updated: Wednesday, February 18, 2009 12:19 PM

Figure 5: The direction of the fall is determined by the positioning of the undercut, the back cut and the thickness of the hinge.	Figure 6: The barber-chair phenomenon can result from felling trees that lean to one side or are felled using little or no undercut.
	Figure 7: The correct sequence of cuts when felling a leaning tree