Popular Mechanics (USA)
OPEN-FACE DIRECTIONAL FELLING NOTCH, 70°
1. The initial step is a felling notch with an extremely shallow angle. The first downward sloping cut is about 70 degrees.
2. Next comes the horizontal cut, which drops out the wedge of wood. This produces a felling notch that removes more sapwood from the tree than the traditional 45-degree method and makes it more likely that the falling tree will snap its hinge at a safe point in its fall.
3. The key difference is the bore cut, which goes in from one side of the tree’s trunk and right out the other. Note two things about this bore cut. It’s level with the ground and about an inch or two above the vertex (the point where cuts one and two meet) of the felling notch. And most importantly, it leaves the hinge wood intact. The hinge produced by the felling notch should have a width equal to 80 percent of the tree’s diameter when measured at chest height.
4. The wood cutter then moves the chainsaw (and its bore cut) toward the back of the tree and stops, leaving a couple of inches of wood on the back.
This uncut wood is called “the strap” or “holding wood.” As its name implies, it holds the tree in position and affords the feller a chance to ensure everything is in order before the fall.
Withdrawing the chainsaw, the operator pounds wedges into the bore cut, one from each side of the tree. These apply pressure upward and in the direction the tree will fall.
5. Finally, they cut the strap/ holding wood. As the saw works in, the tree will begin to lean and makes the distinctive creaking sound that signals gravity is taking over. Stopping the saw and moving back quickly at a 45-degree angle, the feller lets the tree fall in the direction of the notch as its hinge snaps.