| This is one in the "What Could Go Wrong?" social-media series about the risks and rewards of managing our own forests -- particularly the risks. It's one way for us to share what we’ve learned from years of work on our small forest in the Pacific Northwest. |
This 80-foot fir tree was within the Firewise defensible space of a future house to be constructed downslope from it. The owner, my neighbor, asked me to cut it and try not to land it in the construction zone.
The tree had about 7 feet of lean toward the house site. Felling it 90 degrees to the left was borderline for a side leaner, but the tree was healthy and I had plenty of diameter for a strong hinge. What could go wrong?
The biggest risk was that it would not follow the hinge or, worse, "barber chair." My trusting cinematographer and I had plenty of escape routes available to us in either case.
This tree wasn't going to the mill, which is good because I started my face cut too high. I could notch from the top for more accuracy -- and have a 70 degree open face, so the hinge wouldn’t break before the tree was committed to the target.
I set a second wedge on the compression side, right up against the hinge. That was to support the weight of the tree as it falls, to keep it from crushing the hinge and twisting off the stump, missing the target. To trip the tree I cut away the remaining hold wood.
So what went wrong? Watch the video and look at how the stump splits in half as the tree falls. As the tree twists the stump, there’s a gap big enough to fit an axe head in there. Then it snaps closed again. That split allowed the tree to twist and fall more in the direction of its lean.
And it’s not a big surprise. Strong leaners are common here in the Northwest. You can’t trust them to follow the hinge, no matter how hefty you make it.
Boring this tree is what kept it from splitting up instead of down. Still, swinging this tree 90 degrees to the left was borderline in terms of what you can get away with on a side leaner.
It fell 7 degrees off target but it could have been a lot worse. The stump could have pulled completely apart, or out of the ground, if the forces had been stronger. Then all my efforts to aim the tree would be for naught.
The old school technique for aiming a side leaner is to leave a triangular hinge and chase the cut from the back. It doesn't give consistent results because the compression side of the hinge collapses at some point during the cut. If you’re chasing the cut when that happens, it pinches the saw and you’re at the mercy of the tree or running for your life. Nonetheless it's still common in the west today.
Which side of the hinge determines the aim? It turns out to be the back side angle. With a triangle, that means you’ve over-aimed, but you had no choice with that technique. The back side angle is determined by how far you got the bar into the tree before it started falling. If you're too slow, the aim is left to chance. That's why the technique is sometimes called "the race is on." Chasing is quicker than boring, but when it doesn’t work you waste time recovering a pinched saw from a half-cut leaning tree.
Felling expert Jerry Beranek says the most you can aim a leaner with a triangle hinge is about 15 degrees, and I found that to be true. We threw this tree over 80 degrees with the technique shown in this video. I wouldn't call it reliable at that extreme. If this tree were above a house, and not just an empty construction site, I’d want to have some rigging on it to make sure it couldn’t cause real damage.
Species: Douglas fir.
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