Effect of undercut style and post hinge behavior in tree felling

Abstract

This article reports the results from a preliminary field trial, and based on the rotation points found in the field trial, a dynamic model of a tree being felled with either a Humboldt, conventional, or open face undercut is developed. It was found that the holding wood does not completely break until the undercut closes, and the greatest potential for a kickback is when the tree is rotating about the second rotation point. When the tree is rotating about the second point, the slope of the lower face of the undercut has a strong effect on when the tree can begin to move away from the stump. For a given face angle, the tree is able to move away from the stump sooner after the holding wood breaks when a Humboldt undercut is used. Modeling indicates that the step in the backcut is more likely to be required as an anti-kickback measure when a conventional undercut is used. The complicated mechanical process of how the holding wood actually breaks is an area requiring further research, particularly with respect to how it is affected by the step height of the backcut. © 2012 by the Society of American Foresters.