Many newbies to our business don't know about "barber chair", which is a dangerous event that generally occurs while felling leaning trees. They have killed many experienced tree cutters, and are hardly predictable.
There are many threads on this topic, and I don't wish to discuss the many methods available to avoid the problem. What I would like to do in this thread is discuss recognizing the threat prior to starting the chainsaw.
I stumbled across this video, which is the best footage I have ever seen of a full-blown "barber-chair" event (BC for the rest of this post): http://www.youtube.com/user/MrAerialArborist#p/a/f/2/2YAf61zz5VU
From my studies of this kind of event, the general cause of BC is a side force of some sort against the trunk of the tree being felled; either wind load, lean, or perhaps uneven branch load or another tree leaning on it. Most often, we hear of poor technique to resolve the problem, and the fatal results of either getting whacked by the rising split, or the falling tree from unpredictable directions.
Generally, we presume that a heavily leaning tree is prone to BC, but quite frankly, it is a truly rare event in my small portion of this trade, yet it is aparently quite a common concern in other areas.
I have a theory, which I welcome all your thoughts on:
It is not possible to assess the amount of side force necessary to cause a BC, but it isn't going to happen under most circumstances. I think that some trees just cannot be made to BC, and others will do so predictably.
Predictable: significant side load, tree species with easily split logs, and the complete absence of knots, forks, or other interlocking wood fiber that would prevent a longitudinal split of any length.
Notice in the video that there is a rather long trunk section that splits down almost the entire length. Also notice that there are no branches or stubs from branches that were present along the lower part of the tree. Fundamentally, this was a tall pole of parallel grained wood that was not cross linked by any branches for most of the life of this tree. It had obviously been growing in a dense forest that only allowed branching in the upper canopy. Lower branches were sacrificed for rapid attainment of height.
My own single experience occurred when I top cut a 3" diameter maple branch. It was extending about 20' horizontally, and I had no concerns for the landing point, peeling the limb, or wasting time notching and hinging. It split, sending a 6' long split flying upward, which came slapping back down with considerable violence only a moment later. Faster, in fact, than I could interrupt the cut.
This branch had everything previously discussed: long, thin structure relative to it's load, an easily split wood (sugar maple), poor technique that amplified the risk, and this particular branch had NO nodes or cross branching for the 6 feet that it split.
So while I recognize that barber chair is always possible, I think that rather than looking at just the side lean of any given tree, we should put more consideration into how much evidence there is of split-resistant features, and how easily that particular tree specie is to split.
There are many threads on this topic, and I don't wish to discuss the many methods available to avoid the problem. What I would like to do in this thread is discuss recognizing the threat prior to starting the chainsaw.
I stumbled across this video, which is the best footage I have ever seen of a full-blown "barber-chair" event (BC for the rest of this post): http://www.youtube.com/user/MrAerialArborist#p/a/f/2/2YAf61zz5VU
From my studies of this kind of event, the general cause of BC is a side force of some sort against the trunk of the tree being felled; either wind load, lean, or perhaps uneven branch load or another tree leaning on it. Most often, we hear of poor technique to resolve the problem, and the fatal results of either getting whacked by the rising split, or the falling tree from unpredictable directions.
Generally, we presume that a heavily leaning tree is prone to BC, but quite frankly, it is a truly rare event in my small portion of this trade, yet it is aparently quite a common concern in other areas.
I have a theory, which I welcome all your thoughts on:
It is not possible to assess the amount of side force necessary to cause a BC, but it isn't going to happen under most circumstances. I think that some trees just cannot be made to BC, and others will do so predictably.
Predictable: significant side load, tree species with easily split logs, and the complete absence of knots, forks, or other interlocking wood fiber that would prevent a longitudinal split of any length.
Notice in the video that there is a rather long trunk section that splits down almost the entire length. Also notice that there are no branches or stubs from branches that were present along the lower part of the tree. Fundamentally, this was a tall pole of parallel grained wood that was not cross linked by any branches for most of the life of this tree. It had obviously been growing in a dense forest that only allowed branching in the upper canopy. Lower branches were sacrificed for rapid attainment of height.
My own single experience occurred when I top cut a 3" diameter maple branch. It was extending about 20' horizontally, and I had no concerns for the landing point, peeling the limb, or wasting time notching and hinging. It split, sending a 6' long split flying upward, which came slapping back down with considerable violence only a moment later. Faster, in fact, than I could interrupt the cut.
This branch had everything previously discussed: long, thin structure relative to it's load, an easily split wood (sugar maple), poor technique that amplified the risk, and this particular branch had NO nodes or cross branching for the 6 feet that it split.
So while I recognize that barber chair is always possible, I think that rather than looking at just the side lean of any given tree, we should put more consideration into how much evidence there is of split-resistant features, and how easily that particular tree specie is to split.
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