SAW SHOP BY BRYAN WAGNER CHAINSAW & LOGGING SAFETY TRAINER
Hello everyone! Last quarter we talked about proper face-notching. Remember, both cuts of the notch must meet. When we face-notch a tree, we are actually setting up the hinge length. The notch must be at least 80% of the tree’s diameter. That means you will have hinge-wood across at least 80% of the stump if you don’t “bore” the heart. The hinge has two essential functions. Hinge-wood tries to keep the falling stem from rebounding if an object is struck on the way to the ground. The notch angle will tell the hinge when to release. We try to use a 70 – 90-degree notch angle. The “open-face” notch allows the hinge to control the stem through most of its controlled fall to the ground. The theory is, the energy to rebound has been spent. The hinge on a tree serves as the steering wheel. An accurate face-notch leads to a precise hinge set. Accuracy is a significant safety issue in any felling scenario. Accurate felling in a select-cut, or SMZ felling, keeps the timber-cutter safe from being struck by falling or thrown objects. If you don’t brush or hit surrounding timber, nothing gets thrown back at you! The tree goes where the hinge tells it to. This is great if the hinge holds! If the hinge-wood breaks, the tree will go to where the tree is heavy too!
Remember, the weighted side of the tree is the BAD-SIDE! Your body needs to stay on the good side as much as possible.
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OK, now let’s talk about hinge thickness. The basic rule is 1/10th of the Diameter at Breast Height, DBH. Using the formula, a 20” DBH tree would need a 2-inch hinge maximum. FMIC FALL 2021
If we go thicker, some fiber pull may happen. The next question is, what species of tree are you cutting? Long fibered trees such as Sweet Gum and Yellow Pine don’t usually require the maximum hinge thickness. Their fiber is flexible and works well. Short-fibered trees such as White Pine or Soft Maple usually will be given the maximum “called for” hinge thickness. Short-natured fiber can break before it bends! To sum up hinge thickness, I will usually use one inch of hinge on a 20” DBH Sweet Gum. If the same tree was a Soft Maple, I would possibly go with a 2-inch hinge.
Forestry Mutual requires hinge-wood to be continuous across the stump, or if the situation exists, the timber-cutter can center-cut the tree and leave
