This is an excellent time of the year to fell trees in your woods. It is cool enough to be comfortable, but not so cold that you would rather sit by a fire inside the house. However, using a chainsaw can be dangerous, and we covered chainsaw use previously in the CU in the Woods articles. Today, I would like to talk about the five-step felling plan I highly recommend when considering felling a tree using a directional open-face with trigger wood felling technique. The plan is simple and is to be used before you even start the chainsaw. The steps are: 1) hazard evaluation, 2) lean evaluation, 3) escape route considerations, 4) hinge thickness considerations and 5) cutting plan.
The first step, hazard evaluation, is important because it involves examining the tree to identify any hazards and risks associated with it. This could be dead branches at the top that you would want to avoid standing underneath. It could be vines or crowns of other trees intertangled, which may change how the tree falls. Maybe it is a nearby power line or structure that you need to avoid. But it also includes looking around the base of the tree to identify any hazards, such as saplings that may be in your way, or catfaces/scars on root flares and the trunk that may indicate the potential for rot. Once you have assessed the hazards, you can come up with a plan to work with them or decide not to move forward with tree felling at all.
The second step, lean evaluation, is to assess the forward, backward, and side lean of the tree. This assessment is based on knowing the felling direction, so this is what you have to decide on first. For the side lean assessment, walk in line with the felling direction, about one tree length back. Now form a triangle with your pointer fingers (up) and your thumbs (down), and try to capture the entire crown within this triangle. If you can’t fit it all within the triangle, walk back some more. Now move this triangle downwards until you see where your thumbs meet the ground. This spot indicates whether you have a lean to the left or right of the tree, but it also shows you how much lean you have to one side or the other. Now walk perpendicular to the felling direction and do the same thing for the forward/backward lean. These two assessments will now show you in which directions the tree naturally wants to go. This is not always the direction you want to fell in, but that is a discussion for another day. Just keep in mind that the side with lean is your “bad” side, and the opposite side is your “good” side. Always finish your felling cuts on the “good” side, to minimize the risk of being hit by a falling tree.
Your third step is considering your escape route. Once a tree starts falling, it is in your best interest to move far away from the tree to minimize the risk of serious injuries. Your escape route should be backward on your “good” side at a 45-degree angle to your felling direction. Make sure you identify the escape route and cut any saplings or brush that block your way. You should back up at least 20 feet once the tree starts falling; farther is better.
The fourth step is thinking about the hinge thickness. With directional tree felling, a hinge will guide the tree to the ground in the direction you want it to go. The general rule for the hinge thickness is 10% of the diameter of the tree at breast height (DBH). For a 10-inch-diameter tree, a 1-inch hinge would be sufficient; for a 20-inch-diameter tree, a 2-inch hinge would work. Depending on the species, you may adjust the hinge thickness a bit. For example, long-fibered species such as our yellow pines can get by with a slightly smaller hinge, while some oaks with shorter fibers may benefit from a slightly larger hinge thickness.
The fifth step is your cutting plan. For the open-face with trigger wood felling technique, your first step would be to cut an open-face or notch in the side of the tree, which will determine the felling direction. This notch should have an opening angle of about 70 to 90 degrees, and the apex length where the two notch faces meet should be about 80% of the DBH of the tree. This often translates to a depth of about 20% to 25% of the DBH. So for a 20-inch-diameter tree, the apex length should be about 16 inches from one side to the other.
Your next cut to consider is the one that forms your hinge. This is most often a bore cut that starts well behind the hinge. Once cut through the tree, you can move the saw forward to shape the correct thickness of the hinge. It is important to consider from which side you will make the cut, and whether you can make it on one side or need to make two cuts from opposite sides. Once the hinge is formed, you can move your saw backwards to shape the trigger wood that you will leave to hold the tree in place and keep it from falling while you assess the surrounding area. Think about where you want to put the trigger, how you will shape it, and where you will insert any felling wedges to help with lifting the tree so that it can fall. The last step to consider is where you will cut the trigger wood. It is good practice to cut the trigger wood below your previous cuts to avoid cutting into any wedges. Make sure your trigger wood and your final cut can be made from the “good” side, so you can use the escape route once the tree starts falling.
Now that you have made a plan using the five steps above, you can start your chainsaw, clear a path around the tree and down the escape route, and start making your felling cuts. Keep in mind that tree felling is dangerous, and a lot of things can go wrong. If you are unsure about felling a tree, don’t do it and call a professional. Clemson Extension has a chainsaw safety website (https://www.clemson.edu/extension/chainsaw/) that has educational videos and information on upcoming chainsaw safety classes.
Author(s)
Patrick Hiesl, Clemson University, Associate Professor of Forest Operations
Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, religion, national origin, disability, political beliefs, sex, marital or family status and is an equal opportunity employer.
