Last weekend, 27 people became safer sawyers by attending Chuck Oslund’s Chainsaw Safety course which was hosted here at MUCC. I recognized a few people that have volunteered at habitat projects, a few Huron Pines AmeriCorps members, along with many professionals looking to enhance their safety and techniques on the job. Thank you to all of the participants and volunteers for joining us in utilizing this safety system.
In last week’s blog, I stated that the open face-bore cut is the safest felling cut to use. There are many steps to this cutting plan that allows for a controlled felling technique. The use of an open face notch with an established hinge and a back strap are the key elements to this cut; the hinge is established while leaving a back strap by using a plunge cut. Establishing a hinge is the key to a controlled fell. Using an open face notch with a 70 degree to 90 degree angle allows the hinge to hold all the way to the ground, rather than breaking when the tree gets to 45 degrees through the fall.
Oslund emphasizes that "the hinge is the only control; protect the hinge." It's important to start the the plunge cut with adequate space to leave a hinge. The general rule for felling a tree is 10/80: The width of the hinge should be about 10% of the tree diameter, and the notch should be at the width of 80% of the diameter.
The preferred cutting plan is an open-face bore-cut with a backstrap, which includes:
An open-face notch-cut of 70 to 90 degrees. The too cut of the open face notch should be made first, followed by the bottom cut. Observe the kerf (the opening cut your saw makes) and stop bottom cut when saw chain is viewed through top kerf.
After the notch is made, bore-cut to establish back edge & width of hinge. Start with a side-cut until the rivets towards the nose of the blade are buried, then pivot at full throttle to plunge-cut parallel to the hinge. Cut back at a closed angle avoid cutting into the hinge, then cut laterally back, leaving a “backstrap” of at least 10% diameter at the rear to hold the tree.
To finish, drive wedges into the kerf at either side of the backstrap. Double check the lay, be sure that hazards are clear, then cut backstrap just above the wedges to release the tree and retreat into your established escape route. The hinge will hold and guide the tree down to the ground.
If the tree is too small to bore-cut, use open-face notch cut and level backcut, stopping to drive wedges and leave a sufficient hinge. Trees smaller than eight inches in diameter are not large enough to leave a sufficient hinge with a backstrap using the bore cut method. MUCC, in coordination with DNR and QDMA, will sometimes perform “hinge-cutting” projects. This allows the tree to be cut so that it falls but stays alive due to the cambium layer staying attached.
In some methods of hinge-cutting, no notch is made in the direction of the lay. Instead, the tree is already leaning in that direction and a perpendicular back-cut is made, and the tree is guided down with a habitat hook. For MUCC projects, that method will only be used on trees 4 to 5 inches in diameter or less. Preferably, these cuts will be made with curved hand-saws instead of chainsaws, especially on smaller trees.
On larger trees, the open-face bore-cut with backstrap will be used. To maintain the hinge and cambium layer connection on the sides, the hinge can be left wider than 10%. While this will likely not keep the tree alive as long as a traditional hinge-cut, it will be a safer method to control the direction of the fall. Volunteers will be using this method next weekend at our event in the Grayling State Forest; we will be hinge cutting for snowshoe hare habitat!
Another upcoming project is Saturday, February 20, 2016 at the Gratiot-Saginaw Sate Game Area where we will be building brush piles for rabbitat. This will be a good opportunity to practice the bore-cut method on larger trees and the open face notch with a level back it on smaller trees. We will be joined by the Midland-Dow High School Conservation Club on this project. See more details and RSVP here to volunteer for wildlife!