This video is well done and well produced, but it is important to remember that you never know who is watching your videos, and how dangerous chainsaws and falling trees are.
The tongue and groove cut is probably the hardest kind of cut to make, the least useful, the easiest to screw up, the slowest, and has more things that can go wrong with it. All of that combines to make it more dangerous. A random guy hunting youtube for "how to fell a tree" needs to stay away from this video, not because you did it wrong, but because he will do it wrong and there are other better, easier ways to fell a tree that are harder to screw up. It is a complicated and time consuming cut and it is a mystery why anyone really needs to cut this way. It is hard to imagine a case in which this kind of cut is the best way to get a tree down.
- One thing to watch for is how high you cut it, up near breast height. That just makes it fall farther, giving it more airtime to twist, and more damage at the landing.
Aside from the complexity of it, the tongue and groove cut takes up a lot of vertical space on the tree. This means it falls farther. The longer the fall, the more time it has to twist. The vertical space also takes away useful lumber (if you are cutting for lumber) and also makes it more likely to slam to the ground and crack (again, that is wasteful if you are cutting for lumber).
A humboldt cut will make the base of the trunk slide down and hit the ground first, which usually anchors it and prevents some amount of twisting. It also tends to protect the tree from splintering or cracking which is important if you are cutting for lumber. Cut it as low to the ground as you can, and you avoid the hard landing, and you anchor it quickly, before the rest of it has time to twist.
A traditional face cut is fine too, but it will tend to "belly flop" and freefall flat, hitting the ground all at once. This means it has a longer hangtime to twist, and more likely to crack apart when it slams down.
This tongue and groove cut in the video was all the way up at breast height. That height, combined with the extra vertical space that the cut uses, combined with the steep hill meant that the tree essentially jumped forward several feet (which is evident in the video) and crashed. On a steep grade this kind of jumping is inevitable, but cutting a tongue and groove up at breast height certainly made it worse. A humboldt low to the ground would have been effective here. It is rare that you need much else beyond the humboldt cut and the traditional face cut.
Guilty of Treeson made a great video several years ago with Jed Walters (RIP) about several cutting methods, but traditional face cuts and humboldts are going to solve probably 99% of your felling problems. Here is their video -
3
