In this drawing as the one with the higher back cut gets pushed backwards, in my undrstanding the wood, at the top of the yellow arrows acts as a fulcrum multiplying the upwards pulling forces on the hinge wood. Think if you set a block of wood, or some shims at the front of your face notch. when the log hits that it multiplies the force, the hinge wood pulls out and the tree falls. That step from the higher back cut does the same thing I think.
Looking at the second example, I believe that piece of wood coming off the bottom of the spar thats sits down on the back cut actually holds the tree much better.
That's a very intersting observation.. if indeed true.. wouldn't matter 99+% of the time, but the one time you do need it.. you NEED IT! the reason I always put the step cut below the hinge is not for more control or leverage, it is simply pragmatic in making 1/2 the backcut flush to the ground, while keeping the hinge wood above the trunk flare. That makes for a little less cutting overall, and turns the flush cut on the stump into a half round, which is easier to handle, and often just gets chipped. That makes a lot of sense in a suburban setting, but would have nearly no value in the woods.
It was only after using it to make the disposal of the flush cut easier, that I saw how much holding control it offered, and used that to great advantage in other situations..
Using the step cut gives the faller the ability to set the hinge to his liking, then adjust the placement (forward or rear) and differential height of the snap cut to give as much additional holding power as desired.. Its a lot easier to figure that, than to figure how much more wood to leave on the hinge. Most fallers are pretty particular about their hinges, and there are situations where a fat hinge isn't desireable.. Too fat and you're gonna BBchair the tree, whereas with the step cut the chances of splitting the trunk before step are miniscule.
I rarely stand at the stump these days. most falls do not use the step cut.. just set the hinge , walk away and wave for the pull.. rarely needed, but good to have when needed. On the other hand, I have enough expereince with the step cut to have trusted my life to it on occasion. A couple times the only good DZ for a big top was right where the bucket was parked.. dead oak... some wind... That's saying something...
