"Nature, to be commanded, must be obeyed" -Sir Francis Bacon
My cartoon imagery i visualize as i invoke these mechanix:
The direction of the pulling force of gravity is down; everything is in relationship to this force. i assume we are talking about more horizontal limbs, that are more leveraged weight against the vertical gravity force.
Cutting super fast on small light piece with chainsaw can give instantaneous release so quick it can't rip in right circumstance of speed/ power vs. uncut limb size and leverage.
Cutting straight down places width as more leverage to resist across pulls. But cutting s-lightly across places more of a vertical column of hinge at finish, this has more resistance against vertical axis pulls; that gravity pulls down on. At the hair line where the size of the branch begins to exceed vertical cut strategy's non-rip; can sprinkle in more previously mentioned speed factor; to avoid rip for another range of increasing size/ leveraged branch.
No undercut allows the tension and compression to get real close for no leverage before tearoff, and connected compression tissue to cause rip. The distance betwixt compression and tension is the amount of leveraged multiplier the tension has to support limb. Less multiplier, more tensioned force for same work of support.
Undercutting, allows the gravity direction force to pinch the undercut close, giving push up of support. The outside closes first, and then there is leverage from that pivot to the top of the backcut. The compression pivot (pushes together on own) does not have to be connected, but the upper tension must be connected(is trying to pull apart). So, if we make a deeper undercut, this spreads the pivot of the outside, lower circumference at close farther from the connected piece where mechanix can take a larger amount of leverage before tearoff at end of connection. This places less tension on the connected hold right before tearoff, so there is more of an instantaneous release; more likely to go straight down. The sudden drop, and disconnected tension tissue allow for less chance of rip.
Dan does it write, cutting off leveraged end for less tension/ chance of rip on finishing cut. Alternatively, we can reduce leverage greatly, by cutting down or across a little distance from finishing cut, then follow other pro-cedures with less leveraged load from same branch trying to rip cut!
If the CG of branch is off to side, favour undercutting more to that side, for more support; then back cutting, close this side first to give more pushup; and trigger release from other side with backcut.
i think a curved blade on down or across cut allows more shoulder to be put into it; as shoulder is at angle lower angle then cutting part of blade, but makes it harder on undercutting; as same mechanix now stands against ye.
Orrrr sometin'like that
