Thursday, January 19, 2017

Sixty Feet and 7000 Pounds of Bad Altitude!

The tree shown in the center of the photo is a sixty foot tall Silver (aka Soft) Maple.  It is 18"-to-20" in diameter.  It double-trunks at about 12 feet.

We had been cutting for about three hours when we got to this tree.

It scared us.

As seen from the south, looking north at the tree.
The trunk has a vertical crack that spirals a quarter turn around the trunk.  The crack is visible on both sides of the trunk and it clearly starts at the narrow crotch where the tree double-trunks.

The tree leans about five degrees in the direction of the prevailing wind...leaning to the east-northeast.

Our original thought was to cut it when the wind was blowing in the direction we wanted it to fall.  On rethinking this, this might be a bad idea.  The amount of potential energy increases with the wind speed as the bowing due to the wind adds to the flexing caused by the growth not being perpendicular to the ground.

Trees that lean have lots of potential energy.  In this case, it is easy to think of them as a loaded diving board.  The black circle is the pivot and the green pac-man is where the fixed end is pinned down.

In the case of our scary tree, the crotch is the round, black pivot and the cut would be the green pac-man that un-dogs.  The blue arrows are the velocity vector.  The smiling face becomes unhappy.  The twisting crack makes the direction of the springback unpredictable.
The tree species matters.
The grain of some species interlaces and it takes a lot of energy to cause it to split.  Just ask anybody who split a full cord of elm.

This is similar to how some seat belts and fall harnesses absorb energy.  They are engineered to have the stitching tear out.

Other tree species split like a dream.  Soft Maple falls into that category.  There is no controlled release of energy...it is like the pac-man un-dogging.  BAM!

I am very open to suggestions from my readers.

There are two serious proposals on the table.  One of the proposals involves Tannerite.

The other proposal involves wrapping the trunk with about four turns of a yellow, 4" wide 20,000 pound ratchet strap and snugging it down as much as we can.  The ratchet strap would be just a bit above where we will make the cut.

Either method ought to keep the smiley face smiling.

1 comment:

  1. Not a clue from this end... That's a forester question or a logger!

    ReplyDelete