Wednesday, February 2, 2011

Throwing Your 800 Pound Gorilla

We looked at height measurement and evaluating lean of trees you plan to fall in previous posts; this time we will be figuring whether or not we can push a tree where we want it with wedges, and giving you some useful numbers that are easy to remember, and to use in the woods.  I like to measure the diameter early in the process of sizing up a tree, because the diameter guides your design of the hinge.  This tree measures 38" diameter at breast height (4' 6" above the ground), and the hinge should be 80% of that in length, or 30".  The thickness of the hinge can be up to 10% of the diameter, but 4" of wood is a lot to bend, so let's figure on a hinge no more than three inches thick.
We are checking the height of the tree here.  Charlie is standing at one chain (66'), where you would use the Biltmore stick to measure merchantable height.  I found the spot where my stick showed that I was away from the tree the same distance as the height, and paced in 125'.  That's a tall pin oak!
We decided where we want the hinge, and measured across that spot to see how a 30" long hinge would fit, measured back 3" for the thickness, and then measured to the back of the tree, where we would pound in the wedges.  We had 30" between the back of the hinge and the wedging point, so we break the tree down into 30" segments.  If we raise the back of a 30" segment 1", the opposite corner will move forward one inch.  The far corner of the next 30" segment will move forward 2"; and so on.  This tree is 125' tall, or 1500".  Divide 1500" by 30", and you have a 50 segment tree.  This means that each inch you raise the back of the bottom segment will move the top of the tree 50", or just over 4'.  The crown and weight of this tree appears to be no more than 1 foot behind the stem, so this tree can easily be wedged over against its lean by driving in a set of parallel wedges that are 1" thick.  This one was just for practice; now we will drop one.
We are standing at the aiming spot for a black oak snag, and this spot was chosen because there is no side lean from this vantage point, and there is a relatively clear spot for this tree to fall into.  A quick measurement and pacing in showed this tree to be 50' tall.
Viewing the snag from 90 degrees around, we see that this tree has quite a bit of back lean.  Check the lines added to show where the top is, and you can see that we had about 5' of back lean to overcome.  We checked our segment size next.
From the back of the hinge to the wedging point we had 9".    Nine goes into 600" 67 times, so we have a tree that is close to 70 segments.  Raising the bottom segment 1" will move the top of the tree between 5 and 6 feet, so this looks do-able, but you also need to know some practical limits to guide you before you start cutting.  The numbers you should remember are these:  For a 50 segment tree, you may be able to handle up to 10' of back lean, if the wood is strong, you have built the hinge right, and you feel like pounding parallel wedges until you are blue in the face. 60 segments, 8'; seventy segments, 6'; 80 segments, 4'.  As trees are taller and thinner, you can handle less back lean; as they are shorter and stouter, you can handle more back lean.  These numbers are not absolutes, and it is not much fun pounding wedges on trees that are at the limit, so don't push your luck.  The larger value that you will gain from these numbers is in evaluating side lean.  The hinge you build into a tree with back lean is holding all the way across, and has plenty of strength if you make it right.  Side lean, however is pulling on only one half of the hinge, and compressing the other side; plus, the tension is not evenly distributed, being much stronger on the outside of the hinge.  This means that the limits on side lean are somewhat less than 1/2 of the limits for back lean.  Practice the evaluation process several times before you put it into use, until it becomes second nature to you, and never push your luck around high value targets.
We have raised the back of the tree not quite an inch, and the hinge is handling the stress just fine.

The stem is nearly vertical at this point in the process.  The problem you will find frequently with small trees is the lack of space in the stump to work.  The wedges have run into the back of the hinge, so we had to stack two wedges to bring the tree over.
Cross your wedges when you stack them and they will not jump out when you pound on them.

All done.

Practice your measurements, and practice your cuts on trees that don't have any big problems or risks.  If you want to test your limits on trees, do it on ones that can't fall on anything of value; and that includes you!


strandediniowa said...

In Williamsburg, IA, a man lost his life felling a tree today. No details on how.

I know one of your first rules is safety, but do keep it safe, Sam.

David aka True Blue Sam said...

Thanks, Stranded; I will be cutting firewood again this weekend. I just read about the fatality on KCRGTVNEWs, and my imagination is running on how this may have happened. He was probably working in snow, so he couldn't move away from the tree easily; Right of Way trees are usually heavily weighted on one side, which can cause trouble if one is not trained properly; and etc. The fellow was only 33 years old; it's a horrible tragedy.

Trees that are weighted heavily can really hurt you if don't know how to prevent barberchairs. The black oak snag in this post was near the limit to wedge over, which means that it would have easily made a barberchair if it was cut improperly to fall the way it was leaning. Guns are so much safer than saws. I would rather spend my time plinking this weekend, but we need the heat.

Thanks for keeping us up to date on the carry hysteria in Iowa. The ignorance of the phobic public officials is absolutely astounding.

strandediniowa said...

Too many questions on how it happened, but everything points to a tragic death of a young man.

The barberchair sounds exactly how my dad's neighbor lost his leg on the last tree he wanted to cut that day. It kicked back on him and he didn't react fast enough.

I've been wondering if my readers were getting sick of my hoplophobe posts. There have been been quite a few.

Stay warm, Sam. I hope Bea dug out from the latest snow. We are still moving snow.

David aka True Blue Sam said...

Bea can get out of her house tomorrow! She had drifts up against every door and had to wait for her snow to be moved.

Keep those hoplophobe posts coming!