Topping Fail

[Daniël Bos]

Are you trying to say that a 1/3 us the same as 80%?

 

Think he is... 'cos it is:biggrin:

1/3 of the tree roughly equals the point where it's at 80% of the diameter:001_cool:

[David Goss]

Who was taught 1/3 for the gob? When I did mine I was told 1/5 to 1/4 for the gob and the hinge should be 1/10 the diameter. Basic felling numbers in textbook situations which are rare.

Anyway it's obvious what the guy did wrong... He tried to take too much and didn't have a decent hinge... end of!

[Paul Jenks]

If one cuts a gob 1/3 of the way into the tree the actual width at the back of the cut is95.8% of the diameter.

If one cuts 1/4 of the way into the tree the actual width at the back of the cut is 88% of the diameter

If one cuts 1/5 of the way into the tree the width at the back of the cut is 80% of the diameter.

Hence we are taught to cut 1/5 to 1/4 of the way into the tree for the gob as, allowing for the depth of the hinge, (patently missing in the example we are debating), the width at the back of the hinge should be 85 and 95% of the width of the tree.

To cut any further into the tree may de-stabilise the structure prior to the felling or back cut being started and during the first phase of the back cut for very little gain in hinge width.

To cut 1/4 to 1/5 into the tree as opposed to 1/3 gives a significantly better moment when using wedges or a jack, which, I think is an appropriate way to tip over a tree in confined space in a controlled way.

FYI I prefer g-strings not panties and if the knot is in the right place it's quite nice.:001_tt2:

[skyhuck]

If one cuts a gob 1/3 of the way into the tree the actual width at the back of the cut is95.8% of the diameter.

If one cuts 1/4 of the way into the tree the actual width at the back of the cut is 88% of the diameter

If one cuts 1/5 of the way into the tree the width at the back of the cut is 80% of the diameter.

Hence we are taught to cut 1/5 to 1/4 of the way into the tree for the gob as, allowing for the depth of the hinge, (patently missing in the example we are debating), the width at the back of the hinge should be 85 and 95% of the width of the tree.

To cut any further into the tree may de-stabilise the structure prior to the felling or back cut being started and during the first phase of the back cut for very little gain in hinge width.

To cut 1/4 to 1/5 into the tree as opposed to 1/3 gives a significantly better moment when using wedges or a jack, which, I think is an appropriate way to tip over a tree in confined space in a controlled way.

:

 

But that has no significance what so ever in this situation, as a pulling rope was being used, not wedges.

 

I think Dadio was correct, the gob was fine and could have been bigger without causing a problem, as he said the hinge and lack of pull were the problems.

 

I often do gobs up to 50% and more on occasions, but I rarely use wedges.

[Paul Jenks]

Of course it has significance. In this instance he should have cut a smaller gob to allow for a thicker hinge, not wider, as the tree diameter is quite small. The guys pulling it would have had more chance of getting some movement in the section prior to it actually breaking the hinge.

As you can see from the calculations I posted a smaller gob, (i.e. depth into tree), doesn't appreciably reduce the hinge width whilst still giving a good amount to actually act as a hinge. Cutting further into the tree gives all the operatives less room for error.

If the tree starts to fall, in the preferred direction, with a smaller gob, the cutter can accelerate his cutting to ensure a clean break as the gob faces meet. (It should be noted that a shallower gob might have been used to make it break and come down horizantally and he could have knicked below the hinge too.) With a larger gob there is less capacity for the cutter to react to the rate of fall and therefore the groundcrew to adapt their rate of pulling.

I too use all manner of gobs to acheive all manner of results. When it really counts, and I think that gobbing out a fairly large top into a fairly tight slot counts, I revert to basic principles.

 

To pick up on your point about the pulling rope. The pulling rope was installed. It wasn't being used. Had the cutter given himself more time and stability, by using a smaller gob, he might have been able to instruct his groundcrew a little more effectively prior to the tree giving way.

[Rob D]

To cut 1/4 to 1/5 into the tree as opposed to 1/3 gives a significantly better moment when using wedges or a jack, which, I think is an appropriate way to tip over a tree in confined space in a controlled way.

 

 

Ditto above which is what dadio was asking - and it's prob more relevant to working in the woods where you're felling several trees and avoids having to get a pull line set up.

[skyhuck]

Of course it has significance. In this instance he should have cut a smaller gob to allow for a thicker hinge, not wider, as the tree diameter is quite small. The guys pulling it would have had more chance of getting some movement in the section prior to it actually breaking the hinge.

As you can see from the calculations I posted a smaller gob, (i.e. depth into tree), doesn't appreciably reduce the hinge width whilst still giving a good amount to actually act as a hinge. Cutting further into the tree gives all the operatives less room for error.

If the tree starts to fall, in the preferred direction, with a smaller gob, the cutter can accelerate his cutting to ensure a clean break as the gob faces meet. (It should be noted that a shallower gob might have been used to make it break and come down horizantally and he could have knicked below the hinge too.) With a larger gob there is less capacity for the cutter to react to the rate of fall and therefore the groundcrew to adapt their rate of pulling.

I too use all manner of gobs to acheive all manner of results. When it really counts, and I think that gobbing out a fairly large top into a fairly tight slot counts, I revert to basic principles.

 

To pick up on your point about the pulling rope. The pulling rope was installed. It wasn't being used. Had the cutter given himself more time and stability, by using a smaller gob, he might have been able to instruct his groundcrew a little more effectively prior to the tree giving way.

 

surly the size of the back cut every bit as much influence on the size of the hinge as the gob, his hinge was to thin because his back cut was to deep.

 

Moving the hinge back (which is a fulcrum) makes pulling the top easier not harder.

 

The only advantage to a shallow gob is it allows the use of wedges, but I often find a larger gob means wedges are not needed.

[WoodED]

i was taght a 20% sink cut, and a 70% back cut leaving a 10% hinge

[dadio]

exactly and his back cut was too deep because (in part) it was too high.. a higher back cut requires more pull to trip. Also the angle of the pull line and amount of pull is critical such situations..

 

And its good to know that the brits understand A LOT more about the reasons for the depth of the hinge than do Americans.. I wasn't aware that the guidelines had been changed to 20-25% depth, which is plenty for the average fall IMO.. you can even go quite a bit less if there is no side weight, and you have sufficient pulling power in place..

[Paul Jenks]

You are correct, Skyhuck, moving the hinge back would make the centre of gravity easier to move over the hinge and therefore cause the section or tree to fall more easily. (An over centre gob is a good way to fell big wide monoliths.)

My point was and still is that a smaller gob would have allowed the cutter more time and control as he and his ground crew quite obviously haven't the skills of you and your crew.

 

In this instance I would not have used wedges, notwithstanding the rather tight slot into which he was attempting to get the section into and the narrow diameter of the stem.

You seem to me to be getting fixated by my mentioning wedges. I was using the example of wedges to demonstrate the leverage principle. If you didn't or don't understand this principle I apologise for not clarifying it in enough detail. I commonly use wedges on big and medium fells as I feel it gives a much more controlled operation. This is just my personal preference, possibly as a result of the huge amount of respect I had for the chap from Lantra who taught me some years ago.

Had you and your crew or, I dare say quite a few of the others on this site, cut such a gob as demonstrated in the video, I reckon the section would have fallen precisely where you wanted it. However, in the case in question, with the cutter and ground crew in question, I still maintain that the gob was too big and he was too greedy. If he'd cut a smaller gob he'd have had more time and more control.