Just when you think you're at the top of your game...

[bill]

how long is the lowering rope?

[MasterBlaster]

Long!

[Graeme McMahon]

Thanks for the interest in a special removal in Tasmainia. There have been some valid comments made regarding methodology and logic used in the removal at Tahune. I don't believe you could write a manual on "how to climb and remove", in that situation. People looking for such material to be set down into a checklist will be disappointed.

 

One underlying concept when removing difficult trees is that the thin grey line between success and failure can vary depending on how attuned you are to “input” and the skills of the crew.

 

I had no option for a high natural tie in. If we had bulldozed a track into the site and set up a very large crane and basket, it would have ruined the atmosphere of the forest that we were trying to preserve and its position would have prevented lowering/throwing bits. The option for a heavy lift helicopter was considered. In hind sight it would not have been successful as the rotor wash would have almost certainly damaged vegetation or the tree being removed. Lifting sections off had a high probability of breaking at the point of lift or pulling off a much larger section than anticipated because of the unreliable wood quality.

 

The tree was in a bad state. With only 12% of sound wood holding it up on the compression side, huge defect through its length and fractured rotten top half, removing the top did set me at ease a little but pulling sections off also had to be performed carefully. With the back lean each section required a significant pull. That pull was inefficient with its angle and flexed the trunk. When the section released the trunk recoiled downhill and was arrested by the stablisers. Because of the anchor limitations, the section had to be felled close to the stablisers. While the pressure of work was reduced it was not over until it was over.

 

I used a new type of stablisers and monitoring system to give me more insight into the tree security. The "dyneema" lines supplied by Donaghys ropes were highly suited to the task. 14mm gave about 23 ton (max break) 12mm, about 18ton (max break). These were the support lines for the trees mass and were positioned at points up the trunk. With about 1% elongation at break, when the lines were tight there was essentially no more give at that point. In addition they were very light to handle.

 

When I inspected the tree at the time of the quote, I did not climb any higher than about half way. I felt quite unsafe. It was at the end of day 2 that I actually reached the top of the tree. Special credit to Daniel Kelly who ran the ground operations with only one assistant. An extremely competent climber in his own right with empathy for my situation meant that he was lumbered with the responsibility of organising the ground operations.

 

Regards

 

Graeme McMahon

[MasterBlaster]

Awesome job, but I think "ruining the atmosphere of the forest" is preferable over having a dead climber.

 

But you were the one there, not me.

[Pete Mctree]

 

I used a new type of stablisers and monitoring system to give me more insight into the tree security.

 

Did the stabilisers have any dynamic properties? As the dyneema does not i wondered if there was an issue with bringing the stem to an abrupt halt after removing or rigging a piece, or if the natural flex of the timber absorbed some of the force?

[Old Monkey]

I am curious as to what kind of jobs Graeme says no to?

[Graeme McMahon]

The primary stabiliser had a dynamometer installed to indicate the inline tension. By preloading the line the effects of ascending the tree, removing bits and resting could be observed. The fine adjustment of the second stabiliser could be observed with a steady decline in tension of the primary. Anything but a steady decline would be change caused at one of the many defects between the two. That insight spoke volumes when progressing up the trunk.

 

The stabilisers need to have very low elongation to be effective. The low elongation also assisted when arresting the recoil of the trunk. My assumption was that there would not be much more flexing in the trunk or stump before it could fail. To allow the trunk to recoil any further than when I started to interfere, was to risk entering that zone.

 

Regards

 

Graeme McMahon

[Graeme McMahon]

Old Monkey

 

I have worked in the Dandenong Ranges for over 30 years. On the world scale I have seen little to come close to it regarding large problem trees. The daily grind prepares you for a different set of drafting gates. Many years ago I was often called "dirty Harry". (dirty rotten job,he'll do it)

 

To answer your question, I suppose I don't say "no", just "lets find another way".

 

Regards

 

Graeme McMahon

[A_lopa]

Yes when there is NO one else its a Graeme tree.

 

Nice job Graeme i think i could roughly guess your rate by the ' or maybe not!

[High Scale]

I am just watching it again, love those shots that pan back, shows how silly high that tree was.