Decay images

[Jake Andrews]

 

We didn't measure the actual t/R in relation to the trunk diameter as it was a reduced tree, but if your interested we could revisit the site on passing and get that for you?

 

 

 

.

 

I would be interested in the t/R ratio David, even though it's not a full crown tree. The hardiness of the decay barriers is also a interesting observation. Have you noticed that before when drilling trees? Would you say that's a limitation of the PD400 or the other drills?

 

Jake Andrews

[David Humphries]

Difficult to say for sure if we've noticed it before Jake, as when the needle has retracted early on previous drills (on trees we haven't felled) we've taken it as either hitting an internal crack or a foreign object like stone/nail etc.

 

I'm not sure its a limitation of the dril but it's something we're possibly going discuss with IML.

 

It didn't come up during an IML masterclass at Kew last year.

 

 

Perhaps just an odd set of circumstances.

 

.

[Nick Connell]

Hi David,

 

On my PD 400 I've turned off the auto retract setting sometimes for the same reason as when it hits a small cavity or low resistance it withdraws to not bend the needle after around 5cm of reduced resistance. Have you tried that before?

[sloth]

Interesting, thank you. There are always so many variables when dealing with these big green leafy things!

[Gary Prentice]

As we don't run commercially the access for the public is managed but rarely blocked completely.

There were 4/5 signs out and barrier tape on one of the paths.

We had our new Arb who started this week taking the top down before we felled the trunk, so we're using the job as a calibration exercise for both the climber and the existing team to tune in on efficiency and communication.

 

I don't doubt that the job was safely managed, sorry my attempt at humour didn't travel well

We didn't measure the actual t/R in relation to the trunk diameter as it was a reduced tree, but if your interested we could revisit the site on passing and get that for you?

 

 

 

.

 

I'd been explaining the T/r (t/R?) ratio to a (risk averse) client with a cavity/hollowing tree earlier and was just thinking how the pictures demonstrate how 'safe' the 0.3 ratio is. (Acknowledging the reduced canopy in this instance)

 

Don't go back on my account.

[David Humphries]

Hi David,

 

On my PD 400 I've turned off the auto retract setting sometimes for the same reason as when it hits a small cavity or low resistance it withdraws to not bend the needle after around 5cm of reduced resistance. Have you tried that before?

 

 

Hello Nick,

Thanks for the advice.

Had seen that the auto retract could be changed but hadn't actually tried that, so now have that as another useful Resi tip.

 

So where the needle was retracting after (the factory set) 5cm of reduced resistance through the very spongy resinaceum decay, we reset the auto retract to 15cm and the needle pushed through the barrier between the resinaceum and australe decay and beyond.

 

 

 

 

the above graphs have been flipped around (from being read r-l to l-r) to match up with the image above them.

 

 

 

.

Edited March 9, 2017 by David Humphries

[David Humphries]

........Have you measured the actual t/r on that? It would have been interesting, in a less target rich environment, to have it continue to failure.

 

 

I would be interested in the t/R ratio David, even though it's not a full crown tree

 

We were driving past today so stopped and took a diameter reading.

 

 

The stem is 71cm at the point of where the drills were taken.

 

This makes the radius 35.5cm

 

Focussing on the compression side of the tree (directly under the lean, toward south) and based on the resistograph measurements, the thickness of the remain residual wall was 4cm, this makes the t/R at this point 11%

 

 

On the tension side of the tree the thickness of the remain residual wall was 10cm, which makes the t/R of that side 28%

 

So both sides of the tree had remaining residual wall thickness below a 3rd, but not forgetting this tree having been significantly reduced in the past.

 

 

I'm fairly confident this tree could have been left standing longer with further reduction, but habitat value and aesthetics would have deminished.

 

 

 

.

[Gary Prentice]

Thanks a lot David, every day is a school day:thumbup1:

[David Humphries]

For us also, the dialogue presents questions, and the questions make this job the more interesting

 

 

 

 

.

[Jake Andrews]

Thanks David. Very interesting indeed. 11% on the compression side of the stem is not a lot but as you say has been heavily reduced. All we need now is for someone to do a PhD on the t/R ratio of reduced trees and come up with a new safety margin. I'm not putting my hand up though😉

 

Jake Andrews