Fibre buckling or constriction - Opinions Please

[Tony Croft aka hamadryad]

I agree VTA is a pretty good system for inspecting trees and so mforth. But please rmember that its primamry use in Britain just now is to decide if a tree passes or fails the foreseeability of failure test, even though it is really aimed at going beyond that nad estimating the remaining strength when a defect is confirmed.

 

I'm going to state the blimmin' obvious (again) and say that t/R rtios and Wagener ratios are nit statements or mechanisms for stating whether failure is foreseeable. They are at best thresholds for when you need to start thinking about the foreseeabiltiy of failure.

 

And I'm going to stick my neck out and say that it will never be possible to create a direct and reliable link (and I mean mathematically) between extent of hollowness and relative likelihood of failure. It doesn't mean we shouldn't try. It definitely doesn't mean we shouldn't have a bit of harmless fun speculating in even the most unscientific of ways. But if the t/R ratio could speak, like Mark Twain it might say " Reports of my death are greatly exaggerated". It's a tool, an amber light, a twinge that sends us to the doctor to catch a disease while it's cureable.

 

One other crass quote, but one that I have always liked. "Rules are there for the guidance of the wise and the absolute adherence of fools". VTA sits in my VTA toolbox beside the binoculars, magnifying glass, increment borer and my common sense.

 

One never suggested it should be applied with dogma, and even Claus would agree with all the above, it is just probability (T/r ratio) of failure takes a rapid upturn on the charts, FOR FULL CROWNED and un-retrenched trees.

 

And that is an indisputable fact.

 

Claus is one of the best teachers I've ever had the good fortune to learn from, both from his books and in person, and I've looked at it all with vigour out in the field, and agree with all of his conclusions on the mechanics of trees.

 

he also simplified it enough for my puny mind to comprehend a matter of great complexity, while all others talk in riddles and mathematical flannel.

 

Some accuse me of taking it almost personally on Claus's behalf when people take the science to task, and I guess there is an element of truth in that, but its more to do with Claus's work being of sound modeling and self evident with field study.

 

The thing I like most is his attitude to the debate, not to let it vex him or concern him, simply let the market choose, you pays your money and takes your choices. You gotta respect that, its confidence, not ego that drives that man.

[daltontrees]

One never suggested it should be applied with dogma, and even Claus would agree with all the above, it is just probability (T/r ratio) of failure takes a rapid upturn on the charts, FOR FULL CROWNED and un-retrenched trees.

 

And that is an indisputable fact.

 

Claus is one of the best teachers I've ever had the good fortune to learn from, both from his books and in person, and I've looked at it all with vigour out in the field, and agree with all of his conclusions on the mechanics of trees.

 

he also simplified it enough for my puny mind to comprehend a matter of great complexity, while all others talk in riddles and mathematical flannel.

 

Some accuse me of taking it almost personally on Claus's behalf when people take the science to task, and I guess there is an element of truth in that, but its more to do with Claus's work being of sound modeling and self evident with field study.

 

The thing I like most is his attitude to the debate, not to let it vex him or concern him, simply let the market choose, you pays your money and takes your choices. You gotta respect that, its confidence, not ego that drives that man.

 

I would have said to his credit that it's evidence rather than speculation that drives him.

 

And of course I meant to say that "t/R sits in my VTA toolbox..." etc.

[Gary Prentice]

It's looking likely that this tree is going to be removed shortly - due to reasons other than its condition.

 

So, given the opportunity to investigate the causes of the adaptions etc, how should it be cut and what sections need to be taken. I'm thinking that I might try to get some microscopic cell sections made from thr buckled area etc.

 

Suggestions please, before it becomes firewood.

[treeseer]

I'm thinking that I might try to get some microscopic cell sections ...

 

Great--cut lengthwise and smooth the surface. Would love to see that!

[treeseer]

t/R fell out of my toolbox; there wasn't room for it after incorporating this:

Wessolly How hollow may a tree be.pdf

[daltontrees]

t/R fell out of my toolbox; there wasn't room for it after incorporating this:

 

That was a hard read. Seems to have lost something in the translation from German. But as a piece of science it's badly flawed, so much so that by half way through I had given up on its credibility. A few good points though but just food for thought rather than proof of anything. Looks like an elaborate sales pitch for Elastometers.

 

So the SIA inexpensively gives the required wall thickness in 5 minutes. After climbing the tree, attaching wireless inclinometer sensors and a winch cable and then loading the winch. That might not be so quick. Or inexpensive. And will probably reliably estimate just how much force would be required to winch the tree over or snap it.

 

For me the t/R rait has about one useful purpose - if it is above 0.3 I am not going to be looking for much more evidence that failure is foreseeable. Trying to relate t/R to probability of failure above the 'foreseeable' threshold is just pointless.

[daltontrees]

It's looking likely that this tree is going to be removed shortly - due to reasons other than its condition.

 

So, given the opportunity to investigate the causes of the adaptions etc, how should it be cut and what sections need to be taken. I'm thinking that I might try to get some microscopic cell sections made from thr buckled area etc.

 

Suggestions please, before it becomes firewood.

 

Do it! Or tell me where it is and I'll do it.

 

The best thing would be to try and record as much info about the tree as possible before you touch it, particularly crown volume. I can give you some pinters on how to do this if you want.

 

But once you are taking the tree down it is essential to keep the sections properly referenced. I did this with a smallish hornbeam a couple of years ago and what turned out to be useful was this. As you disc down, every time you complete a horizontal cut put a simple orienteering compass on the cut face and mark (with permanent marker) the direction of north. Repeat until tree is gone. Ideally each disc should be referenced with tree height, but a sequential numbering suffices because it's easier to work out the height of the cut face afterwards by adding all the discs plus all the kerf widths on the ground. Rather than sequential numbering, up a tree I would write the time of cut on the disc.

 

As a minumum I was also taking a high quality digital photo of each disc section. If you do this from a tripod with a fixed distance between lens and face, it is possible to measure growth rings from the photos. Easier and quicker than it sounds. Ideally pin a ruler to the face for absolute scale.

 

Personally I am not sure it would be worth doing more than a coupe of thin sectons. Macroscopic sections might be most useful. I have been casually trying this this week with a fairly small piece of wood. Basically with a cut piece, preferably a radial section with a fairly flat face (a new hardpoint joinery saw works well), you get a big sheet of sandpaper on a table and you rub the face on it in a circular motion, then repeat with finer and finer sandpaper and in no time you will have a nicely polished face that can be examined with the naked eye or a hand lens/magnifying glass or USB microscope.

 

Staining will show up the growth rings and any other differential growth rates that might be a result of microscopic buckling.

 

And I bet we're all wrong about this tree, it will end up being something none of us thought of.