Listening for decay

[David Humphries]

According to Weber and Mattheck in Manual of Wood Decays, one of the disadvantages of the resistograph is that 'only advanced white rots give reductions in drilling resistance'. If the fungus is indeed Rigidoporous ulmarius, according to the AA guide 'Fungi on Trees' it is a brown heartwood rotter (and so is leaving the cellulose intact at least initially or until another secondary decay makes its presence felt). Is this a possible part explanation for the odd readings particularly the first one?

I just noticed as well that Weber etc. sugggests another disadvantage, that tension wood shows increased resistance to drilling, as does early stage white rot.

 

Hello Jules,

 

 

like you, I'm not what I would describe as an 'expert' on the use & interpretation of Resistographs, but I am building a knowledge of different decays and how the drill copes with these through using one out in the field where I can.

 

We've carried out maybe 3 - 400 drills so far on various types of decay including brown, white & soft rot.

 

I can say that brown rot can be detected by resistographing.

 

Here on oak with Laetiporus sulphureusIt kind of says what it does on the tin, ime

 

The references are ofcourse invaluable, but interpretation of scenario & situation really only comes from time in the field, no?

That's how I see things.

 

Thanks for your imput.

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[daltontrees]

David, thanks for the very helpful response. I just noticed in my last posting that I said cellulose instead of lignin. Doh! I hope you got the point, though.

 

You can't argue with a reading taken parallel to a cut that confirms the decay. Laetiporus sulphureus being a brown rotter too. Very very clear. I want one of those gizmos!

 

So back to Weber etc. having looked more closely as I should have the first time it says that one of the advantages if resistance drilling is 'good identification of dangerous brittle wood viz. a steep drop with brown rot'. So, the reference I quoted about white rot namely 'only advanced white rots give reductions in drilling resistance' should be taken to mean 'of the white rots, only advanced ones give reductions...'.

It all leaves my amateur theory in tatters apart from the shred of dignity that I might salvage from my tension wood thought.

So, as I think you said earlier to someone, it's not about this tree but whether hammering would match up to invasive investigation. It looked to me that apart from the anomaly on the east reading your sketch looked to be about right relative to the resistograph readings.

Thanks again for your reply. I have learned quite a bit from this.

[Pete Bannister]

I'm interested in this tread, not because I have any expertise in the field of living wood but I do have experience in testing 'dead' timber structures for decay. We use decay detection most days of the week and have done for decades. However, I remain a fan of hammer testing or 'percussion auscultation’ ( if you want to be paid more for it! ) ever since I tested my own accuracy at interpreting hammer soundings on insitu timber beams (circa 300 x 200 and 400x 400) against decay detection drilling. We found that hammer sounding interpretation was at less than 10% variance of the drill detection. In total we tested 7000 linear metres of timber. All P. sylvestris as I recall and decay would all be by brown rots

[David Humphries]

I'm interested in this tread, not because I have any expertise in the field of living wood but I do have experience in testing 'dead' timber structures for decay. We use decay detection most days of the week and have done for decades. However, I remain a fan of hammer testing or 'percussion auscultation’ ( if you want to be paid more for it! ) ever since I tested my own accuracy at interpreting hammer soundings on insitu timber beams (circa 300 x 200 and 400x 400) against decay detection drilling. We found that hammer sounding interpretation was at less than 10% variance of the drill detection. In total we tested 7000 linear metres of timber. All P. sylvestris as I recall and decay would all be by brown rots

 

Fancy name

 

Clients must be impressed

 

win, win, with it being as accurate & a lot less time consuming I'd imagine.

 

What type of hammer would you use for this, Pete?

 

 

 

 

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[Pete Bannister]

You mean ...Impressed that I can say it.. me too!

I should say that, in my field, this is a technique to apply to find the extent of decay when you know that decay is present. I wouldn't advocate it as a primary decay detection technique.

The type of hammer is entirely dependent on the material being tested and, critically the ergonomics of the situation. Ive used all sorts of tools and have made up a specific tool on more than one occasion. Size, shape and heft range from an engineer's screwdriver (which is always in the pocket of my overalls) through wood mallets, steel hammers, nylon and dead- blow mallets for aesthetically or surface sensitive stuff. I have a particular steel wrecking bar that is better than just about anything else in many overhead applications (ergonomics I guess). Ive tried many others and they dont come close to this particular one for some reason. If Ive learned anything about the technique its that the 'hammer' needs to be 'tuned' with the tested object/structure. So, trying a range of sizes, weights and balances is necessary for the useful results. Ive used a dead-blow mallet on the sensitive decorative surfaces of carved oak beams and found that an engineer's large screwdriver held against the surface of the timber and your scull near to the ear to pick up the resonation works OK but was very awkward to apply.

Estwing Deadblow Hammers

 

Anyone have experience of the technique on thick barked trees?

[Craobh]

This is an extremely interesting thread and you guys really know your stuff. I'm not an arb guy but it is a very important thing to look for decay and to "sound a tree" I guess I might do the sounding etc for different reasons but none the less it is an important thing for me to do from a safety angle.

 

 

This kind of thread although technical in it's content should be brought to the attention of all folks that are going to work with trees in what ever capacity. I have seen and been on the end of trees that looked sound etc then when (ok in my case it is falling them or climbing them to top out for lift lines) the cuts go in things don't go according to plan or when climbing the tree moves or tips (I've made light of saying oh ya become a real believer or I become a tree hugger real quick when this happens but none the less it a very unpleasant experience.

 

 

I know that pro guys are trained over here (stateside to) timber fallers usually get the full instruction in 5 mins and it involves don't cut your flip line and try not to fall and Do not break the saw, you'll learn when to run. However all that said I do feel that for some folks that will read and dip into this forum that aren't pro's and don't want to or can't for what ever reason do any of the courses but still want to cut wood etc (may be for firewood) (there are I'm sure folks in this country that do do things themselves) attention may be should be drawn to this thread or another simplified version to make them aware that it is very good practice and conducive to their own well being that they do check for soundness before doing anything. As has been pointed out in a very good and professional way in this thread that just because a tree looks well it may not be

 

 

 

Sorry if I haven't put across well what I mean but what you raise here is important in fact very important

 

 

 

Thanks for a very good thread

[daltontrees]

I have for a long time put my ear to the bark before hitting with the hammer. Sometimes this is because I am surveying roadside and it is noisy, but sometimes because (if the bark is smooth enough to get a comfortable close contact of ear to tree) you can gauge quite a lot. I find myself having to close my eyes and clear my mind for a few seconds and tune in, before hitting the tree at all. This is not some sort of hippy thing, I think you really have to try and cut out all other sounds and listen to reverberations and tone.

I like to think that the human brain (though not necessarily mine) is capable of assessing the state of the innards of a tree in almost exactly the same way as a sonic tomograph, taking several soundings around the tree and mapping out the likely cavity and/or decay. The tomograph has the upper hand though, it doesn't have to contend with rough bark and can remember forever what it has heard after only one hit wth the hammer.

On the other hand, as the experiment on this thread and the experience of a few people shows, decent results should be possible with a hammer, for a fraction of the price (nylon hammer £10, cost per use till it is worn out £0.001 per tree, compared to picus sonic tomograph, going rate maybe £100 per tree).

[Pete Bannister]

Good points Jules,

[treeseer]

... I find myself having to close my eyes and clear my mind for a few seconds and tune in, before hitting the tree at all. This is not some sort of hippy thing, I think you really have to try and cut out all other sounds and listen to reverberations and tone....

 

 

for those keen to avoiding anything newagey, this clearing process could be likened to recalibrating the internal auditory mechanism.

 

A similar clearing/calming process is useful when wrapping one's bare hands around a branch, to discern signs of dormant buds and other natural targets for pruning.

[David Humphries]

Matt Baker on Countryfile just now, up a tree in Westonbirt with an Arb looking at a tiered bracket and ' listening' to the decay inside with a soft faced hammer

 

 

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