daltontrees

Another one (no.2) for anyone wanting the practice.

Anyone that has passed one unit, say chainsaw maintenance and crosscutting can say they are NPTC qualified, because NPTC describe that as a 'qualification'. As I recall I got given a sticker when I passed it. I have gone on to get a few more, but I am still only qualified. It's the statement 'fully qualified' that I find irksome. Does it mean the person has every single NPTC certificate or would it be more honest to say 'adequately qualified' or 'appropriately qualified'? Can't see a sticker or marketing statement like that being as popular.

Aha! That's wher a schmidt hammer Schmidt hammer - Wikipedia, the free encyclopedia would come into its own. Fitted with different caps (nylon, wood, rubber).

Apologies. I said I didn't want to get into the wording of the law but I also see now that you quoted the Occupiers Liability Act 1957 but there is a different duty in the Scottish Act which is very similarly worded to the 1984 Act duty towards uninvited persons. For the benefit of other readers I shall do my best to quote it here "such care as in all the circumstances of the case is reasonable to see that the person will not suffer injury or damage by reason of any such danger [which is due to the state of the premises]"

Fair enough, you will want to mak your point to other readers. I get the point. With one caveat, I am curious as to the source of your statement of common law. I always found Leakey v National Trust nice and clear viz. "a duty to do that which is reasonable in all the circumstances, and no more than what, if anything is reasonable, to prevent or minimize the known risk of damage or injury to one’s neighbour or to his property".

I thought calcualtor can produce numbers like that, which QTRA then rounds them to 1 significant figure. Anyway it doesn't matter, this would only exacerbate the effect I was trying to illustrate but you have clarified that a precautionary approach for outcomes signalling the potential need for action. And presumably when investigating borderline cases QTRA woudl ahve to calculate exact figures adn ignore the final rounding if the detailed outcome is still borderline?

That is kind of what I expected you might say and answers the question. In effect QTRA allows the non-borderline trees to be eliminated easily leaving only the borderline ones to receive more time and detailed appraisal. That is a good thing as long as the surveyor knows to refine the iffy ones.

The broad principle as we now know is that HSE says that less than 1,1,000,000 is broadly acceptable, more than 1,10,000 is unacceptable and in between is 'tolerable' and should be reduced where it is practical to do so. My question was rather about what QTRA does when the quantified overall risk of death gives the all-clear for a tree but the risk of lesser harm is possibly still unacceptable.

As originally stated, I didn't want a debate ont eh exact wording, I merely wanted to differentiate between the thresholds of death and injury, which I expect are different for the same tree. The UKTC debate on probability etc. I felt was inconclusive, but I don't want to open it here again because I (and I anticipate others) take the general point that QTRA assigns some sort of figure to likelihood/probability/foreseeability of failure and by combin ing it with other factors a figure is arrived at to represent likelihood/probability/foreseeability of harm. So to clarify, my question had been about the thresholds.

I don't recall exactly what I said but I couldn't discuss specific cases where client confidentiality prevented it. I offered to discuss a tree where no confidentiuality exists. However, since then I expect readers will be more interested in learning about QTRA than about my methods, and if I have alluded to my methods it will be anecdotally to emphasise my point or to illustrate my question to a wider readership. So to answer your questions, you don't need to comment on my take on it, your respones to the questions are the important thing.

I nearly barfed laughing at 'Things Holly and I have argued about this week'. Excellent find.

Dismantled big Lime yesterday, soaked and tired when I got home. Fell asleep in front of telly at 8, woke up at 9 with the edge taken off tiredness. Showered and turned in at midnight. It took an hour of 'tree roots in the built enviroment' to get me to sleep again. Woke at 5, wide awake and mind whirring. I have been up ever since, and will hit a seroius dip about midday. Unfortunately this kind of broken sleep is quite usual for me. Infuriating.

TA, I shall get myself a couple of different weights and try them out. They can indeed be bought for little over a tenner.

At 45 deg I would definitely cut over then under and snap it off from above. An inbetweenical cut.

I see Sorbus sells the nylon ones for £27, they weigh just 1 lb. They also seem to be available elsewhere in 1/2 lb., 1 1/2 lb, 2 lb etc. Any recommendations on what size is best? My existing rubber mallet is about 2 1/2 lb. and anything less will not bring out the boom on a big tree.

Well put and point taken.

My techniques were described a little roughly, in practice I am not going round whacking trees like the guy in the Rank Films gong advert. By small trees I mean young ones that I suspect through strimming damage or frost splits are developoing decay from within. In a previous life I studied geology in some depth; in rock mechanics there is a tool which I think was called a Schmitt Hammer which delivered a fixed amount of energy to the hammer blow, the recoil could be used to assess the approximatee dgree of weathering of the rock. I have been trying to get a similar approach with sounding for tree decay. The boot technique involves putting a knee on the stem and swinging the boot from the same distance back. The contact is with the flat vibram front of the boot. Sometimes the reverberation through the knee is as telling as the sound from the contact. The client understands when I explain. I should get a nylon faced mallet for bigger trees. The choice of mallet is intuitive rather than of availability. The rubber one is quite hefty and I don't use it on thin barked trees. But I am fairly confident of the indication it gives of the relative extent of decay on big old Ash, Oak and Pine for example. I am curious now to know what nylon does that rubber doesn't. As a slight aside, I recently surveyed all the trees on a golf course. The stems facinmg the tee-offs were pockmarked, the result certainly of golf ball impact. I imagine a hammer improperly used could do something similar.

Great pics. That Elm stump is a busy place.

Right first time! The whole tree picture was taken in Camperdown Park at the weekend, but the buds pictures were taken in the University Botanic Gardens.

Anything sizeable gets the rubber mallet from me, smaller stuff gets a precautionary gentle kick at about knee level with the rubber front of the boot. I don't know how anyopne could sign off a tree without literally sounding it out. You can tell such a lot with the hammer (or boot) where the eye can't go.

Maybe i wasn't clear. Over then under is a step cut for free fall. If you do it outboard it can take the saw with it but otherwise no problem. Over then under only gets the bar pinched of you cut too far, it's an additional protection against losing the piece. Most of the time over then under is straightforward and the bar comes out no bother. I think I just don't like using saws vertically, somehow it seems less controlled. And it is unusual to be in a position to be able to see through the cuts to be able to check you have got the step right. With horizontal cuts this is usually easy and at about eye level. I'll give it a try though sometime.

Just had a thought, what if you had two climbers at about 100kg, one rescuing the other, total non-dynamic load 2kN. In a rescue situation, descents can be jerky at best and you may have to pull the victim off or over a branch, easily adding another 2kN. So where does that leave you with safety factors? 15kN/4kN= safety factor of 3.75, not great. I don't have a zigzag, unlikely to be getting one, but if I did I would be worried about using one for rescue.

I can't see me doing many fo them... the good thing about teh step cut hand held where you finish with an horizontal undercut is that if the piece of branch to be removed wants to fall off before you wwere expecting it, the cut closes on the saw and not onto a gap; the restriction in movement prevents the step breaking which it otherwise would. You can then stop the saw and get one hand on the piece before pulling the saw out and doing the snap with both hands. If you do this vertical step cut you lose all this control. Personally I have never bemoaned not being able to waggle the step sideways instead of down or upways.

I may as well put my last question to you. As you know, and I mention it largely for the benefit of onlookers, QTRA puts each of the three ingredients (Target, Harm and Probability of Failure) into ranges of probability for example 10 to 36 pedestrians an hour is taken as 1/20 target presence, which is the upper end (36 pedestrians an hour). To put it another way, it errs on the cautious side. This resultant probability is then multiplied by the other factors, which also are rounded in the 'cautious' direction . It appears to me that this has the potential to result in super-cautious conclusions from the QTRA calculator. I took some figures at the extreme lower end of each of the three factors and multiplied them together. I compared this with the product of 3 figures from the upper end of the same range. It is not difficult to find examples where the difference between them is a factor of 2,000. The difference between them in one scenario was a factor of 3,000. Since all QTRAs figures are rounded on the cautious side, what this seems to me to result in is the potential for QTRA to recommend remedial tree works for trees where the arithmetic for the actual constituent parts would not result in such a recommendation. So, for example, a tree is calculated by QTRA as presenting a 1:7,500 risk, which is considered by HSE therefore to be an unacceptable risk; let's say the remedy would be felling. However, the actual figures could when multiplied together be say 2,500 times less, equalling 7,500 x 2,500 = 1:18,750,000, putting the tree in the 'broadly acceptable' category. No work to the tree would be required. These two completely different results for the same tree appear to support the view some have that QTRA produces false precision which (with these rounding discrepancies) can lead to false accuracy. There is a question... how does the practitioner or the client or someone like myself who is a potential future customer of QTRA reconcile this all so that acceptable trees do not get felled?

Another one from a recent excursion, if I said where it would give it away. The bud pictures are from the same tree, the second lot are from twig wherre buds are just starting to open.