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Letter to TCI on Cobra Bracing
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<Scott Cullen>
posted
Interesting letter in Industry Input, TCI, November, 1999, X(11)p.70 from a professional engineer providing cautions about the limitations of Cobra applications in split trees.
 
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<Anon sorry>
posted
Reply to post by Scott Cullen, on November 09, 1999 at 23:14:30:

I have talked with this guy over the phone. I asked him what a PE, professional engineer was. Since he was using the PE to try and establsih his credibility I wanted to know what it meant. He could not explain what it was. His letter has just the smallest base of truth. Cobra should not be used to support limbs that have all ready cracked. But to condemn the whole system is foolish.

This guy sent the company that did the cablin in his neighbor's tree a bill for $1,000 for the research that he did on Cobra. With a chuckle, the bill was forwarded to Sherrill Arborist Supplies where it lies right now. Find out about this clown, you will see he can be ignored...

Here is his phone number if anyone wants to talk to the guy. He does not have internet service because he does not want anyone to spy on him...

Richard H. Kutshcer, PE
1349 Prior Ave. S.
St. Paul, MN 55116-2656
651-690-4212
 
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<Scott>
posted
Reply to post by Anon sorry, on November 09, 1999 at 23:14:30:

I'm a little confused by this response. I did not read Mr. Kutscher's letter as condemning the entire Cobra system, but as saying that in his professional opinion it was not applicable in a specific situation, perhaps the situation in which it was applied in this instance.

"His letter has just the smallest base of truth." Does that mean that the part about the specific situation is true? Does it mean that even the opinion about this application is suspect? Is his opinion in disagreement with Cobra's claims? Have you or has anybody else seen the engineering data supporting each opinion... and do you have the engineering expertise to critique the opinions?

I'm not sure what his billing rate and who got billed has to do with revealing the facts about the Cobra system.
 
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<Tobe Sherrill>
posted
Reply to post by Scott, on November 10, 1999 at 11:27:50:

The fact is that Cobra may not be suitable for "dangerously cracked trees," nor might steel cables or even concrete encasements. The other fact is that Mr. Kutscher is in the middle of a nasty feud with his neighbor and I hope the industry finds something to gain from it. Let more discussion of cabling be that gain.

To date I've received in excess of 50 letters (cc's) from Mr. Kutscher (no exaggeration) to everyone from the consumer products commission to the Pope. Not to distract from the issue but he wants nothing less than this large beautiful oak to be removed and for no other reason than to beat his opponent. You'll notice in the 3rd paragraph (I think, I don't have the article at home) Mr. Kutscher indicated that his belief is that cabling is used to contain trees once they fall, all time prior to that the cable simply holds the tree as long as possible. Other writings have been equally incorrect and I've had to spend many hours writing people I don't know to explain his misunderstandings. C'est la vie.

Back to the issue, and by the way I've only seen the tree by way of a photo provided by the complainant. Dr. John Ball revealed some interesting facts at the TCI forum on Cobra in Indianapolis where he suggested that Cobra not be used to cable cracked trees. How cracked I might ask? If a 200 year old oak with massive codominant structure is severely separated by several inches perhaps it should best be removed. If a large ash with codominants has discoloration at the crotch (revealing a possible crack) but is otherwise healthy and appears to have a long life ahead, a skilled arborist/engineer (by trade) "might" elect to first brace and then cable. These two options, although not that far in difference are as clear as I can see the debate needing to start. If this ash is to be repaired properly it needs bracing whether Cobra is used or steel. The bracing is what's placed to allow the crack to heal, the cabling keeps the spread in check. If a static system is placed above, then during the trees summer growth, when the cable will become banjo string tight, little support wood will form and the cable will ultimately be the trees only means of strength. Of course, what I'm describing and imagining as "my ash" is not what you'll hear so we may never agree without standing in front of some example specimens. I believe that Dr. Ball desires to eliminate the idiot factor by saying that no cracked tree should be supported by this means but the fact is that a huge sector of Europe uses Cobra with and without shock absorbers in both cracked and non-cracked trees with an extremely low failure rate and I believe the trees are better off for it. Ask any other engineer if he thinks a large tree should be bound up with cable in a manner that freezes movement in windy situations and hear what he says, not to mention the boring into healthy wood factor.

As for the splice in Cobra working its way apart "by design," that's a lie. This man simply made that up hoping to score some points. If that were true then previously docked boats would be floating all over the planet. Most lock-stitched splices simply act as indicators that a splice has failed. Yes splices do fail because they are the weakest point of that length of rope, they are not what holds the rope together.

With all said we too believe that trees are best served having Cobra used as cabling when there is no crack present and the said cable is merely placed to keep the tree from going to those "far extremes" during wind or ice. I also strongly believe that there are situations where a tree is too dangerous to cable with anything. As for Mr. Kutschers less than educated opinion... well, he's got one too.

Good luck and work safe.

Sincerely, Tobe Sherrill
 
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<Scott>
posted
Reply to post by Tobe Sherrill, on November 11, 1999 at 09:37:23:

Thanks for the thoughtful reply.

If we assume that Mr. K is not Independent becasue he's in the middle of a dispute we must also assume that if you are a principal supplier of the product in this country you are not Independent either. That might call into question the Objectivity (factual nature) of either opinion. I merely want to point this out so the audience gets the whole picture. That is why third party and competent opinion is so important.

I believe you're right, that a tree which is cracked or split at a crotch is not properly supported by a flexible bracing system (steel cable or Cobra) in the branches/leaders above the crack. A rigid (bolts or rods) bracing system is required here. The intent of such a system is to bring the crack back together to the extent possible but more than that to prevent movement (both opening up and side to side) that would lead to additional splitting below the open crack. The flexible system above then limits the force exreted by the upper parts (from their own weight or wind load or other live load) on the crotch/split that might overload crotch or the rigid bracing.

While there may sometimes be formation of new uncracked wood around the entire trunk I don't think that's a primary goal particularly with older trees. I just haven't seen it happen that often... there was a thread on that recently and I'd be happy to hear other opinions.

That brings us back to the more typical flexible system without an already damaged crotch. As I understand the principal goal it is to prevent crotch failure by "stopping" the moment of force that would cause failure. Secondarily, though this is more anecdotal, it is sometimes said that the system may be capable of holding one of the supported members in the tree in the case of failure.

The question of wounding sound wood with holes for hardware has always been a "lesser of two evils" issue. If the decision is to remove today or take your chances with natural failure or do some controlled wounding to extend the life of the asset-resource you may undertake the fix.

So it seems to me that neither steel systems (rigid or flexible) or Cobra type systems are universally applicable or universally unsound. As always it depends on competent selection, specification and installation.
 
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<Tom Dunlap>
posted
Reply to post by Scott Cullen, on November 09, 1999 at 23:14:30:

This tree has gained international clebrity status. Since last summer I have been following this saga as a side line observer. Today I had a meeting over in St. Paul so I decided to stop and take a look at the tree and try to take some pictures. I did not even take my camera out of the van because we got our first snow of the season and it was too flat to see the cables.

The oak is in the back yard so I walked up to the front door to ask permission to see the tree. I was greeted by the owner and after identifying myslef and explaining that I was interested in her famous tree, she was mildly amused and invited me in to the house. She explained how her neighbor had wanted the whole tree cut down but settled on having a company prune the limbs at the lot line. When her husband came home I was entertained by some rather amusing stories about the neighbor. The couple who own the oak really care aobut the tree and have done more than is required to appease Mr. Kutshcer. Mr K falls into the group of people who worry about trees growing over the property line, even though the trees are sound and healthy. He has flat sided the oaks on his north lotline even though they are the neighbor's tree!

The burr oak is about 30" dbh and forms two trunks about twelve feet off the ground. A heavy Cobra has been installed just above the main crotch. In the upper crown there is a heavy and a standard Cobra installed. This tree survived wind storms in June of 1998 that flattened larger trees no more than four blocks away. This is one tough tree.

Even thought Tobe is the Cobra representative in the US, what he says is still valid. If anyone should be scrutinized on this forum, it should be Mr K. What expertise does a systems analyst with experience in electrical systems know about tree biology? It is obvious that the guy does not understand rope splicing. Further more, his paragraph starting with "This automatic rope-tension-reducing..." shows that he does not have a full grasp on cabling of trees with steel or flexible bracing systems.

Let's give this a peaceful burial and hope that we don't hear any more from Mr. K.

Strong limbs and snug cables,

Tom
 
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<Tom Dunlap>
posted
Reply to post by Scott Cullen, on November 09, 1999 at 23:14:30:

This tree has gained international clebrity status. Since last summer I have been following this saga as a side line observer. Today I had a meeting over in St. Paul so I decided to stop and take a look at the tree and try to take some pictures. I did not even take my camera out of the van because we got our first snow of the season and it was too flat to see the cables.

The oak is in the back yard so I walked up to the front door to ask permission to see the tree. I was greeted by the owner and after identifying myself and explaining that I was interested in her famous tree, she was mildly amused and invited me in to the house. She explained how her neighbor had wanted the whole tree cut down but settled on having a company prune the limbs at the lot line. When her husband came home I was entertained by some rather amusing stories about the neighbor. The couple who own the oak really care aobut the tree and have done more than is required to appease Mr. Kutshcer. Mr K falls into the group of people who worry about trees growing over the property line, even though the trees are sound and healthy. He has flat sided the oaks on his north lotline even though they are the neighbor's tree!

The burr oak is about 30" dbh and forms two trunks about twelve feet off the ground. A heavy Cobra has been installed just above the main crotch. In the upper crown there is a heavy and a standard Cobra installed. This tree survived wind storms in June of 1998 that flattened larger trees no more than four blocks away. This is one tough tree.

Even thought Tobe is the Cobra representative in the US, what he says is still valid. If anyone should be scrutinized on this forum, it should be Mr K. What expertise does a systems analyst with experience in electrical systems know about tree biology? It is obvious that the guy does not understand rope splicing. Further more, his paragraph starting with "This automatic rope-tension-reducing..." shows that he does not have a full grasp on cabling of trees with steel or flexible bracing systems.

Let's give this a peaceful burial and hope that we don't hear any more from Mr. K.

Strong limbs and snug cables,

Tom
 
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<Scott>
posted
Reply to post by Tom Dunlap, on November 09, 1999 at 23:14:30:

Thanks for the guided tour Tom.

I'd like to clarify something on technical terms. Traditionally bracing systems were broken ito two categories, flexible and rigid.

They were all steel.

Rigid systems include bolts and rods of various types. They were intended to prevent movement in all axes or vectors. The tree parts did not move away from each other, towards each other or side to side at the brace point.

Flexible systems were cables (and before that chains). They restricted movement outward from the anchor points (stopping the moment) but permitted movement of the anchor points towards each other and side to side.

Steel cables are still flexible in this regard.

Looking at the 1/99 draft of the new A300 Cabling, Bracing and Guying standard that distinction is no longer used. The characteristics remain the same however. Bracing included steel rods and bolts, cabling steel cables. I understand the committee was addressing the emergence of non-steel cabling materials in the marketplace and may be incorporating additional terms.

In any case, Cobra as I understand it adds flexibility in a third vector. It is not descriptive however to call call Cobra systems "flexible" and others simply "steel" as if they are not flexible.

By the way, I did not intend to imply Mr. Sherril was not objective or not stating supportable facts. I just wanted to point out for this dialogue that even though he may well be one of the best informed people on Cobra performance he cannot be Independent.

Scott.
 
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