Cabling and Bracing as an Arborist

Tree_Frog

Active Member
#1
I recently had a chance to bid a cabling and bracing job. I did not win the bid as another Arborist did. I thought this would be a fun one to talk about as there are quite a bit of discussion that can be made on this tree and what was done to it.
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The DBH = 40 inches
The Diameter of the Codoms are 25 inches.
Quercus virginiana -- Live Oak.
Excellent decay resistance unless topped.
Extremely strong and heavy wood.


I will give you my input soon.
 

Steve Connally

Well-Known Member
#2
I had a champion live oak I worked on. It had an awesome lead that dipped down and was cracking under the weight. I had a metal fabricator come up with twisted iron supports sunk in concrete for the underside as well as some dynamic cabling ideas. It was so cool. It had an elbow that actually sat on the lawn. Man I had a plan. It's was gonna be art. Then they had me cut it off because it blocked their view. I begged them not to do it but I lost. I was crushed. After all the work I did to add it to the va big tree registry. Then I hacked it like a Jack leg. Shoulda walked away from that job.
 

Tree_Frog

Active Member
#4
Well I figured that I would get one person to suggest something.

This is one for the cabling and bracing manual (ANSI A300 Part 2) due to the liability.

Canopy reduction of the outermost 10-15 feet. You can see the line in the canopy where the tree tells you to reduce it.

Static cables - Upwards of 6 5/16" EHS depending on the reduction results using a hub and spoke as well as direct.

Minimum requirements for bracing is 3 for 30" plus 1 for every 8" as per ANSI for a 40". Rod size is 3/4. I recommended 5 - 3/4 Grade 8 rods due to the continued growth capacity and to reduce the costs of using 7/8".

Bolt pattern a per ANSI suggestion, why reinvent the wheel. 2 above the crotch and 3 below in a horizontal plane. See figure 23 in the 2014 edition.

Needless to say it was pricy.

Also recommended remove and replace.
 

flyingsquirrel25

Well-Known Member
#5
this is a project I got back in 2012. A European linden on the big tree register for Pa (number 2). It had a large crack from the union 12 or 14 feet up. I used my interpretation of the ANSI standard (err on the side of heavy).
I prescribed 10 - 7/8" bolts (dia at crotch was 8.5 - 9'), 1 row of 2 above the union, 2 horizontal rows of 3 and a last row of 2 down low (each row was 4' apart). 2 - 3/8" cables in addition to the existing 2. And a 10-15% reduction. I put $2400 (I lost my a$$) on the bracing and cabling and the owner didn't want the pruning. Although I only made about $25/hr it was a huge learning experience and I had a ton of fun.
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Ps the tree is still doing great.
 

Tree_Frog

Active Member
#7
Here is what was done to the tree. It is a head scratcher as it was completed by an ISA Certified Arborist.

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Thinning of the canopy with no reduction in length.

Installation of a Cobra dynamic, what appears to be 2t maybe 4T, cable 2/5 up the canopy.

Installation of 2 - what appears to be, 1/2" rods.

This is where the discussion begins:
 
#8
Here's a few of my thoughts:

1. Canopy reduction, versus canopy thinning. Both will achieve the desired outcome, which is less weight on the limbs, consequently less forces acting at the point of attachment. Canopy reduction reduces the leverage effect, whilst canopy thinning simply reduces that weight along the limbs, and throughout the tree.
I think a balanced, well-executed thinning would have been better for this tree. However, I think both will be pretty close in end result, in terms of force reduction at the point of attachment. I would say it depends more on what the home-owner wants aesthetically in this situation, open canopy (more light, natural tree structure) versus smaller tree.

2. I'm amazed people still bolt trees and drill holes through them to "help" them. I'm a firm believer in non-invasive cabling and bracing strategies.
With that being said: I don't understand why the arborist used both steel cable and textile cabling ... honestly no idea.
Second, you are right in that he did not install his Cobra lines correctly. There should be additional bracing higher up in the canopy. See image below for 2/3 of the tree's height.

3. I'm glad to see that the homeowner wanted to protect / prolong their tree's life. Where I live, if I had submitted 1x $2400 bid to cable, brace and prune it, and 1x $1800 bid to cut it down, you can bet they'd be asking if I can grind the stump too.

Interesting situation to discuss.



What I think can be very helpful in winning these types of bids, is putting down in writing on the written estimate, that you will be adhering to ANSI 300 Supplemental Support Systems specs. (American National Standards Institute). Are you an ISA Certified Arborist? (Just curious why they chose your competitor instead of you)

Also, make sure to include that inspection is necessary every 3-5 years, or however you want to market it. Call the customer back a week later and ask them if they have any questions. Explain everything you will be doing. Tell them why it will cost them $2400, and why they should pay you (you specifically) to do that.

Optimal bracing location.png
 

Tree_Frog

Active Member
#10
CanadianStan

1. The pruning that was conducted is actually one of the best pruning jobs that I have ever seen him do. He has a history of lion-tailing every tree that he touches and I was actually impressed. I will have to agree that the thinning will accomplish the same goal in weight reduction while keeping the natural form. One consideration with these live oaks is that they have the ability to grow fast. So in about 2-3 years this tree will probably have to be thinned again.

Live Oaks like to have a broad spreading form so it will be important to keep an eye on the leverage of the lower canopy against the crack. The crack is the real issue.

2. I am always interested in learning new applications. I have been using Cobra since 2006 and finally stopped selling it a couple of years ago due to the shear fact that inspections are being neglected. I have kept a close watch on the different systems out there but I have not seen the research to use synthetic materials when a crack is present. To my knowledge, Cobra dynamic is not designed for this application and Cobra static is not large enough for a 25 inch stem at the POC. I would have to look at some of the other systems with the 5% stretch capabilities. What system would you recommend without going by the ANSI Cable and Bracing protocals, essentially what is out there? What reasearch would justify your actions in case of failure? Anything to make it done properly and less expensive.

In the placement of the cable, I would go even higher.

3. I am glad to see the homeowner keep the tree as it was the reason they purchased the home.

The bid information the you give is valuable and I have been doing this for years almost verbatim to what you said. The only change is that I recommend inspections on an annual basis. I also made an extra point to highlight ANSI Standards on the initial write up. To answer your question, yes I have been an Arborist for the past 10 years, thanks for asking.

Loosing bids here is pretty typical as I am usually 3 times more than my competition. My competitors have been the hacks we all know. Problem is that they are getting ISA Certified and still charging as before, disregarding ANSI Z133 and ANSI A300 protocols. I know that this competitor charged $1750 for this work.

The job was lost exclusively on price alone.
 
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guymayor

Well-Known Member
#11
Some repeated assumptions in this thread worth noting;

1. Weight reduction matters.

It is load reduction that matters! It's not the net tonnage involved, but the strain on the parts that comes from loading. It ain't the meat, it's the motion; it's the movement that gives it the pop! And that line from the old jazz standard is as true with trees as it is with certain activities. So reduction is definitely more effective than thinning is. Research backs this up.

2. ANSI support standards are merely adequate. but we should show that we are being diligent and safe by exceeding them; erring on the side of safety and so forth.

The truth is part three has a ton of overkill built in. There is very little science behind the numbers that are mentioned in that document, as I recall when I was on the committee when it was being revised. So when 'erring' you adding overkill to overkill.

3. Dynamic cabling is better for the tree.
With an open crack like that, movement is not desirable. The cable that stops the most movement is the most desirable. A whole that is 3/8 of an inch wide into upper stems is much less harmful to the tree than attempting to make a dynamic cable work in the system.

4. Following a 300 part three is the best guideline for managing trees that need support.

Actually part three has very little about inspection. The only A300 standard that covers tree inspection is part eight. If the tree was inspected, then the issue of the buried flair and some treatments directed in that direction would have been considered.
The fact that finding and correcting the root cause is not on anyone's wavelength even while proposing thousands of dollars of work is REALLY hard to understand.

5. I S a certification continues to be repeated as the benchmark for hiring arborists.

However, it is like a high school diploma. Buyers are too lazy to look beyond the ISA certification and it is hard to overcome that marketing that is done for that certification, and demonstrate something superior.

6. When in doubt we should always recommend removal and replacement.

As an arborist we should be oriented to tree care. So why did you express readiness to remove the asset? O and is it honest to say that tree can be replaced?

It looks like you overspecced the work and therefore overbid the work. To big static cables right above the forkto do the bracing function, anda smaller cable or two above, and a 10 to 15% reduction is what I would have SPECT, plus r cox probably coming in just above what the hack proposed and did. I hate to be derogatory about his work but installingdynamic in the tree has no basis in science. I seen too many trees break dynamic cables, just because somebody did not want to damage the tree. Think about that. Crazy!

Yes you probably lost the job primarily on price, because you did not order a comprehensive service. Maybe if you had included a root color examination, that would have set you apart in quality from the other certified arborist. Actually pushing for the examination before the work is specified is really the standard thing to do!
 
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Tree_Frog

Active Member
#12
Guy,

I can alway leave it to you for a voice of reason. Normally I start at the roots. I am sitting here laughing at myself for not seeing this. When I looked at this tree it was pouring down rain on an initial hit from a Florida thunderstorm. I was not happy about being under that tree watching that crack spread back and forth in the winds. I figured that it would fail at any time while under there. I totally missed it.

As far as using cabling as bracing, I have done this before in a Golden Rain tree and it worked well. How do I justify the use of cables with an existing crack in an event of a failure? The legalities of the crack got the better of me. lol


I did over spec the job. I was not happy when i achieved the final price.

The specs that you proposed? Would you use the EHS cable size of 3/8 in the lower part and 5/16th in the upper? Would the lower cables be on the same horizontal plane or are we zippering it as we go up?

If it works and it cost less, I'm there.
 

guymayor

Well-Known Member
#13
How do I justify the use of cables with an existing crack in an event of a failure?

Cite the mfrs verification of the amount of support gained; like 15000 pounds per cable.

I did over spec the job. I was not happy when i achieved the final price.

Live and learn.

The specs that you proposed? Would you use the EHS cable size of 3/8 in the lower part and 5/16th in the upper?

That's about right, but 3/16" above might be good enough.

Would the lower cables be on the same horizontal plane or are we zippering it as we go up?

Depends on tree anatomy, but I think generally the same plane might be best at preventing failure?

More sprawl reduced would make a big difference imo.

I wish the committee was more open to voices of reason!
 
#15
I hate to be derogatory about his work but installingdynamic in the tree has no basis in science. I seen too many trees break dynamic cables, just because somebody did not want to damage the tree.
Seriously Guy? This is simply and absolutely untrue. I'm surprised that you would type such a remark so frankly, as if you've investigated the subject and are reporting facts. CLEARLY you haven't, and possibly even avoided dynamic materials because of that reason. Among all of the arguments that I have agreed with you upon, this one makes me rethink the depth of your reasoning elsewhere ...and not because I'm the know-it-all about arboriculture, but because I've stepped outside of North America to discover that tree care science isn't locked in opinions of the early 20th century. Mainly in Germany, where studies and methods for measuring tree movement and resistance to environmental stresses are light years from those being studied here in ...? well, just where is tree dynamics being studied here exactly? And what results are we able to glean for debate from this recent science? ...something that a large group of German arborists, scientists and mechanical engineers have been doing REGULARLY for the past 2 decades! Not a few employees of a practictioneer charged with vilifying past practices, but passinate individuals excited to advance tree care based on modern science, study and human intelligence. The work of Germany's Z committee is best understood by, at least two German speaking North Americans that I know; Mike Neimyier(sp) and Phillip vanWassenaer.
In the months ahead I will put forth my best effort to import the most recent English written/spoken results of this science for American tree practitioners to digest for themselves. More to come...
 
#16
Hi Tobe, as a Brit coming from the other side of the pond, I could not agree more. I have worked mainland Europe and extensively in the Americas so I think I see where you're coming from. There is a massive difference between attending conferences and attempting to glene workable info and actually working there with those at the front line of development.
Genuine researchers are by nature inquisitive, However there is also a strong desire to retain an element of privacy in their work. It is only by developing trusting relationships that the barriers to a genuine exchange can be overcome. Tobe if you have managed to achieve such relations and been granted access beyond the conference facility then I congratulate you. Its an honour seldom afforded.
 

treebing

Well-Known Member
#17
Yet the instructions for cobra cable clearly state it is not to be used for situations like this one. Europeans and North Americans are also different in that here, this homeowner is likely to move within a few years, leaving an Uninspected piece of rope in a tree potentially girdling it or eaten by squirrels. In Europe, families have lived in the same house for hundreds of years and an inspection routine is more achievable. I don't think what works in Germany can be expected to work the same way here. But maybe.
 
#18
Kevin,
Zero dispute with your points regarding this tree and this situation, just with one piece of Guy's post. In my opinion he was spot on that this tree needs to be zipped up with bracing (botton to top) as well as the other point about crown reduction (vs thinning). The tree's "sail" needs to be reduced, its leavers against wind shortened, whereas thinning will merely create gaps that will be quickly filled and the sail effect returned. The SIA method teaches extensively about lessening the "sail effect." It's truly fascinating and common sense science about tree mechanics and how trees are stressed by nature.
And please Guy, don't read into my previous post something that's not there. I have the utmost respect for your years of NC knowledge and skill (not to mention my wife is a Tarheel grad :). I merely couldn't go about my business ignoring a point that was, either not well researched, or perhaps, not exactly as you meant to word it. Peace
 

guymayor

Well-Known Member
#20
Tobe, I've also seen a lot of 4ton cobra used in europe. In many cases, successfully, and in some cases, that seemed warranted to meet the objective. And yes we agree that steel is needed down low with an open crack like this one. I guess where I have the most trouble is with the egregious amount of wounding needed to 'zip' the crack shut per A300-level bracing (locked in the opinions of the early 20th-century), as compared to EHS through-cabling.

Whether or not dynamic is used higher in the tree is a trade-off between the benefits of increased movement (often overstated imo) vs. cost of higher maintenance, which would be higher yet in FL with the increased rodent/UV issues. (btw I've seen cobra overgrown and girdling after 4 seasons used high up in a euc in Queensland.)

I think we agree that where movement in a cracked fork is not desired, static is the choice. I'm all for importing european technology (like SIA-supported reduction for instance), but based on scientific application, where it fits. As with coronet cutting, dynamic cables can get used because they're cool and new, even though they do not fit the objective. And they can be well-used, to conserve crown volume while building better forks.

O and this Duke guy will forego commenting on tarheels...
 
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