cobra cabling

Rick,

Agreed...tree parts do move apart but not during EVERY load, as you've stated. The karate effect has been used by anti-cabling lecturers as a single dismissive issue. This is what I have an issue with. It doesn't happen every time nor is it the defining criteria for cabling. We're not disagreeing, just fine tuning, on the definition.

" In order to lessen the likelihood of the crotch failure do we want eliminate movement, or merely reduce the extremes of movement, on the crotch?"

With a hybrid system both bases are covered. Codoms and weak unions need additional support to reduce the chance of failure. In addition, reducing end weight is sooooo important.

I've learned so much about cabling/bracing by studying the rigging systems on sail boats, especially 'fighting sail' frigates.

http://www.stvincent.ac.uk/Heritage/1797/Victory/aloft.html

The standing rigging decreases ins size as the size of the structure decreases. Isn't this exactly like trees?

When I first started installing Cobra I always adjusted the size of the eye to consider the diameter increase of the supported part. A fast growing tree would get a bigger eye 'just in case'.

In the A300 Standards there is an accepted life span and maintenance timeline that has been in place prior to dynamic or eye spliced cable systems. One of the loose ends with dynamic is that the reinspection is less likely to take place and the consequences much more severe.
 
Hey Tom,

I think you are right....I think of hybrid systems frequently but had never really considered the static cable as part of such a system. I exclusively use braces or rigid bars.

On a higher risk crotch I'll lock down the crotch as much as possible with a brace bolt and supplement that with a dynamic canopy cable.

You are right too about looking at Sailing rigging...we could learn a lot from just that alone!
 
Tom,
Thanks for posting your ideas on hybrid cabling. I've used similar systems on trees with serious defects, using an EHS with a turnbuckle down low and cobras up top, but confess that I had not thought it out to quite the degree as your process.

mpriley,
Great pics; that's exactly what I've seen many times, and on cobras that I know were installed properly. I think it's important that if we don't expect the loop to expand that we make sure we'll be revisiting the tree to ensure our supports don't girdle the stems. Personally, I've taken to using VERY large loops when I'm not sure if I'll be returning to the tree.
 
[ QUOTE ]
I've taken to using VERY large loops when I'm not sure if I'll be returning to the tree.

[/ QUOTE ]

Good point, although we should all make it clear to our customers that all cables will need to be revisited X number of years down the line. Does anyone religiously follow up on their cable jobs? I know I don't always. And do you set up an appointment and charge a reinspection fee, or do you just drive by when you get a minute and peek at it with the binocs? I find it hard to charge people that second time.
 
[ QUOTE ]
Has WNC been able to do many oil spays between all the weather?

[/ QUOTE ]

Nope. We'll start back up with soap sprays on our hedges this spring, but for 99% of the time I stick with soil injection so I don't have to worry about dormant season spraying. I sure hope that cold weather knocked those little buggers back a bit!
 
We should make it clear that it is the homeowner's responsibility to be sure the cables are inspected regularly.

Of course, we should also make it clear we are happy to perform same. It might be good business to track cables and send out reminders. But IT IS THE HOMEOWNER'S RESPONSIBILITY.

Since I don't have the right software and I'm a little lazy about bookkeeping, I use Sherrill's NATMP: http://www.sherrilltree.com/Professional-Gear/Miscellaneous_5/NATMP-Form-935

I have to take it on faith that they are following through properly, since my copy of reminders seems come haphazardly, but I have had clients call and say they got the reminder. I really have no reason to doubt they are going out as they should.
 
Good thread.

Seans split hemlock (?) could be braced; straightforward work. Puts the lie to the notion that "trees in imminent danger of failing should only be removed". Indefensibly defensive risk assessment and management philosophy.

The karate chop effect and fear of wounding pretty much scared and intimidated europe into accepting standards that disallow steel. speaking of standards, ANSI and BMP's say "periodic" inspections-- timeline is per need as accepted by owner. I use NATMP tags too, factoring the cost into the bill.

And yes charging later is no problem; combine it with PHC monitoring, to ease the client's pain. Mike remember that "cabling job" we took apart in that century tree? Scary to think that one would have been left for much longer.
 
[ QUOTE ]
Mike remember that "cabling job" we took apart in that century tree? Scary to think that one would have been left for much longer.

[/ QUOTE ] Yeah. For some reason, I don't think they were coming back to inspect that particular cabling job...
 

Attachments

  • 214032-IMG_3135.webp
    214032-IMG_3135.webp
    101.9 KB · Views: 54
This was a steel cable wrapped around a large limb (same tree as above), secured with a clamp, run around a leader, and wrapped again around the limb. What a creative installation!
 

Attachments

  • 214033-IMG_3131.webp
    214033-IMG_3131.webp
    58.9 KB · Views: 59
Look at those old boots! You can see an even older cable splice below my foot about 3 feet.
 

Attachments

  • 214035-IMG_3134.webp
    214035-IMG_3134.webp
    94.7 KB · Views: 67
At least the cable didn't damage the cambium....
smirk.gif
 

Attachments

  • 214036-IMG_3136.webp
    214036-IMG_3136.webp
    87.7 KB · Views: 55
Last one. I don't have a picture of the branch union, but there really wasn't a need for a cable. We removed that mess and didn't install a new one.
 

Attachments

  • 214037-IMG_3133.webp
    214037-IMG_3133.webp
    112.8 KB · Views: 65
Speaking anecdotally (from 25 years of tree work), I'd have to say I've never seen evidence of "karate chop" damage. I've seen failure invasive hardware installation into decayed wood, but I think in general it's unrealistic to think of two leads moving rapidly in opposite directions. In wind, movement is dampened by foliage, and while leads move independently, they are generally moving at least somewhat in tandem. Cables are only meant to keep weak forks from opening too far, and any individual cable keeps any individual lead from moving in one direction. It gets more complicated in multi-lead, multi-cable configurations when movement is restricted in more directions, combined with placement and the weight of those leads, and the forces those unified limbs exert down the stem and on each other. Multiple cables is a very different situation than single cables.
 
I like 3/8" EHS on big trees and dynamic for smaller trees with growth defects like included bark or dodgy sprawling leaders. I don't cable trees with big fractures or splits and targets, I know arborists who do but for me, the risk is too high so I recommend removal.

I find myself using EHS mostly on multi-stemmed trees with included bark at the basal unions... tulip trees and sweetgums. On smaller maples I generally go non-invasive to avoid contributing to a decay column.
 
Cables serve one purpose... to have the stems move as one. That is the only purpose for a cable, not to hold the stem up when it breaks or anything else that might be "sold" out there. There has been a lot of research done and hands down it all points to a PROPERLY install static system. All the points in dynamic advertising is against improperly installed static systems.
 
there are lots of 'purposes' for cabling. Above all, risk management.

One of my selling points with cables is to let clients know that if the tree ever fails the damage is likely to be mitigated. This is not the prime reason but it is a way to spread the 'cost' to include a way to justify the cost.

I have experienced a failure that was swung away from the neighbors house. After a heavy storm with 60+ MPH winds...tree damage all over the city. A side leader failed, grazed the neighbor's house, damaged the fascia/gutters then hung from the cable in free air. Without the cable the soffets would have been crushed....in a house built in 1880's.
 
Making two stems move as one is a bad idea, stressing a union is good. Fortunately even with static systems stems can move independently... the idea is that they don't move too far and push stress into strain.

The jury will be out on dynamic systems for many years yet but the principle makes sense.
 
The swinging effect is a nice bonus but shouldn't be a selling point. What if the cable or hardware can't hold and the stem when it breaks out. Then you have sold something that isn't true. I'm not saying that you can't add it as a benefit but it shouldn't be a selling point. Principle and practical are too different things. I've seen the real data and tree's they were installed in. Static out ways the dynamic
 
I never used post breakage as a selling point and I hoped that was clear.

Many other arbos have had this experience too. It makes us look good when we can add this value.
 
You must log in or register to reply here.

New threads New posts

Back
Top Bottom