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Cabling and Bracing

Discussion in 'Commercial Tree Care and Climbing' started by electrictrimmer, Jan 29, 2010.

  1. jomoco

    jomoco Addicted to ArboristSite

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    The pertinent point is that your system can't come anywhere near it's rated strength of 14K without damaging the cambium at both termination points, whereas a traditional steel cabling system can.

    Like rigguy, your system's liabilities exceed it's benefit, particularly in a long term sense measured in decades.

    Rigguy's termination ruins the structural integrity of the steel cable itself, separating each individual strand of cable, stressing it, and exposing it to corrosion and rust, then hiding that weakpoint in the system in a location impossible to inspect.

    Your system can't deal with thousands of lbs of tension without damaging the cambium at each termination point, period, despite your claims otherwise.

    Both these newfangled systems are so poorly designed that they should never be accepted for use in any cabling standard, anywhere, in my opinion as a 37 year veteran climbing arborist.

    jomoco
     
  2. treeseer

    treeseer Advocatus Pro Arbora

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    re the undocumented fear of cambium damage, see the top of the second page. No offense Jon but the university dissertation trumps your 37 years in the tree. Sounds like i got you beat by 6 but that is not relevant data is it? just means I'm more tired.

    "Rigguy's termination ruins the structural integrity of the steel cable itself, separating each individual strand of cable, stressing it, and exposing it to corrosion and rust, "

    this is a concern, but keep in mind that all this happens outside of the fastener. So how much load does each bend bear? and how fast does it corrode? We'll see; that's why periodic inspections are needed.

    "then hiding that weakpoint in the system in a location impossible to inspect."

    ?? the bends in the strands are on the outside of the fastener and are visible and tangible.

    :deadhorse:
     
    Last edited: Feb 23, 2010
  3. jomoco

    jomoco Addicted to ArboristSite

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    Come on Guy, pick say a white alder, Alnus rhombifolia, choose any lateral on it capable of supporting a heavy load, throw your synthetic polypropylene anchoring strap over it and hang a thousand lb load on it, remove the strap and see if there's any cambial damage?

    Whereas I can drill that lateral, install a throughbolt, hang as much weight as that limb is capable of supporting from it, and still do no cambial damage to it beyond the width of my galvinized washers, about 2 inches, which can heal over in a few years.

    So much for using cobra in white alders, or any other tree in my opinion.

    It's ridiculous to try and support a tree with components weaker than wood. If I were to rub an oak limb against even a one inch thick polypropylene rope, which would fail first my very book learned friend?

    jomoco
     
  4. jomoco

    jomoco Addicted to ArboristSite

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    What about fire, say a home fire, or a brush fire?

    How well will a polypropylene strap or rope holdup to the rising heat compared to drop forged galvinized steel?

    Doh!

    jomoco
     
  5. Mikecutstrees

    Mikecutstrees AboristSite Guru

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    I tend to agree with jomoco. I have used Rigguys and wasn't happy with their usability. Maybe after 20 cables I still didn't quite have the hang of it. Ive gone to old tried and true, through bolts / lags, and dead end grips. I figure if there is ever a problem or lawsuit that I'll go with something with years of data behind it in court. Just my 2cs..... Mike
     
  6. treevet

    treevet Banned

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    You boys either were tied into a tree outside the middle school with a text book in one hand and the window open....or you need some batteries in the calculator.....or sooombooody's fiiibiiing.:laugh:
     
  7. Wohn

    Wohn ArboristSite Lurker

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    My opinion and experiences about constant loads of static cables and cambium damages can be read in my previous post.

    But I have to add a few thoughts that may be interesting. It always has to be distinguished between static and dynamic cablings because they are used for different jobs.

    Static cablings are used to immobilize the branches of a predamaged (cracked) crotch to prevent the crack from opening more and more. Or to hold a breaking branch. In the first case they are installed horizontal in the second case (as load system) they have to be installed vertical to prevent the branch from falling into the cable.

    Dynamic cablings have to ...

    ...support a branch by transfering some (not all) wind load to a neighbour branch because the wood of the weak branch is still transfering a lot of the load by itself.

    ...restrict the movement befor the wood fibres were overstreched and fail and it has to avoid a branche from swinging in resonance with the squalls and thus store more and more kinetic energy (as a child’s swing) until the branch collapses. Therefore it has not to be very strong (see below). Furthermore a smooth slow down of the movement is best for a tree. A dynamic system is able to avoid shockloads, a static cable can’t.

    There is no constant load in dynamic systems thus no cambium damage occures. The ingrowth of systems is always a case of not regular controlling cablings. True for rubbed through systems too.

    About loads in trees and the required tensil strength of systems I also want to add a few words.

    There are many hundred thousend cobras out there and not a single one failed because of high loads. cobra standard with 2 t (4,400 lbs) tensile strength has been installed since 1993 in branches with up to 50 cm base diameter. This experience in the field has proven that by installing cablings near the wind load center (around 2/3 height) the leverage force can be minimized thus loads effecting the cable are low thus cables can be sized low too. If the loads in trees would have been higher then in the last 15 years a lot of cables had to be broken. But they have not. If interested read also the results of the field measurements of Ken James (see „Dynamic loading of trees“, Journal of Arboriculture 29 (3): May 2003 ).

    Sure the (dynamic) cable has a small diameter and and its tensil strength is weaker than the wood but it has not to be stronger, it is strong enough to do its job.

    Synthetic cables used for static cabling have that high tensil strength not because they have to resist high loads. They have it because the higher the tensile strength the lower the elongation of the cable, e.g. Dyneema has a elongation of 0.2 % per t of load. Static load cablings are a bit different because they have in case of a branch failure to hold the branch. But the load that effects the anchor is temporary because the broken branch has to be removed as soon as possible.

    Fire seems to be an increasing problem in CA but I guess home owners have other problems in case of a homefire than a burned cable in a smolding tree.
     
    Norwayclimber likes this.
  8. treevet

    treevet Banned

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    Much laboratory sounding rhetoric here and you will have to excuse some of us for the replies to it as some of us have played this out at least a half a dozen times with the same "statement-response" scenarios so :rolleyes: (ho hum) here we are again like groundshog day where everything is played over again and again in a very predictable sequence. I have heard myself quoted multiple times from past threads.

    You are the inventor/manufacturer of this system I surmise? I may have met you or an agent of yours in Nov. 1995 at a week long Shigo seminar where it was first introduced into the US I was told.

    My question for you is why is there a tensile strength listed with this product if it so gradually is hit by the end of the branch's movement? This product should have a WLL. And why would either be necessary if the system is not made to "bang" into the end of the movement in a violent storm scenario?

    Next question....How do you control if the movement is held to where it is not controlled enough (it goes too far and breaks out the codom/multidom) or it "bangs" into the end of the movement (incurring the use of the tensile strength (WLL)) and causes compression of conductive tissue?

    Most of the applications I assume are going to be protection of codoms/multidoms and not the suspension of individual limbs from gravity and their own mass causing failure. Storms give sudden and violent movement of individual co doms. I do not think this system can "gradually slow movement" as advertised predictably. I suppose this system would be of merit in an area where codoms are not subject to any sudden winds. That place is not here. I have never seen one system installed anywhere around here in that 14 year interim. And, on the other hand if there were no sudden violent winds and the codoms were not that high of a risk with no target.....why install anything?

    The premise is to allow reaction wood to develop and maybe enjoy the aesthetic appearance of a tree moving around in the breezes. I do not think the allowance of a few inches of movement is worth the liability one puts themselves into to view such or develop more wood that challenges the defect even more. If there are no apparent defects then the reaction wood will develop quite well on its own thank you.
     
  9. electrictrimmer

    electrictrimmer ArboristSite Lurker

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    My question is more towards which size cables to use on what diameter limbs. I understand how they are used and everything, I just want to know which diameter cable should be installed into which diameter limbs. Any help with that would be great. Thanks guys.
     
  10. Mikecutstrees

    Mikecutstrees AboristSite Guru

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    Its more complicated than just diameter. I'd also consider the weight of the limb, the angle of attachment and the length of the limb. Go bigger if in doubt. Most times I use 5/16 and people usually can't see it up in the canopy. On small ornamentals I may use 1/8". On really big maples and such with say a codominant or included bark I'll use 3/8 to be sure. 5/16 is nicer to work with though..... Mike
     
  11. jomoco

    jomoco Addicted to ArboristSite

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    A combination of extra high strength 7 strand steel cable(EHS), and Tree Grip dead ends, manufactured by Preformed Line Products, makes for the most robust highly rated cabling systems that I know of. Installation is a breeze, provided you have very high quality cable cutters to cut the EHS cable with, like Felco cable cutters.

    EHS cable is impossible to wrap of braid like the old 7 strand softlay cable, you have to use the tree grip dead ends with it or forget it.

    Here's the link you need for tree grips.

    http://www.dulmison.com/artsfest/files/literature/NU-SS-1023TreeGrip.pdf

    jomoco
     
  12. treevet

    treevet Banned

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    If you want standardized direction phone TCIA or the ISA and order ANSI A300 (part 3) Tree, Shrub and Other Woody Plant Maintenance-Standard Practices (Supplemental Support Systems) and go to page 28 Annex A.

    In the event of extreme conditions and system failure then you have CYA by having documented following the current standards if you end up on the wrong side of a law suit. You will find the answer to some of your questions here as well.
     
  13. treeseer

    treeseer Advocatus Pro Arbora

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    You may find more in the ISA BMP, at one-third of the cost. But both together are $20, no reason not to have them if you want to do the work.

    But we are not limited to techniques or products that are described in the books; other work can be quite defensible.

    re the undocumented fear of cambium damage, consider the compression by stem-girdling roots, which trees tolerate amazingly well. So rarely occasional squeezing of upper branches does not seem so damaging to the tree.
     
  14. treevet

    treevet Banned

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    I disagree with that post completely and challenge the comparison to losing a root to girdling and the losing of the top of a tree and its related consequences.

    Better off staying with the standards......that is why they are published.
     
  15. treeseer

    treeseer Advocatus Pro Arbora

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    How about hopping off the soapbox long enough to look at the image and listen? It's not the root that is lost to girdling--it is the squeezing of the cambium in the stem that is done BY the root.

    :agree2:You're right about no comparison--stem girdling is far worse for the tree when done by a root at the base, compared to a belt on leaders. Yet I've dug out SGR's that went 360 degrees, but the tree kept chugging along.

    Also read this German study: I respect you and jon, but if no damage was noted in a PhD dissertation, I gotta go with that over your fears. Dissertations get researched for years, then defended in front of a half-dozen or so professors. That gives more credibility than...what science did you cite again? Years i:cheers:n the tree?
     
  16. treevet

    treevet Banned

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    years in the tree installing successful cable systems (40...over 2,000 respectively)

    ps we don't want our trees to keep "chugging" along....we want them to live a high level of life.
     
    Last edited: Feb 24, 2010
  17. Wohn

    Wohn ArboristSite Lurker

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    Treevet,
    Nothing to excuse I have played this out serveral dozend times by myself too. I am not trying to proselytize anyone only defending our products against unproofen defarmations. Therefore I want to show interested people our point of view so they can form their own view on tree cabling.

    But now to your questions.

    1. Tensile strength:
    To list tensile strength as „easy to use“ benchmark for tree cablings wasn’t invented by us rather it was envoved by arborists in the end of the 1980th. Based on the fact that modern dynamic tree cabling was developed from practice in close collaboration with sience after SHIGO published his new tree biology. At that time arborist were looking for new methods and systems to cable trees. One result of this collaborations is cobra. Still we collaborate very close with active arborists around the world to optimize our systems.

    Sure it would make more sense and it would be more specific to list energy absobation rates or talk about maximum shock-loads that may affect trees at a certain tension. Compareable to the exigencies for developing and producing dynamic climbing ropes (here in Europe: max. 12kN at max 20% tension). But the complexity of tree structures and the difficulties to measure and calculate their dynamic behaviours and characteristic impede to establish a universal benchmark for all trees that is useful in tree cabling practice. So still those benchmark (tensile strength) that came from practice is in use.

    Existing (sientific) calculating models (e.g. see WESSOLLY, 2005: ‚Dynamic and static crown-securing devices and carry/ hold protection – advice on correct installation and control’) are only able to help understanding and explaning what practice found out in all those years of field experience.

    Besides our systems have a security and aging reserve, e.g. our 2 t-system cobra plus 2t has a tensile strength as new system of 3 t. After 15 years it has still over 2 t (the aging rate of differnet cabling systems was object of a sientific investigation (see. BRUDI, SPIESS, LESNINO, 1999)). Those 2 t systems usually are not stressed with more than 30-50% of their load capacity during their service life. So their work load is around 0.6 and 1 t.

    2. Made to „bang“ into the end of movement:
    The „bang“ comes not during the gust of wind because both branches move (more or less) in the same direction. It comes when the branches are swinging backwards because the windward branch swings more backwards than the leeward branch does. The difference is caused through the higher windloads affecting and energy consumption of the windward branch. When the system got tightend it comes to an shock-load and this load seems to be seldom over 1 t (see JAMES, 2003: ‚Dynamic loading of trees’). As I told in my previous post the mentioned shock-load depends on installation heigth (2/3) and thus the affecting leverage forces. All our systems are capable to resits those shock loads, storing energy in the shock-absorber and release it while afterbouncing. Thus our system and the included shock-absorber is lowering the shock-load by 20-40% dependig on the load affecting the system.

    3. How to control the movement:
    As I told you above since the beginning we collaborate very close with arborists. Their experience helped us to size the systems dynamic to fit to the trees needs. To avoid overstretching we recommend to install no shock-absorber from connection length over 8 m.

    To get a better feeling for it many arborists (me too) are creating artifical branch movement by pulling and releasing the branches and look at their swing behaviour to infer the required and possible swing range before installing a cabling. Sure this is not very sientific and calls for some practical experience.

    This all proofed useful in practice.

    4. it „bangs“ into the end of movement and causes compression of conductive tissue:
    Loads occurring in such a case are within the coefficient of elasticity of green wood. That means no tissues getting compressed. In the case they have been compressed the branch should have collapsed without cabling.

    5. Gradually slow movement:
    Sure the system can not gradually slow down the movement to zero anytime befor it has been tigthened. And if the gust of wind is too hard then the thightened system stops the movement more suddenly. But in this case the shock absorber reduces the shock load that affects the branch. It’s a bit like the crumple zone of a car that absorbs energy to protect the driver who wasn’t able to brake early enough to avoid the crash against the guard railing. But as the guard railing prevents the car from falling down the bridge the cabling prevents the branch from overstretching.

    6. codoms/ multidoms:
    The system can be used to secure codoms / multidoms too and often enough was used in such cases. Therefore you have to connect every stem with its neighbour (e.g. as ring connection) and possibly crosswise with its vis-a-vis. Try to secure every load directions – that means back and forth as well as left and right.

    7. Sudden winds:
    Right they could happen everywhere - and cobra is dealing them worldwide since over 15 years.

    8. Not worth the liability:
    This point something anyone has to come in terms with oneself. Thousands of arborists think it is worth to put themselves into this liability and they trust in our system.

    9. More wood challenges the defect even more:
    More reaction wood doesn’t challenge a defect even more. It rather helps the tree compensating that defect thus it is healthy wood that can transfer load down to the roots.

    10. Apparent deffects:
    Not every defect is visible like a crack, often decay is hidden inside the wood. But you are rigth if there is no defect than cabling is sensless – apart from calming a homeowners worries.

    Puh, excuse my answers are that long. Nevertheless I hope they are useful to you or anyone else.

    Greetings
     
    EdenT likes this.
  18. Ekka

    Ekka Diploma Horticulture + Diploma Arboriculture (Leve

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    I applaud you for you tenacity and references. :rock:

    I also mentioned previously that Treevet has no clue about that specific point quoted above. Reaction wood is a tree's natural reinforcement of stressed areas, it is a good thing in most cases, and to encourage via dynamic cabling not diminish via static cabling.

    In general you have expelled much energy on primarily 2 posters (Treevet and Jomoco), the larger arborist community is well aware of these systems and their application, as they may also be more aware of tree biology and anatomy. :rockn:

    You can also buy 5% stretch rope or 20% stretch rope depending on the application. With the ease and speed of fitting these systems, the non invasive aspect, the longevity I would consider it a disservice to not include it in your bag of MANAGEMENT OPTIONS.
     
  19. treevet

    treevet Banned

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  20. treevet

    treevet Banned

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    .....furthermore...let's take 2 very flexible twigs and scotch tape them together at the base (say 3' long)....

    then let's try to pull them apart...very difficult as the willow flexes. Then let's add a steel support to each side (again reaction wood simulated) and then let's try to pull the scotch tape apart by the steel supports....

    very easy now to pull them apart.
     
    Last edited: Feb 26, 2010

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