Switching from Static Cable to Dynamic

A friend of mine works for Point Reyes National Seashore and they have a very large California Live Oak that was cabled many years ago with a steel/static cabling system. Some of the cables have since snapped and failed. They have had the tree looked at by a fellow from the University of California at Davis(I'm forgetting his credentials) and he has suggested reducing some tip weight and switching to a dynamic cableing system like Cobra. Now here is where my question comes in... He has suggested that they cut the other old static system out of it. What is the best management practice for the old system? Part of me thinks it should stay in place, especially if it has been in for decades. If you were switching to a new static system, cutting the old one out doesn't seem that risky but switching to a new dynamic one where you aren't directly supporting limb weight? I am going to send my friend a link to this thread and hopefully this next week we can get some pictures of the tree on here.

Why does it even need to be cabled? Are there defects at critical points?

I'd remove all the cables (unless deemed REALLY necessary), so the branch could move.

What's the target situation like? How compromised is the existing system?

It would be a shame to go to all the trouble of removing the existing system and installing a Cobra setup only to have big splits open up in the first major wind event. . .

Almost nothing is written in the ANSI A 300 BMP manual on cabling and bracing regarding replacement of a static system with a dynamic system. We can probably assume that this tree has a solid foundation, as the existing cables would have limited it's ability to absorb and dissipate wind energy. Reducing branch tip weight is also recommended. If some of the cables are already broken, and the tree has been responding to this loss of support, it could be that those cables are no longer necessary. It could also be that the tree just outgrew it's existing system, and would benefit from a new dynamic system higher in the crown.

From the ISA Tree Maintenance collection of CEU articles: "The installation of cables in a tree represents an ongoing responsibility. Cables must be inspected regularly. Periodic inspections should be made to check the structural integrity of the tree and limbs, condition of the hardware and support system, cable tension, and position of the cable(s) in the tree. As the tree grows older and taller, new cables eventually may need to be installed higher in the tree. Old systems should not be removed until after the proper installation of the new system. Trees that have been cabled may also need to be pruned periodically to remove excess foliage weight and reduce wind resistance."

Of course it all depends, but...

I think it could be a mistake to switch. I'm assuming the steel has been there for years. The limbs have become dependent on the steel (that hasn't broken) and the steel has limited the growth of reaction wood while the limb went ahead and got heavier and heavier.

I'm interested in why the steel broke. What system was used? Was it common grade steel? How many years ago was it cabled? There's a good chance that the steel just needs to be replaced and moved higher up.

Point Reyes is beautiful. I'll install the cables for a discount if they cover airfare and supplies shipping


It's worth noting that I always love installing dynamic cable and it's my first line of attack to consider once the decision has been made that a tree is going to be cabled. (Specifically, I like Yale Guardian Gray)

But after many years with steel, I think they are stuck with it.


love
nick

I've been thinking about this one, and I'd love to see pictures of the tree itself. But maybe replacing the the damaged cables with a dynamic system, while leaving the existing cables in place, assuming they pass inspection. Also perhaps reducing the crown, but I'm really on the fence about this one.

Nick, ime they usually snap because they were installed too tight. The US champ white oak has 5 or so broken cables dangling, a sick sight. Gren, the A300 (which is not the BMP) is really clear about replacing the support before undoing anything. Without more info I tend to agree with Nick re let it be; the tree's dependent on it, and what's there to gain? Dynamic is sometimes overprescribed due to a cool factor imo. OM not sure what youmean by "dynamic one where you aren't directly supporting limb weight?". Cables do support weight; I've seen 4 ton cobra-looking cables in France that directly supported 4' dia. limb/stems.

Point Reyes is gorgeous--I ran a 50-miler out there back when; 1982? Trees were scarce; it'd be a shame to lose any. Or overprune any; that's the nice thing about cabling; keeping the full crown. And please no one tell jomoco about this or it'll be rant city all over again.

Seems like replacing the old static with new would be worthwhile. If too tight on many snapped ones, maybe too tight on the remaining one.

Jeff, my friend out there probably won't see this until Monday when he's back at work. I believe that there is a significant target or it wouldn't have been cabled in the first place. I tried to get him to describe the original cable pattern but he said it was kind of weird which put me in mind of some of the cable happy jobs I've seen Bartlett Tree Service do around the Bay Area.

And Indianapolis; a big bur oak there has ~10 cables, but no bad forks. Also no lightning protection--all that steel's just gotta increase chances of a strike. re significant target or it wouldn't have been cabled in the first place, don't be too sure. The one in Indy is in a seldom-visited park. Sean, a lot of these have turnbuckles so slacking off a bit is possible. The A300 cabling standard just got revised; very few changes, same old same old. The revision managed by a Bartlett guy; market dominance maintained, as usual.

Why would steel increase the chance of a strike if it is not grounded?

I imagine the tree itself is enough of a ground. I've been zapped in a tree more than once.

I understand that, but why would the presence of steel in the tree attract lightning.
Sounds a bit like an old wives tale to me.

There was a survey made here that showed that certain species of trees were more prone to be struck than others.
It was made because of the old, old tradition of planting a tree at a near but safe distance from houses to attract lightning so the house wouldn't get zapped.With the thatched roofs that were common here, a lightning strike was bad news.

stig said:

Why would steel increase the chance of a strike if it is not grounded?

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Good question! It's just a guess based on steel being an excellent conductor of electricity. Put this way: It can't make trees LESS susceptible, so it shouldn't be in there without a good reason.

MB, it's hard to tell sometimes if trees Really need cabling; who knows how the wind will blow? I can see erring a little on the side of holding the structure together, but a lot of big old trees have loads of counterproductive cables. The Wye Oak was reputed to have over 2 miles of it, but no reduction cuts. The current US champ had many "karate" failures from leaders being locked down by supertight cables. The FL champ live oak just lost a huge leader, one of the few that did not have a cable. It may not be champ for long, now.

"I understand that, but why would the presence of steel in the tree attract lightning. Sounds a bit like an old wives tale to me." Perhaps so, but that tale was accepted by authors of the USDA Risk guide, and those guys are not quick to repeat myths.

Re old wives tales, we had a similar survey on species susceptibility here in the US. Very weak science but nonetheless it persists in the US standard on lightning systems.

Zapped in a tree whaaa? how'd that feel?

Not pleasant! I was trimming hi lines, it happened every now and then.

Steel in the tree shouldnt matter. The path to ground determines everything.

I saw it on The Simpsons once. Lisa left a steel bucket up a tree, which was struck by lightning

Well there ya go! If one path to ground includes steel, and an identical one does not, which would you bet on?

What the heck was Lisa doing with the bucket anyway?

She was camping in the Springfield Redwood to prevent its felling, she was using the bucket to have food sent up,
The lightning hit the tree because of the bucket whilst she had descended to get some food at home, oh the irony!

Ben Franklin, key on the kite string...

Maybe an old forefather's tale.

It is...... string doesn't really conduct hardly.

But it was wet and he was holding a key! It has to he true!


love
nick

I'd love to know the entire, true story behind that.

MasterBlaster said:

I'd love to know the entire, true story behind that.

Click to expand...

And I'd love to know the entire, true story behind that tree at Point Reyes. OM, wassup?