cobra bracing advice

[Dean O]

been many years since installing a brace.

 

installed one a few weeks ago and had a call yesterday from the resident to let me know that it had "moved".

 

climbed the tree today to take a look - it seems that one of the loops installed after the main splice had come undone (pulled through) because the main splice hadn't gripped.

 

in effect, movement (luckily from just wind rather than failure) in the tree had pulled the splice through on this end of the brace.

 

I'm worried that if wind can do this to the splice how about a failure??

 

the only way around it I can see is to tension the system so that the splice is tight on itself and so already gripping itself?

 

initial installation wasn't slack but wasn't preloaded.

 

any advice appreciated or stories of experience appreciated.

 

Dean

[humpo48]

We have done cobra bracing twice now, on both of them we have winched the limb up a bit installed the bracing to the instructions then lowered the limb back and doing this stops the slack in bracing. Hope this makes sense?

[Marc]

How are you splicing it?

[AA Teccie (Paul)]

One for 'Arbocop' me thinks...Kevin where are you?

 

Paul

[Dean O]

How are you splicing it?

 

cable round tree stem, with plastic insert inserted, tucked back into itself for around 10 inches, back out again and back in again to form a loop, then back in and out once more, following shaking it all about, to leave a little tail. (same on both ends).

 

should've taken a pick.

 

I don't think the splice itself is the problem, though it may be?

But I think needing to preload it to retain the splices' grip seems wrong.

 

We have done cobra bracing twice now, on both of them we have winched the limb up a bit installed the bracing to the instructions then lowered the limb back and doing this stops the slack in bracing. Hope this makes sense?

 

this does make sense, thanks humpo, and is kind of what I'm wondering should be done.

I haven't reads anywhere in the literature that this is the prescribed method.

 

thanks

[Wolfie]

What length of rope did you feed through between the loop round the trunk and making the expansion loop? I think cobra recommend 30cm, I generally do closer to 60cm to allow extra friction.

I don't think that the system is supposed to be pretensioned but what I normally do is anchor my climbing line above the first end that i install then i'll go over to the other stem and put in a redirect above the second install point. This not only gives you good positioning but also the weight of you on the climbing line pulls the two stems together slightly. I find that just enough to get the right tension but I am 16stone.

[darrin]

here's a link for the instructions.

http://www.cobranet.de/de/datenblatt/cobra_manual_US_20101011.pdf

[Marc]

cable round tree stem, with plastic insert inserted, tucked back into itself for around 10 inches, back out again and back in again to form a loop, then back in and out once more, following shaking it all about, to leave a little tail. (same on both ends).

 

should've taken a pick.

 

I don't think the splice itself is the problem, though it may be?

But I think needing to preload it to retain the splices' grip seems wrong.

 

 

 

this does make sense, thanks humpo, and is kind of what I'm wondering should be done.

I haven't reads anywhere in the literature that this is the prescribed method.

 

thanks

 

Sounds perfect to me, you do not want it to tight especially this time of year, there will always be a little sag in the brace and as far as I understand this is normal, your only limiting maximum movement whilst still allowing the limbs to move freely. It should not be used on obvious defects!

[born2trot]

If you have the first splice to tight around the tree there is no way of tensioning the system up . Sounds if that part has been done correctly but impossible to say without photo . 99.9% of the cobra-ing i see is too slack

[MattyF]

There is supposed to be slack in bracing!! The limb is supposed to move! The bracing just stops it moving to the extreme or acts as a storm

Anchor incase of failure.