I am looking for information on the cobra cabling system which a vendor is claiming to be so much better than traditional 7 strand. He claims degradation is only 2% yearly. He didn't understand an exponential decrease over time when I questioned; nor the effects of salt water. The polypropelene based system is intriguing but I would like to know more about its reliability. vendor- " the effective life-span is 10 years". Any help from fellow arbourists would be greatly appreciated.

Reply to post by John B Wakefield, on December 05, 1999 at 09:54:40:

The 2% per year strength loss is based on tests done on Cobra cables that were installed in trees in Germany for five years and then replaced. The old ones were taken to an independant test lab for breaking. The found that there was less than a ten percent total strength loss.

For more information and discussion on Cobra you should spend some time going back in the archives on this page. Also, go to these pages and look in the archives for other discussions about Cobra.

http://theboss.kern.com/scripts/webboard.dll/~1


http://members.isa-arbor.com:8080/~isa_wb/


There are many desirable factors with Cobra and only a few shortcomings. There are also shortcomings and desirable factors with traditional cabling systems. There are times when a tree will need a hybrid cabling system using Cobra and traditional steel cable.

If you take the time to research the archives you will learn a lot about cabling systems and where to use them.

Livin' la vida del trepador del arbol!

Tom

Reply to post by John B Wakefield, on December 05, 1999 at 09:54:40:

I don't recall making any such claim about Cobra being "so much better than traditional steel." I "admitted" degradation to be 2% per year for your and other good customers benefit, not as a claim. I personally don't recall the question about the effects of salt water passing my way, but can assure you no notable increase in degredation short of possible granular salt abrasion if placed very close to direct spray and extreme evaporation. I have and will continue to expose as much reliability information as we can gather and as time permits. We recently experienced a very ugly storm in my own home town resulting in 80 to 90mph wind gusts that put 80,000 residents out of power for several days. Trees were down everywhere including a large ash in my front yard. An equally large and codominant ash in my back yard faired very well with a 20 foot span of Cobra standard in it. A large sugar maple that I personally Cobrafied also survived without damage.
The system has far more going for it than its short (15-25 year) life span. The fact that arborists in our region have been raised on static steel systems is no reason deny what may be one of the best things to happen to tree care in several years. I appreciate the fact that you remain open-minded to the possibility of your organization investigating a support system that moves with a structure that is (as you know from being there) in constant motion. How many trees have you cabled that, in 15 years didn't require a position adjustment. Oh, you could leave the cable there and it may not break but what would truly be best? Call if I can be of further assistance. Thanks for asking and good luck in future ventures. Sherrill, Inc. 800-525-8873

Reply to post by Tom Dunlap, on December 05, 1999 at 09:54:40:

My concern is the infamous tree rat.I had one chew through a piece of half inch that i was using as a rope swing