V and U shaped Crotch Strengths, included bark| codominant stems etc

Ekka · 12th February 2007, 03:59 AM

This is exceptional stuff with some great data. How strong are these unions and what you can do about making them better.

I wonder how many of us can actually tell the difference between an included bark and non included bark union?

The data shows that a non included bark union isn't that much stronger anyway.

Also, when the diameter of the branch is less than 2/3's the trunk dia the strength is better.

I encourage all to read from page 50 onwards on the second PDF about types of crotches and failures.

codominantstemsincludedvsnot.pdf
crotch strength PDF 4.4mb

And some pictures of crotches to get the ole gray matter working.

001.JPG
005.JPG
008.JPG
010.JPG
011.JPG

Sean Freeman · 12th February 2007, 01:46 PM

Couple of really good papers there Ekka, and raises a very important issue for any Arb assessment we can always find defects and weaknesses in every tree whether its at the crotch or elsewhere, and every tree will fail at some point given enough time or enough loading.

By focussing on the target exposed under or next to the tree we can eliminate a huge amount of unnecessary tree work, no target...no problem. Of course applying the basics of VTA every time in a systematic way and ensuring that for trees with a target we are comprehensive in the way we examine the tree..no drive bys here

A great mental tool to use at the end of any assessment is to imagine how many trees out of 100 of the particular species with the particular defect/weakness etc you would expect to see failures in a year.
So if you had 100 of these trees in the same circumstances how many would fail in a 12 month period (so that would include at least one storm season).

There are very few significant failures, even here in Oz, compared to the actual number of trees we have in urban areas, and managing the risk should follow the same established and accepted rules that are applied to risk management in every other aspect of our lives.

SF

Notahacker · 17th February 2007, 08:27 PM

Thanks for finding this information Eric. I'm going to use this with my customers to show them why I say included bark is bad.

Sunrise Guy · 18th February 2007, 03:56 AM

Good stuff! Thanks for the links!

Ekka · 22nd February 2007, 11:13 PM

Found these two pics of a typical type of failure.

Sean Freeman · 23rd February 2007, 12:41 AM

Really good pics Ekka, is that a public park/picnic area?
What sort of gum?

SF

Ekka · 23rd February 2007, 01:02 PM

That's a guys place, lives on acreage in Rochedale.

That was Australian Red Cedar (Toona ciliata), shame, rare now.

mdvaden · 23rd February 2007, 10:28 PM

One thing is for sure, included or excluded, I can still break apart codominant stems with my hands if they are 2" - 4" in diameter or less.

I think that if the not too much bark has become trapped or included, the extra 14% may be a reasonable assist, but not the most desireable.

The trapped bark as trees get older really seems to "do them in".

It's nice to see that someone took the time to analyze this.

If they post, here's a few...check out all the trapped included bark in the flowering plum tree cross-cut...

Ekka · 24th February 2007, 12:28 AM

Actually your last pic, looked like that one had no included bark but couldn't see the other side ...

... I once heard if the branch bark ridge is pointing outward like a small mound then it's likely not an included bark union, if it's inward then it is. But the ole elephant ears on advanced cases is a dead give away.

#8 below is definately included whilst #13 maybe not

Mike Poor · 1st March 2007, 11:06 AM

I've noticed "u" shaped crotches eventually become "v" crotches! (Huh?) Yeah, as the stems increase in diameter over several years and they are growing in the same general direction, the "u" eventually closes and invaginates the branch bark ridge inward! Has anyone else seen this?

Sean Freeman · 2nd March 2007, 07:14 PM

I think that its very species specific, have seen it on trees with the tendancy to form scaffold very low on the stem.

SF

TrevMcRev · 3rd March 2007, 12:06 AM

Heres a classic co-dom failure. Tree was a Spotted Gum Corymbia maculata. Split right to the base. Looking at the stump i think it was doomed from day 1.

Trev

Ekka · 3rd March 2007, 12:30 AM

Great pics, well and truly stuffed.

Was that cabling for the dismantle mate?

TrevMcRev · 3rd March 2007, 02:37 PM

Just tied up with rope after they first noticed the split untill tree could be removed. Kept in place while taking it apart.

Oldtimer · 7th March 2007, 02:18 PM

Great pictures. Very Clear showing the failure point. Thanks

12th February 2007, 03:59 AM	#1 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,669	V and U shaped Crotch Strengths, included bark\| codominant stems etc This is exceptional stuff with some great data. How strong are these unions and what you can do about making them better. I wonder how many of us can actually tell the difference between an included bark and non included bark union? The data shows that a non included bark union isn't that much stronger anyway. Also, when the diameter of the branch is less than 2/3's the trunk dia the strength is better. I encourage all to read from page 50 onwards on the second PDF about types of crotches and failures. codominantstemsincludedvsnot.pdf crotch strength PDF 4.4mb And some pictures of crotches to get the ole gray matter working. 001.JPG 005.JPG 008.JPG 010.JPG 011.JPG __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

12th February 2007, 01:46 PM	#2 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,521	Couple of really good papers there Ekka, and raises a very important issue for any Arb assessment we can always find defects and weaknesses in every tree whether its at the crotch or elsewhere, and every tree will fail at some point given enough time or enough loading. By focussing on the target exposed under or next to the tree we can eliminate a huge amount of unnecessary tree work, no target...no problem. Of course applying the basics of VTA every time in a systematic way and ensuring that for trees with a target we are comprehensive in the way we examine the tree..no drive bys here A great mental tool to use at the end of any assessment is to imagine how many trees out of 100 of the particular species with the particular defect/weakness etc you would expect to see failures in a year. So if you had 100 of these trees in the same circumstances how many would fail in a 12 month period (so that would include at least one storm season). There are very few significant failures, even here in Oz, compared to the actual number of trees we have in urban areas, and managing the risk should follow the same established and accepted rules that are applied to risk management in every other aspect of our lives. SF Last edited by Sean Freeman : 12th February 2007 at 08:56 PM. Reason: forgot time component

17th February 2007, 08:27 PM	#3 (permalink)
Notahacker Gettin' motoring Join Date: Feb 2007 Location: Longmont, CO Posts: 17	Thanks for finding this information Eric. I'm going to use this with my customers to show them why I say included bark is bad. __________________ "Quality costs as much as it saves." My great uncle Simon Murphy

23rd February 2007, 01:02 PM	#7 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,669	That's a guys place, lives on acreage in Rochedale. That was Australian Red Cedar (Toona ciliata), shame, rare now. __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

3rd March 2007, 12:30 AM	#13 (permalink)
Ekka Eric Frei Administrator - Brisbane L5 (Dip) Hort Cert III Arb + some Join Date: Jan 2007 Location: Brisbane Posts: 5,669	Great pics, well and truly stuffed. Was that cabling for the dismantle mate? __________________ Remember to use the "search" function, if you have answers/questions post them so everyone can benefit. Free Tree and Green Industry Link Directory Qualified Brisbane Tree Lopping Brisbane Tree Care, Consultations and Arborist Reports Forum Sponsors

18th February 2007, 03:56 AM	#4 (permalink)
Sunrise Guy Newbie Join Date: Feb 2007 Location: Austin,TX. Posts: 2	Good stuff! Thanks for the links!

23rd February 2007, 12:41 AM	#6 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,521	Really good pics Ekka, is that a public park/picnic area? What sort of gum? SF

1st March 2007, 11:06 AM	#10 (permalink)
Mike Poor Cruisin' Join Date: Mar 2007 Location: Urbana, IL,usa Posts: 76	I've noticed "u" shaped crotches eventually become "v" crotches! (Huh?) Yeah, as the stems increase in diameter over several years and they are growing in the same general direction, the "u" eventually closes and invaginates the branch bark ridge inward! Has anyone else seen this?

2nd March 2007, 07:14 PM	#11 (permalink)
Sean Freeman PDF King & Arborist Extrodinaire Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,521	I think that its very species specific, have seen it on trees with the tendancy to form scaffold very low on the stem. SF

3rd March 2007, 02:37 PM	#14 (permalink)
TrevMcRev Astronaut Join Date: Feb 2007 Location: Melbourne, Victoria, Australia. Posts: 672	Just tied up with rope after they first noticed the split untill tree could be removed. Kept in place while taking it apart. __________________ Melbourne Arborist, Total Tree Care, Pruning, Tree and Stump Removal

7th March 2007, 02:18 PM	#15 (permalink)
Oldtimer Cruisin' Join Date: Jan 2007 Location: Austin TX Posts: 57	Great pictures. Very Clear showing the failure point. Thanks