Looking for the equation...?

[flying frog]

I'm looking for an equation that gives roughly how much rot on the inside of an oak is safe. I've got a red oak with a woodpecker hole carved in the center and want to find out if the tree is still stable. The oak looks as looks really healthy, no die off in the crown, no loose bark , no external rot from the base up and no obvious insect problems. I thought I saw a way of calculating how much integrity a tree has with rot in a TCI magazine or other article somewhere.

thanks

 

[Sunrise Guy]

x+y/z X 100=% of good wood.

x=good wood on one side of rotted out part
y=good wood on other side of rotted out part
z=diameter from one side of tree to the opposite side (don't include bark)

20-25%=possible trouble if rotted part is large cavity
30-35%=trouble no matter what

I use the above in deciding if I have enough good wood to justify trying to save a tree rather than remove it. A lot of factors enter into it though where numbers alone cannot be counted on to tell the whole story: If the canopy is in good shape, the bark looking good, etc. The trouble with the good appearance thing is that a good looking canopy may also be a very heavy one and thus tax the weakened trunk to the point of sudden failure. I'm sure there are more involved equations out there that include more variables, but the above has served its purpose for the times I've needed it. Again, don't go by just cut and dried figures. If you're not sure of the hazard potential for a given tree, get a second and third opinion from those who have been in the biz at least as long as you.

 

[Chucky]

http://www.arboristsite.com/showthread.php?p=368685#post368685

 

[flying frog]

thanks for the reply

I Got 39% strength loss. It's a goner. Now with convincing the owners.http://www.arboristsite.com/images/smilies/frown.gif

 

[treeseer]

I Got 39% strength loss. It's a goner. Now with convincing the owners. (

These calculations, carried out in abstract, have meant the needless loss of many a saveable tree. Time to get the owners a 2nd opinion. 39% strength loss (if that's really the case) means 61% strength left. What about reducing 39% of the load?

There is a lot going on besides cavity size. Look at the whole tree. Look at options of reducing risk besides the basal cut, the easy way out. Post a picture and let's see what you are looking at.

 

[flying frog]

I was going to go ahead and suggest more opinions. But, the picture doesn't look good. The tree sits about 25ft away from the house, stands about 100ft tall. The hole is 30ft off the ground with the first limb at about 35ft. There are 3 entrance holes which face the house. This area has frequent high winds and as recent as last winter had a man killed from a tree snapping and piercing through the roof into the bedroom. I would definately consider saving the tree if it wasn't so close to the house, not that it's my choice. We had already considered taking limbs off the house side for weight reduction. I'll try to get a picture.

 

[xtremetrees]

If in doubt take it out. Industry say what 30-40 % saveable. i dont agree with that. I cut trees down that I think may fail its as simple as that.
Thou wound wood can be 40 % stronger still if theres wound wood there rot somewhere.

 

[Ekka]

http://www.arboristsite.com/showthread.php?t=36979