Hollow Spots in Trees

[Froggy]

What is the general rule for hollow spots in trees. How much of the tree should be left in order to consider the tree safe? Or dose that depend on the type of tree you're looking at? Also when there is a hollow spot in a tree how do you determine the max load you'd put on it? I know most of the answers to these questions, but I'd like to see what some others think. Thanks,
BB

 

[MasterBlaster]

I don't think their IS a general rule concerning that. Every situation will be unique.

If it don't look or feel right, DON"T climb it. Lotta help, huh?

 

[Ax-man]

Hollow spots with the rams horn curling on the out side of the decayed spot don't bother me half as much as would the soft ,punky dry rot decay does. It is very difficult to judge how far rot like this has eaten into the wood. With the hollow spot type decay you can at least judge how much wood is left .

As far as how much load to apply. If it was me I would go 1/2 or less than normal as compared to the same situation only no decay present. I like to get a feel for situations like this by being conservative first, then work up from there.

 

[jblimbwalker]

Originally posted by Froggy
I know most of the answers to these questions, but I'd like to see what some others think. Thanks,
BB

Please....do share.

 

[Kneejerk Bombas]

I had a hollow tree break off below me, so I'm a little more cautious now.
The thing to remember is that it is usually not just hollow, there are often other structural problems like cracks or holes. These tend to compound the strength loss.
At the point where about two thirds of the wood is decayed is statistically the threshold where they begin to fail.
As far as working a hollow tree, I've written about using guy ropes to support trees. It only takes about 10 or 15 minutes to set up 2 or 3 guys to make a suspect tree much safer.

http://www.arboristsite.com/showthread.php?s=&threadid=8413

 

[SilverBlue]

Had a willow takedown earlier this year where the only good crotch tip was hollow and punky. Have to go there today anyways, will take an interesting pic if wood is still there.

 

[ORclimber]

Originally posted by RockyJSquirrel
I've read (and it seems to correspond with what I've observed) that a hollow tree can lose 75% of it's mass and retain 90% of it's strength. This has helped me work much more efficiently in large trees with hollow trunks.

Compare to a hollow steel tubing such as a porta-wrap. The tube is still 90% as strong as if it were a solid hunk of steel.

Maybe some hollow trees are as safe or safer than solid trees because they are lighter. I had heard that hollow pipe was stronger than solid pipe, maybe that was referring to strength/weight ratio.

 

[wiley_p]

hollow spots

Is this a catface you're r4eferring to? isthe hollow on the compression side or the tension side? Is it a confier or deciduous?Yes there are a few factors to consider remember each tree is in its own unique situation

 

[John Paul Sanborn]

There are some books out there on try dynamics ad the relationship to structure and decay.

The hazard handbook is a good took to learn, Matthecks writings...

The 25% Rule Of Thumb is for a cylinder that is uncompromised, that is a hollow trunk wothout a crack or a squirril hole.

The 30% ROT Mike talks about is the compromised cylinder that we most often find before starting the face cut.

As with any other breaking strength concideration, species is a big factor.

It is good SOP to carry a hammer to thump a trunk when making any bid, and before setting a line. Cheap insurance.

I've read of guys who will make bore cuts with a chainsaw, parralel to the grain, when climbing a dead/declining tree.

 

[SilverBlue]

Here's a pic of willow that's not to strong to begin with. It was going to be used as a TIP untill I said not to use it and set up a FC instead.

 

[SilverBlue]

And this piece supported quite a load, it was surprising to see a huge amount of large black ants come pouring out as the cut was being made. The ant nest was about 6 ft long inside.

 

[Froggy]

Reply

JB, I wasn't saying I knew all the answers, but I've been tought ways to evaluate a hollow tree. The ones with a vertical split are the ones i've been tought to be most cautious of. A hollow tree should atleast have 25% of it's mass left in order to be considered safe. Also like RockeyJ said a hollow tree with 75% of it's mass gone can still have 90% of it's strength left. RockyJ i like the comparisan to the Porta-Wrap that helps a lot. Mike that's alot like the way a radio tower is set up. That's excellent thinking. Thanks. JP the trees that are on my mind are four locust. Probably 3ft accross and close to 90ft up. Maybe more?? I wish I had pictures, but I don't. The biggest hollow spots are around half way up. Locust are prone to having hollow spots through out the trunk. There is plenty of live growth up in the crown of the tree. I was trying to determine on one of the if I should rig off the tree next to it of just rig off it's self. I'd like to take some pretty good sized pieces, but i might just have to go with picking it apart little by little. Appreciate the advice. Please keep it comming. Thanks,BB

 

[mikecross23]

If you have a stable tree conveniently close to rig off of, then use it. I feel a lot better when a large piece breaks off into a swing away from the tree I'm in.

 

[SilverBlue]

I like the idea of setting a TIP in another tree except that I hate to swing with a saw running.

 

[John Paul Sanborn]

The higher up the cavity is the less hazard involved. Especially if it is above the first branch. But if rigging big wood out this could be moot.

Just remember that these are just rules of thumb and for sound wood only.

If you remember back to the "hollow basswood" thread that Gopher posted. He had is estimations close to these numbers only after doing a some drilling in the area of the defect.

As I in the previouse post, read the books on the subject to get a better hook on the concepts. And then work with caution and respect around these situations. All we can do is make educated guesses when confronted with them, and if you don't have a lot of experiance and knowledge, all your doing is making a wildassed guess

 

[TheTreeSpyder]

Originally posted by SilverBlue
I like the idea of setting a TIP in another tree except that I hate to swing with a saw running.

Alternate overehead or to side support is sometimes not an option. Also to reduce potential swing to such might lightly lace tail of lifeline thru host tree parts for some drag to slow down the potential sweep.


In addition, or when all that is available, i think mountain climber, tie in to low solid below defect, loop runner slings choked every 6' or so up, with both legs of line thru, for failable points, also removable on the way down. A few times on lighter stuff, i have gone with one leg of line in for theoritcally being caught but with shock draining pattern of the allowed run allowable on single line bringing you down automatically to lowest point of total run of loop, rather than of double strand of line with 2 lines in carabiner.

Orrrrr something like that!

 

[Matt Follett]

Froggy

You said locust... do you mean black locust (Robinia psuedoacacia , or Honey Locust, ( Gledistisa tricanthos )

I have seen some scary failures in Black Locust, as their decay points seem to travel for a long time (poor wall 1???) however they seem quite strong prior to decay... they always seem to have large carpenter ant infestations around here... ( I heard somewhere once this wood was used for ships masts, but rarely have I seen a tree straight enough for this... anyone else heard the same?)

Honey locust has never really scared me, seems to have reasonable failure traits... topping wounds, occasional included bark, rarely have I seen huge holes which travel beyond visible cues of reation wood forming etc.

You also ask how much should be left to determine if it's safe...???

Are you condsidering pruning these trees to reduce the likelyhood of failure? Then we are really moving into a whole other issue, which is very hard to wrap ones head around, particularly when looking at the sorrounding environment.

I tend to be an advocate of less is more, there are other opinons here though. Reducing a trees overall size can be considered risk management/prolonging the slow death/ what have you...

If a tree has a cavity higer up in it's canopy, and is in slow decline, (well anywhere actually but for this case lets say it up there) it may not be able to put on enough wood to support the load, as the cavity continues to enlarge. In which case action should be take to reduce the risk of failure/propety damage. As you decide what to do always take into account the targets, a weak point isn't high risk if there is no target within it's grasp... that target may be a pedestrian... it might be a shed... it might just be the garden below.

Ah... I think I'm rambling on, no perhaps off...

I'll shut up now and see if this is the direction you were headed

P.S. I wanted to add in here... good reading for this sort of thing is Mattheck and Breloer's 'The body Language of Trees' This book is great for sorting out in your head some of the concepts of failures, what to look for etc.

 

[ORclimber]

Originally posted by Matt Follett

I have seen some scary failures in Black Locust, as their decay points seem to travel for a long time (poor wall 1) however they seem quite strong prior to decay... they always seem to have large carpenter ant infestations around here... ( I heard somewhere once this wood was used for ships masts, but rarely have I seen a tree straight enough for this... anyone else heard the same?)

Ironically, black locust is sought after by boat builders for its rot resistance. More common uses would be decking and framing. I'll bet some fine standing knees could be made from the crotches.

 

[Froggy]

Reply

Jp,Yeah I agree you probably shouldn't take on removals like this unless you know what's going on and have experiance. Well I'll assure you that I have both. I feel the more knowledge you obtain the better off you'll be. When faced with a situation you hear lots of advice over and over. Which is good, but when you search you just might get that little pice of knowledge you've never heard. That's why I post here to get the knowledge from different climbers who may have experiance something I've never. In a tree knowledge is going to get you far. It might even save your life or someone elses. Thanks,BB