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Trunks vs Branches vs Roots

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I have seen vague references in a few places that branch growth wood is more stable (esp. when green) than trunk growth wood. Maybe this is due to internal stresses and larger distances between growth rings? Does any one have some insight for me on this? Perhaps there is an article someone has come across that explains it well?

Thanks,

:eek:
 
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i do not know about stable, but a tree limb the pith will wander in the wood, while in the trunk the pith may not be in the center but pretty much stays in the same place in the trunk

hope this helps
 
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Mike Mahoney in his latest video talked about how the branch wood isn't as good for bowls as there is a lot of tension in it. I have never noticed that. I do like the way the buttress part of the trunk (base) tends to warp sideways. The trunk is under compression load most of the time, except for high winds, and the limbs are under tension so they can hold up loads. I guess I am saying, I don't really know of any difference, or haven't noticed any.

robo hippy
 

hockenbery

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Generally there is more tension wood in branches especially the load bearing part nearer the trunk.

This can be an issue for natural edge bowls. As you hollow it you cut the tension and the rim springs open.
When you try to turn an even thickness you might get a thicker side because the bowl has sprung open unevenly.

You can leave the center of the bowl full of wood until you get the walls to finish thickness down about 2" and the work down in 2" increments. You most likely will get even walls even with tension wood.

People turn lots of crotches and they have lots of stress wood. The feather in the crotch is the two grains pulling on each other.
Crotches move as they dry in asymmetrical fashion on three axis. It is especially important to get even wall thickness and curves that support the drying.

Turn what you get.
If you have the whole log use the trunk for bowls.

If you only have limbs turn them. I have done lots of natural edge bowls from limbs and I've only thrown a few out because they moved while hollowing. Big bowls I usually turn from trunks wood because the grain is mor symmetrical and often limbs don't have the diameter for bowls.
Although we do occasionally see camphors with three foot diameter limbs.

Al
 
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Bill Boehme

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Bruce Hoadley's book, Understanding Wood describes why wood from trees that lean significantly or wood from large heavy branches is usually unsuitable for commercial use. The problem is that as the tree develops and begins to bear weight, the wood that on the underneath side of the pith will develop to support a compression load while the upper side is doing just the opposite as it supports a tension load. The farther the wood is from the center, the greater the amount of built-in stress. Everything is fine and dandy while the tree is standing and growing because there is an equilibrium between the direction of gravity and the weight being supported. Things get out of whack when the tree is cut into log sections and now the built-in stresses are no longer in equilibrium. Things really get bad when the wood is cut into lumber and now the built-in stresses are even more out of balance. Hoadley refers to this type of wood as "reaction wood". A straight piece cut from reaction wood will quickly warp and if it is jointed and planed to flatten the warp, it will just warp again -- only worse. It is not hard to envision that the same movement will also happen in bowls except that the problem is worse because the grain orientation is not constant as it would be in a flat board.

You can turn green reaction wood very thin; it will warp a lot as material is removed and as it dries and there is good chance that it will not crack. However, I would not waste time trying to turn a dry piece of reaction wood.
 

john lucas

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What Bill said has been my experience. I have been experimenting with small green branch pieces on Christmas ornament balls. Horizontal hanging branch pieces move more than branches that go more upwards. You can often tell by where the pith is. If it's noticeably off center it probably has a lot of reaction wood.
You can get the same thing in trees that grow on the side of a hill and lean. On a tree like that the trunk wood may move as much as the limb wood.
 
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Sorry Bill, I havent forgotten about my question, but the job that pays the bills has gotten in the way of my real job...that is, turning wood.

Thanks all for the information. I will have to try to track down a copy of Understanding Wood and take a leaf through it. It seems that my vague recollection of things that I had read in the past was off the mark.

:eek:
 
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Greg, as a turner I dont care. We can use wood left by others. Here small mill owners just mill the trunk. They leave the branches to rot on the mountain. They say the stresses in the limbs bind the saw blades.Koa trees can be huge. I have cut on branches 8 feet in diameter. the trick is working out a deal with a ranch to take the garbage so to speak. Root pieces can be very pretty and full of stress also, and rocks and dirt. So I just know that some pieces are going to move more than other pieces. And some of the most stunning is from solid stress.
 

john lucas

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Boy do I agree with Kelly. I'll turn any piece of wood from anywhere on the tree or under the ground. It is nice to understand how the wood moves and maybe be able to predict it. As least as much as we can. Lots of turners have used this wood movement to their advantage, John Jordan, Bill Luce, and David Ellsworth come to mind and I'm sure there are many more examples. In fact Todd Hoyer did a wonderful lecture on this subject at the Southern States symposium years ago.
The information is out there. John Jordan's video on the Wood movement and the Aesthetics of wood is really great.
 

Bill Boehme

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A few years ago a Live Oak tree came down in a storm (which is really unusual because they are so sturdy) and the homeowner said that it was OK for me to cut it up and take all that I wanted. It was actually a double tree grown together at the lower two feet which meant that it had two "leaner" trunks. I also got some of the below ground wood from one of the trees. I wish now that I had taken more of the root because the grain pattern was so interesting and beautiful -- nothing at all like the wood from the trunk. I turned it when it was dripping green and because of the tightly interlocking grain, it did not crack nor did it even warp very much. It turned like butter while green. I let some of it dry which was a mistake because it became too hard to turn. I would never cut down a live oak to get another chance at some of this great wood, but if the opportunity arises to salvage a down tree, I will be on it like a duck on a June Bug.
 
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I will have to try to track down a copy of Understanding Wood and take a leaf through it. It seems that my vague recollection of things that I had read in the past was off the mark.

If you'd rather not drop the bucks, get The Wood Handbook here for free. http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p Chapter 3 has the information you're after. Juvenile and reaction wood. Lots of other good information as well. Hoadley wrote a lot of it.
 
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Bill's quote of Bruce Hoadley's book, Understanding Wood, is correct, but just because it's reaction wood and not good for two by fours or furniture doesn't mean it's not good for turning. If you are going to burn/carve/pierce/color, it doesn't matter, but if you want figure and character, this is much better wood than that from a straight trunk.

Hoadley also has a second book, Identifying Wood, and the two should be on every turner's bookshelf.
 
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Greg, as a turner I dont care. We can use wood left by others. Here small mill owners just mill the trunk. They leave the branches to rot on the mountain. They say the stresses in the limbs bind the saw blades.Koa trees can be huge. I have cut on branches 8 feet in diameter. the trick is working out a deal with a ranch to take the garbage so to speak. Root pieces can be very pretty and full of stress also, and rocks and dirt. So I just know that some pieces are going to move more than other pieces. And some of the most stunning is from solid stress.


Kelly, I wouldn't turn down free wood, but I do want to understand the forces int he wood so that I can better predict the result. Next time you see a branch that is 8 feet in diameter, please PM me
 
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