The Great Heartwood/Sapwood Controversy

More data from the Forest Service:


books


from The Commercial Hickories by Anton T. Boisen and J.A. Newlin
USDA Forest Service Bulletin 80, Issued October 27, 1910
http://books.google.com/books?id=ZYUcCJa72gMC&ots=QiomFK2z-0&dq=heartwood%20sapwood%20hickory%20strength&lr&pg=PA50#v=onepage&q=heartwood%20sapwood%20hickory%20strength&f=false
 
filedog said:
What I'm interested in is: have any of you ever had an otherwise sound haft fail at the junction of heartwood and sapwood?
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I've had a hammer handle fail at the junction of heartwood and sapwood. But this handle had a run-out grain.
 
Square_peg said:
I've had a hammer handle fail at the junction of heartwood and sapwood. But this handle had a run-out grain.
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Interesting. I've read hammer handles are some of the worst offenders regarding grain orientation, but due to their short length,

they are less likely to fail. So, I guess the runout was also at the heartwood/sapwood junction?
 
I suspect that the heart wood is not as good in tension as the sap wood. I don't know this as fact. I also don't know what "Modulus of rupture" means in the above study or how it was conducted. Tests and test methods can leave much to be desired in actual practice.
One thing that stands out with those numbers is the higher specific gravity with the less growth rings per inch. That's because the late to early wood will be better(young trees).
 
garry3 said:
I suspect that the heart wood is not as good in tension as the sap wood. I don't know this as fact. I also don't know what "Modulus of rupture" means in the above study or how it was conducted. Tests and test methods can leave much to be desired in actual practice.
One thing that stands out with those numbers is the higher specific gravity with the less growth rings per inch. That's because the late to early wood will be better(young trees).
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Yes, but do handles fail at the juncture of heartwood and sapwood? Does having both make for a weaker handle? Ever seen such a handle fail?
 
filedog said:
Yes, but do handles fail at the juncture of heartwood and sapwood? Does having both make for a weaker handle? Ever seen such a handle fail?
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With some species there is a big difference between heart and sap wood. But we are talking hickory here and I do not know. I have never owned a tool that had both in the same handle.
If hickory grew around here I would be able to tell you. Why not go cut you a piece, split out one sap wood one heart wood and one mixed following the growth rings and of equal size. Dry them and break them. I would be interested to know how that would turn out.
 
garry3 said:
Nope not me. I test things for a living. Before that I built things for a living.
I am going to grab a boys axe and go look for some saplings suitable for making a bow or two. No tape measures, no science, no rules.
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Nice, I like that.
 
One of the more important things with handles is also the operator - the use and also how the handle will get - kept inside vs outside, protective coating(linseed, etc), cleaned, overstrikes, use, etc. these play lore of a role than grain orientation in my experience. Heartwood sapwood I pay no attention to. I will check for grain running the length of the handle and that's about it.
 
garry3 said:
I suspect that the heart wood is not as good in tension as the sap wood. I don't know this as fact. I also don't know what "Modulus of rupture" means in the above study or how it was conducted. Tests and test methods can leave much to be desired in actual practice.
One thing that stands out with those numbers is the higher specific gravity with the less growth rings per inch. That's because the late to early wood will be better(young trees).
Click to expand...

One of the reasons Yew was chosen for bows was the difference in characteristics between heartwood and sapwood, with heartwood being better able to resist compression and sapwood, tension. Regarding modulus of rupture, I wonder if the figures change if you turn the wood upside down (so heartwood on top and sapwood underneath). With woods like Yew, orientation certainly would make a difference IMHO. Self bows utilise the strengths of both heartwood and sapwood. Imagine if you could string the bow "backwards", so the heartwood faced the target and the sapwood was the "backing". Certainly wouldn't last too long or even draw the same poundage. I've seen some footage of guys in thailand using axes with incredibly flexible shafts that would break first go, if hefted "European/american style". Perhaps our "overconcern" with this issue is more to do with the handle's ability to withstand abuse rather than it's suitability when used correctly.
 
Well, we haven't had a single report of failure due to "mixed" handles.

So maybe it's not really an issue.
 
The only handles I've personally seen flat out fail were run-offs, at the run off. All were pure white hickory.
 
parbajtor said:
One of the reasons Yew was chosen for bows was the difference in characteristics between heartwood and sapwood, with heartwood being better able to resist compression and sapwood, tension. Regarding modulus of rupture, I wonder if the figures change if you turn the wood upside down (so heartwood on top and sapwood underneath). With woods like Yew, orientation certainly would make a difference IMHO. Self bows utilise the strengths of both heartwood and sapwood. Imagine if you could string the bow "backwards", so the heartwood faced the target and the sapwood was the "backing". Certainly wouldn't last too long or even draw the same poundage. I've seen some footage of guys in thailand using axes with incredibly flexible shafts that would break first go, if hefted "European/american style". Perhaps our "overconcern" with this issue is more to do with the handle's ability to withstand abuse rather than it's suitability when used correctly.
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Yew is a whole different thing. I think that the sap wood contributes nothing to the strength of the bow at all. To me it feels almost like rubber. Great in tension? Oh ya! If you notice the prehistoric yew bows the sap wood is removed. I think that this is because the wood was worked wet. Get rid of the sap wood and you remove most of the moisture(check out the Ice Mans bow). If you have ever cut yew in the summer and don't take special measures the bow staves will end up looking like spaghetti. A few years ago it was a great honor to pull very old Nez Pierce bow from its case(with much care). No sap wood, unbacked, about 4'. Point being, Yew does not need the sap wood backing. And yew was used for bows without the sap wood long before the English started sticking the French with sap wood backed yew longbows.
Most self bows are either heart wood or sap wood. Yew being the exception but as already stated it was a rather recent innovation in the history of yew bows.
Are we over concerned with heart wood and sap wood in handles? Ya probably. But the fact still remains that there is a difference in the sap wood and heart wood of hickory. Do you think we just used the hickory sap wood handles for a couple hundred years because of a myth?
 
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