Ring thickness correlation to density??

[ssrhythm]

I’m about to have a real good comparison for osage.  I’m finishing a bow from an indiana tree that had phenomenal late to early wood ratio.  The early layers are super thin, and the late rings are whoppers.  So far (just put first shots thru it yesterday) it’s holding the vast majority of the reflex I added (had to remove reflex from one limb and reflexes to match the natural reflex of the other limb). I came in too light, so Im about to take an inch off each end to make bow 63.5” tip ti tip.  Will add slightly more recurves and sinew backnit.

The second bow I have just about at floor tiller is an Ohio stave, and it’s early:late is not terrible, but definitely not as good as the first bow.  It is already ~ 62.5” tip to tip.  Limbs are slightly wider.  At this time, this bow weighs less than the nearly finished first bow, so it is definitely less dense than the bow with thick growth rings.  I’m going to recurve and back it  with sinew also, so while theirs will be slight design differences, they will be very similar.  The comparison will be interesting.

Im interested to see which one produces the better bow.  I tend to think that the tighter ring staves will take less set than thick ringed staves.  Why?  Well, if set is caused my compression of belly cells, my theory is that before the cells of the thin late rings in the compression plane of the belly can compress snd become damaged, the compression forces are spread into the the early wood in that compression plane which is spongy and can “absorb” some of the compression load…providing a little buffer of protection for the late wood rings in the compression plane.  I’m pretty sure that an unviolated thin back ring will withstand any normal draw applied tension, so unless the early wood layers are unusually thick, which might cause delamination toward the back, I’m leaning toward the tighter growth ring Osage producing better bows than fat growth ring Osage.  I know for sure that if two identical bows were made from those two staves I have, with draw weight and profile being identical….the thin ring stave will out perform the thick ring one by a good bit simply due to how much lighter the wood is…less limb mass to move = faster.   

That’s my theory, and I’m sticking with it till I prove myself wrong…which may be as early as the end of this week!

I’m

There was a whole thread hypothesizing that early wood contribute more to set which is opposition to your idea that early wood absorbs the compression. They hypothesized that a belly ring thick enough to not have exposed early wood would perform better.

A theory isn’t right until proven wrong. Just the opposite that we shouldn’t invest heavily in it until proven right.

Oh yes, I'm well aware of that thread.  I was of the opinion that early wood does not contribute to set whatsoever, but lets not resurrect and get the sticks out for that half rotted and decaying horse.  I left that one alone rather early...was giving me a headache.

I'll post pics of both builds from here on out in another thread and we can all see the final results if I don't screw anything up.

[SLIMBOB]

Ryan, I believe you are right. Thin ringed Osage consistently outperforms thick ringed Osage. I have only my observations to go by, and others who have observed the same. Thin ringed staves take less set and they are lighter. I assume the lighter early wood accounts for its lesser physical weight. That would make sense. But it seems to also have more elasticity than thick rings. I can’t say why, but what you put forward is worthy of consideration, though I think it is more than that. I am no engineer, but I read a lot and I take an interest in varied things. My knowledge about most things is a mile wide, and a foot deep, admittedly. I recall reading something some time back, that struck me as odd, but perhaps relevant to what we are kicking around. Badly paraphrasing…when you take a weak metal, and sandwich it between 2 stronger metals, the weaker metal takes on the strength of the stronger, reducing the weight without sacrificing the strength. I wonder if something similar could be true for early wood sandwiched between 2 hardwood rings. Again, only a thought, but, I am curious if there is anything to this.   

[RyanY]

Ryan, I believe you are right. Thin ringed Osage consistently outperforms thick ringed Osage. I have only my observations to go by, and others who have observed the same. Thin ringed staves take less set and they are lighter. I assume the lighter early wood accounts for its lesser physical weight. That would make sense. But it seems to also have more elasticity than thick rings. I can’t say why, but what you put forward is worthy of consideration, though I think it is more than that. I am no engineer, but I read a lot and I take an interest in varied things. My knowledge about most things is a mile wide, and a foot deep, admittedly. I recall reading something some time back, that struck me as odd, but perhaps relevant to what we are kicking around. Badly paraphrasing…when you take a weak metal, and sandwich it between 2 stronger metals, the weaker metal takes on the strength of the stronger, reducing the weight without sacrificing the strength. I wonder if something similar could be true for early wood sandwiched between 2 hardwood rings. Again, only a thought, but, I am curious if there is anything to this.

I can’t speak to your second point. What I believe is the truth with regard to wood density is that wood is massively variable. There could be pieces with thick rings that are lighter than pieces with thin rings and vise versa within the same species. Within a single piece of wood, it is known that the early wood is less dense than the late woods so the ratio should have low early wood for higher density. I know we all agree on that point. I think Mark hit the nail on the head with regard to elasticity. Differences is mass/density can be made up for in design/width.

[ssrhythm]

Ryan, I believe you are right. Thin ringed Osage consistently outperforms thick ringed Osage. I have only my observations to go by, and others who have observed the same. Thin ringed staves take less set and they are lighter. I assume the lighter early wood accounts for its lesser physical weight. That would make sense. But it seems to also have more elasticity than thick rings. I can’t say why, but what you put forward is worthy of consideration, though I think it is more than that. I am no engineer, but I read a lot and I take an interest in varied things. My knowledge about most things is a mile wide, and a foot deep, admittedly. I recall reading something some time back, that struck me as odd, but perhaps relevant to what we are kicking around. Badly paraphrasing…when you take a weak metal, and sandwich it between 2 stronger metals, the weaker metal takes on the strength of the stronger, reducing the weight without sacrificing the strength. I wonder if something similar could be true for early wood sandwiched between 2 hardwood rings. Again, only a thought, but, I am curious if there is anything to this.

That sandwhich thingy, if true…why wouldn’t it apply to wood?  You may have just articulated why we need to be searching for thinned ringed staves. 

[SLIMBOB]

I already do. It’s just, better!

[Allyn T]

That sandwhich thingy, if true…why wouldn’t it apply to wood?  You may have just articulated why we need to be searching for thinned ringed staves.

Because wood and metal have vastly different properties

[ssrhythm]

That sandwhich thingy, if true…why wouldn’t it apply to wood?  You may have just articulated why we need to be searching for thinned ringed staves.

Because wood and metal have vastly different properties

Don't go trying to mess with info I'm using to support my theroy!  Damned facts!

[SLIMBOB]

I realize that. But something is at play with ring thickness and how it effects the bows we make. Just trying to figure out what it is and why.

[dylanholderman]

just to add a wrench to this can of worms 
i can remember one year at the classic clint(osage outlaw) had a rough bow with super thin rings, like sheets of paper but pretty much all of them were early wood and the thing had no draw weight to speak of even though it looked like it should have been a 90# bow.

[willie]

I realize that. But something is at play with ring thickness and how it effects the bows we make. Just trying to figure out what it is and why.

just a thought, no proof. 

A bow whose back stretches and belly compresses can be compared to bundle of layers, each layer progressively shorter from back to belly. The layers want to slide past each other, shear stress in tech talk.

if the layers alternate between high and low density, the shearing or sliding will occur in the weaker material.

a bow with very few rings will have these forces concentrated in just a couple of earlywood layers, maybe to the point where a failure can occur sooner than if the forces can be distributed between many earlywood rings.

just to add a wrench to this can of worms 
i can remember one year at the classic clint(osage outlaw) had a rough bow with super thin rings, like sheets of paper but pretty much all of them were early wood and the thing had no draw weight to speak of even though it looked like it should have been a 90# bow.

wood density is an average of the early and late, so some density is needed to keep the bow weight up or set and width down

[SLIMBOB]

Maybe it is not one big thing, but a number of small things coming together that makes the difference. But there is a difference, and it is significant, in my experience. I simply…want to better understand why. Lots of guys spend a lifetime shooting through a chrono, with varied designs, trying to milk out a few extra feet per second. Flight shooters do the same for distance. The increases are on the margins mostly, but the effort to better understand the dynamics of it all is not diminished. The same applies here I believe. Something, or some combination of things results in better performance with thinner rings. I am speaking specifically on Osage as that is where I have seen the differences. Density drops, cast increases. As mentioned by Ryan, this can be partially explained by the lighter limbs returning faster, but that explanation is incomplete. We’re it not, we would all be shooting Balsa Wood bows. That is what tells me it is synthesis of some kind. The differences may be on the margins, but everything we do with these bows is on the margins. I would like to understand this better.