Is the early wood the weak link to cause set?

[Selfbowman]

Yes Pat. It does not just crush but kinda fold in one direction or the other. I don’t think much would show  in width even under microscope. But probably where its happening . Just a guess. In length it would seem that it would delaminate  because of thickness.

[RyanY]

I would guess any weaknesses in the early wood are overcome by the late wood. Even if the early wood does take set earlier, the late wood would just push it back to its original shape. I think the issues with higher ratios of early wood have more to do with overall density. If early wood does fail in compression earlier I think we would see frets or hinges at the point where growth rings feather out on the belly but I rarely see compression failures in such a specific spot on the limb.

[sleek]

Arvin, I dont know what my opinion is worth to you but....


From an aviation stand point, the crunchy wood is just like the honeycomb core in composite skin structures.  We lay a piece of thin aluminum  the bond to it a layer of honeycomb and another layer of aluminum.  The resulting structure is very light weight and amazingly stiff. It has all of the properties we want in a bow.

If I can find one, I'd like to make a bow that has one ring in the back, crunchy wood in the middle, and one ring on the belly. I dont think crunchy wood is a weak link. However, a badly proportioned stave of that early crunchy wood could cause a problem easily.

[sleek]

I can answer better than what I just did.

To add a more relatable example, structurally speaking: corrugated cardboard uses the same principle.

As for how to proportion the core (crunchy wood) it will vary depending on the stiffness of the belly and back. The stiffer they are, the thicker the core can be to support them. If the core is too thick, the tension and compression properties will be exceeded of the back or belly, or even lead to a torsional/sheer failure in the core.

This being an organic material we really have to learn from experience what a ring count looks like in proportion to the early/late growth, then know what stresses it can handle. A good way to Guage your progress will be the mass formula by Badger. Another is just measure the specific gravity of the wood before building and document your results. Eventually you could just look at a staves ring count, and cut one inch square of wood, and know exactly what that stave can do.

[Selfbowman]

I can answer better than what I just did.

To add a more relatable example, structurally speaking: corrugated cardboard uses the same principle.

As for how to proportion the core (crunchy wood) it will vary depending on the stiffness of the belly and back. The stiffer they are, the thicker the core can be to support them. If the core is too thick, the tension and compression properties will be exceeded of the back or belly, or even lead to a torsional/sheer failure in the core.

This being an organic material we really have to learn from experience what a ring count looks like in proportion to the early/late growth, then know what stresses it can handle. A good way to Guage your progress will be the mass formula by Badger. Another is just measure the specific gravity of the wood before building and document your results. Eventually you could just look at a staves ring count, and cut one inch square of wood, and know exactly what that stave can do.



Interesting.

[Pappy]

Yes the winter growth is weak and I want the ratio as thin as possible, but speaking of Osage i have had some that the whole limb was summer growth, 1 ring and it took some set also. 
 Pappy

[Selfbowman]

Yes the winter growth is weak and I want the ratio as thin as possible, but speaking of Osage i have had some that the whole limb was summer growth, 1 ring and it took some set also. 
 Pappy

 Mark Was the growth rings real big? I’ve noticed the thick late rings have more lunar ring size as well. The ones I’ve seen do not seem real dense. You can’t have everything. Arvin

[Pappy]

O ya it was a large one and to be honest I don't like large thick rings, I would much rather have fairly thin rings with a very fine winter growth , and well seasoned, I find they hold more of what you do to them and don't change much if any after shooting them a bunch, don't know about set, don't really measure it, but will say my best bows come from finer ring well seasoned Osage. HHB would be my next favorite for white wood but again well seasoned.
 Pappy

[ssrhythm]

All this info is interesting and the points are valid.  But to strictly answer the question about the early wood being the weak link causing set...I don't think so.  Set is caused when the belly wood is compressed to the point of cell colapse and once it is colapsed, it stays colapsed...thus causing the set.  That crunchy early wood, it seems to me, would colapse under compression extrememly easily and shear under tension very easily.  The only way...again, this is just what I am assuming/educated-guessing...the only way that early wood crushing could actually cause the set we see is if it, in a colapsed-cell state, was strong enough to overpower the late wood directly around it on the belly side in the compression plane that is resisting compression forces...and that ain't happening.  Can the early wood in a stave with a large amount of early wood to late wood ratio affect the late wood's overall ability to resist compression forces?  I'm sure it can have some negative impacts, but to what degree, I havn't a clue.  That said, I seriously doubt it is anywhere near the top many reasons that a bow takes set.  Like has been mentioned before...set is far more likely due to poor tillering and mistakes by the boyer in the tillering process than anything to do with the early wood ratio of the stave.

[PatM]

Arvin, I dont know what my opinion is worth to you but....


From an aviation stand point, the crunchy wood is just like the honeycomb core in composite skin structures.  We lay a piece of thin aluminum  the bond to it a layer of honeycomb and another layer of aluminum.  The resulting structure is very light weight and amazingly stiff. It has all of the properties we want in a bow.

If I can find one, I'd like to make a bow that has one ring in the back, crunchy wood in the middle, and one ring on the belly. I dont think crunchy wood is a weak link. However, a badly proportioned stave of that early crunchy wood could cause a problem easily.

   I wouldn't say we want that in a bow.  We need a bow to flex, not be stiff.

   You could likely test the  crunchy layer   theory by gluing  lams of bamboo stacked like growth rings with a thick layer of crunchy glue holding them each together.

 Hard to say if there is a glue that mimics early wood.
 
  One thing is  pretty sure, early wood is often not the greatest bond between rings when a piggyback split can often be achieved right down one.

[sleek]

Arvin, I dont know what my opinion is worth to you but....


From an aviation stand point, the crunchy wood is just like the honeycomb core in composite skin structures.  We lay a piece of thin aluminum  the bond to it a layer of honeycomb and another layer of aluminum.  The resulting structure is very light weight and amazingly stiff. It has all of the properties we want in a bow.

If I can find one, I'd like to make a bow that has one ring in the back, crunchy wood in the middle, and one ring on the belly. I dont think crunchy wood is a weak link. However, a badly proportioned stave of that early crunchy wood could cause a problem easily.

   I wouldn't say we want that in a bow.  We need a bow to flex, not be stiff.

   You could likely test the  crunchy layer   theory by gluing  lams of bamboo stacked like growth rings with a thick layer of crunchy glue holding them each together.

 Hard to say if there is a glue that mimics early wood.
 
  One thing is  pretty sure, early wood is often not the greatest bond between rings when a piggyback split can often be achieved right down one.

I think gorilla glue is pretty bubbly?

[sleek]

Arvin, I dont know what my opinion is worth to you but....


From an aviation stand point, the crunchy wood is just like the honeycomb core in composite skin structures.  We lay a piece of thin aluminum  the bond to it a layer of honeycomb and another layer of aluminum.  The resulting structure is very light weight and amazingly stiff. It has all of the properties we want in a bow.

If I can find one, I'd like to make a bow that has one ring in the back, crunchy wood in the middle, and one ring on the belly. I dont think crunchy wood is a weak link. However, a badly proportioned stave of that early crunchy wood could cause a problem easily.

   I wouldn't say we want that in a bow.  We need a bow to flex, not be stiff.

   You could likely test the  crunchy layer   theory by gluing  lams of bamboo stacked like growth rings with a thick layer of crunchy glue holding them each together.

 Hard to say if there is a glue that mimics early wood.
 
  One thing is  pretty sure, early wood is often not the greatest bond between rings when a piggyback split can often be achieved right down one.

Stiffness is just resistance to bending. We don't want a bow that bends, we want a bow that resists  bending. Like in a hydraulic system, pressure is a measure of resistance to flow, not a flow rate. So, when I look at it from that angle, I want a bow that has the most resistance to bending as it can without failure.

thays all theory anyway. I haven't had much opportunity to test it in depth. However, much like Pappy, my favorite bows have thin rings, been that way for years.

[PatM]

It definitely is but I'm not sure how crunchy it ends up in comparison to earlywood.   It still seems a bit like spongy foam rather than being brittle.

 

[sleek]

Maybe some foamy epoxy? Well, now I wonder, do we even know why early wood is so crunchy? What are its actual properties?

[PatM]

Arvin, I dont know what my opinion is worth to you but....


From an aviation stand point, the crunchy wood is just like the honeycomb core in composite skin structures.  We lay a piece of thin aluminum  the bond to it a layer of honeycomb and another layer of aluminum.  The resulting structure is very light weight and amazingly stiff. It has all of the properties we want in a bow.

If I can find one, I'd like to make a bow that has one ring in the back, crunchy wood in the middle, and one ring on the belly. I dont think crunchy wood is a weak link. However, a badly proportioned stave of that early crunchy wood could cause a problem easily.

   I wouldn't say we want that in a bow.  We need a bow to flex, not be stiff.

   You could likely test the  crunchy layer   theory by gluing  lams of bamboo stacked like growth rings with a thick layer of crunchy glue holding them each together.

 Hard to say if there is a glue that mimics early wood.
 
  One thing is  pretty sure, early wood is often not the greatest bond between rings when a piggyback split can often be achieved right down one.

Stiffness is just resistance to bending. We don't want a bow that bends, we want a bow that resists  bending. Like in a hydraulic system, pressure is a measure of resistance to flow, not a flow rate. So, when I look at it from that angle, I want a bow that has the most resistance to bending as it can without failure.

thays all theory anyway. I haven't had much opportunity to test it in depth. However, much like Pappy, my favorite bows have thin rings, been that way for years.

    Still needs to bend though.    Bow woods come in very low resistance to bending and very high.  Both are highly regarded as long as they bounce back.