Mulberry staves with many thorny like pin knots, please help.

[Pat B]

I agree Bowmonk but if he's new at this chasing a clean ring with all the pins could be a daunting task. If Ameer doesn't mind the challenge having a heartwood belly would be the preferred.

[Ameer]

Okay I managed to split the stave again on a growth ring for most of stave and get two staves out. Hopefully two bows.

[bowandarrow473]

Nice, I see one sapwood bow and one sapwood backed bow!

[willie]

I get the feeling that b&a473 is looking at the question of thickness from the physics and Josh and Pat are making their recommendations for more thickness when using sapwood, from experience.
In my book, experience trumps theory. Would Josh or Pat try try to estimate just how much extra thickness they allow for lighter woods? And are we comparing designs with the same over-all set? or permitting more set for the stronger but otherwise equal bow?

thanks

willie

[bowandarrow473]

Oh no, I know that the sapwood bow will be thicker, I trust PatB and JOSH, they know what they're doing. But I was saying, that the sapwood might not be weaker when it comes to compression/tension, but that it is more stretchy, kind of like a thick rubber band and a thinner one, thick = more strength but the same bendability as a thinner rubber band.

[Josh B]

Willie...those are very good questions.  I'm not sure I'll have good answers for them, but I'll try.  When we say that all else being equal(length, width, profile, tiller etc.) that the sapwood bow will be thicker in comparison to one of heartwood to achieve the same draw weight, it's not really a matter of allowing for more thickness.  The thickness is established as you tiller.  After making a few of various combinations, you notice that the more heartwood there is, the thinner the bow will be to achieve your desired weight. I can't give you a set percentage of increase in thickness, I can just report that is noticeable.   Also, if you take for instance the two splits that Ameer got out of this stave and you make two bows of identical dimensions(except thickness), tiller, draw weight and length, the sapwood only bow will take just a little more set and be slightly lighter in mass than the heartwood bow.  That's if all else is the same.  However, if you increase the width of the sapwood bow in proportion to the difference in density(I usually go a 1/4" wider) the mass and set become nearly identical even though the sapwood only bow will still be slightly thicker.  I've only actually played with this kind of in depth study a few times and not always with mulberry, but the results have been pretty consistent.  I wish that I had more time to do such experimentation, but I don't.  I'm sure others have though.  I don't know if that answered your questions or not, but it's the best I can do.  Also remember, wood is not created equal.  Any experimentation is subject to skewed results due to variances in not only the species, but even from one end of a stave to the other.  A lot of the time, regardless of how careful and controlled your experiments are, the results are little more than best guess and assumptions.  There are certainly noticeable patterns though.  And this is one of them.  Josh

[willie]

Josh

thanks for taking a few moments write in detail. Sometimes folks come here to "just get the anwsers", (nothing wrong with that approach), But I appreciate the time you have taken to explain your experience, It helps to understand the basic principles of what we enjoy


willie

[Pat B]

I agree with Josh 100%.  To make a mulberry bow that is the same draw weight as an osage bow I go about 10% over the dimensions of the osage bow. A mulberry bow of the same draw weight as an osage bow can be a faster bow because the mulberry, even 10% bigger that the osage, will probably be lighter physically thus less tip mass. Mulberry reacts well to belly tempering too with adds a bit more zip.

[Chief RID]

I'm learning a lot on this thread, the least of all that I need to get some mulberry.