Bow wood strength and calculations for quartered wood

[WhitefeatherFout]

So some of you guys know me some not.  I buy veneer and specialty wood for a living.  I've been building bows, mostly selfbows and a few boo backed deals the last few years.  I've experimented a good deal with different woods and combos.  I was working on a few bows tonight and thinking, several of the guys I deal with on backed bows like quartersawn boards.  I'm wondering why that would be the case.  A selfbow would be basically flat and we know the performance there.  I don't recollect a backed quartersawn board being a substantially better performer.  So why not use flat sawn wood there?  What would be the different compression and tension numbers?  I know the different properties of differently sawn woods very well but I'm having trouble translating it into bow building at the moment.

[Badger]

  A backed bow will generally outperform a self bow with the same profile by a small margin. I am not aware that guys want 1/4 sawn wood for backed bows. We do request 1/4 sawn wood for making board bows without backing. Could this be the real question?? A flat sawn board will lift on the growth ring when bent, a straight grained 1/4 sawn board will not.

[WhitefeatherFout]

No Steve, the question is  as I stated and I was truly hoping you would be a first responder. I just wasn't sure if I'm not wrapping my head around something or if I was missing out or what.  Without compromising my status here, guys end up with wood from me(mostly gifted or traded) and several of the boo backed Osage crowd would prefer quartersawn boards.  Being a wood guy and testing woods and all that, I don't get it at this moment.  Quartersawn anything is stronger typically, but you still have to tiller it.  In the rudimentary tests I've done I haven't seen a benefit.  That's why I ask.  Thanks for the reply Badger.

[George Tsoukalas]

Interesting. I don't like 1/4 sawn for selfbows. The board's grain has to be straight tip to tip with no run outs on the edge grain.  With plain and rift sawn I allow a couple run outs per limb. Jawge

[WhitefeatherFout]

Exactly Jawge, and you know we think alot alike or I think alot like you from the other site, and I always appreciate you posts.  That's what has me asking the question, and this applies to backed bows.  I just don't get the request for quartersawn.  I think it goes back possibly to a bowyer or two but I'm not sure.  I'm not going to name names and this is by no means an attempt to throw them under the bus.  If it's what and who I think, they have more bowyering in their little finger then most will ever have.  I just want to understand it.

[WhitefeatherFout]

Quartersawn wood is more stable so I get that part. That is why you see alot of old cabinets and furniture that is quartersawn .  It didn't necessarily have to be all the way dry to hold form.  Stability would apply in building a bow but what about the compression and tension rates?  I suppose that is the real question I'm asking.  They would have to be different than the numbers run on flat cut wood, wouldn't they?

[echatham]

Matt i think it may have to do with normalizing the belly surface of the bow.  With edge ringed or quartersawn wood you will have basicly the same ratio of late to early wood for every inch of the belly surface.  Particularly with flat bellies with flatsawn wood you would have areas of the surface that were all early wood.  Tim Baker says in tbb 1 that edge grain tests 10% weaker and takes set 10 percent sooner than flat sawn.... So i doubt the preference has to do with performance numbers.  I think the ideal would be flat sawn with one uninterupted latewood ring as the belly... But thats harder to come by.

[George Tsoukalas]

I guess it could be stronger provided the straight grain requirements are met. Jawge

[WhitefeatherFout]

Eric, I would agree an uninteruted growth ring should be superior, just like chasing a ring.  However, I'm not totally convinced the ratio of late and early wood wood be the same or play the same role, especially in a backed bow.  The rudimentary tests I done with quartered Osage versus other woods, especially exotics showed the same or similar results as Tim Bakers'.  I really wish someone of the quartersawn fan club would chime in and share their thoughts!

[echatham]

With flat grain and flat bellies you get spots like this that are early wood all across the belly.
 

That cant be more desirable than this


Especially considering most of the work is done by surface wood.   That was one of the reasons Mr. Torges advocated round bellies... Avoiding the step downs from late to early wood like in my first picturr.

[WhitefeatherFout]

Very logical way of thinking and I won't dispute that or Mr. Torges's way but growth ring(late and early wood) ratios would come in to play I suspect  not only on flat but quartersawn wood.  I suppose the growing conditions would dictate this ratio.  I've seen and have examples of both extremes.

[willie]

the way I read deans preference to avoid earlywood flat spots was not about the ratios but the ease in maintaining an even taper with the cabinet scraper. the earlywood being weaker needs to stand proud, but tends to valley between the harder latewood steps when scraped.

[mikekeswick]

For backing it doesn't matter one jot IF the grain is running straight. 1/4 sawn boards can actually be harder to read in this respect until you know what you are looking for. I definately prefer to get a flat sawn board for backings and then cut it on the quarter myself.
The beal with people wanting belly wood quarter sawn is really only applicable to woods that are heavily ring porous eg. osage. If you have a flat sawn belly slat then you will at some point get a ring of earlywood crossing the whole limb - this is weak and more importantly it can lead to a washboard effect on the belly. Every time you go over the earlywood a scraper will 'dig in' and remove more of the softer earlywood. If you round the belly then of course this effect is minimised...although you still have to keep an eye on it.
If I had the choice then my backings would come from a flat sawn board that is as thick or thicker than my bows intended width. I would then cut it on the quarter.
Belly wood if ring porous would be quarter sawn but if it's diffuse porous I couldn't give a hoot!
Also by the way you have worded things...do you sell osage staves?

[half eye]

Try google....Mechanical Properties of wood. The USFS has charts for the "strength properties of some commercially important woods grown in the United States." comes in both metric and US inch-pound.
     The categories covered are all applicable to bows (bending wood)
rich

[adb]

For backing it doesn't matter one jot IF the grain is running straight. 1/4 sawn boards can actually be harder to read in this respect until you know what you are looking for. I definately prefer to get a flat sawn board for backings and then cut it on the quarter myself.
The beal with people wanting belly wood quarter sawn is really only applicable to woods that are heavily ring porous eg. osage. If you have a flat sawn belly slat then you will at some point get a ring of earlywood crossing the whole limb - this is weak and more importantly it can lead to a washboard effect on the belly. Every time you go over the earlywood a scraper will 'dig in' and remove more of the softer earlywood. If you round the belly then of course this effect is minimised...although you still have to keep an eye on it.
If I had the choice then my backings would come from a flat sawn board that is as thick or thicker than my bows intended width. I would then cut it on the quarter.


I do the same. I purchase straight grained 8/4s plain sawn lumber, and then cut it on the edge. 8/4 is usually about 2" thick and 6" wide, so 2" wide backing strips are perfect. From a board like this, I can usually get about 15-20 backing strips.
Belly wood if ring porous would be quarter sawn but if it's diffuse porous I couldn't give a hoot!
Also by the way you have worded things...do you sell osage staves?