AZ Ironwood Bow

[willie]

on the side of the beam you have marked out rays, which in the case of your wood, are much more apparent, but they dont tell much about the direction of the grain.

http://www.primitivearcher.com/smf/index.php/topic,68359.0.html  might be helpful.

the ringlines in your beam are quite fine and may be very difficult to follow. As noted in the topic linked above, the bowyers bible has a good explanation and some drawings also .

if your bow stave has much run out, which I think might be the case, it is at risk of breaking. this is why I suggested considering just a belly lam of mesquite. If the best part of the bow has straight grain, and is of a known bow wood like perhaps hickory, your chances of the bow holding together are much improved. If your mesquite is harder than the hickory you may realize a gain in performance for having it on the belly face.  alternately you might be able to make a slightly higher poundage bow compared to a similarly sized all hickory bow, or a slightly smaller bow of the same poundage.

[richgibula]

The rays are longitudinal, the grain lines are the ones I marked with the black marker.  They intersect with the longitudinal grain lines on the top side in the end image. 

I don't intend to shave this wood with a draw knife.  My arms would fall off.  I hope to orient the bandsaw cuts in the best direction possible and use a backing.  The other questions that remain are the width and thickness of the bow arms compared to a softer wood.  Should this be thinner, narrower, wider than hickory?

[willie]

rich,

Sometimes terms about wood characteristics are confusing as different trades and usages speak of some things interchangeably. For me, ring lines represent the annual growth rings on a tree. your beam has very thin growth rings and you can see hundreds of years of growth rings in the end view. I guess a furniture maker would call this a fine grained piece of wood, but grain means something a little different to the bow builder. 
Each years growth consists of long thin cells or fibers. We, as bow builders, would like to have a stave where the fibers grow straight up and down the tree, but sometimes the fiber orientation is wavy as it goes up the tree or the fibers are laid down with some spiraling. the run of these fibers is what we call the grain these fibers are continuous only in a single years growth.

when working with a sawed log, we have to try to do whatever we can to not cut across the fibers when roughing out a bow. as we cannot actually see the fibers we can only make a best educated guess as to how they lie in the board. violated ring line are one of our best indicators. your russian olive photo shows many violated rings, as it is easy to see in coarse ringed wood especially in the flat sawn condition. rings seen in a rift or quarter sawn cut take more care to visualize the run of the grain.

 I highly suggest reading the traditional bowyer bible check out page 19 in both volume 1 and volume 2
https://shop.primitivearcher.com/product-category/books/?product_orderby=default

[richgibula]

Thanks for your help.  I read this book, or at least selections.  I don't know how closely I can keep within a grain line with a bandsaw, particularly when avoiding knots, having grains at an angle to the surface and having wavy grain lines.

Having said that, I am still wondering about how thick and wide to make a bow out of wood like this.

[willie]

your cuts should follow the grain and flow around knots, the stave becoming wider in those areas

not knowing your bow design or length, proposing dimensions is  hard to guess

[richgibula]

So let's say that I use a thin bamboo backing, 1.25 inch wide at the handle, 64 inch length nock to nock. Is there a way to estimate thickness and tapering for a 60 lb draw for a wood this hard? Let's assume this grain lets me put in a little reflex.

[richgibula]

It's hard to see the grain from a distance, so I highlighted it with a marker. I marked a proposed cut for the bow, following the grain lines where I could. I had to start a distance from the end due to knots. 

The problem is that there is a transition at the arrow where I will have to cross grain lines. Since this is a board I don't know a way around that. Is there something I can do with that or should I pick a different part of the board.  I like the current selection because of the reflex.

[Hamish]

The limb shape you have drawn out, is the look for the bow want, but that is not how  you achieve it. A bow of that shape, especially if you use a backing, is derived from the form you use to glue up your laminations. The grain where your reflex/ recurve occurs doesn't look to be anywhere as curved as the drawing, and will therefore be a weak spot.


I would use a long rule and mark a line that broadly follows the average run of the grain. From what I can see, the grain runs out of parallel from the edges of the board. Starts in the middle of the left side, and runs at an angle up to the right side. It looks to be straight enough except at each end. With a backing and perhaps a core that amount of run off will be acceptable.
 I would just saw off straight boards from the new drawn line.

[richgibula]

Thanks for your input, Hamish.  I like your approach.  The only thing I would add is that the picture is hard to see on the low resolution required by this site. So, I did a closeup of the right curvy area to show the grain direction.

[willie]

can you show the ring lines marked out on the side view turned 90 degree? pick a ring about an inch and a 1/4 down from the outermost ring of the tree.

[richgibula]

This is a 90 deg rotation view of the last image. The arrow from the last shot would be on the left side and the tip is marked.

[richgibula]

So I sanded the board and shellacked it. then marked the grained carefully. I did this for my future cutting accuracy, but I noticed that there were queries to me on this wood but no responses. 
Here are the pics of my efforts:

[richgibula]

Next to the right:

[richgibula]

Next to the right:

[richgibula]

Next to the right: