Osage "driftwood" short bow, part 4 - tillering

Now the long but critical part: Tillering.

For those who don't know, tillering is the art of removing wood carefully from the belly (and sometimes sides) of the bow to reduce thickness and/or mass in order to get the wood to bend in the way needed for the particular bow profile. (This bend might be circular and bend through the handle for bows with a straightline taper or it might be elliptical for longer bows, bows with limbs that have a more parallel taper in the midlimb, or bows with a stiff handle. It is also possible to create stiff or "whip-tillered" tips for different reasons.)

Rather than bore one with all of the details, here are some photos of the bow in progress, from start to close-to-finished tiller. Because this particular stave had some dips and whoop-de-doos that fooled the eye into thinking that they were hinges (weak spots), I found it helpful to take a series of photos and then to draw an ellipse or circle over them using the computer in order to see the weak and stiff spots better.

First, the bow braced with only a rough tiller followed by drawn to 40# @ 22". Note the stiff tips and slightly stiff lower limb (left in image):

The next photo is after quite some time tillering. It shows 25 inch draw and the drawing of the ellipse I mentioned. Because the limbs want to pull off center, I had to lighten the tips and narrow the handle a bit, lowering the max draw weight. At this point, I theorized it would probably come in more like 45 @ 28 after all of the sanding, rounding over edges, break in, etc. as it is close to 43 @ 26.

The overdrawing of the ellipse shows well that although it is pretty close to final tiller, the bottom limb (left in the image) is still stiff out near the tip and the upper limb has a slight weak spot (though it looks worse than it is because of the front to back whoop-de-doo in the limb):

At this point I was slightly disappointed that the mass was still as high as it was for the draw weight it appears to be coming in at. I think it has a lot to do with the fact that the rings are not particularly thick/wide and that there is more porous early wood, i.e. it is not the best osage. However, heat-treating the belly might squeeze a few more pounds out of it yet.

A couple of pictures close to final tiller:

Tips are still slightly stiff, but I didn't want to free them up too much, because at full draw (28") it would increase the angle between the string and arrow and cause finger pinch. Tillering shorter bend-through-the-handle bows is a little different than tillering longer bows.  Tim Baker's general tillering mantra from TBB (Traditional Bowyer's Bible) vol 4 is

Make inner limbs wide or long enough for virtually no set. Make midlimbs wide enough for little set. Make outer-limbs and tips narrow enough for lowest possible mass.

BUT, as Baker notes regarding short bows:

Unless designed for short draw, short bows must bend more in the inner limb, far more so than long bows. Whip-tillered shorter bows become shorter in tip-to-grip length during the draw, increasing string angle at full draw, increasing stack and reducing energy storage even further than typical for shorter bows. So mid and outer limbs should bend a little less, inner limbs a little more. (p.127)

Of course, too much bend in the middle or through the handle would shock the hand and, I imagine, cause accuracy to suffer. Bow building is certainly a matter of compromises.

Osage "driftwood" short bow, part 3 - progress

Progress:

7/8/2014:

I got in some substantial time today and took of some significant amounts of wood (I'm hoping not too much - more on that later). After some deliberation, I set a goal of reducing to 12 oz according to the Mass Principle espoused by Steve Gardner. That would yield a bow close to 50# at 28 at that ntn length. The bow was 17 oz when we last left it. I started by reducing from mid-limb to tip, narrowing the tips to 1/2". After this procedure, the bow was down to 16+ oz, and I effectively cut out the red streak near the end of the top limb.

String stayed centered, but I realized the handle section was a tad wider than the 1 3/8" I intended to start with. After inspecting carefully, I realized I could take 1/16" off of each side up until almost mid-limb and get a handle section closer to 1 5/16" wide, which would allow me later to taper the limbs more to get rid of the red streak that made me most nervous -- the one riding the edge of the top limb. So...

1/16" off of each side, and the limb was down to 15.8 oz.

I then decided to effect a straight line taper from the middle of the inner limb (so 3/4 down from the nock to the handle) up to the tip. This would remove more mass overall while lightening up the outer limbs and tips (which will lessen shock, increase cast, and increase arrow speed). So...

4 tapers later, the mass was down to 15 oz., the one red streak ended up on the workshop floor as shavings.... and the string now tracks slightly off center. This wasn't so bad, as I had intended to get to within 3 oz of final target mass before continuing to tiller the belly. So, some more wood will need to be removed in key areas to get the string tracking again. No big deal...

BUT: I then realized I miscalculated my target mass. I should have been aiming for more mass in order for the bow to draw 60 @ 28, with the notion that it'll lose some weight as it breaks in. The natural reflex also requires slightly more mass. So, I really should be looking at a target mass closer to 14 oz than 12!

Regardless, I've still a little bit of fudge room as I work toward final mass. I'll just need to take the tillering slow. There is only one remaining red streak that runs from belly to back, but it is safely within the confines of the limb and I filled it with super glue. Provided that it holds together during tillering and initial drawing, I'll be able to get a patch on it. I now feel far more confident of this drift wood becoming a bow now. It's looking more and more like a bow every day!

Osage "driftwood" short bow, part 2 - complications

Part of the excitement and challenge of working on this project was working with sub-par wood. I did not set out to build a particular type of bow. Instead, I had been generously gifted a piece of wood and decided to try to make something of it. My main goal was to try and take as much as the wood was willing to give and to try and draw the maximum amount of bow out of the wood rather than to force my will upon it.

(I try to take this approach with most of my projects. Given the number of years that wood takes to grow, I try not to take it for granted or waste it. I probably also push that a little too far, as sometimes I have just barely enough material with which to work.)

On to the tillering. From my previous emails to Jarrod:

6/24/2014:

So just when I thought I'd found all the surprises... After I showed the current progress to [Jarrod] today, I went home and started working on bringing the front profile down to the lines and then starting to reduce the belly thickness in order to start floor tillering. As I started working the belly down, more and more cracks started to reveal themselves on the belly -- fortunately all (so far) within the confines of the limbs, though at least one looks dangerously close to the edge of the limb. None have shown through the back. I wonder how far they go?

There is something about working wood with hand tools that allows the wood to "speak" to you. Something that the bandsaw will never tell you. There is something about the way the wood changes in sound as it is being worked that allows one to know that there is a crack, a pithy part of wood, a little "something" that is less than desirable. It's a hiss, a crackle, and nuanced change in pitch that gets ignored over the scream of a cutting bandsaw blade.

Right now I've hit the cracks with some super thin super glue. IF it will hold together long enough for me to tiller and bend it, I'll wrap it with silk thread and zap it with glue again as a safety measure. As of this moment, though, I'm having some serious doubts about the integrity of this piece. Current probability of survival? It's going to be a long shot.

After cutting the profile, the stave as it stood at this point (I can't call it a bow yet because it's not bending) included three major cracks: one near the upper limb tip that threatens to run off the side and two others parallel to each other in the lower to midlimb section of the upper limb. One of the two is closer to the edge than I'd like and also threatens to run off. Current dimension: 1 3/8" at center tapering to 5/8" at the tips. It;s not a straight taper, as I left more wood through midlimb, but now I can't recall the measurement.  Details:

7/6/2014:

I put a long string on the stave and managed to get a glimpse at what it might look like after the limbs moved a few inches. Some tricks of the stave -- some especially snaky bits and exaggerated reflex at the tips around these areas -- made looking for a bend particularly difficult. I read a trick about squinting in order to erase the actual profile and to get just a general impression; I think it worked, as it allows me to find some generalized flat spots and work them down. At least I think it worked. Squint hard enough, and just about anything looks okay.

The next step was to get a string on at a very low brace height - say no more than around 4 inches. I made up a string and managed to get it on, but it had a brace of 6". Rather than worry about rushing things, I took a good look at it on the tiller tree. At this brace height, the limbs came round to a nice arc, i.e. the reflex in the outer tips that caused so many illusions before had now disappeared at brace height (but are still present in the unbraced bow).

So far, so good. I ventured a few light pulls with a scale to see how it was coming along. I got to 20# at 12". Assuming even a gain of 3#/in., the bow would be headed to close to 70# @ 28 if it were done here (which it is not).

I slept on it for a couple of nights to decide next steps. I even dreamt about it! So far the red stripes are holding together, but I'll need to keep a careful watch...

I've been contemplating for some time how to handle the red streaks. There's one near the tip of the upper limb that runs off the side. I've planned that one with the intent of being able to scrape it clean away while narrowing the tips and bringing in the tiller.

Then there are the others in the main part of the upper limb, coming off the handle "fades" (not much of them really, as this will be a bend-through-handle bow) and into the mid limb. One is entirely within the confines of the limb; the other threatens to run off the side in this much-worked area. I've shot all the cracks through with CA glue and pray that they hold. If I can bring in the tiller before it blows, they'll all get a wrap of braided serving or hemp and another overlay of CA glue. 

While I intended these larger cracks to stay within the limb itself, layout of the bow and the eventual planing of wood brought them closer to the edge than I liked. This was truly a "dilemma" -- a choice between two paths. As my boss says, dilemmas are things to be managed, not solved. Layout in the other direction brought me to missing wood, punky soft spots, and too little thickness. Managed, indeed. (It also looks their proximity to the edge will prevent me from narrowing the limb any more than  it is, which means I'll probably end up with more mass at the intended draw weight, leading to a slightly less efficient bow. But I guess it's better to be less efficient than non-existent, no?)

Upon reflection, I realize that working on any of these long-term projects, whether they be bows or instruments, is a lot like building a relationships. Not necessarily a romantic one (though I suppose having a crush on an idea might blind one to the faults of the materials), but more of a long-term friendship. We may have ideas about what we'd like the other person/project to be, but the materials come with their own set of "personalities", kind of like a warped sense of humor or an annoying habit. 

Some of these can be seen from far off and are managed straight away: The wood has a knot, but I'll work around it. (That person has a tight work schedule, but I'll plan around it.) The grain twists to the side when I bend it like that, so I'll have to avoid bending it there. (That person reacts strangely when I mention that, so I'll have to avoid mentioning that thing.)  

On the other hand, like with a developing relationship, the passage of time and getting to know each other can reveal new flaws. (Like the red streaks in the stave.) Some are just plain unavoidable, so we try to manage. (I'm using CA glue to try and hold the wood together; by analogy, what should I use to hold my friends together when they start to fall apart?)

We can choose our materials and our friends, and some are probably better to just let go. But there are still some we choose to stick with regardless, even though we know we're destined for heartbreak and/or a nasty parting of ways. I'm just hoping I can hold this one together long enough to get to know it and put a proper patch on it. Funny how some things can't be fixed until they're close to breaking. That's truly twisted.

Speaking of twisted, the limbs on this stave aren't very well behaved. There's a slight propeller twist to both limbs. From one direction, the string looks perfectly centered down the handle; from another, both limbs look badly skewed off to one side. A reading of the distance from string to belly on either side of the bow show that they're equidistant, so the string *must* be centered, regardless of what my eyes say. The fact that the grain seems to be feathering off to one side doesn't help matters.

Some folks/things are just going to do what they're going to do, and we had better be okay with it. 

Next step in this friendship? Horn tip overlays and narrowing the tips. Wish me luck on navigating that red streak in the tip. Either I'll successfully cut it out or I'll be speeding this bow to its doom.

Osage "driftwood" short bow, part 1 - roughing out

I started this blog as a place to collect my thoughts -- at least the ones I already had started writing down in email for my friend Jarrod so he could be a vicarious bowyer and "build along" with me as I worked on one of my various bow projects. Seemed like since I was writing them into email and attaching photos, I might as well just write it in a blog format. At least that way the photos can be in-line with the text. And this might be of interest to someone else.

The start of this post is a bit of catch-up. I've compiled below some of what I had originally written in email, so it's a little choppy. Before the posts, a bit of context: Jarrod had given me a piece of osage he had sitting around in his garage for several years. It was a sad state of affairs: The rings were narrow, with a fair proportion of earlywood, and one end of it had been worked down considerably through many of the rings. He said a kid had started working on it. It looked more like a beaver had gotten hold of it. In addition, there were several longitudinal cracks (looked like heart shake?) and a dark red streak running down one side. Sadly, I didn't take any photos of the "before," so you'll just have to trust me on it. This was truly a piece of "driftwood," as Jarrod dubbed it. Now onto the previous posts:

6/19/2014:

I started working the osage stave today, just scraping down the sides through the oxidation and rough fibers to get the true layout of the rings. I could definitely resaw it and get 1 backed bow out of it. It might be possible to resaw it in a different way and get 2 backed bows out of it. It MIGHT be possible to get a reasonable-length self-bow out of it by gluing on a handle. It might even be possible to get both a glued-handle selfbow AND get a backed bow out of it. I must have spent 2-3 hours just scraping and looking that piece over today... 

6/20/2014:

So I worked on the osage stave again today. I discovered a red streak in it (just like the one Dean mentioned in HOB!) Whether it is good or ill, it probably doesn't matter. Here's what I've discovered:

The thick rings are way at the bottom of the stave. The red streak is about 1/2" from the sapwood-- the thick rings start 10 rings below the red one, and in total there are no more than 17 rings below the streak (most places 15). This means that I've got about 5-6 good thick rings at the bottom of the stave. (I was able to number the rings on both sides and both ends AND to confirm by tracing around the stave AND able to mark out the rings exposed on the belly.)

Right now I'm thinking of using the bandsaw to capture 1 good inch of thickness from the belly side. This should provide enough room to work down to a thick unbroken ring. I'll have to glue a section on near the handle area to make thickness of 1 1/4", but most of the handle should end up being all of a piece with the bow. The stave has decent reflex in it, so I'm looking forward to it.

Complication: The one end is already worked way down (past ring 10 in some places), so I'm not sure if I'll make enough length for a rigid handled bow. I may end up with a 58" ntn length, in which case I'll need to consider making this a bend-through-the-handle bow. 

With the "waste" wood from the back side of the stave, I think I may have enough thickness left over to saw into two narrow 40" billets which could then be joined and backed. They would likely be narrower than Dean suggests, so they'd likely end up as a lighter weight bow (kid's bow?). I could conceivably even make it a two-piece instead of joining them. Possibilities abound.

In between, it got worked on. As I had thought I might, I took off the back section with the bandsaw. The sawed off section got put aside for a possible second bow (more on that later), then I chased the rings of the remaining wood down to a single growth ring, leaving 60 usable inches of wood in length. The plan to make an unbacked 58" bend-through-handle bow had now solidified. More later.