Friday, January 29, 2010

A Dress Rehearsal for the Tuktut Nogait Bow

The Tuktut Nogait bow is very nearly finished. I had all day Thursday to work on it and made some good progress and a mistake or two. I cut the notches, put the recurve in the limbs, started the sinew bow string, did more tillering and tried a test wrap of the sinew cable.

The hardest part was bending the limbs. I soaked the areas that I want to bend with water and then used a blowtorch to heat them. That's how I bent the limbs on the non-functional version of the bow that I made last fall and it worked great. It worked nicely on one limb this time, but on the other limb there was a swell in the grain and the point that needed to bend was thicker than the wood on either side of it. When I bent it, tension cracks formed on the belly of the bow. They ran flat and followed along two growth rings, so I ground down the excess wood below the depth of the crack and I think everything will be alright. The original bow that I'm copying was in two pieces and the splice in the limb is exactly where this crack happened. I keep telling myself that if a working bow can be made in two pieces like that one was, then this little crack is something my bow can recover from. However, when I filed through the cracked wood to get to the solid wood underneath I rapidly thinned the limb at that point and the tiller was thrown way off. Its still noticeable at the end of the day, but there were times when it was really horrible to look at.

In the photo of the bow in the tiller, the limb where the crack happened is the one on the left. When its drawn, the recurve almost vanishes, whereas the recurve is still visible in the opposite limb. Its a tough sort of discrepancy to fix, but hopefully I can get things looking more symmetrical today. For the bow people out there, it currently draws 22 pounds at 18 inches, with the untwisted cable backing on.

I wrapped the braided sinew cable around the bow to try to figure out a good pattern and sequence of wrapping. In the version shown in the pictures I used about 69 feet of cord, with a couple feet left over, but I think I know how to use up those two feet the next time I wrap it. I started with 30 tight wraps around the elbow in the limb that gave me the problems and then ran a line along the back of the bow to the opposite elbow and did 30 tight loops there. If this bow was made in separate pieces, then these lashings would be important to bind together the spliced joins. From the second elbow I ran the cord to the nearest end nock and stretched six long strands back and forth to the opposite end. After that, I ran 8 cords from elbow to elbow, securing them with half-hitches, so that the cable in the two thirds of the bow has a total of 15 strands (8 running from elbow to elbow, 6 running from end to end, and 1 that runs from the first set of elbow lashings to the second set). I wrapped the final bit of cord around the 15 strand cable in the middle of the bow.

I studied a lot of reference photos and drawings to come up with this pattern and it accomplishes a few things that show up in ethnographic and archaeological bows.
  1. The splices on the elbows of the bow are lashed first and separately. Sometimes this is a different material.
  2. Some strands run end-to-end through the nocks.
  3. The cable bundle in the middle is noticeably thicker than the cable towards the ends of the limbs. More strands run through the middle two thirds of the bow than along its entire length.
  4. The cable bundle is wrapped in a spiral pattern. Again, sometimes this is a different material.
I was surprised to see how much of the belly of the bow is still exposed using this sequence of binding. Granted, some of the crucial thinning that I need to do on my bow is under the lashings, but there is also a lot of tillering that can be done with the cables on. I also didn't expect to be able to fit the bow string on over top of the cords through the nock. It seemed like all the space in the nock was used by the sinew cord, but it wasn't.
The green tillering string fit on without any problem. I'm not quite sure how to proceed, the nocks seem like a good match for the nocks on the artifact at this point, but there is so much force being stored in the bow now that for safety and comfort, I'm tempted to carve them a little deeper and give the bow string a little more wood to grab. Although it certainly looks secure in the photos.

I have a bit more tillering to do and a sinew bow string to finish, but once that's done, the bow should be ready for final assembly. I haven't twisted any tension into the cable yet, but just tying it down to the bow makes things pretty tight. I'll explain how a sinew twister is used to tighten the cable in a future post.

Photo Credits: Tim Rast

Photo Captions:
First: The bow with a trial wrapping of braided sinew cord in the tiller
Second: Successfully putting the recurve in a limb
Third: Failing to put the recurve in a limb - these are the cracks I had to fix
Fourth: The cabled bow in the tiller drawn to 16 inches
Fifth: The unstrung bow with the cable backing described in the text
Sixth: Detail of the limb - you can see the initial wrapping around the elbow, the six long cables, the bundle of shorter cables tied from elbow to elbow and the wrapping of the 15 strand bundle in the centre of the bow.
Seventh: The green tiller string fits on the nock with 3 loops of braided cord underneath.

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