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Sinew Backed, Double Curve Bow
JackCrafty:
1. Marking center of bowstring.
2. Drawing for the first time (slowly).
3. Checking tiller @ 18" draw with the slack string. Looks like the right limb has a flat spot.
4. 42.7 lbs on the scale.
5. Removeable pegs on the tillering stick.
Note:
I've read several posts that suggest that sinew should dry for at least 2 weeks before tillering. The reason I don't wait that long is because of three reasons: (1)The climate is dry here in West TX and (2) I make an effort to keep all excess water and glue out of the backing (I don't soak the sinew in water, I dunk it, and I wrap the sinew with firm pressure so that all excess glue is squeezed out). Also, (3) I put on one or more thin layers of sinew....not a thick layer all at once.
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JackCrafty:
Checking set...
1. About 15/16" distance in the center immediately after tiller check (the bow was left in the tiller stick for 10 minutes). The original distance was 1-1/8" (before sinew).
2. About 1-1/4" on the left (upper) limb. The original distance was about 1".
3. About 1-1/8" on the right (lower) limb. The original distance was about 1".
Overall, very little set....but i still need to finish the tillering @18" draw, "sweat" the bow for a little while, relax it for a day, then shoot it a couple times to check for hand shock. I don't expect more than 3/4" of set on the limbs at this point. I will then add another layer of sinew over the entire back and sides for additional safety because of the relatively poor quality of the stave.
I will not be using the jute twine wrap over the second course of sinew. This should give the sinew a smoother look. I normally let the first course of sinew dry a bit longer but the weather's been very dry lately. However, I'm not going to draw it to 22" until the second course of sinew is dry. I will then wrap the tips (with sinew), add sinew shoulder nocks, and add sinew wraps in the center and at intervals along the limbs.
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JackCrafty:
1. Bow braced at 4". Draw weight is 5.5#@1"
2. Bow drawn to 10" ...24.0#
3. Bow drawn to 12".....29.8#
At this rate, I'm on track for a final draw weight of close to 60# (assuming I don't remove any wood). For 60# final weight short bows, here's the numbers I use:
60#@24"Draw
55#@22"
50#@20"
45#@18"
40#@16"
35#@14"
30#@12"
25#@10"
If the bow is pulling 25#@10", then it's on track to pull 60#@24".
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JackCrafty:
I decided that the upper limbs needed to bend more and that the middle was bending too much....so I thinned down the upper limbs and re-tillered. The new draw weights are:
22.7#@10"
27.9#@12"
I'm now on track for 55#@24" draw but that's OK. I'll try for 60# with the next bow. ;D Here's my chart for 55# bows:
55#@24"
50#@22"
45#@20"
40#@18"
35#@16"
30#@14"
25#@12"
20#@10"
The last pic shows the bow drawn to 18". The limbs aren't bending in perfect arcs yet but I'll stop messing with it for now. I'm going to add a second course of sinew before I do any further tillering.
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JackCrafty:
Measuring set:
1. Bow braced at about 4" for about 30 min, then string removed and let rest for about 15 min before measuring set.
2. Center distance about 15/16".
3. Measuring set in right limb.
4. Right tip distance (upper limb) about 1-1/2".
5. Left tip distance (lower limb) about 1-1/4".
The tiller is asymmetric at this point....but from what I've learned recently, this might not be such a bad thing.
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