Sunday, 24 March 2013

Tillering Progress

I've been teasing the bow back, running calipers along the limbs checking for a gradually increasing gap with no thick spots. The tips have been narrowed an bit and the corners rounded off so its near the final profile. This work has slowly eased the draw length back to about 26" and I can now string it (at a low brace of about 5") without the stringer.
I've noticed the slightly thicker lower limb seems to flex more and the bow looks better reversed on the tiller, so that's what I've done.
The heartwood belly is made of two billets, but they are not from the same log and thus not perfectly matched. They are both from the same batch of Yew cut in the Cascade mountains.
I've gone over the bow with a scraper too and its looking very handsome now. I think it's time to do the horn nocks before taking it back any further, doing the nocks will narrow the tips a bit and get them flexing more, that may well get me to the 28" draw mark.
In the video, you'll see I'm flexing the bow back dynamically rather than winching it back slowly, I feel it's kinder to the bow.
Nearly all the cambium has come off now leaving a lovely clean back except for a bit of staining where another branch had been chaffing against the bark, this will probably clean off in the final stages of finishing.
The tiller looks pretty good. Stopping the video at full draw, displayed full screen and holding a CD up in front of the screen I can see the left limb is a fairly circular shape, the right limb is very slightly weak just right of half way along. The centre section is stiff, but that's intentional to give strength at the splice in the heartwood.
This stage of tillering in my opinion needs to be done very slowly with lots of time for looking and thinking and minor adjustments. It's easy to get fixated on one area and miss something else like the string alignment.
Conversely it's easy to overthink it and start chasing shadows, I'll be looking at the video every now and again, maybe winch the bow back to about 60# and have a good look at it and run my fingers over it.
One problem in my garage is, I can't get far enough away to get a good look at it, hence the use of video.

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