Monday, 28 January 2013

Yew Longbow Almost Ready For Tillering, Video

The video shows the bow I'm working on, just prior to really starting to work it on the tiller.
The video isn't great resolution as it's too big unless it's compressed a bit. But it should give an idea.

The top pic gives shows the knot that was tapped out, you can see that once the hole is cleaned back to sound wood it is substantially bigger, this shows how much crumbly black manky stuff is round even a small knot.
The second pic shows it on the tiller with no force applied, it's certainly got some character and this shape will need to be reflected at full draw. So the left limb should look stiff in the outher 1/3 when finished and the right (upper) limb should look a tad stiff in the middle. Although knowing me, it may still look like an arc of a circle.
Bear in mind some of the shape will pull out.

I've measured the limb thickness at 6" intervals, looking for about 2mm change in thickness every 6".
The limbs were fairly similar and I've rasped a bit off here and there to match it all up to the thinnest point.
There's usually one point a bit on the thin side and that becomes the reference point for adjusting everything else. Doing it like that you gradually reduce the thickness overall whilst retaining a nice even taper. Once it's pulling back enough to see by eye, then it's more down to look and feel.
I put it back on the tiller with a taut string and it's pulling a bit further now, getting close to brace height.
video
I've drawn it a bit by hand (left handed, as it's for a left hander) and it seems to come back nicely without trying to twist in the hand. I'll be keeping an eye on the string alignment and any potential twist in the limbs especially where the bends are. Once it's pulling back a fair bit the bow may fine it's own plane to flex on, and what seemed to be dubious string alignment may settle down.
At this stage I have a fair bit of width to play with. The width doesn't really start getting tweaked until it's coming back to about 20" on a taut string or maybe 18" from braced.
That'll do me for now.

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