Wednesday, 3 April 2013

Deflexed & Wobbly Staves

One of my web friends was asking advice on a couple of tricky staves and I said I'd post a pic of this one which is my last of this years seasoned Yew. You can see it's certainly a tad weird, the link goes to the post showing when I cut it.

There's no right or wrong way to deal with this sort of thing, it really depends on what you want from the bow, what you want it to look like, your experience and if you feel like experimenting.
Why do we expect a bow to be straight and have a nice even tiller? We see too many mass produced laminated ones, yet 'Character bows' are highly prized for their novelty and to showcase the skill of the bowyer.

This stave is hopefully destined to become a 70# @ 28" longbow for a guy who had a 60 pounder from me back in 2011. I'll discuss the various options with him as it progresses.
There is no need to rush into trying to straighten a stave, far better to get down to rough dimensions and flexing first, it can even be tillered to brace height or a reasonable draw before bending.
The big advantage of this approach is there is less wood to bend, so it takes less time to heat it through and there is less bending stress on the wood. leaving it late can also let you get a feel for the wood and allow you to combine heat tempering (treating/hardening) of the belly if you need to gain some extra draw weight (it can also help the stability of any bends you make).
Another option for a deflexed stave is to add some gentle reflex to the outer half of each limb giving a hint of the deflex/reflex shape of a modern target bow. One need not feel that some heat bending is an anyway 'wrong' or not authentic. Many of the Mary Rose bows had some reflex, we don't know why. Was it natuarally in the staves, as stave spilt from a straight log tend to bend outward. Was it heated in? Was it a result of the years underwater, we can't be certain. We do know that heat bending of wood is an ancient and well established process.

My initial thoughts on this stave are maybe just leave it alone, but then which limb would be the upper?
Maybe I could take out some of the deflex making it effectively two straight limbs set back in the handle (E.G. A very shallow V with the limbs pointing away from the archer)

Why are we making the bow anyway? My general aim is to get the best performance I can from the available wood. Sometimes I'll do all the heat treating, bending and correcting, other times I'll enjoy going with the wood.

The big mistake is to take an asymmetric stave and try to tiller it to a symmetrical tiller. Bends and kinks in the stave need to be there at full draw too, and it can be very hard to ignore them during tillering. Sometimes squinting through partly shut eyes will mask the small undulations or drawing a straight line on the side of a wriggly stave will help give the eye something to follow. A gentler undulation takes a different approach, plenty of looking and taking pictures, measurements may help, but the mk 1 human eye and brain is often the best tool if adequately fuelled with tea and toast.

The close up shows the nice thin layer of sapwood on this stave, I won't need to reduce it at all, if only it were straight it would be a near perfect stave as it seems to be knot free.

This was the underside of a horizontal branch, which in theory according to the books isn't ideal as the upper suface is 'better' because it's grow with the sapwood in tension resisting the weight of the branch and the heartwood in compression.
Yes, all well and good in theory, but didn't they notice that Yew shoots twigs and branches invariably sprout from the upper surface of horizontal limbs?
In this case it's irrelevant as the upper surface of the branch had lost most of it's bark and sapwood.
If the performance of the wood is in doubt I can temper the belly.
Only time will tell, but I fully expect it to be very similar to the other English Yew I've worked, which is incidently very similar to the Oregon Yew I've worked too.
(Arrrooogah arrrooogah... Sarcasm alert) Maybe I can get some high altitude Italian Yew which will doubtless feel entirely different and be a complete revelation.

Update:- Ive been taking it down to my usual rough dimensions of about 30mm square at the grip tapering down to about 20mm square at the tip. There was something odd about the stave and it took awhile for the penny to drop.
No knots! Not even a single pin! Maybe because it was the underide of the limb. Once I realised, I put down the spoke shave and went for the draw knife. What a luxury being able to go down smooth as silk to a pencil line with no fear of the blade digging in or tearing out gouts of wood around knots. The norm is drawknife, spokeshave, rasp as it gets closer to size and any tearing is more risky. Maybe no character knots, but certainly some interesting shape to negotiate on this stave..

BTW The blog broke the 5000 hits in month barrier in March which is satisfying... mind, you'd think I'd get a chocolate bunny or summat wouldn't you?

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