What do I/yew do?!

[cadet]

At considerable expense, I've just imported two yew staves which have now arrived.  I figured I had to play with the stuff once or twice in my life if I was to call myself a bowyer!  My staves have significant twist - 45 degrees in one, and nearly 90 in another, but are otherwise long, clean, clear, fairly straight, and fine-grained at 40-50 RPI.  Staves were de-barked for quarantine purposes, and sapwood is between 1/4" and 3/8", so I don't expect I'll have to thin it much.  They're both around 80" x 2" x 2".  To correct the twist, would I best to reduce them closer to final size, then steam-bend them straight?  or something else?  I'm probably aiming at an ELB or mini-warbow style in the end.  Given the expense, I'd like to be patient with them and try and get it right from the start.
Ta.

[Hamish]

 I'd need to see photo's to really know what was going on, if they need steaming.  Buy the time you have reduced a stave to bow width dimensions (leave the tips around 3/4" wide) the problem mightn't appear so bad. Unless the twist is really bad, you can plane/rasp/or file, the sapwood flat, effectively removing the twist(or at least minimizing it). This was commonly done in both warbows and target bows. You still want to follow the grain along the stave, but across the stave you can flatten it. Nevertheless some bowyers planed the sapwood pretty flat in length too, and within reason a good stave of yew can take this.

[Del the cat]

Like a lot of bowmaking problems the solution isn't always do "A" or "B" or even "C" it's often a little of each.
Many yew staves have some twist or a crown that doesn't run straight up the middle or some defect you are trying to avoid.
My first step is trying a string line along the log at varying positions and angles to try and give the best line regarding how the heart/sap boundary looks at the tips, the knot positions and any deflex reflex bends in the wood.
With a warbow or ELB of Yew I find you can go on the diagonal a bit to try and average out or minimise problems and you can't do too much damage with string 
Always leave extra tip width (I rough out to 20mm wide at the tips or more), a couple of reasons being:-
1. The stave can move as wood is removed.
2. The extra width can help you to adjust the string line if needed.
3. It's easy to take the wood off later and the extra tip width doesn't effect the early tiller too much anyway.

As the bow is progressing and say coming back 25-20 inches, it will be easier to remove any twist with steam. There are examples of how I do it on my blog, but by steaming a good length of the limb it's no too difficult and Yew takes a steam bend quite nicely.
Here's a post shown how I've done it on a Yew primitive:-
https://bowyersdiary.blogspot.co.uk/2014/06/removing-twist-from-yew-primitive.html
You can to some extent just ignore the twist but you'll end up with thicker sapwood one side of the limb than the other. There are ways of dealing with this, here's a post from my blog which shows a couple of options...
https://bowyersdiary.blogspot.co.uk/2011/04/different-approach-to-twist.html
Like I said , a little of A and a little of B, it's easy to correct twist and end up with a bit of sideways movement, but your extra tip with can help remove that.
Plenty of thinking time, a little and often, slow and steady etc 
Del

[cadet]

I was hoping you'd chime in, Del, thanks; I keep an eye on your blog and find it thorough, useful, educational, and enjoyable.

I've had a preliminary look at these staves, and every which way I look, they just look too twisted to my eye not to try and take some of it out.  The steamer set up in that link is a little like what I had in mind.  The twists are long and gentle and even, so no one part of a stave would be subject to excessive stress in being gently straightened, I don't think.  Perhaps 15-20 degrees on each end would do it.  I don't feel like I need to iron them dead flat, but my skill level needs the backs closer to a single plane than they are.

I'll keep looking at them, and pondering them from different angles probably for weeks before I start doing anything with them.  They're substantial bits of wood.  In the back of my mind is the hope that each stave might yield more than a single bow; perhaps some extra heartwood for a backed belly, if nothing else.

[Del the cat]

Sounds like you are being V sensible. Gotta remember it's not a race and often it may take a few tries to get the result you need.
Yew can sometimes spring back a fair bit from steam bending, but it can always be "fixed in" with some dry heat at some point if needed.
Del

[DC]

I've taken the twist out of a few Yew staves successfully. If you are going to do whole limb at a time don't taper it much beforehand. If it has too much taper and you put a wrench on the tip and start twisting the thin tip will twist a lot more than the rest of the limb. Yew steams easily so what I do is reduce it too about 1"x2" for the full length of the limb. Steam it thoroughly (maybe an hour) and the twist it and clamp it. Because you will be taking a lot of wood off the tips later, some of the twist may come back a bit. I usually deal with that with localised dry heat. I've found that if you are very careful with the dry heat you can darken the heartwood a bit to really make that "Yew look" stand out. I have had Yew stain from the steaming process and one way around that is to wrap it with Saran wrap before you steam. I think this slows the heating a bit so you have to extend the steaming time. Go slow and overthink every step.
PS I just realised that you may be thinking of a warbow or ELB so adjust the 1"x2" accordingly

[Del the cat]

Some good advice being given .
I'd just add, if you use dry heat, protect the sapwood back with plenty of masking tape and support the limb on a narrow plank (say 3x1 edge on) so the heat can blow past and avoid scorching the back.
Del

[DC]

Yes, good point. Nothing ruins the "Yew Look" worse than scorched sapwood. The scorches go deep too. You have to remove a lot of wood to get rid of them. Don't ask how I know.

[cadet]

Some good ideas there, thanks DC, particularly about not tapering the tips too much so they twist more than the rest or the stave.
By "staining" do you mean the yew discolours on the surface (which seems to be what a lot of timber does, which goes once worked), or does the discolouration run deeper?

[DC]

Deeper, especially in the sapwood if I'm remembering right. We have very soft water here so I don't think that's it. I may have been steaming a stave with the bark on and maybe the stain came from that.

[Hamish]

The different depths of sapwood from one side to the other at the same spot, that Del mentions is a common feature in many of the old yew longbows, and flatbows I have seen. Some may even show a hint of heartwood on one side.

If you can get the tips and the handle in the same plane, it doesn't matter too much what is happening along the rest of the limbs, as long as you treat the cross section appropriately in relation to the plane of the back.