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Yew sapwood/Heartwood ratio

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woodenwonder:
I'm starting a yew ELB with a yew stave that has about 11 mm of sap wood. Should I use all of that? Or should I shave down some of the sapwood.  I'll probably end up with a bow about 7/8" thick at the fades to about 1/2" at the tip.  I'll be using the 5/8 limb thickness to width ratio design. Would it be ok to taper the sapwood?  Thanks for your help.

WillS:
In an ideal world, you want about 6mm sapwood all over.  It's only there as a safety net to stop the bow pulling apart.  Too much sapwood (apparently) will give you a slightly softer, slower cast. 

However, it's wood, and you can never go by numbers.  You'll end up with some areas thicker and some thinner which is fine too.  I would definitely take it down all over if it's even on both sides.  Rough it out to about 8mm, work the belly taper some more and gauge how it's looking.  If it needs more sapwood removed to maintain a good ratio then you can tidy it up in stages.

Is it Pacific yew? If it is, and you're looking for a drawweight over 80# or so (warbow weight) you really want to be keeping a single ring on the back.  Lower weight and the odd run off or island is fine.  Tapering the sapwood is risky, as you can't avoid having areas that violate the growth rings horizontally across the back which is fairly bad news in general.  If you can get the whole lot down to between 4 and 8mm then aim to do so.

Del the cat:
I recently built a 130# Yew Warbow which had some of the issues you are interested in.
I was hoping to use the natural back but had to reduce the sapwood in some areas, you can follow the whole prcess starting from this blog entry.
http://bowyersdiary.blogspot.co.uk/2013/10/yew-warbow-stave_31.html
In fact that entry even points back to the entry where it was cut from the tree.
There are also other bows on the blog that address these issues ... the search facility on the blog is actually quite good (unlike some)
Hope this helps.
Del

woodenwonder:
Thanks you guys. It is pacific yew with 5 knots and only 72 inches long. So I'll doubt it will go over 60#.  I'll check out your blog Del.
Gary

Del the cat:
At 60# you can afford to have some grain violation, but try and keep 'em gentle and running along the limb or at a shallow angle. It's all about being smooth with no sharp changes is section or discontinuities.
On one bow there was big dip in the heartwood and a cooresponding thick spot in the sapwood, I went down trough 8 rings of sapwood over about an 8" length else I'd have had no heartwood on the belly... that's an extreme example and even with that I tired to keep it smooth and gentle.... (see pic)
It's about using the wood you have and going with the flow... I don't s'pose you'll see a pic of a dip like that and how to deal with it in any text book... they all have perfect straight staves with 3/16" of clean sapwood ::)
BTW That was the first Yew bow I ever made it was 70# at 28... it's taken a load of set and lost some weight but still shoots over 180 yards no prob.
Del

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