yew sapwood too thick?

[Aaron H]

I have a yew stave, and it has sapwood that is about 1/4" - 3/8" thick.  I am aiming for a 50 lb bow at 27", and 70"-72" long.  I have heard that this may be a little thick for this draw weight bow.  How difficult is it to chase a ring on yew sapwood?  What if I violate a ring?

[Weylin]

I like having a 1/4 inch on most bows. You should have plenty of heartwood on most designs with that thickness. If the bow was really wide and flat and low weight I could see you running out of heartwood. That being said with a bow at that weight you can just reduce the sapwood down to what ever thickness you'd like and not worry too much about violating the growth rings. You don't have to chase a ring. I've done this on several bows as high as 65# without any problem. I know Del has done it too.

[mikekeswick]

Yes but you should still be aiming to chase a ring. It isn't that hard anyway.
A bow stays together because it has unbroken fibers running from tip to tip. I for one wouldn't want to put a lot of work into a yew bow only to have it lift a splinter due to fiber violation.

[Del the cat]

Non violation of growth rings is a worthy aim but not absolutely vital on Yew.
Aim for a nice even thickness. I tend to try and follow a ring down the centre of the back at first just using a spokeshave (or drawknife if it is V thick) like de-crowning, this is easier as you get a series of parallell lines showing alongside to help you. As the bow progresses you can clean this up and eventually end up with a continuous ring if you really want.
Sometimes there may be a big increase in sapwood thickness and you have to go down a few rings. If you do it as a gentle blend it will be ok. Try to keep any violations angled across the back and as gentle as possible.
If you do try to follow a ring, getting the light right makes a big difference an it will show up a slightly softer layer which I think of as being like dry chicken breast meat just before you hit the next more yellow firmer layer. Going across the grain gently with a coarse file or fine rasp will crumple off the chicken meat layer. I work at it in short burst of 10 minutes, and slowly improve it as the bow comes along. Once you are back to about 3/4 draw you want it clean, even and sound.
Del
PS Like Weylin says... over a certain weight you really do want a continuous back if possible. Mind I have done a 130# warbow where it had some ludicrous dips along one edge and I had to compromise. Pics here, where you can (just about) make out the rings. http://bowyersdiary.blogspot.co.uk/2013/11/dealing-with-dip.html

[Aaron H]

Thank you guys.  I appreciate every one of the responses.   How thin of sapwood is too thin for a bow of this weight?

[Del the cat]

I had a bow with remarkably thin sapwood just under 0.1" ! I made it into a 70# @ 32" bow (Dogleg) with a completely untouched back, it eventually broke after about 9 months, but it had a happy life even appearing on TV and having it's pic in a book 
The sapwood was almost too thin. I prefer about 3/16 - 1/4"
Here's a pic. It's English Yew from Harlow in Essex (low lying land) it shows how English Yew is soft flabby coarse grained stuff with poorly defined sapwood and no good at all for bows 
I cleaned it up as it was such nice wood as a demo/show piece.
I think the rings near the sapwood are exceptionally fine (almost indistinguishable). It was a side branch which had possibly been trimmed at some point slowing its growth, it had been used by kids to attach a swing, the upper edge was chaffed and damaged, but the underside was knot free and perfect. Of course it was compression wood rather than tension wood, but often it's the underside of a branch that's knot free, which shows the difference between theory and practice! Show me a horizontal branch with it's tension side straight clean and knot free if you can!
Del
(There were no kids swinging on it when I cut it, and thre were plenty of other branches for them to tie their swing on )

[Aaron H]

Dang kids, with their long hair, rock n roll, and skateboards

[Aaron H]

Is there any disadvantage in leaving the sapwood thick (3/8")?  I rough faded the tips to about 5/8", and the sapwood is about 1/4" there,  leaving about 3/8" heartwood. Again it has only been roughed out so far.

[Del the cat]

Is there any disadvantage in leaving the sapwood thick (3/8")?  I rough faded the tips to about 5/8", and the sapwood is about 1/4" there,  leaving about 3/8" heartwood. Again it has only been roughed out so far.

I think that's ok. There comes a point where it's down to aesthetics. I've seen a bow where it was all sapwood at the tips, which IMO is a bit rough. Of course there is always relatively more at the tips because it's the heartwood that's removed during tillering.
A little extra at the tips is fine as it can get reduced and rounded a little for fitting the horn nocks.
I aim to be about 50/50 worst case, but you just have to go with the flow. On several bows there are areas of more than 505 sapwood where it's maybe thicker one edge that the other, so it can be 55% on the left and 5% on the right of the limb at the same point.
Del

[Aaron H]

Ok, thanks Del

[DarkSoul]

I've seen a yew (flat)bow with 95% sapwood. All heartwood yew bow do exist as well. It just goes to show that it's all possible. Yew sapwood and yew heartwood can both make a bow, but when combined in one bow, it really shines. Myself, I like the bow to consist of about 1/3rd to 1/4th of the thickness to consist of sapwood. The rest should be heartwood. This means that the actual thickness of the sapwood in a flatbow is less than that of a warbow or deep bellied longbow. Just personal preference though! And some aesthetics.

[Aaron H]

Yea, I am going with a slight bend in the handle, and the traditional English deep bellied cross section on this bow.

[Crogacht]

Del, you made me question everything I thought I knew (didn't take long  ).

I thought that pic was the bow you described in your first paragraph... and thought WOW that's a funky cross section you've got going on there.... and the sapwood is on the edge???.... and... those tips don't taper at all??? Then I realised that was your polished up demo/show piece of wood

I need to go back to bed, is it friday yet? 

[Del the cat]

While I'm at it, here's my standard picture of sapwood violations on my first ever Yew ELB (made about 40yrs ago), since refurbished and pulling 70# at 28", see here:-
http://bowyersdiary.blogspot.co.uk/2014/05/yew-bows-130-vs-70.html
There is a big dip by a knot where the sapwood became really thick, I had to go down about 8 rings or loose all the heart wood. It shows what you can get away with.
Del

[Aaron H]

Now that is a lot of sapwood