Primitive Archer
Main Discussion Area => Bows => Topic started by: Aaron H on May 27, 2014, 11:39:07 pm
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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?
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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.
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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.
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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 (http://bowyersdiary.blogspot.co.uk/2013/11/dealing-with-dip.html)
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Thank you guys. I appreciate every one of the responses. How thin of sapwood is too thin for a bow of this weight?
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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 :laugh:
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 :laugh:)
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Dang kids, with their long hair, rock n roll, and skateboards
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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.
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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
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Ok, thanks Del
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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.
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Yea, I am going with a slight bend in the handle, and the traditional English deep bellied cross section on this bow.
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Del, you made me question everything I thought I knew (didn't take long ;D).
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??? :laugh: Then I realised that was your polished up demo/show piece of wood :D
I need to go back to bed, is it friday yet? ::)
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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 (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
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Now that is a lot of sapwood
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This one was mostly sapwood and performed very well indeed with little to no set.
(http://i121.photobucket.com/albums/o218/dwardo/P1010003.jpg)
(http://i121.photobucket.com/albums/o218/dwardo/P1010014-3.jpg)
(http://i121.photobucket.com/albums/o218/dwardo/P1010009-2.jpg)
(http://i121.photobucket.com/albums/o218/dwardo/P1010006-2.jpg)
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Nice bow dwardo, What is the draw weight and dimensions on that?
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Dwardo, that's gorgeous dude! Very nice bow.
I've found very little drawback to keeping the sapwood thicker. I love seeing cambium on the back of a yew bow so very often I'll leave the sapwood exactly as it is even if it ends up almost half an inch thick in places. I've yet to see this cause more set than usual or significantly decrease performance over a similar bow with much less sapwood. I've got a warbow that came out around 120# - 125# that has 1/8" sapwood on one side and over half an inch in places on the other due to having to lay out the bow across the stave rather than straight down the crown, and it's not suffered as a result.
I think yew is one of those few woods that's perfect for making mistakes on. You can really chew it up and make a mess of chasing a ring or violating knots and it'll hang on in there like a champ letting you learn without too much heartbreak. It's always better to chase a ring as Mike said, as it gives you peace of mind that it won't be splinters lifting to cause a failure (it'll just be something else >:D ) and of course it does look a whole lot neater with one continuous back ring, but with yew it's really not vital. It's almost purely an aesthetic issue at "normal" draw weights - if you want more heartwood in the finished bow take the sap down a bit, but don't expect sudden miraculous performance increase as a result.
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Nice bow dwardo, What is the draw weight and dimensions on that?
Guessing but around 62ntn and mid 50`s at 27.
I too believe yew is one of those woods that you can get away with a lot. Some of Del`s stuff is more patch work, plug work than original wood yet he still managed to get a bow from it. I do wonder if it was one of the reasons yew was favoured in the past over other woods.
I have a bunch of yew staves I am roughing out at the moment where I could have made a whole other bow just from the sapwood as it was 2+ inches thick in some places. I bandsawed most of it off and took to the rest with a micro-pane rasp (which are revolutionary by the way).
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I think it's more down to the fact that yew can tolerate European climate far better than white wood bows. I reckon once you reach a certain level of skill it doesn't matter too much what wood you're working with, but if ash and other meane wood bows suck up moisture and lose performance and go soggy everytime it rains, while yew doesn't seem to be affected as much, it makes more sense to use yew. My thoughts, anyway!
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Hey Dwardo, explain this micro plane rasp to me
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These things are just magical. Require no pressure, weight nothing and don't clog up or need brush cleaning. If you are working damp wood especially elm then they can start to clog but easily removed with your finger. I have the coarse and fine half rounds and both flats. Amazing bit of kit that just hogs wood off. Too fast sometimes, still getting used to them.
http://www.axminster.co.uk/microplane-snap-in-rasp-handles
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What do you think about the fine tooth rasp? Does it still take wood off too fast? I'm looking for something that takes very minimal amounts of material off, but also something that leaves a very clean surface with minimal clean up required.
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You're describing a scraper aren't you? Takes fine shavings off and leaves a smooth, almost polished finish.
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In a way, I guess I am. I have one of those already, I just like to have multiple options
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It's funny - when I first started making bows I spent a fortune on a huge set of tools that I figured I'd need. I bought rasps, files, various shapes of scrapers, drawknives, spokeshaves, knives, hatchets and so on. Now I probably only use 4 at maximum - hatchet and drawknife for bringing a stave down to bow size, then dreadnaught file for everything else until the bow is half tillered, and then just a rectangular scraper. Rarely do I feel the need to reach for anything else!
I did buy a power-planer to reduce staves quicker which usually gets used in the place of a hatchet, but other than that, not much!
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Hi, my name is Aaron and I am an addict. I'm addicted to tools!
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Just realised about the advertising thing. I have no connection to Axminster except using them my self. Please remove the post if its a problem.
For me its an axe, drawknife and rasp then onto a scraper. Maybe some sandpaper to make it look shiny :)