Primitive Archer
Main Discussion Area => Bows => Topic started by: Stringman on August 07, 2012, 01:34:21 pm
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I have a piece of yew 62" long and fairly straight. There is some prop twist to it as well as a variety of bumps, dips and warbles in the sapwood. This is my first go at yew so I'm uncertain if I need to get the sapwood to a single growth ring or if I should just sand it till it's smooth? Also because there is a fair amount of convexity on the back of the bow will that limit the way I lay the bow out. Was kinda wanting a flat parallel limb design with a short 4" handle and flipped tips. Any advise on how to proceed would be appreciated.
Scott
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A couple questions... What state is your sapwood in now? has the bark been removed and the top growth ring is intact or has it been damaged? how thick is your sap wood? if it is around 1/4" it is perfect for a self back and should be left as it is bumps, warbles and all. if it is around 1/2" thick or thicker you need to consider reducing it because you may run out of heartwood on your belly during the tillering process. There is no need to chase a ring on yew and I hear it is difficult next to impossible anyway. You do need to follow the natural contours of the back when you reduce. That should leave an even 1/4" when you are done. You probably dont need to back it even if you reduce it unless there are some worrying defects. Yew sap wood is very forgiving. I hope that helps.
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Check out this one I made (Twister), it should answer some of the questions.
http://www.primitivearcher.com/smf/index.php/topic,28324.msg376265.html#msg376265 (http://www.primitivearcher.com/smf/index.php/topic,28324.msg376265.html#msg376265)
Don't worry too much about following a ring, it's an 'aim' not a 'law', sometimes you will need to reduce the sapwood thickess to maybe de crown it a bit or to maintain a sensible heartwood thickness.
Del
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Thanks Weylin and Del. That does answer some questions. The back has already been scraped some (before I got it) but it does still show the natural flow of the wood. Just want to clean it up a bit before reducing the belly very much. I dont see any major concerns that lead me to belive backin is necessary. So my next question is - what's the best way to scrape off some of the sap wood? And should I decrown this stave?
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You don't need to chase any ring. Violating the ring will do no harm. I usually take my drawknife and take the sapwood down to between 1/4 to 1/8 depending on the density and design on the bow.
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Looks like it's pretty good , but I think you'll prob need to reduce the sapwood near the ends, it looks a bit thick in that last pic (I'd say reduce the sap wood to about half it's present thickness, well a bit over to start with)
You don't have to do it all in one go, reduce the belly as you start tillering and if it looks like you are gtting to the point where the heart is getting down to the same thickness as the sap, then reduce the sap. I think a 1:1 sap/heart ratio is ok, but best if you don't get worse that that.
Mind ,I've seen bows with just a skinny layer or heart down the centre of the belly with sap showing either side. Just feel your way into it, slow and steady. Don't try and reduce it to final dimensions and then stick it on the tiller, get it on the tiller on a long (but tight) string as soon as you can and keep teasing it back. Enjoy following those curves :-* ;) (you don't have to be slavish about following an actual ring, but if you try to keep the sap a fairly even thickness, and follow the undulations, you'll find you don't get too many sharp ring violation anyway and that's just fine).
Del
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Forgot to mention-
Del, your "Twister" bow is what I had in mind for my design. Although, I had envisioned taking the twist out of my stave.
Scott
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Forgot to mention-
Del, your "Twister" bow is what I had in mind for my design. Although, I had envisioned taking the twist out of my stave.
Scott
Cheers, Yes it's a good design for Yew and gives a fast bow.
For me the decision to decrown is made when/if you find the draw weight just isn't coming down and you have removed a fair bit of heart wood from the belly and are begining to feel you are going to run out of heart wood before the weight comes down.
Hope that carifies it a bit.
Del
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DEL 169 FPS Fast for 40 pounds. For all my own personal bows. I'm not into the heating thing either got out of it along time back. I like to build my bows the way they are also. But I use'll start with nice staves.
Thats a SWEETTTTTTTTTTTTTT YEW.
Everybodys petty much told you want you need to know.
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scott i left most of the sister staves to that at 1/4-3/8 sap when done it bends real easey with dry heat that piece has been seasond almost 6 years dean marlow made his bow he had on here a while back from the same log he has pic s check it out im makin a bow out of the last stave in that log now hope it works for ya brock
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Ok so I scraped off the previous layout marks and laid it out like I wanted. Then started reducing it down to closer dimensions. I took off quite a bit of sapwood and also decrowned it a little. I plan to start rounding the edges and evening up the sap wood tonight with rasp and scraper. Sure can't hog thru this wood like I can osage. I'm trying to go slow so I don't ruin this nice piece of yew.
Hopefully tonight I will be ready to take the twist out of that lower limb. I was thinking about using a monkey wrench and some weights and a heat gun. Any suggestions?
Scott
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looks good from that angle 8)
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I use a pipe clamp, jug of water as a weight and a heat gun. Monkey wrench.... Be careful with those teeth. And with the heat GO SLOW it's not a race. Warm up the wood, apply grease or fat, I use bear grease, but crisco or olive oil works as well. Try not to scorch the wood. Start from the middle and work your way towards the tips. Take it just a little ways past where you want it to be. During the tiller some of that twist will come back, but I've had It go both ways. One bow I just finished had a prop twist, took it out....never showed its twist again. Others I've had to heat, tiller, heat, tiller nightmare. Now there's is nothing lost performance wise but when your making bows for other people they seem to see it as a flaw.
-Bryce
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Ok heat corrections are done. Also put some effort into the sap wood and cleaned it up rounded and sanded down. Bow is starting to bend now and showing some promise, though I havent put a string to it yet. I have some questions about knots and whether I should consider backing it.
The second pic shows some rings that were cut thru in the sapwood. Is this normal violation?
The 3rd and 4th pic are of a knot that came out on the side of the bow. I've seen this done before or I would have never tried it.
The last pic shows a little bit of checking that has mostly been removed thru tillering.
Keep the advise coming. As beautiful as this stave is, I sure would hate to mess it up now!
Scott
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Well, if any wood can handle all those knots it's probably yew. I would check the hardness of the knots and if any of them are soft you should dig them out and pack them full of sawdust and superglue. Otherwise, there's only one way to find out if it will make a bow! ;) Del has certainly made beautiful yew bows out of worse.
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I'd be rather worried by the knot in the pic below and the dark line going out left from it.
I would get an old needle file (or some such) ground to a tiny chisel point and clean out around the edge of the knot (and that line), you may find that once you have cleaned out the crud there's no good sound timber.
Don't panic! You can excavate the whole lot, fill with a plug, then take it down to a flat concave face and overlay a long sliver of sapwood which will give the back some continuity (it also eggectively moves the manky stuff in towards the neutral plane of the bow where it won't be under such strain.
A nivce looooong patch can be blended in to almost invisible.
I've done it on a few bows and it's better to be safe than sorry.
I can see you've followed the dips and swoops, but there's that area with pins where the sap is pretty much transparent too, that may be worth a sap wood patch.
This link shows a V similar repair I did on an ELB.
http://bowyersdiary.blogspot.co.uk/2011/05/repair.html (http://bowyersdiary.blogspot.co.uk/2011/05/repair.html)
Del
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scott lookin good do as del said you can also use a rawhide patch and dont be afarid to use a lotta super glue brock
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Thanks, Del for the tip about cleaning out the knots. I did that and then filled them with tbIII and sawdust. At that point I put it on a long string and it seemed to be bending evenly. However, I didn't want to leave it to chance so I backed it with a super thick snake skin (red tail boa.) After that dried I cleaned it up a touch and finally got it to almost brace last night and put a few arrows through it. Feels fine, shoots sounds, but seems to be demonstrating a little string follows after being strung for a bit. Is this normal for yew? Mind you, I have been very careful to not over flex this bow too early and I do not normally have this same problem when working osage. So I assume this is a characteristic of the yew wood?!?
Here's a few "sneak peak" pics of where I'm at. The tiller pics are from both sides and with a long string.
Scott
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Mmmmmm! So fine!! 8)
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I'd say you will generally get a little set. I'd say you've done well with that stave.
Yew can put up with a lot, but you've gotta know when to quit and be thankful it didn't explode on you.
It's odd how non bowyers always ask how did you get that lovely bend? (the set)...
Most of my bows take a little set, If I put 'em belly against a wall and can only slip two fingers between grip and wall I'm happy.
Just say to yourself "It's a design feature" out loud 10 times evey night before you go to sleep,... ;D
Del
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I gotta say that does put my mind at ease somewhat. Resilient is certainly a word I would use to describe yew after having used it.
Now as to your "be thankful it didnt explode" comment... When I started bending it last night and bringing it to close brace height it occurred to me how much money this little piece of wood and animal skin represented to me... Let's just say I nearly started to sweat coming to full draw. :o My wife was chiding me about it later, but your words brought back the intensity of the moment all at once. ;)
Scott