Primitive Archer
Main Discussion Area => English Warbow => Topic started by: swotavator on August 02, 2009, 11:12:31 pm
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Hey all. got a new 73" pacific yew stave. Beautiful. Almost .5" sapwood and about 45 RPI.
I am making my first self yew and I have two questions:
1. The sapwood is a warm yellow, but there is about 1/32 inch layer of pinkish wood between the bark and sapwood that has a very high and hard to follow ring count. Do i remove this layer?
2. the billet was cut such that the sides AREN"T perpendicular to the sapwood. I would say that the dimensions are 2" back, 2" side, 2" belly and 3.5" side. recommendations on how to rough the shape out? should I bring the bow all the way up to the smaller side and cut it off so the sides are perpendicular to the sapwood or does it not matter?
also, have people decided on a generally accepted authentic and durable finish that won't flake? danish oil?
thanks a bunch
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Between the sapwood and the bark is the layer called the cambium. This is the only actual living layer in any tree. Yes, you need to remove it. Use your draw knife or spoke shave and carefully remove this layer until you can see the creamy white sapwood.
As far as stave dimensions go, a pic of your stave would be great. If you have prop twist or relex, etc., you can heat straighten if you need to.
Finishes? I use many, and they all work pretty well... tung oil, wipe-on polys, tru-oil, etc.
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At 1/2" the sapwood is a bit thick. You may want to remove some of that
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A finish? I like emulsified beeswax applied regularly.
Rod.
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Hi,
Any photo's??
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Sorry it took so long to post back. I now have a near complete yew warbow. It has been roughed out and both nocks are almost done. Will be filing and sanding now. But I have a few more questions:
1. There is a pretty big knot I couldn't avoid. It goes diagonally from the belly to the side of the bow, and has a crack in the belly. My uncle works wood and mentioned some type of epoxy used for wood boat repair that seeps into cracks. Do I need to do this? Is this knot goign to blow up? I have closeups in my photo bucket (below)
2. I have removed enough wood so that my bow matches what I have heard are accurate measurements (74", 1.25" across the back, 1.5 deep at the middle tapering to 0.5 at the nocks) When I try to floor tiller this beeotch, though, I can barely bend it - maybe 5" max (I am 200 lbs and pretty strong). I haven't begun really tillering, and have never made a bow, so I have no idea if this is normal. I am worried that if I remove more wood I will make it too weak. I am shooting for around 100#.
Can you take a look and tell me where to remove more wood? I taper the back like this, from the center : 0-20" (1.25") 20-28" (1") 28-33" (.75") 33-37" (.5"). The profile tapers evenly from 1.5" to .5"/
3. How are the nocks looking? Too large maybe? string groove deep enough? Thanks for the help.
Here is my photobucket album
http://s565.photobucket.com/albums/ss97/swotavator/yew%20bow/ (http://s565.photobucket.com/albums/ss97/swotavator/yew%20bow/)
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Hi Swotavator,
Don't waste your time floor-tillering a longbow of this potential draw-weight; you should have had this on the tiller bar before now! You have probably already taken parts of the bow down too far, but it's really difficult to tell for sure without having the bow in my hand. you have done well to leave wood around some of the knots, but that really big one that seems to go right through may be a killer; again without looking at it in real life I couldn't be sure. Following dimensions for a bow of this sort is all well and good but what you should really have done was follow how it was coming round on the tiller bar and gradually remove wood until the curve was even. This process is best done very slowly over the course of several days - once the bow starts to come round it will become easier to bend and if you do this slowly, allowing the stave to relax back to its former shape each time, you will minimise the set.
Dave
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Fair enough. Tough to know when most how to's are aimed at laminates. So I might be looking at a lower poundage, but I still have a significant amount of wood left around the knot. Do I need to glue/seal it somehow? or just tiller, sand well, and finish the bow?
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Well, I know what I could get away with if I was working high altitude Italian Yew, but I've never handled American. The problem with the big knot is that the grain within it runs at a different angle to the rest of the stave, and also the wood within it is very dense and relatively incompressible - so you are asking the sapwood to bend around an incompressible lump that, unlike the timber in the rest of the stave, will barely give - could in fact break along the crack-line (yes try industrial epoxy resin). However, I am continually surprised at what Yew can tolerate, and American Yew is a good timber so all I can do is suggest trying it. Take it very slowly on the tiller to get the initial bending, then relax it and leave it 24h then bend a bit more. I personally take about a week to properly tiller a self Yew bow. As with the tillering of a laminate bow, the initial bending should start about half way along each limb and the middle of the bow should be coming round gently when the bow starts to reach the maximum draw-length. Don't forget that the lower limb should be fractionally stiffer than the upper limb; no matter what people may say, a self Yew bow is not absolutely symmetrical.
Have fun! Dave
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Cool, makes sense. Do you think gorilla glue two part epoxy would be a good candidate? that is what I used for the nocks, and it seems pretty resilient.
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I've heard nothing but bad news regarding gorilla glue. Not tried it myself, however. Why don't you just get some TB2 or TB3? It's cheap, and works awesome. Cleans up with water.
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OK, sealed the knot with TB II. I think it worked. Made my first string out of fast flight and learned a lot. I followed my steve stratton DVD. One problem I had though was that once I wrap the ends of the flemish loop into the string and continue to wrap for about 3 inches, that last three inches come out whenever the string is put in tension, making the string gain a few inches of length. WTF? will serving the center of the string prevent this? do i need to put a spot if glue on the end of the wraps?
Also, I did my first tiller. Please help me figure out where I need to remove wood. The bow, right now, is waaay to strong for me to draw.
[attachment deleted by admin]
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nevermind. I figured the string problem out. Think I will be using a timber hitch also. Please help on the tiller though. Where do I get a scale? Also, how do people prevent the bow from tending to roll over while they are tillering? Is this an issue? Do I have to cut the slot for the bow narrower?
Thanks a bunch guys ???
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Hi Swotavator,
Making a good start there. Tricky to tell at this stage where there are any problems, but the centre of the bow seems a tiny bit thick. I am reluctant to give advice based on a photo in case I say the wrong thing, but anywhere the wood on the belly dips in is a potential "hinge" so go easy there and keep an eye on it! Carry on bending the bow a bit more and post some more photos! Your nocks are too big, but don't worry about modifying them until the bow is completely tillered. How thick are the ends of the limbs at the point that they enter the horn? For a bow of the draw-weight your looking for, they should be about 12-14mm in diameter. Don't be tempted to give the bow too deep a cross-section or make it too D-shaped; I find these bows perform better with an ogival section or even slightly flattened oval section and if you tiller them carefully they will take slightly less set that way.
Good luck! Dave
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The bow is not bending at all yet, so no advice is useful at this point. Next time, don't install your horn nocks until the bow is tillered, as you may end up being whip tillered. Wait and do your nocks at the end. Cut temporary self nocks, and they will disappear when you cut your tapers for the horn nocks.
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The bow is not bending at all yet, so no advice is useful at this point. Next time, don't install your horn nocks until the bow is tillered, as you may end up being whip tillered. Wait and do your nocks at the end. Cut temporary self nocks, and they will disappear when you cut your tapers for the horn nocks.
Quite right adb! Also I think the tillering bar is too short - needs to be about your own height, that way, if you don't have a pulley system to draw the bow, then at least you can use your own bodyweight to do it!
Dave
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You need to shorten your string till there's no slack. You need to remove wood in the center and leave the outer limbs alone for now
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I guess it doesn't need stressing too much but go really careful with the big knot. It looks as though the limb is almost all knot at that point. A knot has relatively little strength. If it goes at that point it may go very suddenly.
Nothig like picking yourself a challenge!
Mark in England
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Hey all,
did a little work, and have tillered again. This is the result. I think that the left side is a little stiff, and something is going on in the center of the bow. Any ideas how I can remedy? Which numbers? Thanks guys
[attachment deleted by admin]
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Hey all,
did a little work, and have tillered again. This is the result. I think that the left side is a little stiff, and something is going on in the center of the bow. Any ideas how I can remedy? Which numbers? Thanks guys
Ok, so you need to have the centre of the bow absolutely horizontal on the tiller bar to make any sense of it. You have too much bend between 10 and 11, and you need a tad more bend at 12 to alleviate this. The centre is too stiff between 6 and 9; start by reducing the depth between 8 and 9. You have what might be a hinge starting at 3, so you need to get a bit more bend at 4, not necessarily by reducing depth here; maybe width, but it's hard to tell from a photo. You've done well to leave a bit more timber around the big knot; this is the point at which the bow should start bending on that limb so it takes more stress than any other point - I still think it will be a miracle if the bow holds together at that knot! Remember that the way a bow bends round on the tiller bar is a combination of depth and width; we can see the depth from the photos, but cannot see the width, so you have to go with your intuition here. take it carefully and remember that, if this is your first bow, it may not come out perfectly - each bow you make is a learning experience,
Good luck! Dave
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Get rid of that long string!
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Thanks for your help dave! - I made a shorter string too and have tillered it to about 2/3 draw. It is still really heavy, and has about a 1.5 inch string follow now.
My newest problem is that the bow seems to want to twist when i pull it to longer draws. The bow has a really straight profile when looking at the back, and the string nocks are very deep and even.
What could be causing this, and how to correct?
I was thinking that removing wood from the belly opposite the direction that the back leans.
The twist isn't huge, but is evident when I draw the bow, and was enough to split my tillering stick.
I am getting a new stick now, and am wondering if I can correct the twist by making the tillering slot VERY tight and leaving the bow drawn for a period of time.
What do you think?
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Feel the thickness of the limbs with your fingers. Use your thumb and forefinger and slide it up and down the limb and also across from side to side. If it is twisting as you draw, one side is thicker than the other. This will also teach you how to tiller a twist out of a limb. ;D