Primitive Archer
Main Discussion Area => Bows => Topic started by: WillS on February 04, 2016, 09:41:43 am
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I've been round the ringer with this on Facebook for days and got nowhere, so hoping someone here can help!
I have a batch of English yew that so far has broken 4 times in a row, and every time the stave has done this before exploding.
This is a dead straight, well seasoned stave that in the photo is pulling to brace height. The arrows show where its bending, and I can't for the life of me work out why, or what the solution is.
(http://i1202.photobucket.com/albums/bb363/Will_Sherman/Mobile%20Uploads/IMG_20160204_140015_zpst3ervgip.jpg) (http://s1202.photobucket.com/user/Will_Sherman/media/Mobile%20Uploads/IMG_20160204_140015_zpst3ervgip.jpg.html)
Thoughts, opinions and ideas needed before I break five in a row!
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Too narrow relative to depth?
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Is it a one piece stave or spliced sister billets?
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One piece. It was roughly 33mm x 25mm in the area that's bending sideways the most.
I say was, because its just blown up. 5 in a row from the same tree. Perhaps it's fate.
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I think you're just seeing what people see when they make narrow reflexed laminated bow that wants to bend sideways and reverse string itself.
It's just following the path of least resistance.
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It wouldn't normally be a problem, and had it been a one-off I'd have ignored it. The trouble is that every single one of the staves from this particular tree have done it, which I find pretty unusual. The wood also clearly can't cope with any sideways bend, as this one blew up just a bit past brace height at 50lb. I've made bows before well into the 100lb range that do this to a lesser extent that are fine.
Very odd! And frustrating.
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Split or sawn stave
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Do you have a picture of the break? Did it break across the back or on the side(sorta)
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My first guess is that it is too narrow in relation to the density of the wood, can you weigh the broken pieces?
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So you just kept doing the same thing five times in a row? ???
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So you just kept doing the same thing five times in a row? ???
No, I'm not crazy ;)
I've been trying different things each time. Heating it out, twisting it out, removing wood from the opposite side and so on.
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Split or sawn stave
Split.
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Do you have a picture of the break? Did it break across the back or on the side(sorta)
(http://i1202.photobucket.com/albums/bb363/Will_Sherman/12631440_10153807398941427_5560545071292621314_n_zpsn1bev01n.jpg) (http://s1202.photobucket.com/user/Will_Sherman/media/12631440_10153807398941427_5560545071292621314_n_zpsn1bev01n.jpg.html)
(http://i1202.photobucket.com/albums/bb363/Will_Sherman/12642816_10153807375536427_1828261597105246827_n_zpspa5za59v.jpg) (http://s1202.photobucket.com/user/Will_Sherman/media/12642816_10153807375536427_1828261597105246827_n_zpspa5za59v.jpg.html)
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My first guess is that it is too narrow in relation to the density of the wood, can you weigh the broken pieces?
936g for both pieces together.
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Could be the working properties of the wood perpendicular to the grain is poor. You should try a flatter profile
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Well I've got five pieces left, so I'll try the next one wider and flatter then!
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How long is the bow?
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78"
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I think I see what happened now, you had enouh mass for more than 100# but it was a bit narrow for as long as it was, I think it may have been too strong at brace, especially if i had a little set back to it. I agree with going wider and taper for slowly in the width until the last 12" or so.
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It actually had some deflex through the stave, about 1".
I'll have a go at keeping the next one wider then. I'll just make it like an ash warbow and play it super safe!
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Steve beat me to it. I was going to say being that narrow it wouldn't take but one or two screpes off of one side to make it want to twist, especially with those large loops on the string and more so as long as it is.
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It's how I've made all my English Yew bows however. They've never done this before!
I rough them out to the same dimensions every time and all of a sudden they're going sideways at brace height, but only from this tree.
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In fact as far as I'm aware these ones are starting life quite a bit wider than I and most people make English Yew bows. 35-38mm in the handle usually ends up with something in the 130-160lb range, and I was going for 100lb on this one to be safe after the last 4 failed.
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Your side taper can allow twist if they are too steep, it doesn't take much to make a difference. I just barely taper mine anymore in the first 2/3 of the inner limb. High weight at brace puts huge stresses on the torsional aspects.
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Well for what it's worth all of these have been virtually parallel from the centre to past midlimb where they start to taper, and even the initial taper at this stage was minimal.
As an example, this particular bow was 30mm wide about 8" from the tips, and 35mm at the centre for a good 6" each side of the middle. There's almost no taper at all until the tip area.
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Hello WillS,
a few years ago I had the same bad luck with a yew. Two or three staves from the same tree just expoloded (I don't recall about a sideways bend though, but it's too long ago). The yew look good, decent ringcount and no overdrying. I did everything like always with my yew bows but it did not help. I was left scratching my head and not knowing why the bows broke. Never had that again.
So it may be just a stupid, not behaving tree :)
regrds,
gian-luca
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I hope so! I've had a couple other people say the same thing to me today. Real shame!
I just hope I'm not missing something or doing something wrong with these.
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Willis I have come across a couple bad yews, but they were obviously bad.
Punky dry sapwood, one black growth ring, or pecker holes.
Its possible you have a bad tree. I'd do like other have suggested and make a wider limb flat bow.
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Even bad Yew usually makes a bow! I've pushed stuff with rot, holes, bug damage and no sapwood all in one bow up to 60lb, but this stuff which looks perfect is kicking my ass ;)
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WillS, I' ve had same experiences with yew over the years. I know a German bowyer, who refuses to make bows of yew, cause of those unexplainable breaks.
I' ve made yew - bows suddenly breaking after some years of shooting, I' ve seen a tournament- winning yew- bow breaking at the handle.
In the meanwhile yew makes me really nervous. Anyway I love it.
A forest- ranger told me that the capablities of yew usually are heavily depending on the location and the growing conditions.
He would recommend yew growing on northern slopes only.
Michael
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Could the wood of that yew tree be too dry?
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Well that's something I don't know enough about to say, really.
I did do a quick sapwood bend test just now, and the sapwood (without any heartwood) broke at very little bend, into extremely short fibres quite unlike usual yew sapwood. If I can chalk this up to the wood and not me I'll be much happier, but I think it's more likely to be user error than anything else!
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This is the result of bend-testing just the sapwood from this particular tree. Have to say, it doesn't look particularly good in terms of tension material ;D
(http://i1202.photobucket.com/albums/bb363/Will_Sherman/12688114_10153808956736427_1887733473384369647_n_zpsdp6kbxcj.jpg) (http://s1202.photobucket.com/user/Will_Sherman/media/12688114_10153808956736427_1887733473384369647_n_zpsdp6kbxcj.jpg.html)
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As you proceed on your bowyer journey, WillS, you develop a feel as to when the bow is ready to get pulled a little further. You have to coax a tiller and take your time.
I can't really tell why your bow broke from those photos. I can speculate that you pulled it too far too fast before it was ready.
Did you long string tiller?
That stave did not even look ready to be braced. Just speculating.
Here's my site.
http://traditionalarchery101.com/
I broke a lot more than 5 before I got a hunting weight shooter.
Jawge
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Thanks George. I've actually made probably about 50 or 60 at this point, most of them over 100lb and normally when this sideways bending occurs it's either an easy fix, or I ignore it and the bow resolves itself. I made a nice 115lb ash bow last year which has very similar twist and it's fine at full draw. The 140lb ash bow I posted in the warbow section actually has some slight sideways bend to it as well. This particular batch of yew just doesn't seem to be able to cope with the sideways forces, however. I'm wondering if it's down to the sapwood just not being elastic enough to hold together.
This one actually blew up at brace height (or just beyond) while long string tillering which is pretty unusual for me! Mine normally go pop at around 32" when I've done all the finishing work ;)
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Sorry, Will. I thought I read that 5 blew up on you. That's what I get for typing before my 2nd cup of coffee. :) Jawge
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Yeah you read it right, it was 5 in a row! But all from the same tree.
The question is - am I doing something wrong when it comes to correcting this twisting problem, or is it a problem with the wood itself? I'd like it to be the latter ;)
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Well, Will, then, it still looks like you bend it too far too fast.
Are we talking a twist or a dog leg?
I don't know about war bows and such but that stave looked capable of 50# anyway.
When I make bow, first I floor tiller 2-3 inches.
After floor tillering, I go to the rope and pulley and long string tiller out to 10 inches of string movement where I want good bending and around target weight. Then I string it.
My early days I'd break staves while stringing because they were too heavy.
The above method puts the stave about 10# over target.
Jawge
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This was going to be around 130lb which is just a bit too heavy for floor tiller. You can floor tiller them at that weight, but its easier to use long string tillering instead. It broke at 50lb, but that wasn't the end goal for the bow.
I do pretty much as you described, regardless of draw weight.
To be honest I still don't know if its twist or something else. Not dog leg, because the staves are dead straight when I start bending them. The sideways bending happens almost immediately, and the back and belly of the bow stay level, while the actual limb itself bends outwards then back again, forcing an S shape down the whole bow. When you take it off the tiller and look down it, its still dead straight.
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Do you know the history of the stave? I'm looking at your sapwood bend test and wondering if the sapwood has started to decay?
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It was cut about 4 months before I got to it, and was left outside without the ends being sealed.
Not the best recipe for success!
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We're talking about three or four BIG logs by the way, that I split and shortened dramatically to get around 13 staves from. I assumed that reducing them so much would remove any problem areas, but perhaps not? Would that be a logical reason for every single one so far to fail?
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I really have no idea how rot resistant yew sapwood is but I do know it's not as resistant as the heartwood. I don't think 4 months in the rain would bother it. I've worked yew that was on a slash pile longer than that. Maybe if it was laying on the ground and the staves you're working were on the bottom? I'm just guessing here. Maybe it's just bad karma. Have you pissed anybody off lately >:D
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I think you just answered your question. Yew heartwood will not rot in that time, but the sapwood will easily. Even if it just started too, the outside growth rings under the most tension have been compromised.
On the 4 or 5 salvage yew staves I've worked, the sapwood was dry and powdery when scraped. It should be creamy and carve like butter.
Maybe make an all heartwood bow, or back with rawhide.
I'd try to get a bow or 2 from that batch still
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It doesn't feel any different to what I've worked before, and certainly doesn't feel powdery. Perhaps it's just started to go, and that's enough?
Still doesn't explain the sideways bending in every single stave however. My plan now is to rip it all into boards and make laminated warbows out of it, but if it still tries to pull into an S shape I'm not sure what the answer is.
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those wide tips put at lot of sideways torque on the limbs !!! if there is a slight tendency to twist anyway...might not be the whole problem , but may have added to a series of problems....it is very long and narrow...like the others said.. a long narrow limb wants to twist if there is a slight misalignment , or natural twist inherent in the wood .all of these things accumulate..then there could be unseen weaknesses in the wood etc .....some bows just blow for unknown reasons!! The wood looks very pale for yew!!, not your classic yew colour?
where did you get your stave? hope you asked permission to cut it.. >:D ;)
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I didn't cut it. That's part of the problem...
It cost me a bottle of wine and a mini yew bow for the guys daughter. Pretty fair price for 13 staves worth of logs. He's a forestry warden and arborist so I also get whatever else he comes across, which wouldn't have happened had I stolen it ;)
The pale colour could be the light/camera as its pretty normal looking compared to what I make most of my bows from.
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Got it!
Will, Jim Fetrow gifted me a beautiful yew stave years ago. Naturally, I felt some pressure to get a good bow from it.
While tillering I even used outside calipers to make sure wood removal was even across the limbs. I floor tillered, long string tillered at low brace and then strung it.
Darn if it wasn't a twisted leaner anyway. I fixed it by scraping wood from the strong side and made a nice bow.
Wood has a "mind" of its own. Even if wood removal is even it does what it wants to do.
Jawge
Jawge
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You wrote down exactly what I was thinking George! Very nicely put.
Perhaps it's a combination of twist and poor sapwood that's causing them to fail? Who knows?! Next step is to try the heartwood in a laminated bow and see what happens.
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It cost me a bottle of wine and a mini yew bow for the guys daughter. Pretty fair price for 13 staves worth of logs.
Don't count your bows while they are still staves. ;)
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Indeed. Clearly this wood isn't worth much more than a bottle of wine!