Primitive Archer
Main Discussion Area => Bows => Topic started by: Del the cat on January 30, 2014, 04:45:37 am
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There has been a spate of recent breakages at the club...
All on the upper limb.
Then I realised, I don't think I've ever seen lower limb go bang!
(Ok I had one with bug damage, but that's hardly fair)
Do bows always break on the upper limb? Discus...
Del
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I think all of mine break topside too del, may have had one break on the bottom
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I had a Samick SKB lower limb break, and 2 holmegaards (not made by me) develop scary looking hinges in the lower limb. I figured it was probably something I was doing wrong, but I've no idea what.
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Top limb for me every time..... :o
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Never gave it much thought, but always the top. ??
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Ive never had a bow break after its been shot several hundred times. My breaks happen at the build. The breaks I get can be explained. Its usually a bad spot I was worried about from the start.
As far as others having a lot of top limb breaks? I think most bowyers have a tendency to put the "better" limb on the bottom knowing it works slightly harder than the top in most situations. I know I build that way.
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Positive tiller?
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I agree, but isn't strange most bottom limbs take the most strain?
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Positive tiller?
If there is a reason for the tip limb breaking more often, that's what I would think.
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I remember posting this same question some years ago on the old PA board. Since day one, I've built my bows as they stand in the tree. And of all the stave bows that have broken, and there have been many, have done so on the upper limb. Only bow with a broken bottom limb was a billeted bow. That's the number one reason I prefer billeted bows built from the trunk of the tree.
Seems like the masters of old knew about uneven working properties and thus many of them compensated by using matching sister billets for there bows. More work, but greater rewards..........Art
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Can't help you on this one Del
On my bows the only thing that makes it the top limb is the way I pic it up that day !
Have fun
Guy
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I've noticed in a lot of 'money shot' pictures that the upper limb seems to be pushed out in front of the bottom limb. Maybe the natural shape of your hand with the thumb on top cause you to push the upper limb harder than the bottom. I posted the December BOM thread. Not all look like this but #4, 5, 8,9, and 12 all look to me like the top limb is leading the bottom limb. I also posted Slimbobs recent bow. Hope yall don't mind being used as an example. I'm new to this sport so I'll let yall confirm or debunk my theory.
http://www.primitivearcher.com/smf/index.php/topic,44457.0.html
http://www.primitivearcher.com/smf/index.php/topic,44825.0.html
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Mine mostly break in my cellar! :) Jawge
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Ive never had a bow break after its been shot several hundred times. My breaks happen at the build. The breaks I get can be explained. Its usually a bad spot I was worried about from the start.
As far as others having a lot of top limb breaks? I think most bowyers have a tendency to put the "better" limb on the bottom knowing it works slightly harder than the top in most situations. I know I build that way.
+1
In 10 years of bow making, I've never had one break in the hand. Plenty have exploded on the tiller tree, and some for no apparent reason.
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But seriously folks...
What PD and Art said.
I tiller from the middle on the rope and pulley. Then I check tiller in front of a mirror, with a digi pic or in front of a window at night.
Nothing approximates your hold.
I like the bottom tiller even or very slighty stiff by 1/4 inch at full draw. Don't much care about brace unless it is way off.
Jawge
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Ive never had a bow break after its been shot several hundred times. My breaks happen at the build. The breaks I get can be explained. Its usually a bad spot I was worried about from the start.
As far as others having a lot of top limb breaks? I think most bowyers have a tendency to put the "better" limb on the bottom knowing it works slightly harder than the top in most situations. I know I build that way.
+1
+1
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Other than one where a de-lamination happened on a bottom limb, mine have always been on the upper limb, but also generally in the tiller process. I've only had one blow up in my hands. Threw those underpants away... :embarassed: :embarassed: :embarassed:
OneBow
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Besides breaking my pride, upper limb 95% of the time. And I broke at least 10. :( >:( :( >:( :( :o
Most of the bows I broke were boards, laminated, not so much self bows. Broke a couple. I think the reason that the top breaks is like what everyone says about trying to get a positive tiller, and about 80% complete.
Most of the self bows were broke because putting to much pressure on the floor tiller, obviously the top one just takes more stress while I'm floor tillering.
Broke one by doing a step thru brace method on the bottom tip. Bow was not properley tillered, it was to stiff in the outer thrird.
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Now, I dont have a huge amount of experience, but I had mostly upper limb limb breaks until I stopped tillering for 1/8" positive at brace. I found I was checking the brace profile to see if my limbs were even instead of checking the full draw profile. I was building these bows with the arrow pass 1.25" above center. I noticed that the top limb was taking more set, and when I put the full draw in to photoshop and lined it up on the grid, the top limb was bending significantly more. Re-tillering, I found that the bottom limb had to be slightly weaker at brace for the limbs to line up perfectly at FD. The higher the arrow pass, the weaker the bottom limb had to be. These were symmetrical bows. Anybody else find this? Or am I crazy?
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Yep, yep, and yep. As PD said, I will put the cleaner limb on the bottom, and if one breaks it's usually during the build. Almost never once it is shot in. I try and use positive tiller but sometimes on character bows it's a guess or feel more than a measurement. If you saw this last one from the other side you would swear I put the wrong limb on top. Btw, the top limb was chosen based on it being what I saw as the weaker(less hearty) of the 2. 😗
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I think there's a few here who hasn't quite figured things out yet. Here's something that Dean Torges wrote in his article " Tillering the Organic Bow":
"As an aside, this might be the place to mention that the reason sister billets were preferred by past masters over full-length staves is that the wood is nearly identical limb to limb. Its working properties therefore are nearly identical. By contrast, if you sift through a stack of full length osage staves you will discover in each one dramatic differences in the growth rings from one nock end to the other. Selfbows of ring porous wood seldom resemble each other not only when made from staves taken from the same tree, but even within themselves, from one end to the other in a full length stave. It may be easier to build a bow from a full length stave rather than having to join sister billets at the handle, but it is simpler not to".
So positive tiller or where the arrow pass is located has nothing to do with the top limb failing. It's about the differences in working properties from one end of the stave to the other. Trunk end of the tree will be denser, stronger and have fewer defects. As you move up the tree the reverse is true............Art
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It's been over a year since I've broke one and that one broke on the upper limb.
Too
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So positive tiller or where the arrow pass is located has nothing to do with the top limb failing. It's about the differences in working properties from one end of the stave to the other. Trunk end of the tree will be denser, stronger and have fewer defects. As you move up the tree the reverse is true............Art
I don't think that makes any sense at all!
.... unless everyone makes their bows with the denser stronger wood as the lower limb, which may or may not be the lower end of the stave.....
How how the heck do we know that... I don't think many people take density measurements from each end of the stave or even consciously pick the tighte end for the lower limb?
Or maybe I'm missunderstanding????
Del
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I can tell you don't split up a lot of firewood Del ;D.
So you're saying there's no difference in working properties from one end of the stave to the other ? If so, then why do folks even bother with matching billets? But if you believe in the premise of different working properties then what are those differences? I think I mentioned a few..........Art
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Would you not account for this difference in tillering the bow? I'm not saying there is not a difference in density from top to bottom, there may well be, but I would suspect the differences to be minimal and compensated for in achieving proper tiller. Either way it would not explain this phenomena, as half the time the bottom would break as it would have been the "less dense" end, as most don't consider this in designing a bow?
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Ill never question Artsy's theory, I believe it myself and practice it on billet bows. However, I don't believe its coincidence that the uppers break the most because the stump end is down on full stave bows. Especially for the bowyers who don't intentionally orient the stave that way, which is 98% of them Im guessing. There are other forces involved causing upper limb breaks most often.
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Where you really notice a big difference in working properties is when you have quite a contrast in ring thickness from end to end. You ever notice bows that look like one limb is thicker or thinner than the other? That's due to wood density. You ever try to recurve a bow and have one end curve perfectly and the other crack? That's due to one end being stronger/denser than the other. Or how about extreme weather changes, you ever notice one limb tighten up/weaken?
Sure, you can tiller out a bow and account for some of the differences. But be aware of this and plan accordingly.
For my purposes, nothing makes for a better bow than matching sister billets.........Art
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I can tell you don't split up a lot of firewood Del ;D.
So you're saying there's no difference in working properties from one end of the stave to the other ? If so, then why do folks even bother with matching billets? But if you believe in the premise of different working properties then what are those differences? I think I mentioned a few..........Art
Nope.... I'm saying nothing! Just pointing out the inconsistencies in what you said!
I'm just quoting your own original statement that the denser wood is at the bottom, but further up this reverses.
Add this to Pearlies assertion that bows are usually built with the stup end down.
The result of these two is that the relative densities of the two limbs is random!
I haven't made any assertions or theories... I was just asking if more bows break on the upper limb.
You are welcomed to make your own theories or assertions...
Me? I'm keeping my powder dry >:D ;)
Del
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I guess I will have to let you know just as soon as I break a bow. >:D
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Nothing inconsistent in what I said Del. From my experience the trunk wood is the strongest part of the tree vs it's upper section. You build a bow as it "stands in the tree" (and most of us do whether we realize it or not) and more than not the upper limb will be the one most likely to break. Not a theory, or an assertion, just common sense..............Art
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I have some doubts as to whether I have ever given a passing whimsical thought to which end of a stave may or may not be stump end. Furthermore, once I have a centerline chased and the stave narrowed down, I guarantee I have forgotten which end is which. Granted, I may be a bit more absentminded than the average severe brain trauma victim.
But to assert that most of us build our bows by consciously choosing the bottom limb to be the stump end is frankly...going out on a limb. Pure conjecture backed only by personal anecdotal evidence unless you can provide copy of your research including a statistically significant database of bowyers that you have canvassed and the numbers of bows that have been verified as being built stump limb down.
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How do boards come in to play here?
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I was about to mention boards. Surely nobody can tell which end was which in a tree when looking at a board?
Out of all you guys who have broken a top limb, how many were boards and how many were staves? Wouldn't that (if the numbers were similar) attribute more to how the bows are tillered than how the wood was hanging around when somebody chopped it's head/feet off?
I reckon it's just a coincidence. Or aliens.
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I think there's a few here who hasn't quite figured things out yet. Here's something that Dean Torges wrote in his article " Tillering the Organic Bow":
"As an aside, this might be the place to mention that the reason sister billets were preferred by past masters over full-length staves is that the wood is nearly identical limb to limb. Its working properties therefore are nearly identical. By contrast, if you sift through a stack of full length osage staves you will discover in each one dramatic differences in the growth rings from one nock end to the other. Selfbows of ring porous wood seldom resemble each other not only when made from staves taken from the same tree, but even within themselves, from one end to the other in a full length stave. It may be easier to build a bow from a full length stave rather than having to join sister billets at the handle, but it is simpler not to".
So positive tiller or where the arrow pass is located has nothing to do with the top limb failing. It's about the differences in working properties from one end of the stave to the other. Trunk end of the tree will be denser, stronger and have fewer defects. As you move up the tree the reverse is true............Art
Ah so we are back to that one again Art. I do believe I disagreed with you the last time and I still do. It may be different with Osage, which doesn't grow up here, but white-woods up here have less dense growth near the stump. You can tell this by the growth rings being thicker at the stump end. In fact I made a short Elm bow not long ago that had that exact problem. The stump end had thicker rings and was taking more set than the other end, I fixed it with some heat-treating.
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WillS, it's very easy to tell how most board lays in a tree by studying it's growth rings from end to end. Well, except for pipe straight trees anyhow.
JW, sure, most of these guys build their bows as it stands in the tree. Haven't you read where everyone's upper limb is breaking ;D.
Yeah, I remember our last exchange Marc. We'll just have to agree to disagree on this subject. But can you explain why, when our bows breaks, it's generally the upper limb? To date, I've heard of no other reasonable explanation then what I've given. But I'll keep an open mind to what you and others have to offer in the way of a viable explanation on this matter.........Art
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WillS, it's very easy to tell how most board lays in a tree by studying it's growth rings from end to end. Well, except for pipe straight trees anyhow.
Yeah but... Are you saying most guys check for that? I know it can be done, that's not the point.
How many bowyers on here for example when starting a board bow check both ends to see which would have been lower in the tree, and use that for their lower limb?
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With boards, you're not dealing with knots and imperfections and such. So why would it even dawn on someone to even consider this? And if you're making board bows, then you're probably new at this game, and shouldn't, at this point, even being concerned with uneven working properties. I would think, just building a serviceable bow at this point, would be more important.
Staves, on the other hand, off their own challenges.......Art
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Yeah, I remember our last exchange Marc. We'll just have to agree to disagree on this subject. But can you explain why, when our bows breaks, it's generally the upper limb? To date, I've heard of no other reasonable explanation then what I've given. But I'll keep an open mind to what you and others have to offer in the way of a viable explanation on this matter.........Art
Positive tiller is one plausible explanation. I read how one person believes that the lower limb is more stressed but I'm afraid I disagree with that one as well. If you look at a bow with a positive tiller you will see that it has a slightly steeper string angle which means that limb is bending more. More bend = more stress. I'm not saying that this is positively the reason, I don't really know as I don't break bows ::)
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art please direct me to this magic flawlist pile of boards of which you speak. >:D.maybe one out of 30 boards have a chance at all.ive only made a few stave bows but i tend to think they are alot tougher than any board i have ran across so far.yes 95% of my failures ,which has been many have been on the upper limb when i had my arrow rest high ,now i go between 3/4" to 1" above center and break alot less nowadays
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the one I broke was on the top limb, It hit my head, maybe thats why I'm just nuts.
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I've noticed in a lot of 'money shot' pictures that the upper limb seems to be pushed out in front of the bottom limb. Maybe the natural shape of your hand with the thumb on top cause you to push the upper limb harder than the bottom. I posted the December BOM thread. Not all look like this but #4, 5, 8,9, and 12 all look to me like the top limb is leading the bottom limb. I also posted Slimbobs recent bow. Hope yall don't mind being used as an example. I'm new to this sport so I'll let yall confirm or debunk my theory.
http://www.primitivearcher.com/smf/index.php/topic,44457.0.html
http://www.primitivearcher.com/smf/index.php/topic,44825.0.html
I guess my 2 cents didn't make sense since it wasn't acknowledged.
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Hahah, iconicmuffin, those damn top limbs! I'm with you that. It would be interesting to see if Yumi's break in the top or bottom limb typically, just because of the extreme asymmetry.
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I think if I attempted a yumi, they'd all break everywhere at the same time ;D
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With boards, you're not dealing with knots and imperfections and such. So why would it even dawn on someone to even consider this?
Yes. Exactly my point. Nobody considers it. So you can't say there's a link can you? If nobody knows which limb was topmost in a tree, you're saying that it's the most amazing fluke that they all choose the same limb as the top limb in their bow.
And if you're making board bows, then you're probably new at this game, and shouldn't, at this point, even being concerned with uneven working properties. I would think, just building a serviceable bow at this point, would be more important.
Wow. Isn't that a touch... Elitist? There are guys on here who've been making bows for countless years who still turn out sensational board bows. I think this is the first time I've ever read on here that attitude towards one type of bow making - and it's not cool. I've never made a board bow because in the UK it's much harder to find decent timber compared to staves of excellent bow wood, but I'm looking forward to trying a board bow one day. I guess I won't be asking you for an opinion on one if I do make it though right?
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If there's an iffy limb I put it on the top so if it breaks it hits me on the head rather than other sensitive areas... my priorities have always been a little out of whack XD
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Nothing inconsistent in what I said Del. From my experience the trunk wood is the strongest part of the tree vs it's upper section. You build a bow as it "stands in the tree" (and most of us do whether we realize it or not) and more than not the upper limb will be the one most likely to break. Not a theory, or an assertion, just common sense..............Art
You obviously haven't read what you actually wrote....
Trunk end of the tree will be denser, stronger and have fewer defects. As you move up the tree the reverse is true.
Can't you see the inconsistency created by the second sentence?
And as for the 'most of us do it, whether we realize it or not' is arrant nonsense. I quite often will reverse a bow in the process of making it, or even after it's virtually finished. Oh I get it! You'll now say I'm switching it to trunk end down subcosciously and thus proving your point ::).
Tell you what, You sit and have a cup of coffee, I'll do your arguing for you...... :o
ok... never mind... I can't be bothered.
I wish people would be more careful with their words and and manage to have a concise logical discussion, asking and answering points in an ordered manner.
Just ain't going to happen. >:(
The interesting thing for me in this thread is how a few people have experssed doubt about the received wisdom of positive tiller. I've always been sceptical myself and only started using it when I had a lower limb go weak on an Ash flatbow.
Del
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Positive tiller is essential in my eyes. How much is the point. The lower limb needs to be stronger to stand upto the strains of shooting. It's simple physics ;)
If you make a bow with exactly the same strength limbs when you come to shoot it that lower WILL come round more.
These things aren't set in stone measurement-wise but the idea should be!
The amount of positive tiller needed is linked to how you shoot/hold the bow. Less is needed with split finger and craddling the bow between thumb and 1st finger. People who use the heel of their hand against the grip will need more and those who shoot 3 fingers under need yet more.
My guess for limbs breaking is uneven forces at full draw. Afterall what else could it be? Unless somebody is going round and putting nicks in the backs of all these upper limbs!
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Positive tiller is essential in my eyes. How much is the point ...
Exactly, I just wonder if maybe we over do it sometimes to the detriment of durability?
Del
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That's kinda where I come down Del. As has been said, I will shoot for a bit of positive tiller, I also will put the less sound limb on top. That seems to me to at least offer a reasonable explanation. My question now is, is this the right call? Mark suggested that the top limb is more strained.??? At least anecdotally, folks are putting the weak limbs on top and then shooting for positive tiller, then the top limb is more stressed, and top limbs break more often. There you go.
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Wow! First time I've been called an elitist. Man, I apologize to you all if I came across like that.
Del, I take your point. I could have been more concise in my meaning. Looking forward to see where this discussion leads. Best of luck guys...........Art
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If your breaking enough bows to cause a personal epidemic, you have bigger fish to fry.
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I have to admit total ignorance here - I thought positive tiller was used in order to make both limbs appear equal at full draw despite the bow not actually being held and shot dead center... Is that wrong? Surely the goal isn't to have the bottom limb appear stronger at full draw is it?
With only 1/4" positive tiller seeming to be the norm, is that enough to cause the top limb to fail completely?
Edit: Didn't mean to call you elitist - that came out wrong. I just felt the comment about only newbies using boards seemed a bit out of order. I actually think staves are easier to work, as I can imagine it's bloody awkward tillering a long flat plank.
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The comment about newbies using boards IS out of order. Smacks of ignorance and arrogance. But, that's the subject for a different thread.
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True PD, but that posts title would be "Why Do They All Break" and the replies could be even more colorful and entertaining than those offered here. :)
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The comment about newbies using boards IS out of order. Smacks of ignorance and arrogance. But, that's the subject for a different thread.
Man, my reply sure doesn't read that way to me. Sorry if you're offended by it. Surely I'm ignorant on many things, but never arrogant I think. Again, my apology...........Art
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You should never tiller just to have a positive tiller when working with wood. You should tiller so the bow has a smooth draw without any pivoting in the hand. That is what will tell you if your limbs are balanced and stressed evenly not a positive tiller
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You should never tiller just to have a positive tiller when working with wood. You should tiller so the bow has a smooth draw without any pivoting in the hand. That is what will tell you if your limbs are balanced and stressed evenly not a positive tiller
Marc it cant be that simple can it?.....;)
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For my bows at least I have to make the lower limb a little stronger or else the bow will pivot.
When you pull a bow with your fingers above measured center of the string you aren't pulling both limbs with an even force
I have to admit total ignorance here - I thought positive tiller was used in order to make both limbs appear equal at full draw despite the bow not actually being held and shot dead center... Is that wrong? Surely the goal isn't to have the bottom limb appear stronger at full draw is it?
That's where i'm coming from too.
No you want both limbs to be equally stressed at full draw. To do that you have to take into account the unequal forces being applied to the limbs during the draw.....making the limbs different strengths is how to achieve this. How much the lower limb is stiffer is the question. Setting out with a goal of making the bow have say 1/4inch positive tiller without regard to what happens along the way would not be a good idea. Watching how the wood is responding to what you are asking from it will tell you what you need to know. :)
Let look at this another way if you have two guys arm wrestling which one will win?
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You should never tiller just to have a positive tiller when working with wood. You should tiller so the bow has a smooth draw without any pivoting in the hand. That is what will tell you if your limbs are balanced and stressed evenly not a positive tiller
I would have to agree. That's how I determine my finished tiller. On average, mine turn out 1/16" positive tillered..........Art.
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The comment about newbies using boards IS out of order. Smacks of ignorance and arrogance. But, that's the subject for a different thread.
Man, my reply sure doesn't read that way to me. Sorry if you're offended by it. Surely I'm ignorant on many things, but never arrogant I think. Again, my apology...........Art
Apology accepted. I've been making bows for 10 years (the last 3 as my living), the majority of which are laminates made from dimensional lumber. I'm not a newbie, and they're not simple bows. I certainly make selfbows as well, but I don't limit myself. Blanket statements about boards being for newbies is an offense to some, as you've realised. It's certainly a good place for newbies to start, but not only that. But, like I said, apology accepted.
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I have to admit total ignorance here - I thought positive tiller was used in order to make both limbs appear equal at full draw despite the bow not actually being held and shot dead center... Is that wrong? Surely the goal isn't to have the bottom limb appear stronger at full draw is it?
With only 1/4" positive tiller seeming to be the norm, is that enough to cause the top limb to fail completely?
Edit: Didn't mean to call you elitist - that came out wrong. I just felt the comment about only newbies using boards seemed a bit out of order. I actually think staves are easier to work, as I can imagine it's bloody awkward tillering a long flat plank.
I find board bows much easier and quicker to build. Almost cookie cutter. The tiller is exceptionally easy to judge when you look at a straight line . The layout is all done with a straight edge. Waste removal is done with a bandsaw in a mater of minutes , and after a bit of cleanup to the sawcuts, your bow is nearly tillered if your design was good in the first place. It almost makes you feel a little dirty :o like you're cheating somehow ;D
As for this thread , I'm on both sides of the argument here I guess. Wood from right at the stump is far more dense than even 2' up . After you get past the buttresses it all evens out (or not. It's a tree. It's organic ,and it follows it's own genetic code for survival, and is primarily influenced by it's environment) . It builds up extra cells around spots that need reinforcing , like a branch or knot. Wider rings don't always mean weaker wood.
Having said that ,I would think the reason for any breakage( other than damage or abuse) , would be an overlooked design/tillering flaw . It may not present itself in the first 300 shots, but a change in humidity , shooting style , etc. could be the start of one tiny little change ,which will eventually spiral exponentially to become a failure. Not always that it was tillered poorly , because it may have been tillered perfectly for the characteristics of the wood at the time. But I think all would agree , the piece of wood is not the same as it was when you cut the tree, or when you dried it ,or when you roughed it out , or when you made a bow.
My suspicion would be that most in Dell's shooting circle of friends would be shooting longbows(?) traditionally made with a positive tiller(?) Common thinking and tradition dictates putting the stronger limb on the bottom. Maybe it's time to revisit this "Theory ". I know I've decreased to 1/16 - 1/8" max, and am still not entirely convinced of the merits, so I'm going with Marc and PD on the fact that it should be balanced first and foremost.
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Thanks Mike - makes a lot of sense! I'll confess, positive tiller is not something I've ever thought about. I don't think I've made enough bows yet to add that to the equation. If there are no hinges or stiff spots I'm happy - but then my bows seem to take a lot of set, so perhaps that's why? Dunno.
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Incorrect tiller relevant to the archer's holds on bow and string should at least bear scrutiny here. That's also why bows tip in the hand at full draw. Tillering, training, and timing the bow limbs to bend in harmony on the tillering tree while drawn from the center of the handle when it will never be shot that way is a bad idea, IMO. Then when it IS shot, the top limb, which many make weaker by default regardless of what the bow needs, realizes more strain than it was trained to deal with. I would also be interested to know how many of our broken bows are symmetrical vs. asymmetrical in design... since symmetrical bows are pulled farther above center and require a greater shift during the draw between the static balance and dynamic full draw balance points.. I'll bet it's a combination of things.
I've had one bow break on me when drawn by hand, and it was an arborvitae shrub I cut in the yard.... not exactly what most bowyers would deem bow wood :^)
Two others, osage selfbows let go at major knots, one a hole through the upper limb broke when I let someone else draw her on a winter day that was very cold... single digits... it just went "tick" and lifted a splinter at the edge of the knot hole.... but that's it in 15 years of selfbow, backed bow, and composite bow making :^)
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I know I put more strain in the top limb while stringing, cause I grip it below the tip.
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Hey Dell,
Being as how I make little, short elfin bows maybe don't have any say in this discussion. I tiller my bows by hand and feel, not on a tiller tree. had them called everything from polished turds to well.....you get the idea. Anyway, all the bows are shot without a designated "top" limb, and are expected to produce the same profile regardless of which end is up, also as others have said the bow should not rock in the hand, just a smooth even draw to loose. Doesn't make any difference if it's lumber I milled, or a stave I cut, all the same to me.
I've made a few that were NOT even in their bend and shot them both ways (up and down) to see what the bow had to say about it, and they seemed to shoot better with the stiffer of the two limbs upward.....but that experience is very limited so may not be worth much.
Sorry for the limited input but that's my experience, and the advantage to the even bend (in my opinion) is that you can "feel" what's going on with the bow all the way from start to full draw.
rich
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So far my failures have been glue releasing the sinew from the back and lower limbs. The glue failure was because I used a penetrating oil finish without thinking. One was a black locust molle that had a slight hing that got worse, so I quit shooting it when it started fretting. The other that exploded was a white ash molle that had a knot on the back. I had shot it a few hundred times, then when I showed it to someone it decided to go and blew apart into 3 chunks, with the break starting at the knot. I'm thinking it held up for a while because I had made and shot it in the early fall when it was still humid. Then it broke in the winter after I hadn't shot it for a few weeks and it had been very dry in the room.
Kyle