Where do they break?

[IdahoMatt]

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
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[Onebowonder]

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

[bow101]

Besides breaking my pride,  upper limb 95% of the time.  And I broke at least 10.     

    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.
 

[bubbles]

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? 

[SLIMBOB]

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. 😗

[artcher1]

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
 

[Joec123able]

It's been over a year since I've broke one and that one broke on the upper limb.
Too

[Del the cat]

...
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

[artcher1]

I can tell you don't split up a lot of firewood Del .

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

[SLIMBOB]

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?

[PEARL DRUMS]

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.

[artcher1]

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 

[Del the cat]

I can tell you don't split up a lot of firewood Del .

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
Del

[JW_Halverson]

I guess I will have to let you know just as soon as I break a bow.   

[artcher1]

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