Primitive Archer
Main Discussion Area => Bows => Topic started by: bentstick54 on January 22, 2021, 07:17:30 pm
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Well my luck finally ran out. I posted earlier this month on my 15th bow under “ tillering a reflexed stave”. It had 1 limb with some knots that I was worried about, and 1 clean limb. I tillered it out to 50# @ 28”. I put the knotty limb to the top thinking less stain. Tiller was not perfect but I thought pretty close. After about 200+ arrows the bottom limb, ( the clean limb) exploded. No warning tic, snap crackle, pop, nothing. Just as I hit full draw, BANG, it exploded.
I’ve had several that had splinters lift that I superglued down and wrapped, that have 1000 arrows through since. But this is the 1st total blowup I had.
This bow came from some old well weathered Osage that I had to go deep to get to good wood, and had multiple side checks that I finally got past any visible signs of just as I reached final width.
Would like opinions on whether it might have been bad tillering, possibly bad stave to start with, or some other defect that more experienced eyes might see.
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More pics
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Hate it when that happens, I had a very nice Maple/Purpleheart blow like that this spring >:( It had a highly strained back and a grain curl in one limb.
Was there a nicked ring on your bow? What is the grain like at the extreme ends of the break? I think that would be where the fracture started. How moist was the wood? I feel that dry wood shatters more.
A high definition closeup of the back side of the fracture would help, thanks.
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lately bows have been blowing cause keeping them inside in very dry climate,, with wood stove etc, any chance you moisture content got to low on this one,,
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I have stored all my staves in my basement as soon as I get them. I work on them in the basement also. No wood heat, gas heat with thermostat set at a constant 70dg. Basement runs 6dg to 8dg less year around in the basement, and I have no moisture meter. I did do some minor heat corrections, and let set for a week after to rehydrate before working on. Everytime I removed wood I exercised 30 times before scraping again. All shooting up to this point has been in the basement under same conditions.
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Here is what I started with.
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I think it is hard for a bow to re hydrate,, in low humidity,, but I am just guessing and that might not be what happened,, dont ask me how I know about this,, ;D but I will say when mine blew up,, it was inside in the heat,, and I stuck the moisture meter in the blown up part and it was below 6%,, I had been shooting it all summer,just fine,, this was cold winter ,, when it blew,, so I am just paranoid,, and have noticed some bows blowing lately,, after heat treating etc,, I think spritzing with water after a heat treat might help,, but I am just guessing,,also bow slightly overbuilt would be less likely to blow in questionable conditions,, that being said,, it might not be the cause of your blow up,, but something to consider in the future,, you didnt say how long the bow was,,
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how long was bow
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Full draw
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Brad, 66” ntn, 50# @ 28”, 1-1/2” at fades straight taper to 1/2” at nocks. 4” stiff handle with 3” fades.
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Pics of work up on tillering on original thread last posted on Jan 7th.
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Now that I think about it, the clean lower limb that blew was the limb that had the most natural reflex in it. I used dry heat on the end only for a little better tip alignment. I made a caul matching the reflex of that limb to use on the upper knotty limb to even the two out.
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Given that it lost all that reflex and the design, I think it was probably close to its limit. That lower limb should have been working more in the inner limb for that pyramid profile. It broke where it was bending the most. Even getting a bit too dry or a small imperfection could have pushed it over the edge.
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I wondered about it being pushed to the limits for the design. I’ve probably been lucky getting away with it up to now. Plus the successful ones before were definitely better staves to begin with. You’re right, it probably wouldn’t take much to push it over the edge. I do need to try and get the inner 1/3rds working more, but seems like I try, on the tillering tree I see them moving, so I quit, then get it in my hand and they show stiffer on the photo.
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No expert, but the tillering I saw you post looked good. I have dry heated the living daylights out of the staves I've made into bows due to twists, bends, and need for recurves...and worked them as soon as they cooled down so I don't think that was the major issue. The only thing that jumps out at me to any degree is that pic showing the growth rings. I'm not loving that early to late wood ratio, and from what I've read, the way the early wood feathers out into the late wood is as important if not more important a factor than the ratio itself as far as determining it's strength/integrity. That's a lot of feathery layers of early wood in a not-great early to late wood ratio compared to what I've experienced with the staves from the 7-10 trees I've cut. Everything else I saw you post looked fine and dandy.
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osage will take alot of abuse as far as tiller ,, so maybe just a combination of several things, or maybe just some unseen flaw, that had nothing to do with anything I said,,pretty hard to tell,,for sure, Im sure your next one will last 100 years,, :) (-S
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I agree with Ryan on it not bending ewnough inner limb. Pyramids must bend enough here. Your tiller was more approriate for a 'parallel width out the fades' bow. Also if the lower limb was more reflexed than the upper it is bending to far overall. It broke at the most strained section.
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Bownarra, all the reflex of both limbs, both natural and induced pulled out to dead straight during the last maybe 4” of tillering. Maybe some of that could have been saved by bending more just out of the fades? Once the reflex was lost, set taken, how does that effect the strain on the limbs? Is it still based off of the original reflexed shape, or does it transfer to the final straight limb shape? Hope that makes sense.
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Good point by Ryan. Also, pyramid bows need a more rounded tiller. The tiler on that bow is elliptical which is fine on a bot that has parallel limbs out to mid limb. Jawge
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It looks to me like you have a slight hinge right where it broke about 8" or so from the lower nock.
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I’m leaning towards Ryan’s train off thought with pushing the design limits with not enough bend n the inner 1/3 being an explosion waiting to happen.
Badger, I’m not saying it’s not a slight hinge, but that limb had a slight “ bump” in that location that helps it look like a hinge anyway. It was a hard spot in the grain so definitely could have contributed.
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IMHO It takes tremendous amount of power to break that way. Looking at the quite good design, specs, and tillering, I feel like questioning the wood itself. As some people here were discussing, this might the result of invisible fungal damage or even very weak early growth rings, deep inside the wood.
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You said the wood had “side checks” from the start. Any time I’ve experienced laminar cracks/growth ring delam during the drying process, the wood is useless. For me, they let go before it ever reaches full draw. I got tired of messing with it so now I turn anything with side checks/wind shakes into firewood straight away.
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It did, and the last one disappeared from eye sight right at final scraping of the edge. It’s possible that there was still some unseen weakness inside. Was hoping from the photos of the pieces someone with more experience could narrow down the reason of the failure. But there is so many possibilities I know that’s not realistic. At least all the thoughts come from lots of experience and may help me fine tune future builds, and what to watch more closely for.
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Between a slight hinge and a delam I'm surprised it lasted as long as it did.
@ everyone else, how would you deal with a delam? Pour in thin glue and bind with sinew?
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I had hoped I got deep enough into the stage to get past any checks or delays. I figured if not they would probably show early. Like said, I didn’t think it would go through finish and 200 arrows, so it gave me hope. I’ve got one other that I finished before moving on to this one that was sort of the same situation. I finished it shot it about 150 to 200 arrows and then hung it up.
I guess I better take it off the rack and shoot it some more to see how it’s going to hold up. Might have to wexx see r safety glasses and a hard hat now until I gain my confidence back.lol
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Or you can use it to turn your tillering tree into a Bowflex style exercise machine. It would be great if you can use a webcam to record the whole session. Just in case.
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Here is what I see; chalky wood without the buttery consistency of good osage, it you had side checks that confirms my suspicions. Side checks indicate inferior wood, every piece of side checked wood I tried to make a bow out off failed, even after I had removed all the visible ones from the stave.
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Thx Eric. This is the 1st I’ve had explode. I’ve had a few tic before, when they lifted a splinter on the back, but this one didn’t. Looking at the inside of the 3 larger pieces, they all look dry and chalky/crunchy through out. The way the breaks stair step in and out multiple levels seems strange. I’ve worked with kiln dried lumber most of my life, and anytime I intentionally broke any, it was a much cleaner break, or feathered out down it’s length.