Primitive Archer
Main Discussion Area => Bows => Topic started by: zenmonkeyman on January 28, 2010, 04:12:56 pm
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Chokecherry selfbow #2: BANG!!
(http://i80.photobucket.com/albums/j191/zenmonkeyman/IMG_3731_1.jpg)
(http://i80.photobucket.com/albums/j191/zenmonkeyman/IMG_3732_1.jpg)
(http://i80.photobucket.com/albums/j191/zenmonkeyman/IMG_3734_1.jpg)
If you don't heat treat it, it takes lots of set and chrysalls.
If you heat treat it, it fails in tension
Next time: Wider, or longer, or both. Probably wider. Heat treated, then backed. I'm taking my latest kindling over to a buddy who has a good moisture meter; there's a good chance this stave was over dry. Thanks for looking! Suggestions/comments welcomed/requested.
Garett
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Hey Zen,
I dont build any stave bows...but in that second picture (with the middle sliver sticking out the side.....it looks like there was a bunch of side pressure, or is that just the way it looks? Does the grain take a whoopy-do at that spot?....just wondering. Sorry about the bow :-[
Blew up my share and it aint too much fun at all.
half eye ;)
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hey zen unlucky was looking good too!!just gotta get on to the next stave huh?
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Zen, give us the gory details, how far was it drawn? how hard were you pulling when it broke? how much set had it taken. Once a bow starts to take set it is time to start taking weight off the bow, if you pull harder it will eithr brake or just take more set.
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Ouch..What was it pulling at time time.Did you scrape the outer growth ring?I've blown up a few chokecherry
I starting to think if you want good poundage gonna have to back.
Thanks Leroy
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Thanks for the responses, guys!
Half eye, there's no whoop te doo in that spot, that sliver is just one of the several separated laminations that ended up outside after the calamity befell it. Did I jus say calamity? ??? ;)
Thanks, Mox, I thought it was looking good too. I had a little evening-up to do on the opposite limb, but this one was impressing me (up until the bang) with its nice circular tiller.
Badger, I was at about 50# and 28". There wasn't much set up until that point, I'd lost maybe an inch off my reflex near the tips.
Leroy, I think I'll be throwing every precaution I've ever heard of into the next one. I'd thought of backing this one, but I like the natural knotty look. There weren't any nicks, either, maybe a few dents from clamping not very carefully, but there's no evidence of a dent where she blew.
I just got back from my buddy's place. We set his moisture reader at .78 (since that's what I got by dunking the wood earlier). 0.0 it said. We thought it was just not reading the wood, like maybe we weren't finding a flat enough spot for it to register. Finally I set the SG down a bit, to .72, and it read something like 2% moisture content. I thought "this can't be right, ok what if I erred in my measurement, AND the wood I tested had some moisture in it when I tested it. I set it down to .65, then .60. The highest moisture content reading I got was about 5%. And there's no way the specific gravity of the wood is that low. So obviously, the wood was too dry.
Maybe it would have failed anyways, maybe not. But I weighed the stave immediately after heat treating so I could monitor the re-hydration process, and 3 days later it had LOST moisture if anything. Obviously this dry prairie winter air prevented rehydration.
Once again I asked Santa for a bow, and once again I got socks. ::)
Oh well, this setback coincides with another trip home to the farm, there are many potential bows still standing! Maybe I'll be optimistic and cut some arrows too...
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Zen, do you have any idea how much the bow weighed when it broke ( mass weight) Steve
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Looks like a typical tension failure. How dry is it where you are?
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Steve, it was 17.3 oz, all the wood was working, flexing nicely in the handle. It was basically at its final weight other than minor tweaking.
Marc, it's very dry here in the winter. My wife is always after me to put lotion on my hands, the dog is itchy bordering on scabby, and shampoo companies from around the world test their latest dandruff-battling concoctions on the local populace. We have a humidifier in the apartment that for the first time I regret not filling with water...
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Mass was way too low, I think like Mark it failed in tension. You can use the mass formula to figure of the wood is too dry also. If the wood appears to be very strong for it's mass, inother words it is not taking set but still strong inspite of being low in mass then it is almost certainly too dry. Bow could have proably been about 20% wider. Steve
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Yes, it's obvious the bow failed in tension. That's a good tip about using the mass formula to monitor dryness, working the formula backwards sort of. I should reread that thread in which you describe the no-set tillering again. Any chance of getting that in the archive/read-only section? The next one will definitely be wider! Thanks again.
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zen PM Justin and request that it be included in the Arcieve section.
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Hi Zen.. Just a thought,I was thinking about bending and straiting with heat.Most of the chokecherry we have around here is fairly
fine grained..Did you use dry heat? If the stave you had was to dry..Would it be better to use steam? I'd like to back one with boo
I think it would be a rocket and hit like a train..cut, rough out ,dry on form, laminate it might take a while but worth the effort.
so many trees so little time..
Thanks Leroy
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A long time ago I made a chokecherry self bow and eventualy it looked like that. With a sinew backing though chokecherry will last forever.
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A long time ago I made a chokecherry self bow and eventualy it looked like that. With a sinew backing though chokecherry will last forever.
thats good to know
i just got a nice chokecherry stave,and some nice sinew
any suggestionss on demensions?
i would like a 26" draw,50 ish lbs.
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Thanks for the comments guys.
Dana, I will do just that.
Leroy, I found that it bent easily with the heat gun; steam might be worth a try. If it works it should prevent overdrying. A good winter strategy? I agree a hickory or boo back would work wonders. I'd still heat treat the belly, I keep reading on different threads about chokecherry chrysalling easily otherwise. I'm wondering if decrowning might have helped me, I think my high crown didn't help.
Chuck, you're the man! I find the blackfoot chokecherry bow you posted to be very inspiring.
Sailordad, keep us posted on your project!
Garett
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Zen, If chokecherry is normally weak in compression, decrowning will compound the problem, and make it more likely to fret, as would backing with hickory or bamboo. Looks like you narrowed it down to moisture content anyway, which will be an issue for any wood aside from hickory. I'm not sure if hickory could even stand 0% moisture. Maybe you could build a 6' long humidor and store them like cigars ;D Otherwise, keep that humidifier running. I had the same issue with dryness in Alaska, but I was using hickory, so it didn't really matter. Good luck, Jude