Primitive Archer
Main Discussion Area => Bows => Topic started by: sharpend60 on February 12, 2011, 05:44:26 pm
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How does one know if their chosen wood is suitable for a high crowned back?
The other part of this question is when do you need to de-crown the back?
Ive seen tons of fine sapling bows and they have a high crown by definition.
I had a wonderful vine maple gull wing profile pop a deep splinter on the back near the fade.
It was 1" in diameter and pulled ~50# at 28".
I patched it with linen then decide I may as well treat like a lesson and chopped it up...
Just curious, if de-crowning was called for, seeing how I ended up backing it anyhow.
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I would think of vine maple as a tension strong wood. The kind that can take high crown not as an inconvenience, but as a performance enhancer. An inch of width might be too thin for 50lbs though.
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I knew the bow would be short lived, I had stressed it pretty hard.
It just got me thinking about a high crown.
Ive heard of folks timming em down just not exactly sure what warrants it.
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I decide how wide I want a bow and what draw weight, if the removing wood off the belly to reach draw weight will narrow the bow too much, then I'll decrown it.
generally only a problem with small diameter logs.
Del
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I've never decrowned a bow and don't see a reason to unless it is too bad to be a selfbow. If I wanted to make a backed bow I would use wood appropriate for the job. When dealing with a high crown make your belly very flat! For weaker woods make the bow longer.
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Leave it a couple of inches longer. No need to decrown. Jawge
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I see no reason either unless your going to back it with boo or a slat of some kind.
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having played with a bit of small diameter VM, i agree that one inch is narrow for this bow. i don't see the length mentioned, but a bendy handle would probly help.
But what caught my attention was decrowning- i have thought of this too . With VM there are plenty of 2 or 3 inch dia staves, but the high crown would tend to make these less efficient than a more flat-backed profile. I wonder if anyone here has any experience decrowning saplings of a less-snakey wood. Vine Maple suffers from lumps moreso than snakes, it builds thickness around even small knots , leaving the back quite irregular , but i wonder if one could decrown and lightly back a VM sapling with good results. Perhaps i should do just that...
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havn't used vine maple, but maybe a backwards bow?
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having played with a bit of small diameter VM, i agree that one inch is narrow for this bow. i don't see the length mentioned, but a bendy handle would probly help.
But what caught my attention was decrowning- i have thought of this too . With VM there are plenty of 2 or 3 inch dia staves, but the high crown would tend to make these less efficient than a more flat-backed profile. I wonder if anyone here has any experience decrowning saplings of a less-snakey wood. Vine Maple suffers from lumps moreso than snakes, it builds thickness around even small knots , leaving the back quite irregular , but i wonder if one could decrown and lightly back a VM sapling with good results. Perhaps i should do just that...
I believe in decrowning small diameter staves if it's needed. Have a look at my website (the globe symbol beneath my username). The Hazel bow section has a couple of decrowned bows and the tillering videos show an Ash bow being decrowned and tillered.
Obviously a natural back is least work, but a few strokes of a spokeshave up the back can help bring down draw weight while maintaining maximum width, it actually ends up giving you the 'trapped' shape cross section which is seen as a good thing.
I'd say try it and draw your own conclusions.
Del
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In TBB4 chapter 2 Bow Wood by Tim baker, Tim said in the vine maple section of bow woods that John Strunk noted when working with vine maple as with any strong in tension woods, there can be an advantage to crowned backs. The crowned back has less mass, and being narrower, stretchesfarther, doing more work, reduceing belly strain, all resulting in greater arrow speed. I have the pleasure of living very near John here in Tillamook and have worked with him a bit and seen allot of his bows I recall most all of his vine maple bows having pretty good crown to the backs and they can fling an arrow ;D I do agree 1 inch is a bit narrow for 50# but its cool to know you took a shot and got it to pull 50# anyway, thats impressive!