Primitive Archer
Main Discussion Area => Bows => Topic started by: bearbowman on April 17, 2009, 01:45:06 pm
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I know I have been hammering you guys with a lot of questions lately, but I am starting to turn out some bows now, and it's provoking me to ask more questions.
How much poundage (on average) should I expect to lose on an unbacked selfbow or boardbow after break in? Assuming I am using seasoned wood.
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Most loose 2 to 5 pounds during shoot-in. I made a friend two osage bows with very well seasoned wood, both gained 5# over time, still scratching my head and wondering why.
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A 2-5# is about right. 10# if you build it quickly.
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You shouldn't loose any weight after final tillering and sanding.
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I don't really have a "break in" or "exercise" period for my bows. I start shooting right after tillering and finishing. My bows will loose about 1lb for every 100 shots I guess. I also loose (and gain) poundage when the humidity level changes. Some wood species will loose more poundage than others and all will loose poundage after a few shots just after bracing....and then stabilize.
I suppose this simple formula would apply to my bows: loose 1lb for every 100 shots (up to 5lbs), loose 1lb for every shot after bracing (up to 2lbs), and loose up to 7lbs in very humid weather.
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None.
ART B
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Ive had a couple of self bows that lost 0 but 98% of mine will drop 2# to 4# over a few thousand shots..
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Thanks guys. I left my last bow a little heavy. It's the best tiller job I've done to date and I didn't want to screw it up by trying to take a few pounds off. Truth be told it doesn't feel bad and it spits the arrow out pretty good.
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I had one ash bow that gained about ten pounds over five years. I think the moisture content was a little high when I made it, and the wood was quick-dried.
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Hmmmm....I'm surprised that a couple of very experienced guys would say "none". ???
This means that when you measure the poundage of a self bow, it will be the same every time regardless of when you measure it: long term or short term, after a few shots or after hundreds, pausing at full draw or "snap" shooting, in humid or dry weather, hot or cold, etc.
This is what you would expect of modern, synthetic materials, not wood.
Or maybe I'm using the wrong kind of wood? If so, I need to get me some of that "magic wood" stuff. ;)
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You must be referring to my answer Jackcrafty. Go back and read Bearbowman's question. Lots of variables with natural materials as you alluded to. But a well made bow, with the right moisture content, I would not expect to lose any weight even after ten thousand shots. But then I mostly use hickory and osage and if anything and I will get weight gain. My draw length is short, and that is one major element in a bow's longevity. That and experience.
ART B
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This means that when you measure the poundage of a self bow, it will be the same every time regardless of when you measure it: long term or short term, after a few shots or after hundreds, pausing at full draw or "snap" shooting, in humid or dry weather, hot or cold, etc.
Patrick, the draw weight of a wooden bow will vary based on various enviromental factors. But that was not what the poster was asking about. Environmental factors notwithstanding, a well executed wooden bow should maintain it's weight for most of it's useful life after the bow has been tillered, sanded and broke in.
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I think the key question here is "after break in"? If a bow is weighed along the tillereing process and one gets to the weight they want,they shoot it a while and then finish it. It ain't broke in, so yes it can loose weight.
A dry wood,well tillered,shoot in bow,(before finish) should stay close to original,even after much shooting,(after finish). Long brace times come into play here.I suppose if a bow was braced for a year(exagerations here) it would lose integrity,therefore losing weight.
Many variable to consider,but as for an answer to the question, then I would have to agree with Art and Gordon on this one.
The key in my mind is shooting the unfinished bow along in the process,whether @ 20" or 22" etc. I have learned to brace my bows and sweat them for long periods of time as I am working the wood off, gaining ground on intended weight.This of course helps the wood to attain a new memory, and allows the wood to respond to removal. (sometimes we get impatient),So there are fewer surprises.
Just my two pennys.:)
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Art, I went back an re-read Bearbowman's question. If I understand it correctly, he is wanting to know if a self bow made from seasoned wood will loose weight after "breaking in". Breaking in meaning that the bow has taken all the set it will take and will not deform further.
OK then......so the answer is no, there will be no loss of poundage...but perhaps a gain? Isn't an increase in weight related to the further drying/seasoning of the wood (an environmental factor)? Or is it due to something else? I remember reading something about the structure of the wood changing over time but the issue is controversial and not proved (as far as I know).
Gordon, so a bow should not use weight during its useful life. And if you exclude environmental factors, wood will act exactly like a synthetic bow material?
I guess I'm still too new at this. I'm a bit confused :-\
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After break in, it should not loose weight. Jawge
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One good way to keep an eye on the "breaking in" process is to check the nose (beginning tension) of the bow. I do this by taking a weight measurement at 3" past normal brace height (5 1/2" for me). One thing that I've noticed is that I'll always lose 1# of nose weight. This effects cast but does not effect final draw weight. Once that nose weight and positive tiller stabilizes I don't expect the weight of the bow to change.
So if you're losing weight as you claim then it's time to start digging for answers.
ART B
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Patrick, if you keep it fifty years and shoot 500,000 arrows through it, I would assume that at some point it would begin to break down, but most of us won't ever shoot a bow to death. Or if you abuse it by leaving it strung day after day at a 10" brace height in humid conditions without a good finish, it will probably take more set and lose some weight that way. But in general, I agree that a broken-in stable bow should stay pretty much like it is for a long, long time unless you do something wierd to it. I've never had one that had a noticible drop in weight over time, and some I shot thousands of times. If you haven't completely broken the bow in by exercising it while tillering and leaving it strung for awhile, it might drop a couple pounds after you shoot it a while, and/or the tiller may change.
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Draw weight is somewhat variable, based on temperature and humidity. How much that varies largely on where you keep your bows and the level of moisture resistance the finish has. If you keep your bow in your climate controlled house, there may be little, if any draw weight difference through the seasons. And if you've used a good finish, you can take it out and shoot in the rain, probably without any temporary weight loss. But, if kept in the garage, and lacking a good moisture barrier, the draw weight may bob up and down several pounds as conditions change. Draw weight is variable too, on immediate useage. A freshly braced bow can pull 1 or 2# more than after shooting a couple dozen arrows. (But not always.) The key is measuring the weight against the relative conditions. I prefer to weigh bows after they've been stored indoors (never a problem) and have been braced and shot at least several times.
How much weight the bow looses during shoot-in depends largely on how much you've exercised the bow during construction. If you've drawn it a few dozen times along each increment of length after every round of wood removal, and particularly if you've allowed the bow to remain braced at full draw once or twice or more overnight near final tiller, then by the time you shoot it in with a couple of hundred arrows, you'll loose virtually no weight. The less you've exercised it, on the other hand, the more weight you stand to loose and the bigger the chance of the tiller changing during shoot in.
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(http://i246.photobucket.com/albums/gg112/jackcrafty/prairedogdigging.jpg)
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While I building a bow I exercise the limbs after each wood removal. I believe this helps the wood removal register so it eliminates any unexpected weight loss. After I have completed the tillering I will brace the bow and "sweat" it for a few hours. I have left them strung for up to 4 or 5 hours, similar to being strung while on stand or at an archery shoot. Generally after I have finished the bow, the weight remains the same.
Humidity does have some effect of some woods, mostly whitewoods but other than that, they remain stable for lots and lots of shots.