Primitive Archer
Main Discussion Area => Bows => Topic started by: Eric Garza on May 30, 2008, 03:11:48 pm
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Hoy folks,
I've been thinking about how wood density relates to the ideal width of a wood bow, particularly since reading about the relatively easy method of estimating wood density offered in the Bow Design and Performance Revisited chapter of the Traditional Bowyer's Bible, Vol. IV. I used some data from the Traditional Bowyer's Bible, Vol. I (Bow Design and Performance chapter) that gave a number of woods, their average density and the ideal width that the chapter's author recommended for a bow from each. I graphed these data and fit a curve to it, with the graph and equation describing the curve shown below.
What do people think about the idea of using a piece of wood's density to determine the width of the resulting bow? What other factors do folks think should be involved, if any?
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I think it's a pretty good general guide, but you also have to factor in other variables such as length, variation in individual pices of wood (ring thickness, earlywood/latewood ratio, etc.) Sometimes things just work that shouldn't according to the rules-I saw a normal length, 1" wide hickory bow last weekend with a deep stacked, rounded belly that drew around 60# and had a good unstrung profile-go figure.
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Actually I think Badgers Mass Theory accomplishes the same thing, when I use his mass principle I start wide, then belly and side tiller to the desired weight.
I let set determine the finished width, in other words when I start to see set develope I don't go any narrower. Denisity is a factor of mass or how heavy a
piece of wood is.
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I think it works fine and there is a correlation between those factors with the caveats mentioned by Hillbilly. But bow length is also a factor. Jawge
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It works pretty well, bearing in mind it's purpose is simply to offer a starting point. The width a bow should be is easily, well fairly easily, deterimined by making one as narrow as one can while limiting set to around 2", depending upon ones prefrerences. If you get up to within 4" of your finished draw lenght and on schedule for weight on the tree and have say 1/2" or less of set, you could probably start some side tillering. Doesn't take much and you don't shed much weight. But it can really opitimize performance and hand shock. Generally folks do this, at least on the outer limb, and don't realize, perhaps, it's just adjusting the initial design to fit the bow as it actually turned out.
I very general terms I feel most bows would benefit by being made a smidgin' more narrow or short, but one's skill in crafting has to be up to the challenge.
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Needed width for a bow will vary depending on relfex, draw length, tiller shape, draw weight and design. A buddy of mine has been working on a red elm stave at my house recently, yesterday he got it pretty close and is ready to start final tillering stages. He wants a 60# bow, I checked the mass weight on the bow and recomended he not go over 50# as I feel he doesn't have enough wood for the holgarde design he is building. I think you have to factor in everything. There is a huge difference in the width of a bendy handle bow and a stiff handled bow. Steve