Primitive Archer
Main Discussion Area => Bows => Topic started by: Andrew H on January 25, 2016, 09:18:09 pm
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Hi all -- I need some guidance. I have a 70” long piece of osage with some nice deflex through the middle that I would like to make up into a 68” ntn D/R design for target and 3D shooting -- so somewhere in the #40-45 range. I am planning to use a 4” Dean Torges style bulbous handle with 1.5 to 2” fades.
The stave is slightly crowned; came from a section of probably around 6” diameter (about 5mm rise over 2 inches). The piece is a little more deflexed in on limb than the other, but it has a total of about 1” of deflex from mid-limb to mid-limb and 2 3/4” from end to end. Maximum usable width of the stave is about 1 5/8".
My questions:
- For a target bow, where is the best location to place the reflex? I was thinking at midlimb, but maybe farther out?
- What should the front profile look like? Parallel out to the reflexed portion? Or parallel for a lesser amount, then taper?
- What type of tiller should I be going for? What should the fully drawn bow look like? More bend in the inner, deflexed parts of the limbs with fairly stiff still-reflexed area? Or even bend throughout with only slight stiffening at the tips? Or more movement in the outer limbs?
- How much reflex should I induce? I was contemplating trying to get the tips reflexed anywhere between 1” in front of the handle to dead-even with the front the handle, but I could go more or less. For target shooting, I’d like to have some performance for flatter trajectory, but I’d also like stability for accuracy. (Are these two ideas at odds?)
- What would good starting dimensions be for this length, profile, and draw weight? I’ve used Tim Baker’s “rule of thumb” for 66” bows (2” width at fades = SG as a safe draw weight.) Osage has a SG close to .80, so I could see using limbs only 1.25” wide as a start for #40-45. But should they be wider because of the deflex or parallel limbs and slightly longer length? Or narrower because of the slight crown?
- Lastly, what kind of final mass should I be thinking of with regard to all of the above? I’ve read and reread Steve Gardner’s “Mass Principle” in TBB4 and have used it with my Pyramid-style flatbows with good success. However, I’m getting tripped up when he discusses tweaking the mass formula for R/D designs (longer fades; stiffer tips = longer draw)...
Many thanks to all for your input.
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If you go 66" long and keep the outer limbs narrow about 19 oz should work nicely, that will give you plenty of width for your working areas of limb, about 1 1/4" most likely.