Primitive Archer
Main Discussion Area => Bows => Topic started by: dave young on January 16, 2018, 05:15:18 pm
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I have an osage board and just got some bamboo for backing. I have never worked with osage, or a backed bow before. Any words of wisdom? What are some good dimensions/designs for this type of bow? I am looking for about a 40lb bow. Last 2 bows i have made are pyramid style and I like them real well but not sure if that is a good design for this type of bow?
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A pyramid design is good for boo/osage but keep it narrow, like 1 3/8", no more than 1 1/2".
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How thick on the Osage limbs? Also, do you sand the nodes on the bamboo at all?
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As far as the boo lots of us can tell you, but James Parker has a YouTube video on finishing one of his boo backed blanks. Huntworthy productions and you can see how to clean and finish the boo. Maybe better to watch than read ;)
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The thickness of the limb will be determined by how much wood you take off to achieve the draw weight you want.
I'm working on a hickory backed lemonwood bow now so I started with a 3/4" board which will be that thickness at the handle but the belly portion of the limb could be 1/4" to 1/2" thick. The boo shouldn't be more than 1/8" at the handle at the crown of the boo and slightly tapered to the tips.
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Also Dean Torges has a excelent DVD covering every thing A to Z on making a BBO it really helped me a lot on the BBH I just posted.
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Hunting the Bamboo Backed Bow is the name of Dean's dvd.
I've never made a pyramid style(tapered only in width), bamboo backed osage bow. It would have to be wider than I like, or is necessary, and that width could create difficulties associated with the crown of the bamboo. In order to make it wide enough to get enough width taper, the bamboo would be quite thick unless it came from a very large diameter pole. Those are just some things to keep in mind when coordinating the design of the bow with the material you have on hand.
I've made d/r bamboo backed osage bows over 70# at 1 1/8" to 1 1/4" wide... and that's starting with a 1/2" thick osage slat, radiused belly, trapezoid cross section, front profile being a convex taper... a straight taper works too. If you're going to bend it into a reflex or deflex/reflex shape during glue up, it helps to pretaper the limb area from dips to tips.
I strongly suggest getting that dvd and watching it before you begin. Tons of good info in there.
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Pyramid style isn't only using width taper for tillering. IMO. Any bow that has a straight taper from the fades to the tips is considered a pyramid style bow.
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One common rooky mistake is when reflexing the bow the curve where the reflex starts is to abrupt and too close to the center of the limb, Pre tiller the belly slat so any curves are very gradual, once you get near the tip you can make the curves a little steeper. Very hard to tiller a bow with an abrupt curve about 1/3 of the limb down from the tip.
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I believe JD Jones wants to, at some point, post a build along on his style of BBO
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I'd like to see JD's build along.
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So an English longbow is a pyramid bow... gotcha ;)
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So an English longbow is a pyramid bow... gotcha ;)
ELB's don't have a straight line taper
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:P An ELB is more like a semi-pyramid style.
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Everything is a semi pyramid ;D ;D ;D
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A bow with the center section parallel before tapering to the tips is called a semi-pyramid. The length of the parallel is not important but if only the last few inches are tapered then it's called overbuilt.
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On mine I keep the middle 18" parrallel then straight taper to tips
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When I lay the bow up I usually taper about the last 14" and then once I start cleaning it up and tillering I smooth out the transition area by hand extending the taper a few inches further in.
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If going with a reflex deflex profile i taper from the peak of the curve out to the tips then blend it in like badger said.
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I just ordered Deans video. So I will watch it before I start.