Primitive Archer
Main Discussion Area => Bows => Topic started by: burn em up chuck on April 26, 2013, 07:04:56 am
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how is the 5/8s rule applied to making longbow type bows? I know it's some type of ratio but thats as far as my knowledge goes on this subject.
chuck
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If you Google it there's lots of info out there on this.
I personally tend to ignore it when making ELBs though. The "rule" is fairly straightforward - the width/depth ratio needs to be 8/5. If your bow is 1" wide, the depth needs to be 5/8" (1" is 8/8)
Here's a quote from the GNAS (UK) regs. At no point shall the depth of the bow, measured from back to belly, be less than 5/8 (five eighths) of the width of the bow at the same section.
Trouble is, getting that accurate along a stave (especially if you have knots or deflex/reflex areas) is quite tricky. If your front profile looks like an ELB, and it's tillered properly, chances are it will apply anyway as far as I can tell.
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something tells me Del will contribute to this thread. but what Will said is good. SS
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The trick is to design the bow narrow enough, so you don't get below the 5/8 rule during tillering. The midlimbs are most crucial; it's not difficult to get a 6/8 ration at the handle and a 7/8 ratio at the tips, but the midlimbs are the thinnest sections generally.
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thank you for the help. The general description was exactly what I was looking for. I have some narrow bow material to use and this gives me a place to start.
chuck