Primitive Archer
Main Discussion Area => Bows => Topic started by: DC on September 25, 2017, 05:04:48 pm
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If you look at this limb you can see that if I hadn't necked down the tips it would almost be a pyramid. Since the working portion is pyramid-like should it be a constant thickness?
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No. It should be tillered to bend properly.
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I know what you're asking DC, as I have asked myself that question on a similar bow. I went about it by starting at a conservative thickness and keeping it uniform along the working limb as the width gradually tapered. From there, as Bob stated, I tillered it to bend properly (as best as I could at the time). Worked out well! :)
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Thickness is determined by tiller.
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You can start with an even tiller, it wont stay that way though
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Why not, bubby?
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I know in the bible it says a pyramid bow with a constant limb thickness gives an automatic perfect tiller, but in my experiance building a lot of pyramid bows they always end up with a slight thickness taper to get the tiller down, jmho . Like i said just what i have found out after lots of bows and what i consider tiller to be
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That looks like a great bow you have going there looks like 50/50 bet it will be fast ! post as you go I'm following this one (AT)
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I know in the bible it says a pyramid bow with a constant limb thickness gives an automatic perfect tiller, but in my experiance building a lot of pyramid bows they always end up with a slight thickness taper to get the tiller down, jmho . Like i said just what i have found out after lots of bows and what i consider tiller to be
+1
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Why are tillered bows not constant thickness? Got an explanation from Dell the Cat year or two ago.
In summary, wood's variable strength properties and because bow "pyramid" shape is not a true pyramid due to width at tips.
Del did an experiment using pc of plastic of typical bow limb dimensions (consistent strength properties) which he shaped to a true pyramid profile.
Result was perfect (or near perfect) arc of circle tiller.
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Why are tillered bows not constant thickness? Got an explanation from Dell the Cat year or two ago.
In summary, wood's variable strength properties and because bow "pyramid" shape is not a true pyramid due to width at tips.
Del did an experiment using pc of plastic of typical bow limb dimensions (consistent strength properties) which he shaped to a true pyramid profile.
Result was perfect (or near perfect) arc of circle tiller.
Exactly a true pyramid will be a constant thickness BUT you would need to goto zero width at the tips, quite hard to cut a set of nocks into the air :) So a slight taper results.
DC - yes but with a slightly thicker spot right off the fades, tapering into a constant thickness out to the levers.
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Another variable I thought of after I posted is that this is a high crowned limb. A pyramid "even thickness" only works if the limb is a full rectangle shape. High crowned limbs start out crowned and then get more rectangular as you move out the limb.