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Author Topic: Limb shape and thickness  (Read 1965 times)

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Offline DC

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Limb shape and thickness
« on: September 25, 2017, 05:04:48 pm »
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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Offline SLIMBOB

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Re: Limb shape and thickness
« Reply #1 on: September 25, 2017, 05:13:57 pm »
No.  It should be tillered to bend properly.
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Offline upstatenybowyer

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Re: Limb shape and thickness
« Reply #2 on: September 25, 2017, 07:59:20 pm »
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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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

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Offline Pat B

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Re: Limb shape and thickness
« Reply #3 on: September 25, 2017, 09:43:15 pm »
Thickness is determined by tiller.
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Offline bubby

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Re: Limb shape and thickness
« Reply #4 on: September 25, 2017, 10:44:43 pm »
You can start with an even tiller, it wont stay that way though
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Offline Dances with squirrels

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Re: Limb shape and thickness
« Reply #5 on: September 26, 2017, 04:38:13 am »
Why not, bubby?
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Offline bubby

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Re: Limb shape and thickness
« Reply #6 on: September 26, 2017, 01:17:13 pm »
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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failure is an option, everyone fails, it's how you handle it that matters.
The few the proud the 27🏹

Offline Stick Bender

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Re: Limb shape and thickness
« Reply #7 on: September 26, 2017, 01:29:02 pm »
 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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Offline upstatenybowyer

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Re: Limb shape and thickness
« Reply #8 on: September 26, 2017, 07:25:59 pm »
Quote from: bubby on September 26, 2017, 01:17:13 pm
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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"Even as the archer loves the arrow that flies, so too he loves the bow that remains constant in his hands."

Nigerian Proverb

Offline Knoll

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Re: Limb shape and thickness
« Reply #9 on: September 26, 2017, 09:26:32 pm »
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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mikekeswick

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Re: Limb shape and thickness
« Reply #10 on: September 27, 2017, 02:49:25 am »
Quote from: Knoll on September 26, 2017, 09:26:32 pm
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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Offline DC

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Re: Limb shape and thickness
« Reply #11 on: September 27, 2017, 10:48:33 am »
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.
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