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    White Ash Prod

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    fullmetalbodkin
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    White Ash Prod

    Post by fullmetalbodkin on Sun Mar 09, 2014 3:17 pm

    Hey guys.

    I got a white ash blank, 1"/ 1.5" about 28" long. Ive been working it with a spokeshave till its like this:







    it eases down to about 3/4". but i dont want so much power I cant even string the thing. I plan to back it with fiberglass cloth, and ill be using a belt spanner for simplicity sake. Im thinking 200lb draw weight would be good. but im not sure how much i want to work the ash down to.

    summary, how thick is a 200 lb white ash prod?
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    kenh
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    Re: White Ash Prod

    Post by kenh on Wed Mar 12, 2014 7:45 pm

    Thing #1 -- you don't need, or necessarily want, that "handle" in the middle of your prod.  Serves no real good purpose on a crossbow prod.  IMHO a crossbow prod should be designed and built like a "bendy handle" bow tillered to a circle not an ellipse.

    There's no way that anyone can tell you how thick that prod should be to get the draw weight you want.  This is the process called tillering.  Make yourself a tillering tree, and start with what's called a Long String.  There are a number of good places on the net that describe tillering a "selfbow" or "board bow" like this (although they'll describe a longer bow of course).  

    I'd start with Sam Harper's PoorFolkBows Red Oak Board Bow Build-along:

    http://poorfolkbows.com/oak.htm
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    actionbow
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    Re: White Ash Prod

    Post by actionbow on Wed Mar 12, 2014 10:20 pm

    You won't get 200 lb from a glass cloth and solid wood prod @ 28". Shoot for 140 lb or so. Use ea40 glue and compress the fiberglass in a few layers and get the perfect grain on the belly and you might get a 150@12" or so prod.

    Wood has limits. I have composite recurve limbs that draw 200 lb at 16" and they measure 36" nock to nock with about 2" hidden in recurve by about 1 3/4" center to 7/8" at nock and the limbs go down to around 3/8" thickness at the tips.

    My all wood prods are rounded on the belly and flat on the back so are much harder to describe. Hickory and Osage are best for high draw weight solid prods. Ash is brittle and not as tough.
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    actionbow
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    Re: White Ash Prod

    Post by actionbow on Wed Mar 12, 2014 10:25 pm

    kenh wrote:Thing #1 -- you don't need, or necessarily want, that "handle" in the middle of your prod.  Serves no real good purpose on a crossbow prod.  IMHO a crossbow prod should be designed and built like a "bendy handle" bow tillered to a circle not an ellipse.

    There's no way that anyone can tell you how thick that prod should be to get the draw weight you want.  This is the process called tillering.  Make yourself a tillering tree, and start with what's called a Long String.  There are a number of good places on the net that describe tillering a "selfbow" or "board bow" like this (although they'll describe a longer bow of course).  

    I'd start with Sam Harper's PoorFolkBows Red Oak Board Bow Build-along:

    http://poorfolkbows.com/oak.htm
    I gotta say I disagree with almost everything you said here. I have built more wood crossbows than I can even remember offhand. All have risers that fade into a non bending section and wood can most certainly be calculated by dimensions to net a certain draw weight with a high degree of accuracy.
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    kenh
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    Re: White Ash Prod

    Post by kenh on Thu Mar 13, 2014 5:30 am

    Well OK then.  If you're so good, instead of ragging on me, why not give the man the dimensions he needs??
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    actionbow
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    Re: White Ash Prod

    Post by actionbow on Thu Mar 13, 2014 8:22 am

    Because he can't do it with a 28" blank like I said. Also I did not claim to be a library of wood spring dynamics, only that it could be calculated. You said no one could tell him. I disagreed.

    If disagreement is "ragging" in your opinion maybe you should think harder about your responses before posting misinformation that can steer new builders in the wrong direction.

    Just a suggestion. Cheers Kenh.

    fullmetalbodkin
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    Re: White Ash Prod

    Post by fullmetalbodkin on Thu Mar 13, 2014 2:21 pm

    The Harper article is good. Ive only got a six inche track, which i thought would be good when i started this project, but im definitely reconsidering.

    I may even chop the prod down a bit. Just cause 6 is a little short, and seems disproportioned with a 28" prod.
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    actionbow
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    Re: White Ash Prod

    Post by actionbow on Fri Mar 14, 2014 12:00 am

    Ok, with a 6" draw you might possibly be able to get a 28" 200lb prod with fiberglass. Having said that you will get greater arrow speeds with a 28", 150lb prod drawn to 10 or 12".

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