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    prod width for jayhawk prod

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    panne
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    prod width for jayhawk prod

    Post by panne on Thu Nov 08, 2012 7:41 am

    i recently picked up some jayhawk parts. among them are one "assembled" pistol, a full length zebra wood stock and an oak stock.

    the tillers all have different widths 1 1/8". 1 1/2" and 1 3/4". i'm wondering what would be the best/safest width to use and also wondering what the draw length should be. the assembled crossbow i have has a 13.5" draw and the draw weight is 75#. seems a bit long to me?

    i plan on adding a stirrup and most likely a set of bow irons in addition to the stock center bolt to make it easier to span and so it's not all held together by just a stud anchored into a crosswise hardwood dowel glued through the stock.

    not sure if i should use linen or polyethylene for the string, but know the cable definitely has to go. i'm also not concerned if i have to go a bit shorter on the draw as long as i can stay over 50#. it's just for me to plink in the backyard with and occasionally poke possums bugging my chickens.

    i'm also wondering what the minimum bolt weight should be.

    thanks
    panne
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    Geezer
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    Re: prod width for jayhawk prod

    Post by Geezer on Thu Nov 08, 2012 9:25 am

    Panne: Geezer here. I've built about a jillion bows with either Jayhawk prods, or prods based on their proportions and shape.
    First, Jayhawk prods with holes in the center will eventually fail through the hole. That's no problem, so long as the prod is held down tightly. A set of bow-irons should do nicely, as long as you have some sort of support for the prod thru the center... say a block of wood over the lag-bolt mounting.
    The draw you're getting is pretty long... 13.5 inches. I usually don't exceed 8 inches from a 3.5 inch brace, which comes to 11.5 inches. 13.5 won't necessarily kill your prod right away, but it will fatigue faster at that length, particularly if you shoot fast, in hot weather.
    Stock width isn't terribly important. If your stock is wider, and the prod mounting is really solid, wider stocks, will reduce the working-length of your prod-limbs, so wider prods make for stronger bows, and greater stress for the limbs at any given draw length.
    Bowstrings: You're right the steel string is an abomination, it needs to go. But it does give you a fair idea how long your Real bowstring should be. Jayhawk's steel strings were made for a fairly low brace-height, @ 2.5 inches, as I recall. I go for a slightly higher brace and shorter draw to get a proper medieval look for my bows. Certainly making the string half an inch shorter wouldn't hurt if you reduce draw-length an inch or so. As for materials, many people use Fastflite for bowstrings... it gives very high performance, but it will also reduce the working life of your prod by a considerable margin. For many years, I used 'artificial sinew' for bowstrings on Jayhawk prods. It works fine, but will stretch a bit in use, so you'll have to take it off and twiste it up once or twice. Nowadays, I use Dacron b-50 for bowstrings. It's available at a reasonable price from archery-outfitters and makes a good, strong string. A little less efficient than Fastflite, but your prod will last much longer.
    Good luck with your project. The old Jayhawk prods will give you many hours of fun backyard plinking. That's what they're best for. Geezer/David Watson, New World Arbalest.
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    Re: prod width for jayhawk prod

    Post by Geezer on Thu Nov 08, 2012 9:26 am

    "so wider prods make for stronger bows, and greater stress for the limbs at any given draw length."
    Correction: Wider STOCKS make for stronger bows, and greater stress... etc.
    Geezer

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    Re: prod width for jayhawk prod

    Post by panne on Thu Nov 08, 2012 4:00 pm

    much appreciation for the info geezer. do you have any pictures of some of your jayhawk builds?

    is extra barrel length beyond the prod a cosmetic addition or does it serve a specific purpose?
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    Re: prod width for jayhawk prod

    Post by Geezer on Thu Nov 08, 2012 5:50 pm

    A fair number of extant medieval crossbows carry the bolt- track several inches beyond the prod. SCA combat bows do so, partially to support the very heavy-headed bolts. Some 19th century Belgian crossbows have a long nose that actually curves away below the bolt-groove. The place a very low blade front sight out there, for long sight radius, and also use the long nose for leverage for a cocking lever. You can find that in Ralph Payne-Gallwey's 1907 opus "The Crossbow Medieval and Modern" which is still in print.
    As for my bows, you can find lots of pictures of my stuff on my website... www.crossbows.net Sign in to the gallery and there are oodles of pics. Careful observation should tell you which have steel prods and which are aluminum-alloy prods based on the old Jayhawks. Geezer/DRW
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    Re: prod width for jayhawk prod

    Post by Zardoz on Wed Nov 14, 2012 9:09 pm

    But what is the width of a Jayhawk prod?
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    Re: prod width for jayhawk prod

    Post by Geezer on Wed Nov 14, 2012 9:12 pm

    Jayhawk prods: approx 1.75 inches wide at the center, and about half that at the ends. Rise of the ends, 3/8 above the center. Length of the metal before bending 28.8 inches.
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    Re: prod width for jayhawk prod

    Post by Geezer on Wed Nov 14, 2012 9:13 pm

    Woops, forgot. Made of 190 thousandths of an inch thick aluminum alloy 7076-T6
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    Re: prod width for jayhawk prod

    Post by Geezer on Wed Nov 14, 2012 9:14 pm

    typical typo: 7075-T6. Geezer

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