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    Prod construction

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    bigcountry_ky
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    Prod construction

    Post by bigcountry_ky on Mon Dec 05, 2016 7:38 am

    I have made a bunch of longbows.  Most osage, some yew, some composite bamboo backed IPE, etc.

    So, trying to figure out the best dimensions for a crossbow prod.  I am thinking heavily sinewed backed osage would be best.  But maybe sinewed back hickory.  I hate working with hickory, but its tough. 

    any ideas?
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    Re: Prod construction

    Post by actionbow on Tue Dec 06, 2016 1:29 pm

    Recurve or straight?
    Fiberglass lamination ok?

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    Re: Prod construction

    Post by bigcountry_ky on Tue Dec 06, 2016 3:16 pm

    I am thinking Recurve if I use osage as its easy to bend.  No fiberglass.  Just sinewed backed.
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    Re: Prod construction

    Post by actionbow on Tue Dec 06, 2016 3:21 pm

    So, sinew backed self-bow style?
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    Re: Prod construction

    Post by actionbow on Wed Dec 07, 2016 1:10 pm

    I have made a few solid hickory prods backed with fiberglass fiber rather than laminate. What I have found is that the solid wood prods work best for short draw lengths but over 10 inches or so prods less than 32" would have a pretty short life. They weaken pretty fast when pulled past their optimum range. Great tiller in will help but over 120 lb or so it gets real tricky.
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    Re: Prod construction

    Post by OrienM on Thu Dec 22, 2016 9:23 am

    My crossbow has a prod made like you're describing:

    http://thearbalistguild.forumotion.com/t1422-new-medieval-finished

    This prod is osage orange wood, 35" long nock to nock, 2" wide and 3/4" thick at center, with an additional 1/4" thick elk-sinew backing added. The backing was covered in a snake skin for looks and water resistance. The prod pulls about 160#, with a 9" powerstroke. I steam-bent about 4" of deflex in before sinewing, to lower the stress on the belly wood....adding some deflex seems to be a good idea with any wood or wood/sinew prod. The finished product throws a bolt nicely and seems very safe; if anything, it's probably a bit overbuilt.

    I'm also in the beginning stages of a second, similar osage/sinew prod...this one is designed for a smaller xbow, and is quite a bit shorter overall at 26" NTN. I'm hoping to wring a bit more power and efficiency out of the wood/sinew combo this time, so it's narrower and has less deflex than the first prod, and is intended to pull over 200# at 5" or so. I think the materials can handle the additional stress, but time will tell... Very Happy.
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    Re: Prod construction

    Post by actionbow on Thu Dec 22, 2016 10:56 am

    Sounds doable. I would make a batch of two or three and hope to get a good one. 200# @ 5" is a tall order for a 26". Some deflex might be a good idea for that. Not familiar with sinew. I'd like to see how it turns out.
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    Re: Prod construction

    Post by OrienM on Fri Dec 23, 2016 9:17 am

    Yeah, it's asking a lot of a short little bow, but I think it may be within the realm of possibility. I often learn the most from projects where I push the envelope a bit! I'm real curious how much draw weight I can get out of the wood/sinew combo, without an added horn belly...I figure a very compression-strong wood like osage is my best bet.

    If it doesn't survive, I can actually soak the sinew off and re-use it in a different prod. I will definitely post pics of the process here, once I get a little farther along.
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    Re: Prod construction

    Post by actionbow on Fri Dec 23, 2016 9:20 am

    Yep, Osage or hickory will be your best bet. I think it's definitely possible with the right limb tiller.
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    Re: Prod construction

    Post by actionbow on Fri Dec 23, 2016 12:32 pm

    And grain selection of course...the real biggie.

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    Re: Prod construction

    Post by bigcountry_ky on Tue Dec 27, 2016 2:41 pm

    I usually make osage bows.  So I have lots of Osage.  But with the bright yellow look, might look goofy.  I know I am vain. 

    If any wood I imagine could handle the stress, it would be osage, or a boo backed ipe. 

    Thanks for the replys.

    I have made hickory bows, and they usually are strong but usually take quite a bit of set.  So, I asked the question on primitive archer and other pages, why not sinew a hickory bow?  It would take out that set.  Hell to work with in my opinion.

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    Re: Prod construction

    Post by bigcountry_ky on Tue Dec 27, 2016 2:42 pm

    Another reason I osage might be a good idea, is its easy to heat bend to make into a recurve type.I have never been able to get hickory to bend and stay that way.
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    Re: Prod construction

    Post by OrienM on Tue Dec 27, 2016 3:28 pm

    Osage is awfully strong, and steam-bends like a dream, too...it's known as Bois d'Arc (bow wood) for a reason!  Here in the desert where I live, hickory acts a bit snappier due to very low MC, but I'd still choose osage for the workability and low set. (It grows locally, too Very Happy ).

    The yellow color is a little bright at first Shocked . You could always cover the belly with parchment or something, like the medieval composite prods. The sinew back will probably need some sort of covering anyway. I'm real fond of snakeskin backings, and have a nice rattlesnake skin in the freezer for backing my next prod.

    I've never made a recurved crossbow prod, but if I were to try, I'd probably go for working-type recurves, to get as much of the prod bending as possible. Stacking isn't really a factor with crossbows, and static recurves might overstress the inner limbs.
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    Re: Prod construction

    Post by kenh on Wed Dec 28, 2016 5:19 am

    Most European wooden prod crossbows were NOT selfbows.  Historically Europeans would have used Yew, Wych Elm and perhaps Ash;  but for crossbows they would have been combined with sinew and horn to make a composite prod  Steel prods were available as early as abut 1300 and by the mid-1500s virtually all crossbow pods were steel.
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    Re: Prod construction

    Post by OrienM on Thu Dec 29, 2016 9:17 am

    I made a few tiny selfbow-type prods, sub-75#, but anything heavier than that IMHO needs sinew. I think draw weights up to 200# are fairly do-able; get the weight TOO high up there, the belly wood will be crushed without an added horn layer to take the strain.

    Overall, making steel prods is/was probably much quicker than making composite ones...no months of drying time for sinew layers, and no worrying about moisture affecting the finished prod. Smiths set up to make swords would also be pretty well set up to forge and heat-treat a prod.
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    Re: Prod construction

    Post by OrienM on Thu Mar 02, 2017 12:34 pm



    Found this pic of an interesting antique (1500's?) bow with wood/sinew prod. The prod appears to be yew wood, with a relatively thin sinew back covered in parchment. The lugs on the tiller are for cocking with a goat's foot lever, indicating possible draw weights in the 200-400 lb. range. Note the massive thickness, deflex, and short draw length.

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