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    Fiberglass prod draw length

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    woodsmith
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    Fiberglass prod draw length

    Post by woodsmith on Sun Dec 29, 2013 11:58 am

    Does anyone know the draw lengths for the Taiwanese fiberglass prods, the 80lb and the 150lb ?
    I'm starting a build based on a PVC prod but would like to change it out later for a stronger prod.
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    Geezer
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    Re: Fiberglass prod draw length

    Post by Geezer on Sun Dec 29, 2013 5:07 pm

    If we're on the same page, the Chinese 150 lb. fiberglass prods (often closer to 125) are essentially knock-offs of the old Barnett Panther and later "San Marino' crossbows.  approx 28 inches from end to end.  They'll tolerate @ 8 inches of draw from 3.5 in. brace... maybe 9 inches, but I never went for more than 8.  Does anybody else have more info?  Geezer.

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    Re: Fiberglass prod draw length

    Post by phuphuphnik on Sun Dec 29, 2013 5:12 pm

    I don't know about the 150s but I just bought 3 of the 80s. I'm measuring 6" with a 17" string. Thae might go further, but I can't pull it back any more. I got them from the crossbow store's ebay page for just shy of $10 each.  I'll gladly let you buy one off of me, as they won't do for my stonebow project. All that said, I'll be getting one of the 150# or the 120# and I'll let you know what that draw is in a week. I'm hoping they are around 11"
    cheers!
    chriso

    EDIT Geezer beat me to it with the 150s. Glad I didn't order one yet. Might need to redesign the stock...
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    Re: Fiberglass prod draw length

    Post by woodsmith on Mon Dec 30, 2013 5:11 pm

    Thanks Geezer and Chriso, I'm glad I asked at this stage. The PVC prod I made is drawing 11" on top of a 4" brace. I have some decisions to make before I go any further.

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    Re: Fiberglass prod draw length

    Post by jeep on Tue Dec 31, 2013 3:31 am

    About the Taiwanese fibreglass bow 150#. (Referring geezer measurements: brass 8,89cm draw20,32cm) I am a regular user of those for various experiences.
    For my first bullet crossbow (Midleton inspiration)
    I used split limb 150# fibreglass
    brass 10cm  draw 22cm
    For the slur-bow (fibreglass)
    brass 10cm  draw19cm
    XIX th cent hunting 2x 150 fibreglass
    brasse 10cm  draw 23,5 cm

    For the bullet crossbow Richard Midleton point out that he don't succeed to use fibreglass limb because of the poor torsion resistance  (bullet need extra angle). This is the reason why I used split limb (centre shot, no angle)and there he work pretty well .
    I most of the time use the fibreglass over draw. I found a lot of tolerance but by precaution I all-way wrap them with  tape string or leaser. When is going to give up it produce crack before.
    my bullet crossbow

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    Re: Fiberglass prod draw length

    Post by jeep on Tue Dec 31, 2013 3:31 am


    jeep
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    Re: Fiberglass prod draw length

    Post by jeep on Tue Dec 31, 2013 3:45 am

    This kind of bullet crossbow with 150# bow is not a toy!!! it is incredibly powerful and potentially dangerous if not well cantered and balanced. This is a weapon....
    Some time the bow brake. Look the  last development  post  XIX th cent crossbow
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    Re: Fiberglass prod draw length

    Post by Gnome on Tue Dec 31, 2013 11:42 am

    For the full size 150lb prod, you should be able to draw 10 inches from a 3.5 inch brace height with no problem. I have one build that draws 12 inches from the same brace height. Now that I've explored the limits of the prod I can tell you I probably won't ever do that again. Too scary, even with a very strudy wrapping around it. I draw it with a cocking rope, and even then, the last inch or two I can feel a lot more resistance. So I would say 10 inches is a safe maximum draw for the designed brace height of 3.5".
    I'd also reccomend testing each individual prod- they may look identical, but there are definitely some variances in their construction. I had one crack on me while stringing it on my press, it wasn't flexed more than a few inches.
    Gnome

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