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by Geezer Sun Feb 19, 2017 8:31 pm


    Wood Prod II

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    GodricSwin
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    Wood Prod II

    Post by GodricSwin on Sun Jul 05, 2015 5:25 am

    I haven’t reported in lately but I’m following the notes here on The Guild and appreciate them very much. 
     
    Am making progress – but very SLOWLY!   Currently working on the third wood prod; first one the back blew out, the second is only about 50 lbs draw weight (will be a gift to two young brothers); it will be the Skane type.  Hopefully this third one will be heavier - I would really like it to be at least 100 lbs.  All are hazel.
     
    Geezer, you mention a “string snubber” - where can I get a description?


    I would really like to hear how the oak prod progresses – that’s true for any wood prods.


    (Hope I didn't screw up by starting a new topic.)
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    Geezer
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    Re: Wood Prod II

    Post by Geezer on Sun Jul 05, 2015 7:29 am

    I don't have a pic of a string-snubber handy, but it's simply a little structure (I make a stiff brass clip) fastened over the string-notch that allows just enough clearance for the string to slip underneath fall into the notch.  It's not unlike a bolt-clip, and can double as a clip, but it's stiff enough so the string CANNOT jump above the bolt and cause a misfire.  Lots of modern crossbows employ a solid housing.... sometimes it includes the lock/release, above the bolt-track that also serves as a string-snubber.  Geezer
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    Re: Wood Prod II

    Post by Geezer on Sun Jul 05, 2015 7:32 am

    Of course the original Skane bow doesn't have a string snubber or a bolt clip, though they might have used something sticky like a blob of bee's wax to hold the bolt in place before shooting.  I have heard of that being done with primitive African or Asian crossbows (forget which) Maybe it was mentioned in Josef Alm's book. Geezer
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    Re: Wood Prod II

    Post by OrienM on Sun Jul 05, 2015 9:25 am

    Have you given any thought to sinew-backing wooden prods? I've found it really adds a lot of power, and makes the back much more resistant to splintering/breakage.

    I recently finished up a sinewed osage orange prod that pulls well over 100#...I think it's around 160#, although I still need to take it to the bow shop to be weighed and chrono'd. (Shown here: http://thearbalistguild.forumotion.com/t1422-new-medieval-finished#13585 ).

    I applied the backing much as is shown in this link, although I tend to glue down one thread at a time, rather than in bundles...I feel like I get a more homogenous, tough backing that way. I got the Elk sinew I used on Etsy.com, but ebay and others have it available, too.

    http://sensiblesurvival.blogspot.com/2012/03/how-to-sinew-back-wooden-bow-part-1.html


    Last edited by OrienM on Mon Jul 06, 2015 10:35 am; edited 2 times in total
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    Re: Wood Prod II

    Post by Geezer on Mon Jul 06, 2015 10:05 am

    Orien: your wooden prod looks great, and I'm sure the sinew backing adds plenty of strenth and speed.  Good looking project.  Geezer.
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    Re: Wood Prod II

    Post by OrienM on Mon Jul 06, 2015 10:25 am

    Thanks! I feel like I should add, using a proven bow wood like osage, and also steam-bending a deflex into the prod as recommended here, probably helped it to survive. On wooden bows as short and high-powered as crossbow prods need to be, you kind of need to maximize your advantages!

    Even so, I blew up several wooden prods before thinking to add the sinew... tongue

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    Re: Wood Prod II

    Post by GodricSwin on Tue Jul 07, 2015 2:37 am

    Yes, after the back blew out on my first prod I decided that I would definitely sinew the back of the next one; however that next one (no. 2) is just about the right weight for a kid so that one I probably won't sinew.  But on the third one I will after I have it tillered to the weight I think it should be but before I draw it to the full draw length because when I drew out the first one was when it broke. (Hope that makes sense!)
    The sensiblesurvival . . . site you added is a good one.
    Thanks guys - I need all the help I can get! scratch
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    Re: Wood Prod II

    Post by kenh on Tue Jul 07, 2015 7:45 am

    Here's another thought.  Build your wooden prod in the Chinese style, from several loose laminations.  Not glued together, but loose slats held together with simple bindings.  The advantage is that you can increase/decrease the power readily by adding/removing lams.  The Chinese developed this concept nearly 2000 years ago, using bamboo slats.
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    Re: Wood Prod II

    Post by hullutiedemies on Sat Aug 01, 2015 4:49 am

    Somebody might find this useful

    A prod I have been recently breaking in.
    Yew self bow , braced at halfway the bolt table, steamed to full deflex. This allows much fatter and heavier bow than straight stave.
    String is 47cm, thickness of prod in middle 30mm , tips 20mm.
    I have been too lazy to test the draw weight at full draw , but half draw weight is ca. 50kg - extrapolating from there it should be around kiloNewton (200-250#). Power stroke is 114mm (4.5"). Bow is quite small. A 50% larger prod would still be practical and 2-3 times as powerful.


    27mm diameter bottlecap is for scale.

    Tiller is temporary, I'll make a proper one if the prod is alive after some shooting. And goat foot unfinished but fully functional.

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    Re: Wood Prod II

    Post by c sitas on Mon Aug 03, 2015 7:24 am

    Hullutiedemies; on your goats foot. It appears that the handle folds. Is that true?  I am new to the concept of the goats foot. It also looks like maybe made from 3/4 x 1/4" stock ? No problems with twisting? I like like your bow.
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    Re: Wood Prod II

    Post by hullutiedemies on Mon Aug 03, 2015 8:51 am

    Yes it folds . This is basically simplified version of the Payne-Gallwey model, done without any forging , welding or heavy machining.
    The levers are bent cold from 4x12mm slat. The hooks are 5x15mm.
    Idea is to replace those wire crossbars with solid metal, just have to decide wether to screw or rivet.
    Axles are 3.5mm hardened pins.
    Material strenghts are similar to typical garage foot pumps, wich have to handle comparalable stresses.


    Oh yes, the deflex curve in upper lever eliminates twisting.

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    Re: Wood Prod II

    Post by c sitas on Mon Aug 03, 2015 10:01 am

    One more question as long as your willing.Would you say one or the other is easier to use. Comparing between a goats foot and a whippe.
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    Re: Wood Prod II

    Post by hullutiedemies on Tue Aug 04, 2015 2:13 am

    c sitas wrote:One more question as long as your willing.Would you say one or the other is easier to use. Comparing between a goats foot and a whippe.

    I have never used much whippes. In theory they should work better with this kind of notch lock. But here I managed to break two hastily assembled ersatz whippes before I decided that my household could really use a goat foot.

    That extra piece of rope you see hanging in front of the prod was intended for a whippe. But they just kept bending too much and the second one split in quite dangerous manner.

    A sheep foot aka. metal whippe is something I have been thinking about trying in future. That should combine the best properties of both types.

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    Re: Wood Prod II

    Post by GodricSwin on Tue Aug 04, 2015 5:04 am

    I would like to go back a little:


    Hullu- said, "A prod I have been recently breaking in."

    If you've time could you write a brief description of how you "break in" a prod.   I have one started that looks like it may be more in the range of I want (100 - 150lbs) but I'm a little skittish about over-stressing it while tillering.
    Thanks.

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    Re: Wood Prod II

    Post by c sitas on Tue Aug 04, 2015 7:11 am

    Ah yes, I use the same piece of rope.It works fine.I made my foot out of oak,so far haven't broken  it.It's just kinda scarey the first few times you use it and realize how much pressure and power is really involved here.150# is substanial.
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    Re: Wood Prod II

    Post by hullutiedemies on Tue Aug 04, 2015 8:57 am

    GodricSwin wrote:
    If you've time could you write a brief description of how you "break in" a prod.  
    Just leave it strung for a few days, shoot some bolts, have it survive some accidential dry firings. See that string tension remains constant. If it does not show any sign of failure, it might be worth a proper tiller.

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