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Question for horn bellied bow builders

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colin1991:
Hi all,

Recently I have been playing around with crossbow designs and had come up with a working design using a laminated timber prod (40" ntn and 120lbs @ 16 inches, 3.5 or so inch brace height) but due to the timber being worked so hard it has failed on me.

Ive seen examples of composite prods for crossbows using a sinew back and laminated horn belly so I though I would incorporate a horn belly onto a timber back and core (either hickory or bamboo as the back and a hardwood as the core most likely.)

My question is, will laminating a series of small sections onto the belly of the bow work if I overlap (cut on an angle and married together) the ends and use a heap of glue, or do the horn pieces need top be full length of the limbs? I would try to get pieces as long as possible for the sake of less joins.

The one example I have seen had very, very small strips (maybe 3-4mm square) all laminated together in the cross section to make up the belly...

Any advice will be very much appreciated.

Colin

james parker:
Colin,  I think you will be much better off to just butt joint the horn pcs together,.if you lap joint the horn on the belly, then put compression stress on the belly,  the pcs will slip one across the other, especially at the high poundages you are looking to attain. I think you will  have problems  with this happening  even when trying to brace the prod, keep in mind  if you position the butt splices  somewhere in the  non working area of the limb you will also have a better chance of success.
 I have used the process in the building of my horn composite bows with much success.
post some pics of the prods you have now.
hope this hepls.
james

colin1991:
Hi James,

Thanks for the information!! I will keep that in mind for my build.  Firstly I have to get a hold of a decent quantity of horn.

Another question, probably a hard one to answer but I'll ask it anyway. What kind of thicknesses are the limbs on very heavy horn bows (100lb + ) since I've never built one I have no experience with them and dont know how large or small the limbs will be.

the one prod I have, which is now failed, was basically a miniature English warbow, at 40" ntn. I'd like to keep the new prod the same length or even possibly slightly shorter, since I know horn can take so much more compressive stress than timber.

Cheers,

Colin

Aaron H:
There is no straight forward answer to that question Colin, depends on the material being used, the width, and the length.  Among dozens of other things...

mikekeswick:
Youcan use multiple strips either side by side or butted along the length. However much easier for you would be to use 2 pieces butted in the center.
Multiply your drawlength by 1.6 to get your necessary width.
You will be safer building it in the traditional way. Horn/maple/sinew. A gentle recurve will aid performance too.
My starting point for thickness would be around 12 - 13mm in the working limbs.

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