Crab Bow 2

JJ · Post by JJ » Wed May 21, 2014 9:35 am

An observation:

On both horn strips the area around the "kasan eye" zone the glued horn surface looks as if tiny flat flakes are rising. I think the delamination of the horn started at this place. On both limbs...

In this area the lever effect of the long siyahs has probably the greatest force...

So perhaps the horn should be thicker at this place??

JJ

mongolianarcher · Post by **mongolianarcher** » Wed May 21, 2014 1:26 pm

But isn't it a gluing problem rather than a horn problem?

Bj?rn Sofeit · Post by **Bj?rn Sofeit** » Wed May 21, 2014 4:10 pm

First of all, great bow!

Since this is a good opportunity to ask, there's a few things that I'm curious about. The original bows were wrapped with a thin layer of sinew as a read, and also the horn is supposed to be very thin?

Did you plan to wrap it in sinew? How thick is the horn that you used?

lurz · Post by **lurz** » Wed May 21, 2014 7:25 pm

I tend to agree with Mongolianarcher, that it may be a problem with glue. If the horn delaminated I would have expected to see bits of horn remaining on the wooden core?
Did you use matching groves btw? If not, I'm thinking of a debate here some time ago about the grooves being sufficiently filled with glue?

Kviljo · Post by **Kviljo** » Wed May 21, 2014 9:33 pm

http://198.170.107.188/phpBB2/viewtopic.php?t=2569

I agree. It looks like the same problem as I have had with some bows. On mine I have concluded that the joint have not been filled with enough glue, which is strong enough for sectons that have little glued in reflex, but not strong enough for the "pulling apart" forces in sections with more reflex. The horn on mine have always popped off at the most reflexed sections, and the delaminated surfaces look very similar.

The main reason for having a larger portion of horn at some place along the bow, as I see it, is that you want that place to be bending more than the rest. On the other hand, too little horn will simply give the bow more string follow at that area. In any case, some of these bows apparently had very little horn, even down to 2mm and only 1/3 of the total limb width (?!).

Uli · Post by **Uli** » Thu May 22, 2014 9:18 am

meh..
good luck with repair and thanks for sharing experience !

JJ · Post by JJ » Thu May 22, 2014 9:29 am

Bj?rn, I will wrap it now I guess (because I?m a little cautious about two cracks in the horn).
Originally I wanted to paint directly onto the sinew/ horn without adding additional mass to the bow.

And yes there were small and thin flakes of horn on some places on the core. Unfortunately i do not remember the spots exactly.
But the horn seems to have developped tiny cracks on the inside at the siyah splice. I?m not sure if they were the reason for the delaminations or if they developped during the separation when the horn suddenly straightened.

Anyway i have glued it together again and hope it will hold better this time.