Bow Cross section Analysis

bheggeseth · Post by **bheggeseth** » Mon Aug 20, 2012 12:52 am

On my previous bow and my current bows I used a router bit to mill 2mm deep matching grooves. I followed the grooving up with 20 coats of 2% fish bladder glue for sizing. After letting the parts dry for a day I heated up everything with a halogen light and glued the horn and core with 30% fish bladder glue. Clamping was done with C clamps. My previous bow broke during tillering last spring, everybody?s best conclusion for the bow breaking was improper tillering and core dimensions. I cut some clean slices off the broken limb to examine how well the horn/core glue joint was. Below are pictures for everybody to analyze. All comments welcome, thanks.

Note the slight discoloration is from the saw burning.

Break, note the horn looks to have held well.

Uli · Post by **Uli** » Mon Aug 20, 2012 6:08 am

very neat work. glue-up sounds correct. strange that it broke, what a pitty.
maybe use more sinew next time for security.

redhawk · Post by **redhawk** » Mon Aug 20, 2012 7:29 am

It looks like the core is not made according to the growthrings of the wood plus there had been a crack within the horn. Is the horn cut from the curves or is it a sidewall?
Grooving and glueing seems to be o.k.
I?m always wondering why many ATARNOS are using fish- bladder glue. O.k. bowyers of the past have used it, but they didn?t have had acces to actual hide- glues which are available in really high quality now, easy to get and to handle. Maybe a well prepared fish- glue is a bit better but much more delicious to handle.
Michael

Kviljo · Post by **Kviljo** » Mon Aug 20, 2012 3:33 pm

I'd say that looks very-very good between the horn and core

Makes me want to try it too, hehe.

Regarding the break, I'd say you could have used more sinew, and a lot more on the edges. Without enough sinew on the edges I would imagine the limb could be torn off just like a paper, if there ever was some sideways unstability when bending it.

PAZUZU · Post by **PAZUZU** » Mon Aug 20, 2012 6:25 pm

bheggeseth
glue line looks good. I would put more coats of glue. my guess is a bad horn strip. I had a similar strip, but to my joy broke it before gluing it. similar dry and brittle wood. and very little elastic ....