Sinew backed bamboo bow

[superdav95]

I forgot to post a full draw pic on this build.  Here are some stats.  It is 42lbs at 28”.  It’s 58 1/2” ttt and just under 58” ntn.  It spits out a 9gpp arrow at 185-188 fps.  It is a bamboo backed and bellied bow with a few layers of sinew covered with thin roo rawhide and stained with leather dye and painted up.  All sealed with several layers tru oil.  The black stained belly is also bamboo lam.  Leather wrap handle with some cork for palm swell shaping.  Red dyed Ostrich leg leather on the fades area.  I used black sting ray for the arrow pass on both sides.  I played around with the brace height a bit prior to settling on a endless loop string in red and black.  Felt it shoots best at lower then typical brace.  Thanks for looking guys. 

[Aaron1726]

Wow, beautiful bow!  Love the color scheme and paint job too.  Really nice

[Selfbowman]

Looks great Dave and those are good speeds also.

[superdav95]

Thanks gents. 

[smoke]

That is a truly lovely bow!  Very, very well done!

[sleek]

I've made a bamboo backed bamboo belly bow with an osage core once. That's a tough build you pulled off. I got to ask though, why did you feel the sinew was needed?

[superdav95]

That is a truly lovely bow!  Very, very well done!

Thankyou sir.  It was a fun build. 

[superdav95]

I've made a bamboo backed bamboo belly bow with an osage core once. That's a tough build you pulled off. I got to ask though, why did you feel the sinew was needed?

Thankyou sleek.  When I initially finished this bow it was just a boo backed and bellied bow at about 38lbs.  It shot just fine and was gonna just leave it as it was but my curiosity took over and thought why not!  It spit out an 400 grain arrow in the high 170’s.   I added about 60grams of sinew to the back and then added the thin kangaroo hide over that.  Then I thought I was done.  I just couldn’t leave it alone.  I kept adding to it little decorations and such.  So it didn’t need the sinew but had some on hand and was more or less just curious on what it would do to the bow if anything.  It did improve performance some too.  It also retained its reflex with added sinew. It’s speed increased with the added sinew by a few fps.  It pulls around 40lbs now or just a hair over that.  Got consistent reading in high 180’s fps with 10gpp arrow.  Was pretty happy with that.   As a side note the idea of Osage core sounds like a great idea.  On this one I toasted the belly lam fairly well on both sides to harden it up a bit.  I did another bow like this one too without any bindings that was glued together with handle power lam of black walnut and thin wedges lams at the v notched tips at each end.  This enabled a strong glue up that didn’t need the bindings.  This bow came in at 45lbs and also shot in the high 180’s at around 9gpp with no sinew.  Anyway I ramble on.  Thanks for looking.  Here’s some pics of that bow similar to this one. 

[sleek]

Well color me impressed. It makes sense why you added the sinew then. Glad you got some positive gains from it. That's good knowledge to keep on hand. I also heat treated my bamboo belly  but I did it by putting the two belly lams ( one for each limb ) into an oven and baking them at 400 until I chickened out, I mean, u til they were golden brown. That bow is narrow but way to stout.

Id not say osage core is a GOOD idea, it's just kinda how it happened for me. A lighter weight wood would certainly be a better option. I had a bow I didn't like so I boo backed it. It turned to be a dog, so I decided to grind the belly down and do a boo belly. It's so heavy now I just let it sit in the closet. The bow is too narrow and the recurves made it unstable. I had to cut the recurves down to keep them from twisting, but of course, that made it even stronger. I think it's around 60@26? I prefer 45@26.

[superdav95]

Yup that’s a puller for sure. Not sure I’d be able to pull much more then that now these days.  FYI. There is an interesting study that was done in the heat treatment of bamboo for structural strength for building and such that was done years ago by someone over in Asia I believe.  They also recorded moe and moisture content too if I recall.  The take away I got from this study was that they found that there was not much benefit over 180 degrees for heat treatment of boo.  I’ve done some of my own crude in comparison tests and found that anything higher then 200 I was breaking limbs or having more failures as the wood was too brittle.  When I heat treat my limbs I use only radiant heat source as well and found positive results vs heat gun forced air.  The radiant heat element worked nice to more control a slow even cook on the belly and back sides.  You’ll notice that only a slight Color change occurs and moisture escapes the end cuts and leaves a hard discolouration almost sugary like substance at the end.  There are lignins and pectins naturally in the boo that harden up and transform it into something that is already good in tension even better and better in compression then before.  You’ll find that a simple fingernail test will prove this too after heat treating the belly.  You don’t want much Color change on the back power fiber side that will be under tension.  Just my thought on this.  Compression side is fine to toast a bit more if putting boo belly lam on your bow.  These bows are essentially no core bamboo bows with power fibers on both belly and back.  I broke a lot of these testing the limits of various heat treats and thicknesses.  Bamboo is crazy strong stuff and I feel I’m just scratching the surface with its potential.  Getting the thickness of the lams down is the biggest thing to get a shootable bow.   My first few lam attempts were all way over heavy and hardly bending limbs.  The glue up adds so much more then expected.   My first successful boo back and belly lam bow was a challenge.  I ended up with a decent shooter but in the end still had to scrape so much of hardened belly lam off just to get the thing strung up.  My thicknesses were tapered too.  From handle area thickness was If I recall I started at around 2.5mm thickness at highest point on the boo for both belly and back slats.  The belly slat tapered slightly toward the tip starting about mid limb to about 1.5mm.  These are rough numbers I’ll have to see if I can dig up my written down stuff if your interested.   Cheers

[JBL]

Amazing work, BRAVO!!

[bassman211]

Shooting those speeds at that poundage is impressive at  the very least.

[superdav95]

Amazing work, BRAVO!!

Thanks jbl.   Much appreciated

[superdav95]

Shooting those speeds at that poundage is impressive at  the very least.

Thanks bassman211.  Yes I was surprised at those speeds being what they are.  I blew up a few along the way here to get the speeds I ended up with in the end.  All worth it for sure.   Thanks again.