6 piece Asiatic style bamboo bow

[superdav95]

So I decided to do more testing and tweaking of my bamboo bows while I’m waiting for my horn bow to dry. 

This bow is a typical 5 piece Asiatic style bamboo bow with extra added little peice on top of the handle section making it a 6 piece technically. It was built with the belly and back having the power fibers of the bamboo exposed.  Not sure if this will work or not in the end but we shall see it’s fun to experiment. It’s about 57” long and is 6 pieces glued together which will then be wrapped with thread or linen at the glue joints.  Each bamboo strip was ground to approx thickness of .200”.  So total thickness at the height of the crown on both sides is approx .400”.  Each limb is 24” long and approx   1 5/8” wide.  Each limb strip was lightly heat treated to rid the excess moisture and lighten up and strengthen the limbs. The levers are maple as well as the handle.  I used ea40 to do glue up of the bamboo strips and induced some slight reflex.  This thing is only roughed out so far and some more weight needs to come off the levers and scraping of belly for tiller for more weight reduction.  That said it currently only weight 481 grams.  I’m guessing it will be around  under 400 grams when finished.   If it survives tillering it will be a fast bow I think as it will have the benefits of good tension and good compression of the power fibers of the bamboo.  After heat treatment the bamboo added a bunch of strength and became lighter.  I’ve had to tweak this heat treatment process to get it right after breaking several of these bamboo bows so here’s to hoping it works this time.   I’ll post a few pics of the build and bow as it sits now. 

Thanks for looking

Cheers.
Dave

[superdav95]

More pics…

[bownarra]

Cool stuff
 Just be careful about those handle pieces. They will 'pop off' like that. They may be ok if you wrap them. Ideally on this sort of bow you would want the handle piece/s inbetween the 2 boo strips. like a glass bow riser - the riser is a big powerlam and no glue joints will ever fail. The problem is that you have to prep the riser properly...true feather edge fades, and very good taper rate, no thicker than 1/8" 1 inch from the tips.

[superdav95]

Cool stuff
 Just be careful about those handle pieces. They will 'pop off' like that. They may be ok if you wrap them. Ideally on this sort of bow you would want the handle piece/s inbetween the 2 boo strips. like a glass bow riser - the riser is a big powerlam and no glue joints will ever fail. The problem is that you have to prep the riser properly...true feather edge fades, and very good taper rate, no thicker than 1/8" 1 inch from the tips.

Thanks man.  It’s a neat and weird little experiment anyway.  It’s just a test bow so I just used high heat hot melt glue to glue on handle so that I can reverse it quickly and change up my tapers on the new limbs.  The final product will likley have it glued up with a lam riser in between the lams like you say.  Thanks for the tips on this.  Have you ever tried an Asiatic style bow like this with outer fibers of bamboo on both side of the limbs?  I’m going to try scraping the belly to fine tune tiller and see how it goes.  I’m just not sure if on compression the boo will take me scraping it on the belly side when stressed.  My thoughts are that if I get the taper correct like you say I would only have to do a little side tillering without touching the belly much at all for better results.  Do you have experience with something like this? 

Cheers

[Bob Barnes]

I'm following your experiment...it looks like it would have a very heavy draw right now.  Very cool... 

[superdav95]

I'm following your experiment...it looks like it would have a very heavy draw right now.  Very cool... 

Thanks.  It would be nice if it survives.  Ya it’s quite heavy in draw right now.  I’ll get to scraping belly and narrow up the limbs bit more before bending too much.  I’ll post results good or bad of what I find. 

[bassman211]

I will be anxious to see how much limb reflex you lose when you are finished  tilllering ,and  hitting poundage at you draw length.

[superdav95]

Well I got part way thru tiller and got it braced at about 5.5-6” at which point I heard a pop!   I’ll post a couple pics but looks like the failure may have been due to my over toasting the top boo lam a bit.  Under the lift it looks pretty dark and brittle.  I had it rolled out to only 21” so still had a ways to go and it was at 48lbs draw.  I’m guessing that it’s a failure of the top strip or and a combination of a few things on my part.  The other thing I think may have contributed to this is no wraps either at the handle.  Also the hot melt glue I used for purposes of reversible nature of it and swapping out different limbs may have failed.  My hunch however is that this is a simple failure of that particular slat of boo.  The reason I say this is that after making about 20 of these little bows over the past year this is the first time I’ve seen a failure like this at the handle.  The hot melt glue I use for these test bows is quite strong.  Surprisingly strong.  Obviously I never shoot these with out wraps on the glued sections for safety but often I would brace them up for some final scraping and them wrap them. I wonder that maybe the reason it popped off a lift like this at the handle when braced and not when on the tiller tree is that it’s being held at brace for a longer timeframe then when pulling on the tree and releasing almost instantly.  Other failures that I’ve seen in these bows have mostly been splits in the limbs running with the grain.    I believe due to over heating the boo and making it brittle.  It’s a fine balance heat harden bamboo and rid a lot of the moisture without going too far.  If done right though you can end up with a good little quick bow.  Prior to the failure on this little bow it seemed like it was going to survive and hold up.  It lost about half of the induced reflex as seen from the pics.  I’m gonna keep at this concept and try what mike said and taper the strips out to the tips to a thickness of 1/8”. 

Here’s a few pics of where it failed. 

Let me know what you think and your theory’s as to
Why it failed. 

Cheers

[Bob Barnes]

sorry to see that.  I hope that you can figure the break out and reuse most of the parts.

[bassman211]

 That is were they will let go. I have broken a few limbs off  in the same place right in front of the riser.  Though the side profile of your bow looks really nice you can only reflex a bamboo slat , so far before it takes a lot of set, or lets go. Sinewing the back may, or may not help. I never tried one that way.

[superdav95]

So update.  I did an autopsy of this bow and discovered the reason.  It was my mistake not the wood in this case the top boo strip that failed.  I had filed down the top sections of the limbs at where they meet up at the handle to place the top piece onto violated the top limb integrity and it popped off.

So in the end my mistake and will not make that mistake again. 

Here’s a pic of where it pulled up


Cheers

[Bob Barnes]

cool beans...that's an easy mistake to make and an easy fix.  Looking forward to the next one.  Thanks!

[superdav95]

Update on this little bow.  I made new set of limbs and tapered thicknesses towards the tips.  I measured as carefully as I could and measured every 2” along each slat of boo.  Glue up and put about 2-3” reflex induced glue up.  Used stretched bicycle tubes to hold together on glue up.  The problem I noticed with using tubes is that it introduced a bit of twist.  I had to shim and straighten them up and then we’re fine.  Assembly was hot glue method as before.  Tillered to about 26” then put a thing on it.  It’s about 45lbs.  Brace was still low at around 5 3/4” from string to belly at deepest spot.  I then did a few more scrapes and sanding to fine tune the tiller.   It all went pretty fast.  I still had to remove more then I wanted from the belly in scrapes.  I lost about half of the reflex as expected so far.  Have a look here a few pics.  More to come…

[superdav95]

Sorry forgot to mention.   It weighs 450grams at the moment which will likley end up around 400grams when I thin down the and shape the siyahs.  Gonna wrap it tomorrow and shoot it a bit and post another update.

Thanks for looking

Cheers

[Bob Barnes]

It looks great.  congrats.  It's pretty amazing how thin the limbs need to be for 45#.  Looking forward to the rest of the build and shooting results.