boo backed bamboo bow

[superdav95]

Ive taken a brief break from my arrows to build another bow ive had rattleing in my brain for a while. Ive done similar ones like this but this deflex reflex design in a boo on boo is a first for me.  Most of the time spent was figuring out my thickness tapers and selecting the right 2 sections of boo slats.  I plan to side tiller only this bow to retain all of its belly and back intact.   I have a three part video series on youtube that I started and will continue to post updates.  the first link here is the 3rd video showing where im at now with it.  More work to do on it yet.  Im hoping to have something close to 70lbs. if i miss this mark ill shoort for 50lbs.  If i feel like its performing well ill bring it to flats. 


https://youtube.com/shorts/rut6d_2v0Qs?si=njvBsEtxnJg7-KNK


Link for pics

https://share.icloud.com/photos/024rIt--4qhbW2NPBgd50kpqw

[Hamish]

I saw your utoob video of this coming bow. Very promising.

[superdav95]

thanks hamish!  glue lines look good so far so good.   I did a deeper cook on the belly lam prior to glue up.  I figured on the belly that would be best we shall see.  the back i only did a mild cook.  The cook on the belly maintained color change deeper then the back.  The nodes are spaced accordingly belly and back. 

[sleek]

Good luck! I built something similar and it got so narrow I was loosing side stability and it wanted to flip on me. I had to reduce the reflex by cutting the tips, which caused the weight to go back up. Im expecting to see you fight a similar fight.

[superdav95]

Good luck! I built something similar and it got so narrow I was loosing side stability and it wanted to flip on me. I had to reduce the reflex by cutting the tips, which caused the weight to go back up. Im expecting to see you fight a similar fight.

Thanks I’ll need it.  I hear ya. These are a challenge.  I have been able to get lucky with these so far.  I’ve had my share failures too prior to that however.  The neutral plane is also important factor with these type build.  Also careful measures.  I carefully measured my tapers and got pretty close.  Fingers crossed and time will tell if I got them right.   

[Bob Barnes]

Love it.  Thanks for doing this because I want to do the same but in a lighter 45# draw weight.  The side profile looks good.  If it works for you, I plan to do one with just a little more deflex in the middle.   

[Doug509]

Im following along as well.  Silly idea...  instead of removing wood from the belly or sides could you tiller by drilling holes or a vertical hollow groove along the center of the limb?  Starting small and varying size and placement to achieve perfect  tiller?  If anyone can figure this out its you. 

[superdav95]

Im following along as well.  Silly idea...  instead of removing wood from the belly or sides could you tiller by drilling holes or a vertical hollow groove along the center of the limb?  Starting small and varying size and placement to achieve perfect  tiller?  If anyone can figure this out its you.

not sure on that Doug.  i could see it splitting under stress though. 

[superdav95]

Love it.  Thanks for doing this because I want to do the same but in a lighter 45# draw weight.  The side profile looks good.  If it works for you, I plan to do one with just a little more deflex in the middle.   

Thanks Bob.  Its doable but be accurate when measuring your slats for thickness and get them to about .225" mid limb for about 8-10" and then increase taper thickness towards tip and handle. it may seem thin but bamboo is a different animal! The tip thickness on each slat would be .260-.280".  if doing one similar to mine here the handle section leave as thick as you can and then taper from that to mid limb at .225".  if doing a power lam in handle section instead then i would actually thin it down more for the 10-12" the is centered in the handle. This will allow it to conform well and give good glue lines around your power lam.
 This is all of course based on previous builds notes anyways.  results may vary wildly depending on your bamboo quality and crown and heat treatment if used or length of your bow.  Ive always believed in sharing my so called secrets and feel that for the most part its all been done already anyway by somebody out there. I believe that is what this site is for.   the bow im making here had thicker slats of about .250" in the mid sections for a combined overall thickness of just over .500" when glued up.  similar tapers as described above.  i figured it would get me the wiggle room needed to potetially get a a 70lb bow.  Also.  when side tillering be sure to round your edges and almost like a shallow faceted style tiller to help control weight reduction and prevent lifts.   The last bow i did in the weight range you described was a great shooter and used these measures.  it was a much shorter bow then my build here though.  it also incorperated a power lam in handle and the tips.  Ill keep posting updates here too but my utube channel is where the video updates on this will be.   reach out with any questions too.  cheers

[superdav95]

so Ive got this bending not too bad.  its heavy which i want! shooting for 70lbs.  to my eye the inner limb is bending little more on the right (bottom limb) side then the other.  its at around brace height here.  reflex is hold around the 4" mark so far.  I will continue to monitor it.  Im hoping to retain around 3" after its done.  this bow will have semi stiff tips or recurves.  its a tall order for these kind of builds as the tillering is on the side only by choice.  heres a couple pics of the bend so far.  what you guys think.

[Hamish]

Have you seen any of Meadowlark Adventure Gear's Youtube videos? He does lots of boo back and belly bows. He will even do some tillering on the belly, usually only to tweak tiller, rather than large adjustments. Too much work you risk going through the power fibres and exposing the softer fibres to compression.

[superdav95]

Hey Hamish.  Ya I have checked his vids out.  I do like his methodical approach.  He’s made some really nice bows.   He normally uses a core wood more often if I recall and with a power lam riser on his builds.  I’ve done these type builds too with some success and failures. Always some failures.   The biggest issue I had and I think him also was splitting of the thinner strips of boo at the riser ramp.  What ive done to combat this is heat in this ramp on the slat before taken down to final dimensions.  This allowed me to get more safety in that area.   I also heat treat mine more heavily than I think he does.   We shall see how mine goes as I tiller it out more.  You are right about the belly power fibers.  I’ve made that mistake on a previous attempt.  It actually stress fractured on me as I was trying to get it to brace.  Hence the failure on that build.  I also used to torch the belly rind side and I don’t do this anymore since a failure there too.  Cracks developed.   Instead now what I do for the belly lam is do a much deeper cook on the flesh side leaving the rind side alone.  I will go with the cook long enough however till I see a shiny glaze appear on the power fiber side.  This indicates to me that it’s a fully cooked from the inner out to the outer rind where the lignins and pectins ooze out and harden.  When it cools it’s actually like a laqure hard finish on there.  I’ve had better luck doing it this way.