Newbie Bamboo NAF Problem

[2son]

Howdy Everyone!
What a pleasant surprise to find a Forum dedicated to this subject! I'm a "Newbie" to bamboo flute making. I have been making NAF style flutes for some time using different kinds of wood. I've always wanted to try using bamboo, so I have begun a bamboo flute project.
The piece I'm using is 21 inches total length. I have finished the two air holes on either side of an internal "node". The bore is nominally 7/8". The sound chamber right now is 16" from "wall" to flute end. I have an air flue of about 1/32" between the two holes and using a flat-bottomed block to get to the root tone. I'm trying for an F# base tone.
My problem is getting that base tone. No matter how softly I blow, I keep getting that jump to the next higher octave. I haven't had this problem with my wood flutes. But I'm going crazy trying to get that nice stable base note without a "jump" to the next octave! I know you can purposely cause that jump to the higher octave by blowing with more force on a "normal" flute:)
Anyone have some advice? Maybe I should be making the air flue in the block bottom instead of the flute body? Any ideas would be appreciated. I'm getting very interested in bamboo! what a Kooool material! Thanks!

[2son]

I have to say, that learning never ceases with this "interest" ! I got no replies for my issue, but quite understandable:) After many hours of trying to resolve my problem, I finally happened onto the solution. I have no idea why it worked! The physics of air movement through a tube makes my head spin. I'll pass along what I discovered in case it might help some other soul struggling to make that first bamboo flute (Native American Style).
When I've made traditional wooden flutes I always kept a distance of about one-half the bore diameter between the proximal edge (the mouth end) of the True Sound Hole (TSH) and the front or distal face of the internal "wall" inside the sound chamber. I did the same with this bamboo flute. The front of the wall was about 7/16" behind the proximal edge of the TSH for a nominal 7/8" bore. As one of my last desperate fixes, I pushed a 3/8" slice of a wine cork, which fit perfectly in the bore, down to the internal "wall" and glued it in place. This effectively lined up the proximal edge of the TSH with the front face of the internal wall. My problem went away! The base or root note of F# came out nice and clear. No more "jumping" up to the next octave. Hallelujah!
Simple fix, but took days to discover...maybe this will give someone else an option to try if they encounter the same problem.

[cs2sw]

I have to say thank you because I was having the same problem as you.
I figure something like that might had to be done but did not wanted to brake the node.. tried it and it works.. Thanks