What this is
Native American style flutes have a distinctive split-chamber architecture: a Slow Air Chamber at the mouth end, a totem block ("bird") that directs air over a sharpened splitting edge, and an open-pipe bore voiced by six finger holes in a pentatonic minor scale. Drone flutes add a second parallel chamber that produces a sustained tone alongside the melody — like a low-tech bagpipe drone you can shape with your breath.
This packet covers a family of four such flutes, in the most popular keys for the form. Each flute ships with three swappable drone blocks (unison, perfect fifth below, octave below), so the player can change drone tuning without retuning the melody side.
Drone-flute form: elementalflutes.com/gallery. CNC inlay style: broinwood.com. Engineering reference: the flutes repo for NAF K2 empirical corrections from 150+ measured flutes.
The design
Open-open pipe physics with end corrections and Tony's empirical NAF K2 bore-size correction. Hole positions follow pos_from_foot = L_acoustic_corrected × (1 − f₀/f_hole). The drone chamber is a separate parallel bore in the same body, with its own bore_ID, K2 correction, and acoustic length.
Family table
| Member | Key | f₀ (Hz) | Bore ID | L_total | Chamber:bore |
|---|---|---|---|---|---|
| DRN-Am | Am | 440.000 | 0.750" | 21.97" | 20.4 |
| DRN-Fsm | F#m | 369.994 | 0.875" | 24.99" | 21.0 |
| DRN-Em | Em | 329.628 | 1.000" | 27.23" | 20.7 |
| DRN-Dm | Dm | 293.665 | 1.125" | 29.82" | 20.8 |
All chamber-to-bore ratios sit in Tony's 17–21 sweet spot.
Family overview drawing
All four flutes shown to common scale, foot-aligned. Hole positions shift as fundamental changes; total length scales inversely with frequency.
The build
The construction is a hybrid: the bore is cut on a CNC router (in two halves of a split blank, then glued), the round exterior is turned on a lathe, and the octagonal facets and inlay pockets are then cut back on the CNC. Every flute uses the same workflow; only the dimensions in the design table change.
Stock prep
Mill walnut blanks to S4S. Verify long-grain runout under 1:12. Mark center reference lines and drill three 3/16" datum holes per blank. Acclimate seven days.
Split-body CNC
Bandsaw each blank along centerline, plane mating faces, then route the bore profile, SAC pocket, and splitting edge wall on each half using the dowel-and-vacuum fixture.
Glue + lathe round
Titebond II, six clamps, 24-hour cure. Mount glued blank between centers and turn to body_OD_round, leaving a 0.05" facet allowance.
CNC faceting
V-block jig with eight 22.5° rotations. Each pass flattens one facet. After eight rotations the body is a clean octagon ready for inlay.
Tone holes & window
Drill the six finger holes from the foot datum. Plunge the window with a 1/16" upcut spiral and finish the splitting edge with a chisel. Tune each note with a chromatic tuner.
CNC inlay
Pocket each band and the feature panel on the body, then cut matching plugs from 1/16" maple at +0.001" oversize for an interference fit. Glue in with thin CA, surface-sand flush.
Drone blocks & bird
Lathe-turn three drone blocks per flute (unison, fifth, octave). Cut and laser-engrave bird blocks. Slip-fit clearance on drone tenons is 0.005".
Finish & tune
Tru-Oil, 4–6 coats, sand 600 between coats. Cure seven days. Final tune with chromatic tuner; record measured cents error in validation.csv.
The numbers
Bill of materials (excerpt)
| # | Part | Qty | Material | Supplier | Line $ |
|---|---|---|---|---|---|
| 1.1 | Body blank, Am+F#m | 2 | Black walnut | Hardwoods to Get | $44 |
| 1.2 | Body blank, Em+Dm | 2 | Black walnut | Hardwoods to Get | $60 |
| 1.3 | Inlay band stock | 2 | Hard maple | Bell Forest | $16 |
| 1.4 | Inlay feature panel stock | 1 | Hard maple | Bell Forest | $14 |
| 1.5 | Bird block stock | 1 | Black walnut (1.1 offcut) | offcut | $0 |
| 1.6 | Drone block stock | 1 | Black walnut | Hardwoods to Get | $15 |
| 2.1 | Leather lacing | 4 | Leather | Tandy | $6 |
| 2.2 | Tru-Oil | 1 | Tung-oil/varnish blend | Brownells | $10 |
| 2.3 | Howards Feed-N-Wax | 1 | Carnauba+orange oil | Hardware store | $10 |
| 2.4 | Painter tape, 1 in | 1 | Crepe paper | Hardware store | $6 |
| 2.5 | Sandpaper assortment | 1 | Aluminum oxide | Hardware store | $15 |
| 2.6 | Wood glue | 1 | PVA | Hardware store | $8 |
| 2.7 | CA glue, thin | 1 | Cyanoacrylate | Starbond | $10 |
| 2.8 | CA accelerator | 1 | Aerosol | Starbond | $8 |
Full BOM in bom.csv. First-build total: $516 ($193 materials + $245 one-time tooling + $78 hardware/finish).
Tuning & validation
Each finished flute is tuned with a chromatic tuner against the predicted frequencies. Pass band is ±5 cents per note. Measurements are recorded in validation.csv and fed into Tony's per-family corrections database — so the next family in this lineage benefits from this family's empirical data.
| Member | Note | Target Hz | Tolerance | Measured |
|---|---|---|---|---|
| DRN-Am | fundamental | 440.000 | ±5 ¢ | pending build |
| DRN-Am | m3 | 523.251 | ±5 ¢ | pending build |
| DRN-Am | P5 | 659.255 | ±5 ¢ | pending build |
| DRN-Am | oct | 880.000 | ±5 ¢ | pending build |
| DRN-Fsm | fundamental | 369.994 | ±5 ¢ | pending build |
| DRN-Fsm | m3 | 439.999 | ±5 ¢ | pending build |
| DRN-Fsm | P5 | 554.365 | ±5 ¢ | pending build |
| DRN-Fsm | oct | 739.988 | ±5 ¢ | pending build |
| DRN-Em | fundamental | 329.628 | ±5 ¢ | pending build |
| DRN-Em | m3 | 391.996 | ±5 ¢ | pending build |
| DRN-Em | P5 | 493.884 | ±5 ¢ | pending build |
| DRN-Em | oct | 659.256 | ±5 ¢ | pending build |
| DRN-Dm | fundamental | 293.665 | ±5 ¢ | pending build |
| DRN-Dm | m3 | 349.229 | ±5 ¢ | pending build |
| DRN-Dm | P5 | 440.000 | ±5 ¢ | pending build |
| DRN-Dm | oct | 587.330 | ±5 ¢ | pending build |
Known risks
A red-team failure-mode walk lives in risks.md. The headline items:
A-1 Hole 6 (octave) sharp
Tune-step inspection on each flute; capture a per-flute correction if >+5 cents on more than 2 of 4.
A-2 Drone–melody chamber leak
Pre-glue ridge-feel check on bore halves + post-glue isolated melody puff test.
S-1 Walnut splits along glue line
Same-blank halves with matched MC; Type II glue + 6+ clamps; 40–50% RH storage.
E-1 Em/Dm reach for small hands
5th-percentile span check: H1↔H6 must be <6" for the lower-key flutes.
Su-2 Walnut sapwood streaks
Order with explicit 'no visible sapwood' spec; reject if >10% sapwood by area.
F-1 Inlay flush-sand removes too much
Pre/post caliper at each band — diff must be <0.005".
Family members
Each member has the same workflow but its own bore size and total length. Click through for the per-member detail page.
Resources
Sister repos in the open-pipe woodwind cluster: flutes · fujara · transverse-flute · shakuhachi.