ALTO G TRANSVERSE FLUTE - bansuri-style, cylindrical bore

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ALTO G TRANSVERSE FLUTE - bansuri-style, cylindrical bore

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A six-hole cylindrical transverse flute in G. All six holes covered sounds

G4 (392 Hz, A=440). Prints in three parts plus an optional cork-setting

rod. Needs one non-printed part: a natural cork.

Built and playing. Tuning and octaves confirmed on the assembled

instrument.

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WHAT IT IS, AND WHAT IT IS NOT

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This is a copy of a bamboo bansuri in G that I own and like playing -

measured with calipers and reproduced in PLA. Bore, wall thickness,

embouchure size, chimney depth, headspace and all six hole positions and

diameters come from that one instrument as a matched set.

It is NOT an Irish flute. Irish flutes are conically bored, and the cone

is most of where their reedy, focused tone comes from. This is a plain

cylinder, and it sounds like one: sweeter, purer, more open, with an easy

low register and a bright second octave. If you want an Irish voice, you

want a conical instrument, not this one.

What it IS is easy to play. That was the whole design brief. A cylindrical

tube has a genuine harmonic series, so the second octave sits where it

should without being fought for; the bore is fat for its length; the tone

holes are large and vent strongly; and the embouchure is wide with a

shallow chimney, so it speaks at low pressure and lips a long way in both

directions. Those four things together are why the donor instrument is the

one I reach for, and they are what has been copied.

A note on scale. At G4 the tube is around 390mm, which is comfortably in

the range where cylindrical six-hole flutes have always worked well -

fifes, Renaissance traversos, bansuris. The contracting cone earns its

keep on long, low instruments. At this pitch it mostly just costs you

octave stability.

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SPECIFICATION

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Nominal pitch G4, 392 Hz, A=440

Bore 18.0 mm, cylindrical throughout, no taper

Wall 3.5 mm (outer diameter 25.0 mm)

Embouchure 10.0 mm round, 3.5 mm chimney

Headspace 15.0 mm (cork face to embouchure centre)

Embouchure to foot 392.9 mm at nominal slide setting

Tone holes 9.0 mm as printed, ream toward 9.5

Overall assembled approx. 433 mm

Tuning slide +/- 10 mm of travel

Material used PLA, approx. 97 g for the three tube parts

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PARTS

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Head 140.00 mm embouchure, cork bore, slide socket

Body 1 175.00 mm tone holes 1-3 (top hand), slide tenon

Body 2 / Foot 151.86 mm tone holes 4-6 (bottom hand), open foot

Cork rod 88.00 mm optional, sets the cork depth exactly

Longest part is 175 mm, so this fits any common bed diagonally.

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PRINTING

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Layer height 0.2 mm

Perimeters 3

Infill the tubes are hollow shells, so infill barely matters;

40% or more on the cork rod, which gets pushed hard

along its layer lines

Supports none needed on the tubes. The cork rod's flange is a

9.5 mm bridge on each side - either accept a rough

underside, which does not matter, or support it.

Material PLA. Do not use PETG unless you enjoy stringing inside

a bore you cannot reach.

ORIENTATION MATTERS MORE THAN ANYTHING ELSE HERE.

All three tube parts: print DIAGONALLY, with the holes facing UP.

Upright is slow and the sockets suffer. Flat on the bed and the tone holes

sag into ovals. Diagonal with the holes upward is the compromise, and the

reason is that the upper surface of a hole is the one the air actually

works against - it gets the good side of the print. On the head, the

embouchure is that surface AND the one your lip rests on, so it matters

twice.

The cork rod prints standing on its tip, so the pushing face is flat

against the plate.

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THE CORK

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You need one natural cork. A printed plug can be made to work with PTFE

tape, but I have now tried it on two flutes and the cork wins both times.

A printed bore is slightly oval and layer-ridged; cork conforms to that by

nature, holds position by friction, and does not creep while you play.

- NATURAL ONE-PIECE cork, not agglomerated. A composite core crumbles

once you sand through the natural end discs and will never seal.

- Sand it to a light interference fit, roughly 0.5 mm over the 18 mm

bore. SIZE THE CORK TO THE BORE, NOT THE BORE TO THE CORK - bore

diameter is a primary acoustic parameter and opening it up to swallow

a wine cork unmodified would put the whole instrument out.

- 10 to 14 mm long. Longer means more friction and worse fine

adjustment; shorter risks cocking in the bore.

- Cut the embouchure-facing end FLAT AND SQUARE against a bench. That

face is the acoustic termination of the instrument.

- A small woodscrew in the crown-side face gives you something to pull

on, and marked with a pen from the cork's front face it reads

insertion depth directly.

Set it 25 mm in from the crown to start. The head's bore runs its full

length, so you can push from the crown with the rod and push it back from

the tail with body 1 removed.

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FINISHING THE TONE HOLES

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The holes are deliberately printed UNDERSIZE at 9.0 mm and want opening

toward 9.5 mm.

This is not an oversight. Reaming a hole makes it larger, which makes the

note sharper, and there is no way back - so every hole is printed on the

flat side where it can still be corrected. Open them one at a time with a

round file, with a tuner running, and stop when each note is where you

want it.

Do this only once the whole instrument is assembled and the cork is set.

A note read on a part-assembled flute means nothing.

If a hole stays stubbornly flat or stuffy after reaming to size, undercut

it: flare it inward with a round file so it opens out into the bore. That

also only ever makes a hole bigger, so it follows the same one-way rule.

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ASSEMBLY AND TUNING

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The joints are friction fits and are NOT glued. If a joint is loose, a

turn or two of PTFE tape on the tenon fixes it. If a joint is tight, sand

the tenon, never the socket.

The slide joint at the head is meant to move. Nominal setting is 22 mm of

insertion, which leaves about 10 mm of tenon showing between the head's

tail and body 1's shoulder. Pushing in shortens the tube and sharpens;

pulling out flattens. Full travel is roughly a semitone.

THE ORDER MATTERS:

1. SEAL FIRST. Blow with all holes closed and listen for a stable note.

A leaking cork moves the acoustic end of the instrument and every

reading you take afterwards is worthless.

2. CORK BY THE OCTAVE. Compare the bottom note against its overblown

octave. Moving the cork AWAY from the embouchure widens the octave;

toward it narrows the octave.

3. SLIDE BY PITCH. Only now, and only for absolute pitch.

4. REAM, one hole at a time.

Steps 2 and 3 in that order, always. The cork changes the octave

relationship without changing length; the slide changes length without

changing the octave relationship. Do them the other way round and you will

chase your own tail.

If you assemble it and it reads sharp of G, check the slide before you

check anything else - pushed fully home it sits about a semitone sharp,

which is exactly what it is supposed to do.

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PLAYING IT

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Hold it like any transverse flute, left hand uppermost, embouchure rolled

to taste. Hole 1 is nearest the embouchure.

all six closed G4

open 6 A

open 6,5 B

open 6,5,4 C

open 6,5,4,3 D

open 6,5,4,3,2 E

all open F#

Second octave by overblowing, same fingerings.

The native scale is G major. Accidentals come from cross-fingerings and

half-holing, and it is worth knowing that a CYLINDRICAL bore gives weaker

and less well-tuned cross-fingerings than a conical one does. Check them

by ear rather than trusting a chart - on this instrument half-holing is

often the better answer, and the large tone holes make half-holing easy.

The bottom G is a touch weaker than the same note on a conical flute would

be. That is the cylinder, it is normal, and it is the price of everything

else being easy.

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IF SOMETHING IS WRONG

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Will not speak at all, or only squeaks

Almost always the cork. Check the seal first.

Everything is flat

Expected before reaming. Ream the holes, then reset the slide.

Everything is sharp

Slide pushed too far in. See above.

Second octave flat relative to the first

Move the cork away from the embouchure, a millimetre at a time.

Second octave sharp relative to the first

Move the cork toward the embouchure.

One note out, the rest fine

That hole. Ream it if flat; if sharp you have gone too far, and a

thin sliver of tape on the inside of the bore under the hole edge

will bring it back.

Airy, breathy, needs a lot of pressure

Embouchure. Try rolling the flute in or out before touching the

instrument. If it is really the print, the embouchure can be opened

slightly with a round file - but it is one-way, and it sharpens the

whole instrument, so take the slide setting into account.

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LICENCE

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CC BY-NC-SA.

Share it, remix it, print it, sell nothing made from it, and pass on

whatever you change under the same terms.

If you build one, I would like to hear how it turned out - especially the

octaves, and especially if you used a different cork.