Conical Irish Flute (in D)

# 3D-Printed Conical Irish Flute (in D)

A transverse flute with a cylindrical head and a conical body — the

bore narrows from 22.35mm at the head down to 16.76mm at the foot. That

taper is the whole point. On a stopped-end transverse flute it is what

brings the second octave into tune with the first, and it is what

separates a real Irish flute from a whistle with a blow hole.

Five printed parts. No fasteners, no glue, no supports. About 646mm of

tube, split into four sections so nothing exceeds 202mm.

---

## What you get

| File | What it is |

|---|---|

| ConicalFlute_Headjoint.stl | Head. Embouchure, thick-wall boss, socket at the tail. 130mm |

| ConicalFlute_HeadExtension.stl | Plain tube. Tenon up, socket down. 132mm |

| ConicalFlute_Body1.stl | Upper body, top-hand holes. 182mm |

| ConicalFlute_Body2_Foot.stl | Lower body and foot, bottom-hand holes. 202mm |

| ConicalFlute_StopperPlug.stl | The cork. Tapered plug, wrapped with tape |

Assembled, the foot sits 510mm below the centre of the embouchure.

Two things are deliberately left for you to finish by hand, and both

only go one way, so neither can be got wrong permanently:

- The joints are sized to come out slightly loose, and are taken up

with tape. Printers differ by more than a joint's worth of clearance,

and a joint that arrives too tight splits a socket — which is not

recoverable, whereas loose is a wrap of PTFE.

- The tone holes are printed undersize at 9.5mm. Enlarging a hole

sharpens its note, so they can only be corrected upward. See the

tuning section.

---

## Printing

PLA, 0.2mm layers, 3 perimeters. Tested on a Creality K1.

**The two hole-bearing sections print diagonally, tone holes facing

up.** Printed upright they are slow and the sockets suffer; printed flat

the holes sag. Diagonal is the compromise that works.

The head and the extension have no tone holes, so they can go either

way. Vertical gives a rounder bore and cleaner sockets, which matters

here — the plug has to slide in that bore and two joints depend on it.

At 130mm that is not a long print.

The foot section is the longest part at 202mm. Give it a brim.

The plug is small; print it standing on its flat sealing face, and

print it solid. Sparse infill is not airtight, and the plug is the

closed end of the instrument.

---

## Assembly

1. Order. Head, then extension, then upper body, then foot. Each

joint is a tenon into a socket — firm hand pressure, no glue anywhere.

2. Expect to need tape. The joints are meant to arrive slightly

loose — see above. Wrap PTFE tape round each tenon, building it up until

the joint holds firmly under hand pressure.

If a joint comes out too tight on your printer, sand the tenon, not

the socket. It is the accessible surface, it is the cheaper part to

ruin, and forcing a tight tenon is how sockets split.

Check the joint still seats fully home after taping. If the tape stops

it closing, the assembled length changes and every hole shifts down the

tube.

3. Do not glue the joint below the embouchure. That one is a

tuning slide. Pulling it out a few millimetres flattens the whole

instrument, which is how you bring it to pitch or match another player.

It is the same joint a wooden flute puts a metal slide on.

4. The cork. Wrap the plug with PTFE tape until it slides firmly

rather than freely — too loose and it creeps while you play, too tight

and you cannot adjust it. Push it in until its face sits about 22mm back

from the centre of the embouchure hole. That is the usual rule of thumb:

one bore diameter.

The handle is there so you can pull the plug back out again. Trim it off

once you have settled on a position.

Check the seal before anything else. Blow with all holes closed and

listen for a stable note. If it is breathy or unsteady, the plug is

leaking — add tape. The plug is the closed acoustic end of the flute, so

a leak there does not merely waste breath, it moves the effective end

and puts the whole instrument out.

A wine bottle cork, cut down to 15–20mm and trimmed to fit, is a better

long-term stopper than the printed plug: natural cork conforms and keeps

conforming, where taped plastic loosens over time. Find the position

with the adjustable plug first, then replace it.

---

## What it sounds like

It plays a D major scale, D4 up to C♯5, on six holes, with the usual

cross-fingerings available for C natural and F natural.

Measured on first assembly — holes unreamed, cork untouched:

| Fingering | Measured | Wanted |

|---|---|---|

| all closed | 290 Hz | 293.66 |

| 5 closed | 325 | 329.63 |

| 4 closed | 358 | 369.99 |

| 3 closed | 380 | 392.00 |

| 2 closed | 440 | 440.00 |

| 1 closed | 485 | 493.88 |

| all open | 525 | 554.37 |

| all closed, overblown | 595 | 580 |

A little flat — worst about half a semitone on two notes, most within a

third. That is well inside what an embouchure adjusts on the fly, and it

is perfectly playable as it stands.

Your numbers will differ. Embouchure, cork position and how firmly

your joints seat all move these.

The holes are printed deliberately undersize at 9.5mm, so everything

lands flat rather than sharp. That is on purpose. A hole can be made

bigger and never smaller, so the instrument is designed to be approached

from below and corrected upward with a file.

---

## Tuning it, if you want to

Only worth doing if something bothers you. Follow this order — two

adjustments and six holes is a lot of ways to go round in circles.

1. Cork, by the octave. Play all-holes-closed and its overblown

octave, and move the cork until they agree. The cork changes the

relationship between the registers without changing the length.

Convention says moving it away from the embouchure narrows a wide

octave — move it 2mm and check which way your instrument actually goes

rather than taking that on trust.

2. Slide, by pitch. Now bring the whole flute to concert pitch by

pulling the head joint out or pushing it in. This changes length without

changing the octave relationship, which is why it comes second: do it

first and the cork adjustment undoes it.

3. Holes, last. One at a time, round file, tuner. Enlarging a hole

sharpens its note. Target is about 10mm.

If the bottom hand feels like a stretch, do not ream those holes

wider — undercut them instead, flaring the hole inward into the bore

with the file. That vents the hole better without growing it on the

outside, where your fingers are.

---

## Hand reach

The quiet advantage of a conical bore, and worth knowing about.

A conical flute is about 13% shorter than a cylindrical one at the same

pitch, because the narrowing bore raises the pitch. Everything moves up

the tube together: the lowest hole sits roughly 60mm closer to the

embouchure than on a cylindrical D flute, and the widest gap in the

bottom hand shrinks by about 6mm.

If you have played a printed cylindrical flute and found the bottom hand

a reach, this is noticeably better.

---

## Credit

The hole positions, taper ratio and overall length are copied from a

cheap mass-produced wooden conical Irish flute of unknown make, measured

and checked for tuning before anything was designed. The embouchure

geometry comes from an earlier cylindrical Irish flute of my own, itself

derived from a Low D whistle fipple.

One thing worth passing on if you design a conical flute of your own:

do not calculate the length from the wavelength. The reference

instrument is 510mm and plays a true D, where the cylindrical formula

demands 584mm. A contracting bore raises the pitch, and the arithmetic

that works for whistles will hand you a flute 74mm too long.

Designed in OpenSCAD. Licensed CC BY-NC-SA.