Stick Dulcimer version 1.1

STICK DULCIMER

A 3D-printed four-string dulcimer on a broom-handle spine

=========================================================

Held and fretted like a guitar, with a 550mm scale, the same as

the Box Dulcimer. A beech broom handle runs from the pegbox through the

body and carries the string load; the printed parts slide over it and

locate everything. The body is teardrop-shaped, narrow where it meets

the neck and round at the tail: printed walls with a printed soundboard

on top, clamped at its edge by a printed hoop, and a printed back

screwed on underneath.

Acoustic, and made to be heard unamplified in a fairly quiet room.

Licensed CC BY-NC-SA.

The neck carried on straight through the body comes from "Homemade

Banjo Ukulele" by balno on Instructables (2009), also CC BY-NC-SA:

https://www.instructables.com/Home-made-banjo-uke/

Version 1.1. Removed the wedge fretboard, went back to an old flat fretboard design, because of difficulties in screwing/gluing down the wedge fretboard, and also because the fretboard was too high in places.

WHAT YOU NEED

-------------

1 beech broom handle, 28.4mm diameter, at least 770mm long

(see THE HANDLE before buying or cutting)

1 set D'Addario EJ64 loop-end dulcimer strings (.012 .012 .014 .022w)

4 open-gear individual tuners, the classical-guitar kind with a side

plate and a roller (sold in sets of three left and three right;

plate 30mm long, axle 6.2mm, roller 5mm x 28mm)

8 pan-head self-tapping screws 3 x 16mm, for the hoop

6 pan-head self-tapping screws 3 x 12mm, for the back

4 2.1mm nails with small round heads, about 40mm long, for the

string pins: each cut from its point end to 31mm overall

1 3mm nail, at least 35mm long, cut to 30mm for the bar

across the tailpiece's tip

1 guitar strap button, with a wood screw that reaches no more than

12mm past the button's base; or a leather lace instead

(see STRAP)

7 countersunk self-tapping screws 2.2 x 9.5mm, to hold the

fretboard down

2 more of the same screws, for the tailpiece's cover

epoxy putty, for the caps on the bridge and the nut

slow-cure liquid epoxy, for the fretboard's plates and the string

pins; masking tape, and a few strips cut from a bicycle inner tube

1 guitar strap, and a flat leather lace no thicker than 2mm

THE HANDLE

----------

The printed bores are sized for a 28.4mm handle with 0.2mm of

clearance. Broom handles vary, so check yours before printing

anything big:

1. Measure the handle with calipers at both ends and the middle,

twice at each place at right angles. Use the largest reading. It

wants to be 28.4mm, within about a tenth of a millimetre.

2. Print ONE neck segment first, and slide it along the whole

handle. The segment only touches the wood for 20mm at each end,

so those two places are the fit.

Slides easily and stays where you leave it: the parts will fit.

Drops freely under its own weight: your handle is thinner, and

the parts will be loose on it. Try another handle.

Tight or will not pass: your handle is thicker. Try another

handle, or sand the tight places.

The handle runs the whole length of the instrument: from its end in

the head, along the neck, and straight on through the body, where its

tail end takes the cap the strings pull on. Nothing but the handle

carries the strings; everything printed slides onto it and locates.

CUT LENGTH: 760mm, from the end that goes into the head to the

end that takes the tailpiece's cap. Cut both ends square: the strings

pull on them.

Cut it a little long first, and take the last of it off against your

own parts. With the head, the neck, the body, the soundboard and the

hoop on, push the body forward against the neck. The handle's tail end

should then stand 26.7mm past the outside of the soundboard's skirt

at the tail. Mark that, cut, and try the tailpiece: its cap should

bottom on the cut end with the arm lying down in the hoop's slot. A

handle a millimetre long only moves the tailpiece back a millimetre; a

short one leaves the cap against the skirt, so err long.

THE SOUNDBOARD

--------------

A PLA plate, stiffened underneath by two long bars running with the

strings, one either side of the handle, which the bridge bears on. A

shallow trough in its face takes the bridge's base. A skirt round its

edge drops over the body's walls, with notches for the handle and the

heel socket printed in. It is its own part, held on by the hoop, so a

different soundboard can be tried without printing anything else.

THE PARTS, AND HOW TO PRINT THEM

--------------------------------

All in PLA. Each file is already turned the way it prints, so lay it

on the bed as it opens. Orientation matters on every part: it decides

which way the layers run, and the bores are only round in one

direction. The file names are in brackets.

neck segment, print TWO (neck_segment)

Standing on an end face. 50% infill is fine: the segments

carry no string load. The two are identical. When each comes off

the plate, pencil the end that was on the bed.

head, the pegbox (head)

Standing on the end of the scroll, with a brim. No supports.

100% infill. It is the one printed part that carries string

load in bending, so do not skimp on it.

comb (comb)

Base down, fins up. 100% infill.

fretboard plates (plate_1, plate_2)

Flat, with the face that has the shallow pocket and the small

tabs UP. The other face, the one the fretboard sits on, then

comes out as flat as the bed. 100% infill: the glue grooves

and the screws both need solid plastic under them, and at 3mm

thick it costs only a few grams. If you print on glue stick,

rinse the plates in warm water and dry them before assembly, so

the fretboard beds onto clean plastic rather than a dried film.

fretboard, two sections (fretboard_1, fretboard_2)

On its side, either long edge down, with a brim. The playing

face and the frets then print as walls and profiles rather than

as stacked layers, so every fret stands the same height. It is

screwed down, not glued, so it can come off to be replaced when

the frets wear, and it can be printed in PLA or PETG.

100% infill, so the screw heads' countersinks have

solid plastic round them.

nut (nut)

On its front face, the face nearest the pegbox. 100% infill.

soundboard (soundboard)

FACE DOWN, the playing surface on the bed: the plate, the skirt

and the bars then all grow straight up from it, with no overhang

and no supports, and the top comes out as smooth as the bed. Use

a brim. It is printed as a sandwich, solid skins over a firm

core:

30% gyroid infill, 3 walls, 1mm solid top and bottom.

That is stiffer for its weight than a solid plate. Printed

solid, the same file makes a stiffer, heavier top, if a first one

ever sags.

body, the walls with the heel socket (body)

250 x 230mm. Upside down, standing on the face the

soundboard sits on, which is the one flat face it has: the top

of the walls, the top of the heel socket and the tops of the

bosses inside. The holes for the handle and the soundhole then

run sideways, and are pointed toward the top of the print so

they need no supports. 100% infill.

hoop (hoop)

Flat. 100% infill.

back (back)

Flat. 100% infill.

bridge (bridge)

Standing on its base. 100% infill.

tailpiece, and its cover (tailpiece, tailpiece_cover)

The tailpiece stands on its end face, the flat face the strap

button screws into; the cover lies flat, plate down. No supports:

the back of the arm's web is cut at 45 degrees for that.

100% infill: the tailpiece carries every string.

WHICH PRINTER. The body parts were printed on a Sovol SV06 Plus ACE,

with a 300 x 300mm bed. The body, the soundboard, the hoop and the

back are each too big for a 220mm bed, such as a Creality K1's,

whichever way they are turned: they need a 300mm bed. Everything

else was printed on a K1. On a 220mm bed the fretboard sections and

the plates only fit corner to corner; on a 300mm bed they lie square.

THE BODY ON A 300mm BED. It is 287mm long, which leaves 13mm, and

a slicer that adds a brim can take it past the edge. If yours will

not place it laid square, turn the brim off or turn the body on the

bed until the slicer accepts it. Printed turned, it comes out the

same. The soundboard and the hoop have room to spare.

ASSEMBLY

--------

Everything goes onto the handle in order, from the head end:

1. Push the handle's front end into the head's bore until it bottoms.

A small vent lets the air out; if you ever need the handle back

out, push a rod through the vent from the pegbox slot.

2. Slide on the first neck segment, then the second. The flat face

goes up, level with the head's top. At the joint with the head,

check the bed end for a little flare of the first layers and

scrape it off the outer edge, so the joint is flush under your

hand. Put the two segments' PENCILLED (bed) ends at the head and

at the body, so their clean top ends meet in the middle of the

neck.

3. The body. The neck goes into the open channel at the mouth of the

heel socket, flat face up; it only fits one way. The neck stops

about 2mm short of the bottom of the channel. That gap is

deliberate: it takes the plastic's expansion in a warm room, so

do not try to close it.

The body goes on with the socket, the handle passing straight

through its walls at both ends.

Then the soundboard, face up: the narrow notch in its skirt goes

over the handle at the tail, the wide one over the heel socket,

and the skirt drops over the walls. Then the hoop over it, its

cut-away at the neck end, screwed down as THE TOP, CLAMPED says.

Then the back, underneath, as THE BACK says.

Then the tailpiece: push its cap onto the handle's tail end until

the end face bottoms, with its arm lying in the slot at the

tail of the hoop. Push the cut nail through the holes across the

arm's tip. Glue the pins in, as THE TAILPIECE says, and give them

a full day before any string goes on. Leave the cover off until

the strings are on.

4. The fretboard's plates, glued on. This part is permanent, so

dry-fit everything first, and read it all before mixing any glue.

With all the parts on the handle and the neck seated in the

socket's channel, put masking tape over the socket's top where

the second plate's wide end will lie on it, and over the

channel's edges. The plates are glued to the head and the neck,

NEVER to the socket: the second plate's wide end must stay free

to slide there as the plastic grows and shrinks with the room.

The plates line themselves up. Small tabs along their edges drop

down either side of the neck's flat, so each plate goes on in one

place across the neck, centred and straight, and cannot slide

sideways once the glue is on. Along the neck: the second plate

widens where it reaches the socket, and that step goes at the

socket's front edge; the first plate butts against the second.

Dry-fit them that way first. They should drop on without forcing.

Keep the fretboard well away until the glue has cured: do not

screw it on to hold the plates, and do not rest it on them. Until

the neck is drilled the screws stand out under the plates and

would hold them off the neck, and a fretboard lying on fresh

glue can pick up a smear and be glued down for good.

Scuff the head's top, the neck's flat and the plates' pocketed

faces with 120 grit and wipe them with alcohol.

Spread slow-cure epoxy thinly in the shallow pocket on the plates'

underside, and on the plates' end faces where they meet. The

pocket stops 10mm short of the socket's mouth; keep all glue

inside it, and a few millimetres clear of each screw hole, so it

is not pushed up the holes. Do not fill the grooves across the

pocket: they are there to take the excess as the plates are

pressed down.

Lay the plates on, tabs down either side of the flat, and butt

them together. Cover them with one layer of cling film or baking

parchment, which epoxy does not stick to. Wrap the neck from end

to end in inner-tube strips straight over it, each turn

overlapping the last, firmly but not hard; the plates are stiff

enough to spread the pressure between turns. Check the plates are

still butted together and the step is still at the socket's edge,

since wrapping can nudge them along. Leave it a full day.

5. The fretboard, screwed down. Unwrap the neck, peel off the film,

and clean any squeeze-out off the plates' edges. Through each

pilot in the plates, drill 1.8mm on into the neck, 4.5mm deep

measured from the plate's top face and no deeper: a flag of tape

on the drill marks it. Blow the dust out.

Lay the first section, the one at the nut, on the plates, its

holes over the pilots, and drive a screw through the hole nearest

the nut until its head sits just under the playing face. That

holds it in place; then drive the rest. Butt the second section

against the first at the joint and screw it down the same way,

the hole nearest the joint first. Snug the screws and stop: PLA

strips if they are forced.

Do not glue the fretboard. Screwed, it comes off to be replaced

when its frets wear, and the second plate's wide end, with the

fretboard on it, stays free to slide on the socket.

THE BACK

--------

The back is part of the instrument: print it and fit it. It is held by

6 screws into the bosses inside the walls' lower edge. Snug them,

no more: they only hold the back on. With it on, the air inside the

body resonates through the soundhole in its side, the round hole

facing up toward you as you play, and the low notes come out fuller

and louder.

It comes off only to reach inside: to fit a pickup (see PICKUP), or

anything else that needs a hand in the body. Put it back afterwards.

If the bass is ever too strong, partly covering the soundhole tames

it. If it is weaker than you expect, the gaps round the handle are

where the air leaks: a strip of felt or foam tape round the handle at

the soundboard's notch at the tail closes the largest.

THE TOP, CLAMPED

----------------

The hoop clamps the soundboard's whole edge down onto the body's

walls. That stops it rattling, stiffens it, and leaves it removable.

Tighten the hoop's screws a little at a time, in a star pattern, the

way a drum head or a car wheel is done, never one screw all the way.

How firmly is a matter of ear: tighter is brighter and louder.

There are 8 screws, through the hoop and the soundboard's edge

into the bosses just inside the walls' top. The hoop is cut away at

the neck end, where the fretboard's end comes over the body.

THE TAILPIECE

-------------

The tailpiece is a cap over the handle's tail end, with an arm that

reaches forward over the hoop and 32mm in over the top. The

strings pull the cap onto the end of the handle, so the wood carries

them. The arm rests in a slot in the hoop, which keeps the tailpiece

square to the strings: the handle is round, and without the slot the

cap could turn on it. The arm never touches the soundboard itself.

The arm is a tunnel, open underneath. The strings come down from the

bridge, pass UNDER the nail across its tip, and run back inside it,

almost level, to the pins. That turn under the nail is what makes them

fall steeply enough behind the bridge, about 6 degrees, to

press it firmly onto the top.

Each string hooks over its own steel pin, a small-headed nail glued

upright in a hole in the well behind the handle's end. The cover lies

just over the pins' heads and keeps the loops on, held by two small

screws through its flange into the tailpiece's end face. Snug them, no

more.

The pins are glued in for good. Cut each nail from its POINT end, head

kept, to 31mm overall; a millimetre either way does not matter.

File the burr off the cut end so it slides down the hole without

scraping the glue off its wall. The holes are 3mm, wider than

the 2.1mm nails on purpose: the epoxy fills the gap and carries

the load. Butter each nail with slow-cure liquid epoxy, not putty, and

push it down with a slow twist so the air can get out, until it

bottoms, its head about 7mm over the well's floor. Wipe off what

comes up, keep the heads clean, and leave it a full day before

stringing. Without the glue the pins are not strong enough: do not

fit them dry.

To change a string: slacken it, undo the cover's two screws, lift the

cover, slip the old loop off over its pin's head and hook the new one

on, and put the cover back. The other three strings stay at pitch.

Thread the new string under the nail and through the tunnel before

hooking it on.

Cut the bar from a 3mm nail with a hacksaw or bolt cutter, head

and point off, and file the cut ends smooth so they cannot catch a

string.

STRING ORDER

------------

Built for a right-handed player holding it like a guitar, head to the

left.

bottom, nearest the floor: .012 .012 the melody pair, 5mm apart

.014 middle drone

top, nearest your face: .022 wound bass drone

At the pegbox, the two .012s go to the two posts nearest the nut,

the .014 to the third and the wound .022 to the furthest. The

nearest posts give the steepest angle over the nut, which the thin

strings need most.

Suggested tuning: D3 A3 D4 D4 (bass to melody).

TUNERS

------

Check your tuners against the sizes in WHAT YOU NEED before printing

the head. If yours differ, they may not fit it.

Each tuner's axle goes through its own wall into the slot, roller

inside, plate outside. The posts alternate walls. Each plate position

is marked by two shallow dimples and a scribed line along the axles'

height. Sit the plate on the line, mark through its own screw holes,

and drill small pilots there. The dimples show roughly where the

plate goes; they are not pilot holes.

Glue the comb to the head's top face, 25mm ahead of the nut,

centred. Its slots line up with the nut. It must not carry any string:

every string passes through its slot clear of the floor.

STRAP

-----

The head, with its tuners, is heavy, so hung from the tail alone the

instrument dives neck-first. Strap it at both ends.

Tail: either a strap button, screwed into the tailpiece's end face

below the cover, or a leather lace through the hole across the end

of the tailpiece, tied to the strap's end the way the head is.

Head: tie the lace round the head between the end of the fretboard

and the comb, UNDER the strings, the way many acoustic guitars are

strapped at the headstock. Push it back against the fretboard's

end, where the strings stand highest over it, and put the knot

underneath, on the round back. Then tie the strap's end to the lace.

That spot is over the end of the handle, so the strap pulls on the

wood. Never tie round the pegbox beyond the comb: it already carries

the strings, and that is enough.

No string may touch the lace, even with the lace pressed down. If one

does, the lace is too thick, and that string will buzz.

THE NUT

-------

Not glued. It sits in its seat at the head end of the fretboard, held

there by the strings, so it can be lifted out, lowered or replaced

without touching anything else. If the action is ever wrong, the nut

is the first thing to look at, and the bridge the second.

Cap it with epoxy putty exactly as for the bridge, below, and let it

cure fully. It is printed tall on purpose. File the four slots at the

marks on its fretboard face, a little at a time, until each string,

pressed down at the second fret, just clears the first. Slope each

slot down toward the pegbox, so the string touches the nut only at

its fretboard edge.

THE BRIDGE

----------

Not glued. It stands in the trough in the top, held down by the

strings, which pull on the tailpiece, not on the bridge: it only

presses down. The trough holds it square and lets it slide for

intonation, 2mm toward the nut and 4mm toward the tail. The

neck is not tilted to the body, so the bridge's height alone sets how

high the strings stand over the far end of the fretboard.

Cap it with epoxy putty pressed into the rebate along its top and

scraped flush with the ends. Let it cure fully, about 24 hours or

until a leftover scrap files cleanly instead of clogging. Then file

the four string slots at the marks on its face toward the nut. Do not

press slots into soft putty.

It is printed 1mm taller than the strings should sit, so

every slot is filed. Start each one 1mm deep, which puts the

strings 15.8mm over the top, and file deeper only if the action

at the high frets wants lowering. Each slot can also be filed to touch

the string a little further back than the others, for intonation.

THE ACTION IS HIGH TOWARD THE BODY. The fretboard is flat, and the

bridge is tall, to keep the strings well over the top where you strum,

so the strings stand higher over the frets the nearer they are to the

body. It plays, most comfortably in the lower half of the neck. Filing

the bridge's slots deeper, up to 1.5mm below where they start, brings

the strings down a little over the high frets.

Push the body forward against the neck first, as far as it goes: the

body can float a couple of millimetres along the handle, and the

bridge moves with it. Then start with the middle of the bridge's top

550mm from the nut, toward the front of the trough, and move it by

ear.

With a tuner, compare each string's fretted 12th-fret note with its

open-string harmonic there. If the fretted note is sharp, move the

bridge back toward the tail; if flat, forward. Expect it to end up a

millimetre or two behind 550. Once it is right, mark its place on

the top in pencil.

PICKUP, IF YOU WANT ONE

-----------------------

Not needed: the instrument is acoustic. If you do want to amplify it,

a bare piezo disc taped to the underside of the printed soundboard,

between the long bars under the bridge, works. Take the back off to

reach it, move the disc about until it sounds right, and screw the

back on again. A piezo needs a high-impedance input: the instrument

jack on an audio interface or an acoustic amp, or an active DI box.

Into an ordinary microphone input, or a passive DI, it sounds thin.

LEFT-HANDED

-----------

The parts are drawn for a right-handed player, and there are no

left-handed files. The neck and the body are symmetrical, but the

head, the fretboard, the bridge and the tailpiece are not, so

mirroring them in a slicer does not make a left-handed instrument.