This page contains a video update on shaping the airflow plus some instructions for the building of a Fujara-type bass overtone
flute from household materials - similar to the one pictured left
Sent: 02 January
2007 12:10
To:
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Subject: [junkmusic] PVC and
such>
I've started
building my waste pipe Fujara - it's got a lovely tone already (although I still
need to learn more about fipple cutting !) and just needs holes and a hose. Do
you have any suggestions for the hose part ? I've used the 'quick and dirty'
split-ring and bung fipple, using a retired demi-john cork, by the
way..
I had to devise my own way
for overcoming this issue with thin-walled PVC and it remains an area of
continual RnD refinement for now. It's not strictly part of my paid work so I
can't spend loads of time on it yet although I'm self-employed and
temptation....
I'll try to explain
what I do but I suspect that a few pictures will be a couple of thousand words
worth!
Basically, you need
to make a 'angled' fipple plug (5-10 degrees off horizontal) but the 'angle'
does not extend to the input end as it would if you were to end-blow it like a
pennywhistle. So your plug has the front angled but the back is solid to act as a stopper (in a
trad fujara the windway hole extends to the end of the tube and they block it with a small
piece of leather). With me so far?
The air comes into
the opposite side of the tube from where the fipple is cut. If the flute is
lying flat on a surface with the fipple uppermost, the entry point is from the
underside and some way back toward the blocked end of the flute. Tuning in the
upper overtones can be sensitive to this distance (research a little about plug
positioning on transverse flutes although it's not exactly the same effect) and
don't forget to give the very exit of the fipple plug a 2mm chamfer (45 degrees)
this creates a slight 'curve' in the windsheet and improves tone
To allow access for the air
to the windway, you need to drill a hole through the *tube and fipple plug
together* from the underside so that when you insert the tube, the air can enter
the flute and then can only exit by passing through the windway / edge
arrangement. Make sure the input tube isn't butted against the top of the inside
of the intrument tube, I generally take a wee sice out of the input tube where
it pokes through the inside of the fipple plug to allow the air to exit
smoothly, or drill two differently sized holes so the input tube butts against
the inside of the plug.
Because the fipple
plug positioning in relation to the window determines a lot of the tonal output,
you will need to juggle the overall length of this plug design (where I am at
now) so that it satisfies both the 'transverse stopper' and windway/edge
elements of the positioning. I've in part dealt with this by making the hole
through the tube into a slot allowing me some adjustment for fipple edge
positioning. When I get that right, I'll start messing with the 'transverse
stopper' (for want of a better description)
The construction of
a fujara fipple is something that I am still refining but I am somewhat advanced
in my workings.
Here are some
points to note, bullets save me lots of typing and I'll be happy to try to
clarify.
The ratio of
instrument tube's inner diameter to length should be around 50-55:1 to get the
proper overtone relationship
The size of the
gap where the windsheet exits the fipple plug will largely determine the blowing
pressure and the efficiency of the flute (the breathing tube length and its
diameter also affects) It should be the width of the window but the height is
likely to be just 1-2mm high.
The window
(between the sharp plastic edge and where the windsheet exits the fipple plug)
is longer than it is wide (i.e the longest dimension is along the length of the
tube.)
A fairly standard
window width for a 1.7m (G) instrument with 40mm OD (1.5") tube is somewhere
about 10mm wide and 12-13mm long
The angle of the
plastic edge should be shallow i.e if the flute body is laid horizontal, the
edge angle is about 5-10 degrees down and the flattening extends quite a ways
along the body of the instrument
The edge should
split the airstream approximately 50:50 but you can err on the side of having
more air into the tube than out.
You will therefore need to be conscious of
the angle of the fipple cut and how that directs the windsheet onto the opposite
angle of the edge, this is more diffiult obviously with no direct visual sight
line.
The window gap
between the sharp edge and windway really needs high (3-4mm) vertical walls to
focus the air. You can do this in thin walled tubing by glueing slices of tube
material over the window, building up the requisite height and trimming to
requirements.
Don't have the
breathing tube too long - it greatly increases backpressure
Condensation will
form quickly in the breathing tube - my current design priorities haven't
allowed me to work in a spit valve or spit collector yet - Be
warned!!!!!.
When making holes
be aware that most hole positioning calculations (percentages) assume that you
are using a thicker tube than the 1.5 or 2mm of standard plumbing. I have been
finding commonly that the bottom (83%) hole is generally slightly
sharp.
It's not necessary
to place the holes exactly like a fujara, you can put some on the back if that
suits your whim or physiology - I do this for my left thumb on some
designs
It's not necessary
to use standard penny whistle hole positions - consider using a NAF pentatonic
positioning (not exactly sure how this affects only 3 holes though)
Ok so it's not 2000 words (but gets closer
every time I re-read it!) but I hope that it starts to explain a little of the
balancing act that goes into making all these kinds of instruments Tony. I left
my camera at a friend's house on NY eve but I'll take some photographs when I
get it back in the next days or so.
As I said, despite
having built hundreds of flutes and whistles, the construction of fipples is
something that I am still refining although I am making progress through direct
and applied research. If there are any professional builders here who can
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on the finery of edgetone
mechanics I'd be delighted. I have books &
research material on organ and flute building that tell me *how* to build X
and do give some reasoning behind variations, but I'm looking for one that helps
me *understand* how the various factors interrelate, e.g the relationships
between the window length and width, wall height, windsheet dimensions, cut
angles etc etc and anything which can give calculations or (simple) formulae for
working out optimals in all of these would be brilliant (I'm waiting for
Fletcher & Rossing's 'physics of musical instruments' to arrive as I type).
Design Help 
ur plug has the front angled but the back is soli
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