tongue-shape -> sound impact ? tongue-size calculation?

Profile Image for Janick W. Janick
  • Sun, Aug 10, 2008 12:35 PM

hello to the members of the hank drum collective!

i am new here, but already infected by the "hank-drum-virus". i will try to make my first hank this week during holiday and found a lot of helpful information here. thank you very much for sharing your experience and know how!

So my question is about the shape form of the tongues. is there a noticeable difference in sound comparing the rounded tongue shape versus the straight cut-tongues (like the HAPI)? Has someone experience with the different shapes?

i like the rounded design very much (like the beautiful millton drums) but the straight tongues seems to be the easyer way to cut out (i am not a very talented artificerEmbarassed).

My second question is about the size of the tongues. Does anybody know how to calculate roughly the tongue-size (dependently to the material) to pitch?  Just as a rough pointer for different hank-designs/tunings.  i already googled for "slit- and tongue- drum building tips" but didn't find any solutions yet (but i found some helpful hints in calculating flute holes for PVC-pipes Laughing ).

Thank You and best regards!




Edited Sun, Aug 10, 2008 12:40 PM

Replies to this Topic

Profile Image for forsyte S. forsyte
  • Sun, Aug 10, 2008 2:08 PM

Hi Nick & great having you onboard. Especially since you are a novice just like myself.

My experience so far regarding different shapes is, there isn´t.. At least not so much I´m able to detect it by ear..

About the size.. I have made it extremely simple for myself lately, I just cut the upper part of the tongue to approximately 5cm and then I just let the length decide the pitch. The thickness of the material in my tanks is around 2mm.

Have you been able to find propane tanks in Germany?

PVC-pipes.. I can recommend flutomat at:

Good luck and regards


Profile Image for Janick W. Janick
  • Mon, Aug 11, 2008 12:20 AM

Hi Forsyte,

thank You for Your information. I will cut my first Hank with straight cuts. while learning to handle the material the next one maybe will be in different shape...

To get the tanks i found 2 ways (it isn't as easy as in the usa, no local dealer sells empty tanks):

a) to buy online at a camping-store. (they are not allowed to send fulled tanks, so You will receive a new and empty one. costs for an 11kg tank about 35 Euros + Porto)
b) i bought mine via internet from a tank recycler ( i payed 58 Euros for 2 11k tanks including the porto. The next time i will order only the tanks without the valve. So there is less work and even more security that there is no gas inside.

yeah, the flutomat... maybe in the future we will have an HANKOMAT Laughing

Best regards


Profile Image for forsyte S. forsyte
  • Mon, Aug 11, 2008 4:15 AM

Gasfritzen.. Very useful information! I´ll bookmark that page. With a dictionary I could almost understand all they wrote. Thank you! I have been treated as a completely lunatic while asking around here in Sweden. Buying online will for sure save me from that embarrassment. 

 With straight cuts you can be a little more familiar with the material, and you will for sure save some saw blades. It´s also very dangerous with broken blades bouncing around. Be sure wear all kind of protection!

 We all hope to see/hear your creation in the future (if possible).

Good Luck 2 U.


Welcome to the group Nick, If you are buying from a recycler I suspect they are used tanks that have been previously used for propane. This is a very dangerous tank. Propane is heavier than air and also gets into the metal. You must purge a used tank or have the recycler do it for you in exchange for giving them the the valve. Please be very careful used tanks are very dangerous to cut into unless properly purged.



Profile Image for Janick W. Janick
  • Mon, Aug 11, 2008 8:03 AM

Hello Larry,

thank You very much for Your warning, this is really very dangerous! I asked the recycler about the tanks. All the tanks have been purged (sucked off and blasted out with nitrogen). After that procedure the tanks got a new valve and a safety-certificate.

but to be absolutely shure i'll fill the empty tanks for 2 days with water bevore cutting into it. the water should crowd out potential rests of propane gas.

The next time i'll buy the empty tanks without the valves.

Best regards


Edited Mon, Aug 11, 2008 8:18 AM

Hi Nick,

Ask them if they coat the inside with a rust preventative after sandblasting. New tanks have a coating or use galvanized steel to prevent rust.  If not I would recommend coating the inside yourself before adding any water.


Profile Image for Janick W. Janick
  • Mon, Aug 11, 2008 8:38 AM

Hello Larry,

thank You for the quick response! This is a very good hint. Tomorrow I'll meet my brother in law. He is a professional engineer and has a lot of more experience in those materials than me and he will help me to build this hank.

Meanwhile i simulate different tunings on my sampler. I have seen Your great double-action Milltone-Drum on ebay. This looks real cool! I like the idea of having 2 Drums in different tunings. Instead of the double pentatonic Scale. I am looking forward to have 2 Arpeggio-Drums: (Am7 and Dm7). This would give access to the whole diatonic scale but separated on the 2 drums. But i don't know if the Hank will sound in Am.

So a lot of research is to do...

Best regards


Edited Mon, Aug 11, 2008 8:39 AM


Sounds like you and your brother in law are going to have some fun!


Profile Image for Janick W. Janick
  • Tue, Aug 12, 2008 5:12 AM

Hello together,

yesterday i asked the recycler about the coating and the tanks are coated inside. The tanks had not been sandblasted but blasted out with nitrogen.

Now i have screwed up the first valve and filled the tank with water! So i think i should be safe for drilling and cutting. Another possibility would be to fill the tank with fine sand for cutting into it.

The recycler told me, that they normally fill empty tanks with water bevor they do welding works.

best regards



Profile Image for forsyte S. forsyte
  • Tue, Aug 12, 2008 8:14 AM

Hi Nick & thanks for priceless information! Clever idea to fill with sand.. THAT would for sure make it safe.

Since propane is heavier than air, it could also be possible to put the tank upside down for a couple of days,(after taking away the valve). Maybe including some compressed air to ventilate it.

Larry, Coating.. What would you recommend to coat with? Up to now I have been using some kind of Zink spray (rattle can). Is it something similar you refer to? My tank are galvanized, but I do it anyway.


Welcome aboard Nick,

Looks like everybody has you on the right track.  I have just a few things to add.

Tongue shape - I can't tell the difference in square or round tongues or even some very sloppy jagged tongues with my ears.  Interesting shapes could be cool artistic touch but you would need a plasma or water jet cutter to do it efficiently.  After some early experimentation I make only curved end tongues now.

Tongue size -  I recommend printing Dennis's template and use that as the basis for your first hank. Then branch out from there.  Using the template for the general layout on my first hank, I created thick paper patterns with nice straight sides and perfect curves for each size tongue.  i figured my cutting would be sloppy so it would be good to start with precise patterns. My tongues vary in width from 5CM to 7CM.  Basically the length (mass) of the tongue (oscillator) has the most effect on the pitch.  Oscillator width has more effect on volume and timbre.  Also, when a tongue is set into motion all of the others vibrate sympathetically.  This can enhance or bury the fundamental tone especially on the smaller tongues and complicates scale design and tuning greatly.

The tanks are also (and the hang folks will scoff at this) Helmholtz resonators.  That vibrating mass of air inside the tank will have a resonant frequency that helps determine the upper and lower ranges of a useful scale.  I don't pretend to understand all of this thoroughly but maybe your engineer brother-in-law will.  He can certainly help you figure out a formula for computing tongue sizes.

Tanks - If you plan on experimenting a lot  consider using new tanks from 1 source.  Consistent raw materials will reduce your variables considerably.  Here in the US we get tanks imported from all over the world.  They all have the same general form factor but vary in design detail.  Important differences like bend radii, metal thickness, welding methods and finish that can make 2 hanks of identical design sound dramatically different.  I can buy new tanks here in Austin from at least 4 different manufacturers from Canada, thailand, portugal, and the US and see many more when I look at used tanks.  New tanks sell for under $30.00.



Profile Image for Janick W. Janick
  • Fri, Aug 15, 2008 3:08 AM

hello RP,

thank Your for Your good tips. I have to dig deeper into the oscillator length & with thoughts so i will search the web for more informations. Regarding the tongue-shape we also cut a round-tongue out because it looks more smooth to me.
My brother in law is a precision engineer and not experienced with audio-physics but i am looking forward to contact an sound-engineer for more information in audio-calculation.

I am not sure if the Hank remains a Helmholtz resonator after cutting the tongues into it. Particully when cutting a wide soundhole. But i agree this should be a good way to draw near the scale ranges.

Regardig the raw-material in germany there a only a couple of standard tanks allowed. While measuring and recording my hank i will circumstantiate all the details of the tanks and post it in a few days. best

regards - Nick


Edited Tue, Sep 2, 2008 2:45 AM

Profile Image for Janick W. Janick
  • Tue, Sep 2, 2008 2:43 AM

Hi to all, i just uploaded this file. The sizes worked for my 11kg standard tank. This should give a rough starting point for hank design. The length is taken from the middle of the tongue. - cheers - NickScale Tongue Size length

Edited Tue, Sep 2, 2008 12:19 PM

Profile Image for jay M. jay
  • Sat, Sep 6, 2008 11:33 PM

What do you all thing about tounges that become smaller towards the bottom of the tounge? In my mind a big mass with a small "connection point" would ring a lot longer (and maybe louder) than a straight tounge, or a tounge that go wider at the bottom. That imaginary line from end of cut to end of cut is basically the "spring"... smaller spring on bigger mass = bouncy ride! No matter what you think though, i'm going to try and cut my next hank like this, and see what happens. The smaller tounges at least would benefit from this I think. The bigger tounges may end up ringing for too long and make the whole thing noisey. We'll see.

Edit: Now that I think about it more, i guess the whole tongue acts like a spring, with the end "line" being the more critical section. and having more mass at the tip of the tongue acts like a weight at the end of a springy lever. man, it's hard to describe, but I can see it in my head.

Edited Sat, Sep 6, 2008 11:43 PM


It sounds like a worthy experiment.  I believe there is an ideal height to width (and here width means connection point) ratio for each tongue though.  You can vary the shape of the tongue within some limits .  One limit is the length of the "spring."  Sure, as your imaginary line grows shorter,  it provides less resistance to the mass vibration.  Less resistnce means the mass will vibrate at a lowering the pitch.  Will it vibrate longer?  Well, maybe all of the lower pitch tongues ring a bit longer.

Cheers, RP

Edited Sun, Sep 7, 2008 5:39 AM

Profile Image for jay M. jay
  • Sun, Sep 7, 2008 10:08 AM

ahhh, i see. It would vibrate slower at a lower pitch. So in this way tounge shape would effect pitch a lot. You could tune a hank to some really low pitches with the limited space. Today i'm planning to cut diferent shaped tongues all over a tank just to see what happens. I'll post results when i'm satisfied with it. continue to give suggestions please!


Profile Image for jay M. jay
  • Sun, Sep 7, 2008 7:15 PM

Soo... experiment was a bust. i made a large mushroom shaped tongue and it was so low it was barely audible. I made a "keyhole" kinda shape that sounded fine, but it created 2 little side tabs that I can imagine would mess with the harmonics a bit. looks like straight tongues are the most efficent simply because they don't create accidental tongues. I could have cut a striaght sided hole around the weird shaped tongues, but then you've got extra holes that might also do undesirable things for sound, and whats the point? still sounded about the same as straight tongues.. maybe rung for slightly longer, but not much.

This sounds sooo good and with a Cmajor scale which I didn't think would be possible on  a hank.   I almost think it is a  hoax  "H".

That tongue shape breaks all the rules for me.    So much for ideal height to width ratios.   It does maximize the space between the tongues which tends to reduce unwanted sympathetic vibration.  What else is going on here?





Edited Tue, Oct 14, 2008 7:28 PM

Profile Image for Dave S. Dave
  • Wed, Jun 1, 2011 1:28 PM

Your chart is great.  My problem is that I want to make wood tongue drums and the chart doesn't cover the tongue lengths I need.  Any chance of extending it or helping me make one of my own with the right curve and longer tongue lengths?  It would really help me get started.

Dave,  sorry for the delayed response.  Since this forum is geared more toward steel tongue drums you may have to find another source for your answer.  However, the chart may still be of some use for calculating wooden tongue lengths.  Since the lengths given in the chart are for ~1/10 inch thick steel,  they will be useless for wood.  But the relative proportions of the notes should apply to almost any material.

You will have to experiment with your desired species/thickness of wood to get an idea of the limitations of the material. 

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