Minimum Disruption Tenon

The issue

The normal tuning slide

Supposing you withdraw a normal tuning slide say 10mm (3/8").  Because the walls of the inner slide are not infinitely thin, it introduces a small disruption to the bore - about 11% increase in bore area over that 10mm in length.  Fortunately, the impact is very minor and, under most circumstances, not noticeable.  (The 19th century maker Siccama however provided a sawn-off section of tuning slide to fill that tiny gap.)

You can see the gap introduced here in the image below, where the arrows to the right of "Silver Slides" point.

But at the socket?

Do the same by pulling out the head at the tenon and socket joint at the top of the body though, and the increase in bore area and consequent impact is much greater - typically about 53%.  You can get away with a few mm of such disruption, but a 10mm extension achieved this way would introduce very noticeable problems in accuracy and efficiency.

I've come up with a new tenon-socket arrangement specifically designed to minimise this disruption (hence the grandiose name!); its impact will be about 30%.  That's less than halfway between the disruption caused by normal slides and the normal socket-and-tenon joint, and so permits the tenon to be withdrawn much more for the same overall level of disruption.  So if you are forced to do without a tuning slide, the Minimum Disruption Tenon could well be the way to go.

In the traditional arrangement (which is fine when you have a tuning slide), the cork or thread lapping is on the outside of the tenon.  Consequently the bore of the socket has to be big enough to accept all that. 

In the MDT (note the sneaky introduction of the acronym, as if it had been around since the dawn of time), the tenon is made much thinner, about the same thickness as the bottom of the lapping trough.  The cork is installed on the inside of the socket, instead of the outside of the tenon.  So you can see by comparing the images above, when the tenon is drawn out to tune the flute, the cavity created has a much smaller volume. 

Strong enough?

You might wonder if a thinner tenon can stand up to the forces imposed on it when inserted into the corked socket.  Indeed it can and easily.  Wood is truly wonderful in compression (e.g. railroad ties/sleepers), and can withstand enormous pressure.  Wood is a bit like people - it achieves its best under pressure, but easily comes apart under tension.

Neat and firm, too.

A visual advantage is that when the MDT is extended, no lapping cork is visible (remember, the cork is on the inside of the socket, not the outside of the tenon).  The late 19th century flutemakers pulled a similar visual trick with their integral slides and tenons by putting the cork only at the front of the tenon.

But you'll also find that the MDT is firmer (ie rocks less) than the normal arrangement when extended.  You can see why from the sketch above - all of the tenon inside the socket is supported by cork, not just some of it.

And light!

For those who find holding a flute up for long periods difficult, the MDT approach also has a pleasant surprise in store.  A keyless Grey Larsen Preferred model in Mopane weighs in at just 246 grams - less than 8.7 ounces.  Compare that with a typical English 19th century flute at about 410gms - just 60%.

Belt and braces

Finally, if you do find you are one of those very sharp players that needs the tenon well extended, we can supply a "tuning ring" to your specifications to take up the internal space - et voilá - no disruption at all!  (Actually, we'd recommend making the tuning ring just a little short of the extension you normally play at, leaving a little room for tuning sharp if needed while still taking advantage of the ring.)

Business end of a "Grey Larsen Preferred" model in Mopane, with the head withdrawn
to reveal the clean appearance of the Minimum Disruption Tenon.

Exeunt slides?

Does the MDT make tuning slides a thing of the past?  I think not. 

But if you're up against a tight budget, and particularly if this is not your everyday flute, it's a great improvement over just pulling out the normal tenon and socket, especially when it enables you to buy a better quality flute than you might otherwise have been able.  Or to add a couple of keys you couldn't otherwise afford.  It might also make sense for a flute that you don't expect to be your main instrument, eg a flute in Eb or Bb.

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Created: 4 September 2005