A Repair for Cracked Heads and Barrels

One of the problems the wooden flute player fears most is a crack, and especially a crack in the head or barrel section of the flute.  This has been a major problem for the wooden flute until the invention of my New Improved Tuning Slide.  Nonetheless, we still have to deal with old flutes with the problem, and many modern flutes made according to the old system.  The head below, from an early 19th century Clementi C.Nicholson's Improved illustrates the problem.  Incidentally, the combing on this flute head was characteristic of Nicholson's flutes, but certainly complicates any attempt at neat crack repair!

The problem occurs because normal and natural movement in the wood is impeded by the presence of the metal liner.  Unlined sections in the same flutes and indeed much older flutes rarely crack.

The problem is worse in this flute as the crack has chosen to go through the embouchure.  This is quite common, as the embouchure represents a weak spot in the fabric of the timber.

Several things happen when a crack passes through the embouchure:

  • the width of the embouchure is increased by the width of the crack
  • the metal liner protrudes into the embouchure chimney on one or both sides
  • leakage through the crack is more common and more troublesome.
In the case in question, the crack chose the very worst place to break through - right near the middle of the blowing edge.  

The discontinuous surface and the additional hurdle presented by the brass liner jutting into the hole gives the air molecules rather too much to think about as they rush past at high speed.  This conspires with the leakage (in both head and barrel sections) to reduce the responsiveness of the flute considerably.

Previous repair methods

Previous repairs for cracked heads included pinning, stitching and flush-banding - all methods designed to force the crack closed again.  Because that usually turned out not to be possible, the remaining gap was filled, either with a strip of wood, or a hard or a pliable filler.

The problem with these approaches is that they didn't attack the problem at its source, but simply tried to deal with the symptoms.  Because of that, the repairs tend to generate as many problems as they solve.  Classic problems include:

  • cracks that open up with changes in weather
  • leakage between the wood and liner
  • misshapen embouchures
  • unsightly repairs
  • pinning that pulls out or splits the wood further
  • new cracks forming elsewhere

The Solution

The problem is that the wood has shrunk too small for the liner and this is where the solution is to be found.  In my experience, the only long-term solution is to remove the liner, glue the cracked wooden tube back together, bore it out to re-admit the liner with neither leakage nor stress and finally reinstall the liner .  (This is obviously something you don't try at home!)

The same head after repair (compare with the first picture).  The flute now speaks enthusiastically and richly.

The Prognosis

Because the old wood is unlikely to shrink significantly more and because it is reassembled without stress, the repair should be permanent.  Because the gap is closed during the gluing process, the repair can be invisible for practical purposes.  If the crack runs through the embouchure, the embouchure will revert to correct size and geometry, and its surface can be returned to as-new condition.

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