Fixing broken bars (or trying to tune UP!) - The Experiment

Three bars so far have fundamental frequencies that are too low by approx 30 cents. Now tuning up is really hard, it is possible to do maybe 10 cent by removing quite a bit of material at the end of the bar, but that's about it.

While contemplating the effort involved in redoing the whole bar, the following idea came to my mind: Removing material reduces the stiffness of the bar in the area, and the frequency function is proportional to the stiffness^3. That is why removing only fractions of a mm in the last few steps drops it to the final frequency - or below, if you're not careful. So why not try to give back a little stiffness directly at the node's area, I was asking myself?

Here's how:

 The high B is too low...

 ..as is the high Bb.

 This F has a perfect fundamental, but two nasty peaks at f4:...

...one at E directly below the desired f4 and one at F# directly above; this 7th and 9th interval really sounds nasty, even when the bar gets hit in the center.

Here are the patients: Low B and Bb to the rear, double-f4 in front. Notice the uneven surface of the bar in front, I think that is the reason for the 2 close-to-f4 frequencies.

Now here is the idea: Let's take some of the sawdust, mix it with wood glue and apply this goo directly to the node!

All three patients resting now. I am very keen on measuring the bars again when the glue has dried. I'll give it a week or so, to let it thoroughly dry. If this works out well, then the fear of tuning too low can be somewhat reduced ;).

Stay tuned!