Fixing node holes in the wrong spot (Qs Rhonda Taylor)
-----Original Message----- From: Rhonda Taylor Sent: Wednesday, 15 November 2006 12:04 PM To: firstname.lastname@example.org Subject: marimba barsHi Jim,
Our school built 4 marimbas, and on several bars we drilled the holes in the wrong spot!
I was wondering if I just need to throw those bars out and make them again, or if it's possible to use wood filler and drill another hole. (Would they still resonate?)
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If it was me I would drill another hole, but just leave the "wrong" ones as they are. Any sort of filler has the potential to interfere with the vibration of the bar - potentially quite a bit. The hole might have an effect on the tuning, so the bars may have to be slightly retuned after the new holes are drilled. Ironically... Filler or anything else is likely to have very little effect on either the bar's vibration or tuning if it was in the correct spot - ie the nodal position. The wrong spot, ie a part of the bar which is normally in vibration, can be effected much more. The wrong holes may as I said effect the tuning slighly, but you shouldn't see any difference in the bar's ability to create a good long vibration. If in doubt as to the correct spot to drill, try the ole' "dusty node" technique. Sit the bar so it balances freely on some kind of slight ly bouncy surface. Sprnikle with some sort of light dust - I would usually use saw dust that is sitting around from sanding/tuning - and tap the bar in the middle a few times. As you hit it, it should sound a bit, and the vibrations will throw the dust. As you do this more the dust will tend to congregate in a little spot on either end - the nodes - as these are the only spots not vibrating - drill here.
Hope this helps...
answers by Jim MCCarthy - 01/12/2005
For more help on instrument building you can email Jim.