Ron O writes: As someone responded to Dean's suggestion, we've been trenching boards for many years now (since about the mid 90's). Seiler have been trenching the entire sound board perimeter for even longer. --------------------------- Just got back from the NPTA convention in Stocholm where this exact subject matter was discussed by Joachim Leonardy from Seiler in his lecture. Unless I totally mistunderstood it was his position that the reasons for doing this exact proceedure were based on an assumption that the wood in the soundboard that lies above a line of force that exists from the highest point of the soundboard to the underside of the panel where it joins to the rim along any given axis is really unneccesary from a structural support perspective. This was at least part of why Steinway and Sons came up with their tapered soundboard. Seiler would do the same thing except the proceedure is very expensive, so they decided to come up with an alternative method of accomplishing more or less the same thing. As I read his comments, this was a way of cutting costs quite a bit at an exceptable reduction in the effectiveness of the scheme comparied to the S&S method. Btw... Joachims lecture was one of the best I've ever heard on the general subject matter of soundboard function and construction... in the sense that it wasnt flooded with a lot of math and physics concepts that go over the heads of 90 % of the audience. Tho it was extremely understandable for the layman average tech on the beat, it was still very well explained, clear, and left nearly everyone there with a much better understanding of soundboard function as he views it. Also, for what its worth. Seiler subscribes to the idea that the highest possible stress levels need to be achieved in the assembly for the best possible and most enduring tone. Seiler takes particular pains to create as much along the grain compression in their soundboards, and use every device to obtain as much compression in both directions as possible, including installing the assembly while very dry to a very tight fit to the rim so that upon taking on humidity end grain support of crown is also in the picture. They also tension the bridge on attachment to the soundboard. Of other interest... Petrof tapers their soundboard planks before glueing them together so that there is a slightly increasing gap between planks towards the middle of two adjacent planks. Their research shows that this proceedure increases the stiffness to mass ratio significantly as I understood Jan Scalas lecture. They also have been doing this for several decades... from before there was any kind of scientific method applied to see if there was any real benifit to doing so. Where they got the idea in the first place I am sure I dont know. Cheers RicB
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