Sound board trenching and stuff

[Overs Pianos]

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Hi all,

A couple of weeks ago (can't remember the name of the thread or to 
which list it was posted), Dean May floated the idea of trenching the 
sound board at the rear, adjacent to A1, as an alternative means to 
cutting a full soundboard float.

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. We 
tried this also, but after a serious of experiments over several 
years the idea has evolved to that which you see below. This image is 
of a Kawai KG6 that we're rebuilding at the moment. The trench depth 
is 5 mm, half that of the panel thickness. We fitted rib extensions 
and re-crown the board, fitted an Overs action and are in the process 
of a full refinish. We've kept the original bridges, even though the 
long bridge is a little lower than my preference. We've re-cut the 
notching and refinished the board. The plugged perimeter bolt hole 
(to the left of image) is a consequence of the Oak rim in these early 
KG series pianos. Oak is a good wood for rims but it is prone to 
corroding the fittings. Its not usual to twist off two or three 
perimeter bolts when removing a KG plate (we replace the original 
bolts with heavier gauge zinc plated coach bolts - with dome nuts 
fitted for looks - to avoid getting cursed-in-the-box sometime mid 
century). Normally, if replacing a board, we would use the Baldwin 
plate mounting system. But when re-crowning an existing board we 
leave the original plate mounting dowels in place. We typically will 
need to pack the stringing pillows by up to 5 mm at the mid-board 
area to establish a workable down bearing with a re-crowned panel.

I've taken a series of images of the re-crowning process for this 
rebuild. I'm putting them together for a class I'm giving in Auckland 
on the 29th. The New Zealand branch of the APTTA is holding a 
mini-convention in Auckland on Oct 29 and 30. Anyone feeling like a 
tax deductible weekend in New Zealand?

Ron O.


-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron@overspianos.com.au
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