Sound board trenching and stuff

[David Ilvedson]

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Ron,
What does the trench do again?   I'm trying to figure out what a extrem=
e thinning of the board in a small area does?

David Ilvedson, RPT
Pacifica, California




Original message
From: "Overs Pianos" 
To: Pianotech 
Received: 10/15/2005 5:41:14 PM
Subject: Sound board trenching and stuff


Hi all,


A couple of weeks ago (can't remember the name of the thread or to whic=
h 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 trenchi=
ng the entire sound board perimeter for even longer. We tried this also=
, but after a serious of experiments over several years the idea has ev=
olved 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 th=
e panel thickness. We fitted rib extensions and re-crown the board, fit=
ted an Overs action and are in the process of a full refinish. We've ke=
pt 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 consequenc=
e of the Oak rim in these early KG series pianos. Oak is a good wood fo=
r rims but it is prone to corroding the fittings. Its not usual to twis=
t off two or three perimeter bolts when removing a KG plate (we replace=
 the original bolts with heavier gauge zinc plated coach bolts - with d=
ome 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 esta=
blish a workable down bearing with a re-crowned panel.


I've taken a series of images of the re-crowning process for this rebui=
ld. 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 wee=
kend in New Zealand?


Ron O.



-- 

OVERS PIANOS - SYDNEY
   Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron@overspianos.com.au
_______________________

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