<HTML><HEAD><TITLE>Sound board trenching and stuff</TITLE> <STYLE type=text/css></STYLE> </HEAD> <BODY style="BORDER-TOP-STYLE: none; BORDER-RIGHT-STYLE: none; BORDER= -LEFT-STYLE: none; BORDER-BOTTOM-STYLE: none"> <P>Ron,</P> <P>What does the trench do again?   I'm trying to figure out = what a extreme thinning of the board in a small area does?</P> <P><BR>David Ilvedson, RPT<BR>Pacifica, California<BR><BR></P> <DIV style="PADDING-RIGHT: 5px; PADDING-LEFT: 5px; PADDING-BOTTOM: 5p= x; BORDER-LEFT: #000000 3px solid; PADDING-TOP: 5px"> <HR> Original message<BR>From: "Overs Pianos" <SEC@OVERSPIANOS.COM.AU><BR>To= : Pianotech <PIANOTECH@PTG.ORG><BR>Received: 10/15/2005 5:41:14 PM<BR>S= ubject: Sound board trenching and stuff<BR><BR> <DIV align=left>Hi all,</DIV> <DIV><BR></DIV> <DIV>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 cut= ting a full soundboard float.</DIV> <DIV><BR></DIV> <DIV>As someone responded to Dean's suggestion, we've been trenching bo= ards for many years now (since about the mid 90's). Seiler have been tr= enching the entire sound board perimeter for even longer. We tried this= also, but after a serious of experiments over several years the idea h= as evolved to that which you see below. This image is of a Kawai KG6 th= at 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 l= ower than my preference. We've re-cut the notching and refinished the b= oard. The plugged perimeter bolt hole (to the left of image) is a conse= quence of the Oak rim in these early KG series pianos. Oak is a good wo= od 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 re= place the original bolts with heavier gauge zinc plated coach bolts - w= ith dome nuts fitted for looks - to avoid getting cursed-in-the-box som= etime mid century). Normally, if replacing a board, we would use the Ba= ldwin plate mounting system. But when re-crowning an existing board we = leave the original plate mounting dowels in place. We typically will ne= ed 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.</DIV> <DIV><BR></DIV> <DIV>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 o= n the 29th. The New Zealand branch of the APTTA is holding a mini-conve= ntion in Auckland on Oct 29 and 30. Anyone feeling like a tax deductibl= e weekend in New Zealand?</DIV> <DIV><BR></DIV> <DIV>Ron O.</DIV> <DIV><BR></DIV> <DIV><IMG src="cid:kg6trench.jpg@38640.9195466204.708"></DIV><X-SIGSE= P><PRE>-- </PRE></X-SIGSEP> <DIV><FONT face="Times New Roman" color=#0000ff size=+1><B>OVERS = PIANOS - SYDNEY</B></FONT></DIV> <DIV><FONT color=#000000><I>   </I></FONT><FONT color== #0000ff><I>Grand Piano Manufacturers</I></FONT><FONT color=#000000><B= R>_______________________</FONT></DIV> <DIV><FONT color=#000000 size=-2><BR></FONT><FONT color=#000000>W= eb http://overspianos.com.au</FONT></DIV> <DIV><FONT color=#000000>mailto:ron@overspianos.com.au<BR>___________= ____________</FONT></DIV></DIV></BODY></HTML>