<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT color=#008000>Comments below:</FONT></DIV> <DIV><FONT color=#008000></FONT> </DIV> <DIV><FONT color=#008000>Terry Farrell</FONT></DIV> <DIV> <SPAN id=__#Ath#SignaturePos__></SPAN> </DIV> <DIV>----- Original Message ----- <DIV>From: "Delwin D. Fandrich" <<A href="mailto:pianobuilders@olynet.com">pianobuilders@olynet.com</A>>= </DIV> <DIV> </DIV></DIV> <DIV>> I was debating with myself as to whether or not I should warn = you about<BR>> this, ultimately deciding that experience is a really = great teacher and you<BR>> weren't jeopardizing any priceless pianos on = your road to discovery. You can<BR>> use a spruce panel as a humidity indicator = but you have to allow it to<BR>> free-float. I.e., you cannot allow it to = come under compression.</DIV> <DIV> </DIV> <DIV><FONT color=#008000>Gee whizz. Nice guy! It was a very good = educational experience. Now how can you free-float a gauge? The only way I can = imagine that is to not put a rib on it, and simply measure the change in length = across the grain. Is that what you have in = mind?</FONT><BR> <BR>> Yes, what you are witnessing is 'compression set.' This phenomenon = takes<BR>> place any time wood cells are placed under compression and are particularly<BR>> observable when the compression is applied = perpendicular to grain. It is<BR>> difficult for people who have a nearly religious = belief in viability of the<BR>> compression-crowned soundboard to understand = just how devastating<BR>> compression set can be to the stability of the = completed soundboard panel.<BR>> Or how quickly compression set can occur. Your = little experiment graphically<BR>> illustrates both the speed and extent to = which compression set can occur.</DIV> <DIV> </DIV> <DIV><FONT color=#008000>I be a believer! I be seen it with my own eyes!</FONT></DIV> <DIV><FONT color=#008000></FONT> </DIV> <DIV><FONT color=#008000>This quickly brings to my mind the sight of = several semis full of (compression-crowned-type) new pianos for a local = "University Sale" that sat for a week in a blacktop parking lot in Tampa Florida in = the full sun during the hot monsoon month of July. Not a pretty thought.</FONT></DIV> <DIV><FONT color=#008000></FONT> </DIV> <DIV><FONT color=#008000>Is it possible this had anything to do with = the negative 1/4" of crown in MY new "famous NY manufacturer" = piano?</FONT></DIV> <DIV><FONT color=#008000></FONT> </DIV> <DIV><FONT color=#800000>"Ideally, your S%$#*&y piano should = reside in a temperate atmosphere where relative humidity ranges from 45% to 65%. = Don't position it in the path of an air conditioning outlet or a heating = outlet. Don't put it near an evaporator cooler or a room humidifier. Don't put it = close to an uninsulated outside wall. .....the instrument subjected to such = environmental insult may be permanently damaged."</FONT></DIV> <P><FONT color=#008000>Again, I be a believer! I be seen it with my = own eyes!</FONT></P> <DIV>> Actually, compression set follows a log curve. If you place a = sample under a<BR>> given amount of compression, compression set starts to = deform the wood<BR>> fibers immediately. This, of course, reduces the amount = of compression<BR>> (pressure on the fibers) and the rate of compression = set decreases.<BR>> Ultimately, the pressure against the wood cells will = deform them to such an<BR>> extent that further compression set is reduced = to virtually (though not<BR>> exactly) nothing.</DIV> <DIV> </DIV> <DIV><FONT color=#008000>So, like, check the weather report before you = have the movers put your piano in their truck - pick a good humidity day!</FONT><BR> <BR>> Keeping a piano with a compression-crowned = soundboard in a hermetically<BR>> sealed environment would not = relieve the problem unless the atmosphere in<BR>> the hermetically sealed = environment were maintained at such a level as to<BR>> keep the soundboard panel = at 4% MC.</DIV> <DIV> </DIV> <DIV><FONT color=#008000>Does a semi in an August Florida monsoon meet = this criteria?</FONT></DIV> <DIV> </DIV> <DIV>> In this environment, of course, the<BR>> soundboard = assembly would not have any crown. The problem of compression set<BR>> is = present any time a panel such as a spruce soundboard panel is placed<BR>> under perpendicular-to-grain compression and this occurs immediately = upon<BR>> returning the newly-ribbed soundboard assembly to normal atmosphere. It is<BR>> only exacerbated by installing a bridge, gluing the assembly = into a piano<BR>> and loading it with some amount of string bearing.</DIV> <DIV><BR><FONT color=#008000>Ouch! Hurts just thinking about = it.</FONT></DIV> <DIV> <BR>> Del<BR> <BR>> ----- Original Message = -----<BR>> From: "Farrell" <<A href="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A>>= <BR>> To: "Pianotech" <<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A>><BR>> = Sent: Wednesday, April 09, 2003 7:00 PM<BR>> Subject: Re: Soundboard = Torture - and Failure!<BR>> ><BR>> > My gauge has been in the shop now for = a week at 45% RH. It did not settle<BR>> back at the two/three-inch crown = position. It is nearly straight, with only<BR>> about ONE INCH of crown. I = thought that because the ribs are so thin it<BR>> would bend quite a bit (which it = did) at high humidity, but not crush the<BR>> spruce panel. Apparently, the = panel suffered quite a bit a damage<BR>> (compression set I suppose) with = just the one several day exposure to high<BR>> humidity. Just imagine what = that would do to a piano soundboard that has<BR>> one-inch by one-inch ribs and = all the strings only allowing it to expand a<BR>> tiny bit. CRUSH, CRUSH, CRUSH!<BR>> ><BR>> > I'm getting the to the point where I = think a good piano should spent its<BR>> life with museum-like environmental = control - nothing less will do.<BR></DIV></BODY></HTML>