Pressure Ridges

[Phil_Glenn@yca.CCMAIL.compuserve.com]

     Cracks and pressure ridges are not a common problem but obviously do 
     occur on occasion. Young Chang soundboards are rib crowned.  It is not 
     necessary to dry  the solid Sitka Spruce as much as with compression 
     crowning, so ridges are not likely to appear do to the manufacturing 
     process.  My feeling is that ridges will sometimes turn into cracks, 
     but it is not inevitable. High humidity causes the wood's cells to 
     absorb moisture and expand. With nowhere to grow but into itself, a 
     ridge could be created. If the  climate then becomes very dry, the 
     opposite occurs and as the cells around the ridge contract, a crack 
     may be the result. Extreme fluctuations in humidity are probably the 
     cause, so stabilizing the environment can often make a ridge 
     disappear.
     I consider ridges more a cosmetic problem than a structural defect, 
     but I would still like to know about these situations.  I want our 
     customers to be glad they chose Young Chang.  All of our pianos have 
     either a 12 or 15 year transferable warranty, so I usually suggest a 
     wait and see attitude when it comes to pressure ridges.   Go ahead and 
     contact me with the serial number and other information and I will 
     file a report for future reference.
     
     Thanks,
     Phil Glenn
     National Service Manager, YCA
     
     (800) 874-2880   Service X110  Parts X 132
     fax/ 253-584-5910
     POBox 99995
     Lakewood, WA 98499-0995


______________________________ Reply Separator _________________________________

     
At 12:46 AM 3/19/99 EST, you wrote:
>I have a customer with a brand new Young Chang PG 150.  It has a nice big 
>pressure ridge running the length of the sound board.  From what I have read, 
>this will eventually turn into a nice big crack since the wood is crushed in 
>this area.  I haven't officially taken a humidity reading, but the environment 
>doesn't seem bad.  The piano isn't sitting in the sun or between two heat 
>vents.  The temperature doesn't seem excessive one way or the other.  Should 
>this be grounds for replacement by the manufacturer?  What are some of your 
>opinions in this matter?
>
>David Porter
>St. Louis, MO 
>
>
     
Hi David,
I seriously doubt that it's grounds for warranty replacement, and so will 
YC. The pressure ridge probably wouldn't be there unless the piano had been 
through at least one humidity high that was considerably above the original 
assembly RH. I don't know if YCs are compression crowned, or rib crowned, 
but it makes a difference. The compression crowned boards form compression 
ridges much more quickly and with narrower humidity swings than rib crowned 
boards. In any case, you'll see lots of compression ridges in new pianos, 
right off the truck, so I doubt that you'll have any luck with a warranty 
claim. 
     
 Ron