Make a soundboard--Measurements

[David Love]

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So just how important is it for function, noise, whatever else, that the ribs fit precisely and snugly in the notch in the rim.  I see all kinds of variation on pianos of high quality.

Dale (and others):  I would be curious to hear your rib crowning procedure when you can.

David Love
davidlovepianos@earthlink.net


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From: 
To: pianotech@ptg.org
Sent: 10/29/2003 8:59:00 PM 
Subject: Re: Make a soundboard--Measurements


        More stuff to add to your list
          I'm not sure where we left off but I think we were into taking out the old board. Glenn ,you posted about the way cool inflater things. Send me some ehh?. ANy way we'll assumne the board is now out.
  Now the next few jobs are to keep the board and all it's pieces together for reference. The next step is to thoroughly clean the rim joint. I sharp chisel will remove the drift wood left on the rim by the board. Take care to avoid digging into the rim. If you've drilled the dowells too deep then they need to be filled with something I use  a, well ,...more dowell in those cases where the dowell driller went to far.  Its wood & it's an easy patch.
      We then use vinegar and water 50/50 and soak the rim joint then applyDamp/wet strips of terry cloth  over this on the rim & a hot iron is applied. Then as  the glue loosens, use flat scrapers and chisels to extricate the gooey sludge as you go. You may have to go round twice on this but a clean joint is critical. Use chisels and more soaking to get at the notches. A heat gun can also be used to fry the soft glue & then easily scrape  off the ash.
  When every thing is clean it's time to lay out you rib stock. On smaller pianos I typically use tight grain sugar pine in the bottom end and white or sitka spruce along the belly rail. I've tried a variety of configurations. 
     I'm not going to attempt to tell you how to dimension your ribs claiming I have some magic formula or superior method.  I don't. But in general I'm making the ribs a bit narrower and a bit taller& crowning them.  I lay out the ribs across the top of the case and over the rib notch,then mark the rib on the under side next to the rim. I cut all the ribs to fit the case for length & then cut the width on the table saw slightly wider than my final dimension. I then run them thru the planer to smooth up the sides & remove the saw marks. Way less sanding later.
 Now it's time to cut the radius but it'll have to wait.. I was on jury duty 2 days Its' time for R&R.
  Please add comments ,additions & alterations
   Dale Erwin



 Michael, Ric Glenn

Well, Michael, I don't know if you'd call it research. List you proposed on measuring things & observations are really probably already outlined in the journal & are just some of the measurements all soundboard installers use. 
  I.E. Measuring string heights, Plate height, bass & treble 88, mark the front corner of the plate & measure the distance fore & aft in mm to the case side. These locate the plate. Note any odd things about the bridges. I.E. inadequate side bearings, strings not going straight to the hitch pins, funky notching angels you don't wish to duplicate. Measure down to the top of the plate at the bosses. This allows you to set the height of you dowels later if you use them.
  Measure the string scale. If funky after unstringing measure string lengths & crunch the no.s. Often note 88 is too short for decent tensions in the last section. You may want to move the bridge as on many older 1800s S&S grands.
   Note the angle of the bridge top to the board. I don't often do this but every piece of info can be helpful.
   (Observation)Look at the thickness of the board thru the action cavity at the belly rail & see how it tapers. (Mental note)
  Observation) Any crown left any bearing left. Does the bearing string still touch the bridge now the strings are removed. is the bridge below the string plane?
  Pull the plate. Pull the bridge pins. make a GOOD pattern noting hole side notch cut. Use a bridge pin bit drilled straight down thru the bridge to locate the mylar pattern. Place mylar (I use 10 mil) over bridge and tap no. 6 pin thru mylar. It make a cleaner hole than drilling thru it.
  I always measure at least first and last string lengths on the long bridge & bass bridge. 
   Very important: Bridge location markers.
   I do this 2 ways. I drill straight down. straight is very important thru the top of the bridge at not 88 with a 3/16 bit and thru the board & into the belly rail. This will help locate the top of the bridge very precisely. I also do the same in the tenor end, drilling into a beam if possible. I also take direct measurements with a metric ruler to the side of the case at each end of each bridge. 
  I also measure the distance from the no. 88  bridge pin hole to the side of the case & stretcher. This eliminates the possibility of getting pattern located  wrong. There are other ways. Rebuilders please chime in.
   Drill out dowels remove treble cap screws. Now the fun part. It's time to knock the board out
   Any body tired yet? More later. going to work
  Later--Dale
  
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