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Do Soundboard Cracks add Stability to Humidity Changes

  • 1.  Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-01-2017 23:11
    Just read an intriguing article called "Soundboard Cracks, compression ridges, and natural Laws of Physics" Jan 1983 by Samuel Nock Phoenix Chapter. 
    In it he makes the case that soundboard cracks allow a soundboard to breathe, and thus not have the drastic movement from season to season, with the result that tunings are more stable. Similar to the installation of a wooden floor and leaving space around the edge for the wood to breathe.
    Anyone else have similar observations? Thoughts? Refutations?

    (Thumbs up imogee here)
    -chris

    ------------------------------
    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
    ------------------------------


  • 2.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-02-2017 00:19
    No. Only insofar as they may be less reactive. but that comes at a price.

    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 3.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-02-2017 01:53
    I would love to change the name of this thread a bit and re-direct it to one of my "issues":

    Somewhere along the way piano manufacturers decided that aligning the grain of the soundboard at 90 degrees to the ribs produced "more", "louder" or "better" sound; this has become the industry standard.  If you go back about a hundred or more years and look at antique pianos (I hope to write a PTJ article about this) you will find that many, if not most soundboards were made with ribs at another angle to the soundboard grain, often at 45 degrees.

    At 45 degrees the different glued woods are better able to expand and contract and the wood fibers are able to absorb the movement without cracking.  In antique soundboards I have examined there are seldom cracks, whereas in more modern 90 degree glued soundboards cracks are common (note: this may be sampling bias as antiques with cracked soundboards may be more likely to have been discarded).

    I have tested this by gluing two pieces of oak together at 45 degrees and using these in a wet-clamping application where the wood part was subjected to saturation and drying over a period of months.  The wood remained completely glued and intact.  Compare this to an old piece of plywood (usually with the grain at 90 degrees) and see how much separation you get.

    If you made two soundboards in otherwise identical pianos with one with ribs at 90 degrees and one with ribs and grain at 45 degrees (the bridge is another issue) what difference in sound would you see (note, this experiment would actually have to be repeated many times to support may conclusion; a test with two pianos would NOT be conclusive)?

    If this has been well discussed or tested I would love to know when and where!

    ------------------------------
    Blaine Hebert
    Duarte CA
    626-795-5170
    ------------------------------



  • 4.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-02-2017 08:54
    Blaine,

    It is interesting that Del Fandrich's research into laminated soundboards at Baldwin pointed to a similar conclusion about the laminate direction. Probably not for the same reason, but it is certainly interesting. 

    I don't go for the crack theory though. As long as the ribs and board are intact, the expansion factor appears the same to me. If they're loose...well then...but that stinks too.

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 5.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-06-2017 20:48

    It is possible-probable, in fact-that an older piano with a soundboard panel having a few cracks may be more "stable." I question the reason given in the references article, however. 


    Most cracked soundboard panels-assuming the manufacturer maintained adequate moisture controls-crack in, or adjacent to, compression ridges. They may be very small compression ridges, but they are usually there. Compression ridges develop during periods of high humidity because the relatively weak earlywood fibers have tried to expand (primarily in the perpendicular-to-grain direction) but, because this expansion is prevented by the ribs, they have instead compressed. 


    Something has to give and it is the earlywood fibers. This shows up in several ways. In areas where the latewood grain is relatively close to being perpendicular the wood cells simply compress. Initially this increases the internal compression within the panel. But, due to compression set over time, the wood fibers change shape and, for a given moisture content, the amount of compression decreases. But there may be no visible damage to the panel. 


    In areas where the latewood grain is not close to being perpendicular-usually at one edge of a given board, next to a glue joint-the latewood grain can be forced up (the rib generally prevents the hard layers from being forced to the downside) and a compression ridge is formed. This can be felt by running a finger back and forth across the affected area. The "washboard" effect will be sharper in one direction than in the other. Compression ridges are indicators: 1) the earlywood fibers have been severely damaged, and 2) a crack is virtually inevitable during a dry season. 


    Once compression ridges are visible we know the soundboard panel has suffered from some amount of cellular damage and it is a pretty good bet that at least some cracks will appear. But the crack is a symptom, not a cause. The compression damage (which may be invisible to the unsuspecting eye) is the problem. 


    At this point the piano may well be more stable. But the reason is because the wood fibers have been damaged and are no longer able to form or maintain the amounts of compression that they were capable of prior to this damage. 


    ddf

    --
    Delwin D Fandrich
    Fandrich Piano Company, Inc.
    Piano Design and Manufacturing Consulting Services -- Worldwide
    6939 Foothill Ct SW -- Olympia, WA 98512 -- USA
    Phone 360.515.0119 -- Mobile 360.388.6525





  • 6.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-06-2017 20:59
    Thank you for explaining that Del. 
    What's curious to me is Ed McMorrow told me that compression ridges are a feedback loop when installing new boards. 
    Is there a conflict in ideals here?





  • 7.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-06-2017 21:09
    I have no idea what Ed meant by that. 

    Wood technology is what it is. Just because a few pieces of wood are used to make a piano soundboards does not alter how they respond to moisture or compression stress. These principles are well known among wood technologists. Most of whom are horrified by what traditional piano makers do to the wood used in soundboards. 

    I ran the "traditional" compression-crowning process by R Bruce Hoadly at a PTG conference a few years back. He flat out didn't believe anyone who knew anything about wood would treat wood that way. 

    ddf

    --
    Delwin D Fandrich
    Fandrich Piano Company, Inc.
    Piano Design and Manufacturing Consulting Services -- Worldwide
    6939 Foothill Ct SW -- Olympia, WA 98512 -- USA
    Phone 360.515.0119 -- Mobile 360.388.6525





  • 8.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-06-2017 21:46
    Hilarious! So when you asked Hoadley what changes to the procedure he would recommend. What did he say?





  • 9.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-02-2017 09:01
    Hard to tell, as those cracks are often accompanied by some degree of rib separation...rib separation means lost structure, as the panel all by itself, ie senza ribs, has almost no cross-grain structure to speak of.

    I have noticed that dead boards are more "apparently stable"...after all, death is the only really stable condition. I say apparently, because, though metrics like global frequency drift and unison drift may be somewhat stable, the amount the various tonal parameters can drift before sounding bad is vastly reduced, relative to a resonant board.

    So one may say, that it can sound stable, mainly because it sounds bad all the time...I think that qualifies as stability...of a sort.  



    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 10.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-02-2017 10:12
    Interesting Blaine, never thought of it from that angle before!
    When it comes to grain direction, and deciding whether to change it or not. I watch for were it points from the bass. It should not hit the bentside(imho), but run parallel to it, aiming for the belly rail.
    #sorryforthepun 
    -chris





  • 11.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-02-2017 11:48
    Jim,

    Kind of like the "bar room" tuning being the most stable of all tunings.  ☺

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 12.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-02-2017 11:53
    hehe

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 13.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-02-2017 11:55
    Blaine,

    Thank you for your comments. I wish that you had posted this as
    a separate discussion. It really did not speak to the original
    question. I wanted to comment on the initial topic,
    but as it has been now convoluted by input that does not pertain
    to the original discussion of soundboard cracks in particular, it
    has dampened my inspiration. 

    I often lurk, but rarely actively participate in the discussions,
    mostly because of time constraints. It is helpful to me to gain
    input of others and remember that I am not the smartest guy
    in the room. I gain a tremendous amount of insight but only
    reply if I feel compelled to do so and think it will add to the
    discussion. Thank you all for your ongoing input. 

    Please keep discussions on topic. If there is something else
    one wished to comment on, please do so, but under a new thread.

    Best.,

    Dave


    ------------------------------
    Dave Conte
    Owner
    North Richland Hills TX
    817-581-7321
    ------------------------------



  • 14.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-03-2017 09:38
    Blaine, why don't you start a new thread with a new Subject?

    ------------------------------
    Dorothy Bell
    Associate, PTG
    retired piano technician
    Bell's Piano Service
    Newton, MA
    617-835-4716
    ------------------------------



  • 15.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-05-2017 22:59

    Notion??
    Article is presented anyways??

    Some editing, geez.

    ------------------------------
    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 16.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-05-2017 23:05

    Now that's interesting!
    Crushed fibers more damaging that cracks?

    ------------------------------
    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 17.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-06-2017 00:08



    7 feet?   Amazing if true.

    Here's an erroneous idea?


    No one noticed the effects of humidity in 1983?


    ------------------------------
    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 18.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-06-2017 00:37
    So his points are:

    What was strange about this article to me, was that he was concerned that the public was misinformed about cracks being bad, and that the piano trade should educate the public by designing pianos with soundboards with expansion joints. 
    So, it would have been nice if he built a piano with expansion joints to show us.
    -chris
    #articlereview​

    ------------------------------
    I have a piano in my Nuclear Fallout Shelter, and my competitors don't. How silly is that?

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 19.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-08-2017 18:53
    Why don't builders cut a kerf inside the perimeter of the rim so the board has room to expand? Was this technique used historically in pianos or harpsichords? How would it affect the performance of the board? If makers dont do this what is the reason?

    ------------------------------
    Jason Leininger
    Pittsburgh PA
    412-874-6992
    ------------------------------



  • 20.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-08-2017 19:05
    "Why don't builders cut a kerf inside the perimeter of the rim so the board has room to expand? Was this technique used historically in pianos or harpsichords? How would it affect the performance of the board? If makers dont do this what is the reason?"

    I think Mason & Hamlin was doing this at least on the BB back in the early '90s with the expansion cut under the molding on the straight side of the board. No Idea if they continued after the current  ownership took over.

    ------------------------------
    Karl Roeder
    Pompano Beach FL
    ------------------------------



  • 21.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-08-2017 21:03
    Plenty of brands these days have the board assembled on the inner rim before it is all glued into the outer rim. You've seen the the various braided velvet ropes etc I'm sure. There is a gap there to "hide". One could call it an expansion gap if one was looking for an expansion gap...but it is simply a manufacturing expediency.

    I don't think its an expansion gap anyway...Why?  Boards don't move across the whole length of the ribs as they expand. If they did, the rib to panel glue joint would be toast. They move only the amount that the glue and the localized resilience will allow. So, I would say that the expansion movement, is taken up in internally compressed force within the restricted parameters allowed by the ribs and glues. If there is expansion, locally in width, it is taken up mostly, I think, by the cellular resilience...ie the elastic zone which exists up to the point where compression failure occurs.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 22.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-08-2017 21:05
    Current Mason's, by the way, are assembled using this inner rim assembly glued in its finished state into the outer rim, which is why you may have seen that gap under the straight side molding.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 23.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-08-2017 22:53
    Pianos have been built -- Marshall & Wendell (Designed by Chickering), among others -- with gaps between the inner and outer rims. I don't know if the purpose of these gaps was to allow for the expansion of the soundboard or not. But they certainly didn't do the sustain rate in the upper tenor and treble any good.

    Pianos with gaps between the individual boards -- Vose? -- making up the soundboard have also been built. The only one I've seen had crown machined into the ribs. Worked well, no "cracks." Although I suppose one could call it "pre-cracked."

    ddf

    --
    Delwin D Fandrich
    Fandrich Piano Company, Inc.
    Piano Design and Manufacturing Consulting Services -- Worldwide
    6939 Foothill Ct SW -- Olympia, WA 98512 -- USA
    Phone 360.515.0119 -- Mobile 360.388.6525





  • 24.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-08-2017 23:02
    Addendum: Your question, "Why don't builders cut a kerf inside the perimeter of the rim so the board has room to expand?" really requires a more complete answer.

    As noted, pianos like the M&W did have gaps between the inner and outer rims. This, however, would have nothing to do with whether or not the soundboard panel would crack. As constructed, a soundboard panel expands or contracts very little no matter the humidity. Because the soundboard panel is glued solidly to the ribs, its motion is constrained by the interface between the panel and the ribs. In short, the ribs simply do not allow the assembly to expand. 

    What happens when the soundboard panel takes on moisture is that it tries to force more crown into the assembly. Since the string downforce prevents most of this, the wood fibers simply compress. And now we're back to the problem of compression set.

    ddf
     

    --
    Delwin D Fandrich
    Fandrich Piano Company, Inc.
    Piano Design and Manufacturing Consulting Services -- Worldwide
    6939 Foothill Ct SW -- Olympia, WA 98512 -- USA
    Phone 360.515.0119 -- Mobile 360.388.6525





  • 25.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Posted 11-09-2017 10:04
    Thanks Del. Makes sense now.  Seems there is no way around the compression issue.  Has anybody taken pictures (with a microscope) of the damaged/crushed cells of a soundboard?

    If the cracks/compression is not caused by expansion of the entire board, but by local and internal stresses, then gaps at the rim, or cracks in the board should not help prevent more compression/cracks from occurring? Cracks will continue to show up in other places providing that the humidity is fluctuating enough?  Am I following this right?

    ------------------------------
    Jason Leininger
    Pittsburgh PA
    412-874-6992
    ------------------------------



  • 26.  RE: Do Soundboard Cracks add Stability to Humidity Changes

    Registered Piano Technician
    Posted 11-09-2017 18:07
    Yes.

    ddf

    --
    Delwin D Fandrich
    Fandrich Piano Company, Inc.
    Piano Design and Manufacturing Consulting Services -- Worldwide
    6939 Foothill Ct SW -- Olympia, WA 98512 -- USA
    Phone 360.515.0119 -- Mobile 360.388.6525