crowning methods

[Richard Brekne]

Hi Dale..

This, and Terrys post as well,  has got to be one of the most agreeable 
postings I've read on this list about all this from those I know to be 
rib-crown enthusiasts.

Cheers
RicB

    Dale said:

    Terry

    Very well said. You took the words out of my mouth. I *don't think*
    any one is saying the a *rib crowned* board sounds better than a
    *C.C. Board*. I believe Del ,Both Rons , & probably You & now me
    have gone on record as saying so. What has been said is that the
    dependabliltiy of maintaining crown  & mechanical impedance qualitys
    are more dependable over time & less subject to failure. We all have
    our biasis though. But Consider this
    Terry you are right ,most small shop rib crowners I Know Dry down to
    a range 5.5 to 6.5.% E.M.C. So some panel compression is still
    utilized but  crown not dependent on compression that much to form
    crown or maintain it & even in the driest invirons the crown won't
    shrink out of exisistence.
    This is dry. This is equal to an environment of 85 or 90 degrees &
    25 or 30% R.h. Now any body who's lived thru a dry summer knows this
    is dry. 
    Many C..C.Boards are dried to 4% to 4.5%(or less) Which is more like
    100 Degrees plus 15% to 20% R. H. To me this Nevada desert dry.
    This is why the damage to panels In C. C. thru compression will be
    greater given huge swings in climate change. They are more reactive
    because of their inherent panel dryness.

    The other problem with C. C crowning is that it has a very narrow
    range of parameters in order to be successful & live long. I think
    the small shop rebuilder has *way* *more* control over the EMC of
    his/her panels prior to ribbing than most mass produced facilities.
    If I wanted to build a board this way I would be absolutely sure
    that the board was at 4.5%emc.No less &  no more when the board has
    it's ribs pressed on.

    All that being said I've heard many fine examples of both in older
    pianos. Older rib crowned board are out there but far and few
    between. I've heard many newer versions I like equally well.

    I have a 1929 Steinwya B Calif. piano. This C.C board has text book
    crown & bearing. I have documented this when it was apart. I rebuilt
    a 1960 L from Fresno same thing.

    There are no cracks in either board & the tone just floats. Two
    small examples but there are many more. I've also heard Older boards
    with little or no crown or bearing that are magic.   ???

    The reason this can be so is that the mechanical impedance of the
    system is working with that scale,board shape, crown & bearing for
    some reason. I find this especially plausible In old As, 2 & 3.

    I have a 1905 gigantic Ludwig upright that sings like an soprano
    with endless air thru out the scale. It has taller than wide ribs
    and plenty of them. The board is not cracked up. I do not know it's
    history but it's stunning.

    Viva la difference. When you hear something that's working ask why
    ,marvel & observe the ribbing , it's height/width, no. of ribs
    etc this the way we learn from the folks that have gone before. I'm
    grateful to them all. what a great journey.
      
     Blessings--- Dale