Belly rail crown - Why???

[Erwinspiano@aol.com]

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In a message dated 11/24/2002 9:12:34 AM Pacific Standard Time,=20
RNossaman@cox.net writes:


> Subj:Re: Belly rail crown - Why???=20
> Date:11/24/2002 9:12:34 AM Pacific Standard Time
> From:<A HREF=3D"mailto:RNossaman@cox.net">RNossaman@cox.net</A>
> Reply-to:<A HREF=3D"mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> To:<A HREF=3D"mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> Sent from the Internet=20
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>            Dale writes
> >     I see nothing wrong with the beveled rim personally, if my boards ar=
e=20
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> > retaining a good amount crown even when strung I see no reason to induce=
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> > another unnecessary possible strain at the edge of the board by changing=
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> > all the beveled rastens that come through the shop to a flat edge. No,=20
> > I'm not saying you were advocating that either.
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> Hi Dale,
> There's nothing wrong with beveled rims, but if you find no performance=20
> advantage to beveling rims and are building a piano, you wouldn't be too=20
> eager to spend the time to cut the bevel.
   I agree but there has to be some surface cut anyway flat or beveled and A=
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we've discovered through lengthy discussions some things are easier than=20
others to determine as to there actual performance benefit. Stwy's=20
diaphragmatic sound board design is a case in point. Murky water perhaps but=
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as I recall the treble edge rasten was raised to meet the edge of the board=20
so as to eliminate a bending strain by so doing. The idea was that it freed=20
up the board. What's the proof?  Probably subjective ears but hey we all do=20=
a=20
good deal of our authenticating that way I.e. improvements in raw hammers by=
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voicing, tonal improvements from new strings. In the case of the stwy=20
experiment the same type of subjectivity was used. Even if they used same=20
action in 2 different pianos the sound board wood is different, possibly=20
e.m.c.s'. I believe there concessus was it tonally better. I couldn't say.=20
You, Del or Ron O might have A different slant on these findings. I Bet you=20
Do.=20
     At any rate the best judge of that kind of subject determination in my=20
mind woud be the guys in the factory who were so familiar with the old desig=
n=20
compared to the new one that there opinion would carry some real weight
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    In rebuilding, if the bevel is > there, you leave it. The point being to=
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> not go to              unnecessary trouble to incorporate or eliminate any=
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> "feature" that has no clear effect either way.

     Uh huh. I'm with you
     > Also the board is often thinned down to as little as .250 at the edge=
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> > so undue stress once again not desired.
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> Why would you thin the board edges in the first place (except maybe in the=
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> bass if you don't float it), and why would it be less desirable to unduly=20
> stress these edges than it would a thicker edge.=20
>  Tail thinning from the corner,around behind the bass bridge and  clear up=
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> through the curve but leaving the top treble end thicker as you well know=20
> is fairly common practice in boards where tails aren't floated which  is=20
> the majority of pianos that get restored in America.  My personal=20
> experience is that thinning in these areas does provide a significant=20
> performance gain in sustain and clarity in conventionally reproduced  bell=
y=20
> systems. Meaning In my case rib crowned boards at 5 &1/2 to 6% emc
        I think it an important distinction to the readers on the list that=20
particularly You and Del are using techniques that are, at least in some=20
cases, a radical departure from conventional belly replacement. Your focus i=
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completly on belly redesign which is great and many will hopefully=20
incorporate your ideas and find out if this a desirable direction they wish=20
to go.For some the tonal difference may not be what satisfys them compared t=
o=20
what is considered good to them. Also every one has to start somewhere. The=20
redesign cost could be a significant impediment adding cost to an already=20
pricey project.
      It would be good for us who have heard much about the superior design=20
traits in these hybrid board systems to actually experience it for ourselves=
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As yet I've not heard anyone weigh in on this illusive experience. Being a=20
sustain freak myself I'd love to hear the improved sustain and color you bot=
h=20
speak of.

>   As to the stress question the answer is, thick or thin, any unneeded=20
> bending strain should be minimized or eliminated. Isn't Floating a tail=20
> simply a removal bending strains and stiffnesses caused by panel=20
> restrictions due to a clamped edge system?

      And what constitutes undue > stress?
>       again Any unwarranted bending strain


> How is a board stressed more by a rim beveled 1=B0 less than the=20
> angle at which the rim meets the panel under load, than it is by a rim=20
> beveled 1=B0 more? Doesn't compute.
>        Ron N

     I think you misunderstood my thought. Or maybe I did. The rim bevels on=
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stwys roughly equating  1 & 1/2 degrees will mate with a board in the 60ft.=20
crown range with no  load. What I was trying to say was  that a lesser board=
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angle due to string load might more closely match the crown of the board=20
under load. Yes I see your point though.
     It is however interesting as to how much faux crown can be exhibited in=
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an old board only to have it disappear completly upon it's removal from the=20
case. A condition or anomaly I attribute soley to the rim bevel  capturing=20
the rib ends and panel edge. It does have some ,albeit, small influence. Any=
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way I don't dismiss it completly.
    Regards
     Dale Erwin

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