[CAUT] Riblets

[Barbara Richmond]

Ric,

Sorry, I would define it as killer octave syndrome in this piano--
short sustain on one note in particular and generally lacking power in the 
upper half of
the 1st  treble section.

(Mr.) Bill Ballard told me about using a riblet  with great results in the 
treble of a rebuilt Chickering (if I remember correctly).  If he's reading, 
perhaps he'll chime in about the sound before and after.


Barbara Richmond, RPT
near Peoria, Illinois


----- Original Message ----- 
From: "Richard Brekne" <ricb at pianostemmer.no>
To: <caut at ptg.org>; <pianotech at ptg.org>
Sent: Monday, September 24, 2007 3:29 PM
Subject: [CAUT] Riblets


> The Riblets yes.... definitely interesting and worth a try.  Let me  know
> how they work on the Seiler... as I have a similar Seiler with what sounds
> like exactly the kind of sound you refered to in the same place.  Not
> exactly a killer octave syndrom is it.. ?... just a weakish (tubby??)
> thinned out sound.  Not particularly percussive or short sustain... just
> not very nice and full.  Anyways...  to my own idea.
>
> Seems to me that the idea behind these and other schemes... if it is about
> adding stiffness... is that it really is about the downbearing pressure of
> the strings... both in static and in vibrational modes.  I mean where are
> these riblets installed yes ??...
>
> I'm not an engineer... but the idea I had was to use opposing neodymium
> magnets... very powerful things.  Two opposing 45 mm Ø 5 mm thick magnets
> will support about 50 kilos at 2-3 mm distance.  Anyone figuring how much
> load support there is right under the bridge by any given rib will quickly
> understand that an added 50 kilos for what amounts to about 10 grams of
> mass tops is quite a bit.
>
> I did do a very coarse experiment a couple years back on one of these
> little Knudsen pianos we have all over the place here... very easy to
> access the back.  At the time I was more interested in looking at what
> kind of pitch change they would cause when adjusted closer or farther
> apart as part of the whole pitch change for season change discussion....
> so I didnt pay so much attention to what kind of sound difference there
> was created.  Wrong kind of instrument for that anyways me thinks.  In any
> case... strikes me that opposing magnets might have an even better result
> then riblets or other such devices... and to boot one can actually
> <<tune>> their effect by simply adjusting the distance between them.  One
> magnet screwed into the soundboard directly under the bridge... the other
> on a cross beam attached to the bracing so that one can adjust the height
> of the magnet from underneath with a simple screw.
>
> Worth a try anyways...
>
> Cheers
> RicB
>
>
>
>    Well, since my boss, Ed Sutton, has spoken up, here's a sneak peek
>    at a TT & T item from the November Journal.
>
>    If you are going to make riblets, Darrell Fandrich has modified the
>    design (see picture)--he reported to me that by stepping off the
>    back they perform better than the originals (with the curved back).
>
>    Barbara Richmond, RPT
>    near Peoria, Illinois