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From: Bobbie Giordano
Date: Tue, 13 Apr 1999 00:41:16 -0400 (EDT)
Subject: Re: leak fix by reed plate bending

On Mon, 12 Apr 1999, James Rossen wrote:
> The strategy as I understand it is to bend the reedplate so it curves
> off the comb at the ends, this shape applying more pressure to hold the
> reed plates against the comb at the reed areas when the plates are
> secured.

It's important to note that there are diminishing returns involved here if
one bends the reedplates TOO much, or in the wrong areas. This is minimized
in short harps, like Marine Bands, but gets more critical as the reedplates
in question get longer. I believe this was recently discussed on Harp-L
with regard to sealing the plates on CX12s and other chromatics. As we've
found with the Renaissance, this is generally not a good idea, and that a
flat plate and a flat comb with pressure points well-distributed generally
achieves the best results.

This can easily be tested using any flat strip of metal, firm plastic, or
such, that can be bend slightly in a gentle arc. While looking at the arced
material edge-on, and pressing down the two ends [simulating the process
being discussed here with reedplates,] you may well see the center of the
material rise off the surface. In reedplate fixing, this would mean a
miniscule but very real airleak in the center, and most played, area of the
harp. Any arching, therefore, must be a whisper's breadth, because the
pressure centers move outward left and right as the ends are depressed and
the center becomes, contrary to the desired effect, LESS forceful and is
raised allowing air to pass through between reedplate and comb.

> I figured that the high end of the plate would be more resistant to
> bending as it has shorter slots and more metal...

Which I agree with completely.

> I found that putting an uniform arc on the plates was difficult, and I
> inadvertantly made a localized bend on the low end of one reed plate.

Yep... it happens! :) As Bluesgeek then reported:

> >What is the best bend profile for the plates? Uniform arc, flat in the
> >center with arc at the ends, an arc at only one end, or what?
> >How much bend? It seems like a good way to describe this is in terms of
> >reed plate end standoff from the comb with the center screw tight.
> >How do you do the bending?
>
> If I remember correctly, Rick Epping only recommends an arc of a couple
> of millimeters. He also suggested trying to center the arc where the
> troublesome leak is found.

Although I think a couple of millimeters is still a bit drastic for an arc,
the second tip seems the wisest course of action, partly because reedplates
AND combs are rarely perfectly flat. RARELY!!! Trust me on this one!!
And as a result, the leaky areas may be different from one harp to the next.
If you must "arch" the reedplates, though, probably a very, tiny, tiny bend
in a uniform manner is best... but I still say flat against flat is the way
to aim for.

And remember... metals can do strange things after production... even just
sitting! For example... our Renny sliders are constructed of stainless
steel blanks, considerably thicker than any other slider material that I
know of, and yet, they have been known to take on a new "twist", literally,
if the blanks are worked into sliders too soon after the blanks are cut.
So they must be allowed to settle for a time and then be ground into the
desired flat form to make perfectly flat sliders.

An interesting phenomenon, but one which we'd have preferred not to have to
learn to deal with. If you think unflat reedplates are a bear to work with,
you ought to try a twisted slider!!

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