laminated bridge question

[Ron Nossaman]

At 11:50 AM 7/27/98 -0500, you wrote:
>Generalities are important as they apply in this case, if a choice of glue
>has been made on practical grounds. Using hide glue effectively isn't a
>question of changing working style, rather applying the proper technique
>for the product. Thin glue. Sizing. Toothing. Of course hide glue can be
>used (and can be made to work) if it is too thick, and you can skip the
>sizing and toothing, but then you have to fight with the problems and
>limitations created. It is only natural that these limitations are then
>associated with the product, rather than the usage. Why discard the option
>on this basis, even once? 

*A choice of glue has been made on practical grounds, which I stated. It
just didn't correspond to your personal choice by your criteria. The major
limitation I noted with hide glue, as I said, was working time-to-jell. I
see no reason to tooth, size, and glue, say, ten (arbitrarily) laminations
of maple with thin, yes, I do understand, thin hide glue which could very
well jell before I can get the stack in the caul and clamp it up. Instead, I
choose to use Titebond, which patiently waits for me to get everything glued
up, in the cauls, and securely clamped before it sets up. I have also saved
the time that I would have spent toothing and sizing and don't need another
pair of hands to hurry everything into the clamps before it self-destructs.
I see no problem with the reasoning here. I haven't maligned hide glue
because my inability to grasp the concept of sizing, toothing and a thin,
that's thin, glue mix has rendered me incompetent to use the stuff in spite
of it's sterling qualities. Quite the contrary, I use it often. I also use
epoxy and CA on occasion. That doesn't mean that I'm doing another glue a
disfavor by not insisting on using it exclusively. I am not doing museum
restoration work, or historically accurate reproductions. I am free to use
the glue I think is best suited to the application, and under my hands.
Sometimes it's hide glue, sometimes not. Knowledge and the habit of the use
of hide glue weren't accidentally lost overnight, like Atlantis. Hide glue
was slowly abandoned in industry, and the small shops, because something
they considered handier came along. Just my opinion, of course.       


>
>As we are talking about bridges, there is the acoustic issue which I
>hesitate to raise. It might be interesting to compare a solid maple beam,
>with laminated stacks glued with titebond, titebond II, and with hide
>glue. It's quite possible the dynamic properties of the four will be
>significantly different. Not having done this I can't say what might be
>the outcome. On early pianos there is a noticeable acoustic difference 
>when bridges are sawn instead of bent...presumably associated with 
>different impedance parallel to the soundboard.
>
>Stephen

*I don't see a problem with raising the accoustic issue. It could prove to
be a valid point, whatever "it" proves to be. Until someone sets up a series
of experiments, with enough examples of each type of construction to get a
statistically average example of each type, and blind evaluations,
reinforced with measurement by instrumentation it is, however, speculative.
I'd love to see it done. There is also some evidence that research has been
done to attempt to match bridge impedance with soundboard impedance by
varying the lamination mix and/or capping material. I sure would like to see
the test results on this stuff. I suspect there is as much dead-reconning
and speculative guesswork going on as there is hard physics but it would be
great to rummage through the files and pick and choose. 

While you're still here (you are still here aren't you?), I have a couple of
questions. How would you go about slitting a maple plank into a number of
parallel laminations without the laminations being too far apart at the
connected end to be clampable without either breaking the strips loose from
the end, or wasting a foot of maple, or leaving the surfaces too chopped up
to make good joints? How about sizing and toothing here? Can you,
personally, do a bridge this way by yourself, without the extra pair of
hands during gluing and clamping? How many laminations are there in one of
your Viennese frames? What's the minimum radius bend? How many people does
it take to muscle the beast into shape? Just trying to sweep up on the way out.

 
 Ron