Bridge Root Spring-Forward

[Ron Nossaman]

> A modified two-part urea-formaldehyde adhesive. The two parts are a 
> liquid resin and a powdered hardener - so it cures like epoxy, it does 
> not dry like wood glue. I could have used Titebond, but my fear 
> of warping during the drying process is one reason I haven't used it. I 
> think maybe Ron Nossaman builds his laminated bridge roots with Titebond 
> - but I'm not sure. Ron?
>  
> I think most manufacturers use an adhesive similar to what I am using.
>  
> Terry Farrell


Yes, I'm using Titebond mostly so I can slop it all over me, 
and likely will, without turning into Swamp Thing. I have to 
leave it in the form for about three days though, to cure, 
which wouldn't do in a manufacturing process. Out too soon, 
they spring back a couple of millimeters. Left in for a week, 
they sometimes curl in a bit. I have no idea why. 
Occasionally, one exactly matches the form a couple of days 
after I've taken it out and cleaned it up, but not often. 
Planing them to height changes them some too. I suspect you'd 
find the same thing in a high volume manufacturing situation. 
I used to try to be very careful about maintaining my design 
speaking lengths even when the unison footprint went 
considerably off center on the bridge. Now, I've decided after 
looking at the results on the scaling spreadsheet, that a 
couple of millimeters length change either way in the lower 
third of the tenor bridge is realistically undetectable. Now I 
put the top two thirds of the scale on the bridge where I want 
it, maintaining design lengths as closely as I can, and center 
the unisons on the bottom third where they fall. Play it where 
it lies. Again, I suspect this isn't unheard of, if not 
advertised, in manufacturing. Horrors!

Ron N