Bridge question

[David Miller]

Looking for some information / background about adjustable vs. not on arched top vs. flat-top instruments.
I recently picked up a TC bouzouki. I am loving having the low end to play around with. However, being the eternal tinkerer, I am already thinking about upgrades I could accomplish. One question I have centers around bridges. It seems to me that one never sees adjustable bridges on flat-top instruments. Is there a reason for this? Couldnt one simply take an adjustable bridge and shape the bottom to match a flat instrument, or is there some reason that adjustable bridges are no good on flat-tops? It seems that there is enough material in an adjustable bridge to do this, but just wanted more information before I go tinkering.

Thanks for any help!

[Mattg]

I'm with you on this. I think an adjustable bridge is a necessity because the action on some flattops can noticably change with the weather. However, the few flattops I've seen do not have the same back angle as a typical archtop so it's a tight squeeze to get a foot, sturdy saddle, thumbwheels and adjustment space under the strings.

I used an old adjustable bridge from a cheap/broken Montgomery wards A style and cut it down to fit my flattop. It was not a typical Loar style bridge it was close. I shaved a bit off of the saddle and even more off of the foot until it fit, there was good contact with the top, and there was room to move the saddle in either direction. My flattop sounds about the same as when it had the one piece bridge but the action is much, much nicer.

I did notice a potential problem, the length of the foot was substancially reduced by flattening out the arch enough to get good contact with the top. I'm not sure if this would affect the tone. Mine sounds nice but I might have gotten lucky. You'd really need to make some careful measurements to make sure that one of the available Loar or Brekke's would work. It seems like it would be a simple thing to make a flat foot that would work with the Loar saddle and the post and thumbwheel hardware.

[8ch(pl)]

If it sounds good I would not worry about the shorter Bridge length.

[Eric F.]

It seems to me that one never sees adjustable bridges on flat-top instruments.

Check out Arches and Bill Davis for flattops with adjustable bridges. I don't know why others do not do this. Maybe a luthier or someone else more expert than I am will chime in.

[mandomadman]

How's it goin' Dave,
Though I'd chime in a thought on this. An adjustable bridge may be a liability on a flat top. Builders may not put one on because the tension on a flat top can't be as great as an arch top. If an adjustable bridge saddle is raised to high the added string tension on the top may cause the top to cave in. The higher you raise your action and increase the distance of the strings from the top the more tension and stress the top experiences. This added tension does produce more volume for the mandolin. Arch tops because of the arch construction handle this extra string tension. Take care, Ron
ps. Just an educated guess. I really don't know why http://www.mandolincafe.net/iB_html/non-cgi/emoticons/coffee.gif

[Mattg]

Madman

I believe that the tension would be the same for the same for a given saddle height regardless of whether the bridge is adjustable or not. I was promoting the idea of the adjustable bridge just give finer action adjustment up or down not just up. It pays to be careful with a flat top, but I simply use a lighter gauge for strings as they have lower tension for a given note.

The problem with a 1 piece bridge is that it can only be lowered by sanding off material from the foot and that it can't be raised back if too much material was removed or if the instrument was subjected to dry conditions and the top lowered.