Top sinkage?

[shiloh]

Hi everyone,

Would someone please address "top sinkage" for me? Specifically, on an old instrument which is stable, does it matter?

What are the cons? (I can't imagine there are any pros!) For example, with the top sinkage in the bridge area (common), wouldn't that mean the action is "lower" and possible buzzing can occur? Is sinkage worth fixing? Can it be fixed?

If you have a really good sounding instrument is the sinkage worth dealing with? Can you just ignore it?

I realize that a mandolin is an instrument "as a whole" so one thing effects another.... Top sinking = bridge lower = buzzing = need to dress/change frets = ????

Thanks

Jill

[F-2 Dave]

I'd get it to a luthier. Top sinkage can be caused by a brace that has come loose and is easier fixed sooner rather than later. Left unchecked, it can destroy the top on your mando. I don't know what amount of sinkage is acceptable on older instruments. If it truly is stable, you may be able to get by with a good set up. Maybe some experts will chime in with some good suggestions, but if it was mine i'd take it to a luthier that knows mandolin construction.

Good luck.

Dave

[chriss]

+1 to getting it fixed now. (you might want to move this over to the repairs/builders section??)

Keep in mind that there's like 200 lbs of tension on those 8 strings, and those strings are strung over the top of the bridge, with the result that the bridge is pressing down on the top with a good deal of pressure all the time. Maybe a luthier can give us an idea of what sort of range of pressure we're talking about. I'd venture an uneducated guess of 30? 50? 70? pounds? I might be way wrong and it obviously varies from instrument to instrument but you get the idea I hope.

From my experience I'd think you're better off getting it fixed now and not wait. I've heard from several people that it's not very common that sinkage is completely stable. It usually progresses with time. The "progression" can be either gradual or cascading/catastrophic (ouch, bad words but mechanical engineers would use 'em) or some combination of the 2.

-- If the progress is gradual, the bridge sinks as the top sinks, and usually strings start buzzing on frets. If you try to keep the string height up, you increase pressure on the top again, increasing the odds of further sinkage.

-- As one tone bar lets go, the others are subject to more strain. This can lead to the so-called "cascading failure" - the "catastrophic failure" - being that the majority of the underlying structural support lets go all at once one day. If it goes this way, the top often collapses and usually cracks and/or breaks.

I went thru something like this with my 35 yr old Ibanez 511 that I like very much. 3 years ago a tone bar was coming unglued, resulting in 1 side of the top sinking enuf that the strings started buzzing. I took it in for a setup. The luthier said he couldn't-wouldn't do the setup due to the sinkage, and would not reglue the tone bar cuz he'd have to take the back off to do it, and that all that would cost more than the instrument was worth, and I should go buy a new one.

I've owned it for decades, it was/is my first mando, I've ridden 1000's of miles with it on the back of a bicycle, courted my wife with it 35 yrs ago, etc yadda yadda. It's an old friend and I just like how it sounds, like how it plays, like it. I re-glued the tone bar myself, went in thru the F-hole. Took some pics, see this thread -
http://www.mandolincafe.com/forum/sh...uing-tone-bars

It was sort of like endoscopic surgery (so said my brother the surgeon). The joint is a long way short of perfect or high-class workmanship, and I'm sure the weight of the excess epoxy deadens the sound a bit. Don't care, it's structurally strong, + I got my old friend truly stabilized.

This all might be different if it's a 100 yr old antique. But hope it helps, good luck with it.

PS Jill I see you have a Sweet Pea too. I have one + love that lil thing! Don't have to take that old Ibanez travelling anymore.

[Astro]

Ohh, mando top sinkage.

I thought this was a bikini related thread