Negative Impacts of caving/sinking/collapsing top

[daveviale]

Hi gang, 1st post to the forum. I've done a search for caving/sinking/collapsing top and found some info on repair, but haven't come across on what the actual negative impacts are. I figure this is the area of the forum to post this question.

For this example I'm talking about some minor sinking (hardly detectable to me) under the feat of the bridge. I haven't had a luthier look at it yet, but assuming a fairly easy repair to prevent further collapse, what are the negatives?

I assume there is some adjustment to action that may need to occur to fix buzzing or string height preference, (due to any loss of bridge height). But what else?

Is there loss of volume or tone due to the top losing some ability to vibrate? I'm not picking up on any such loss, and my guess is that any loss would be so small that the vast majority of us couldn't detect it.

I'd bet on some decrease to the economic value due to a "flaw" in the mandolin....if one was to ever try to sell it...

Are there any other considerations I'm missing? At first I was devastated about the prospect of the "collapse" but I'm getting a little more comfortable with it....pending your responses:)

Thanks,
Dave

[bernabe]

Hey dave,
Some more specific info may spark some feedback. Im not an experienced repair guy and do not see the volume of instruments many on here do. But, Ive played and owned mandolins for 35 years so ill try to get things churned up for ya. Is it sinking in [indentation] or flattened? Is the "sinking" in just isolated to the feet contact area or the surrounding bridge area? How old is the instrument and how long has it been that way? Did you buy it new or second hand? Was it that way when you got it? Is the bridge fit properly i.e. even applied pressure along the feet contact area. I have owned and still own mandolins where the tops have slightly flattened or slightly bulged in certain areas but have stabilized at some point. One in particular was built by an individual a long time ago [he is now deceased] and no further problems or movement in years. How long that will be is unknown-maybe the rest of my life. Provide some more details and maybe a photo or two.

[daveviale]

Hey dave,
Is it sinking in [indentation] or flattened?

Not concave/indented...more flattened. Honestly I can't tell...but have been told so by 1 shop that I trust. So, for the discussion, let's assume some flattening.

Is the "sinking" in just isolated to the feet contact area or the surrounding bridge area?

Yes, as far as I can tell.

How old is the instrument and how long has it been that way?

2007, not sure how long.

Did you buy it new or second hand?

Used.

Was it that way when you got it?

Not sure, but buzzing is new, so I'm assuming no. Probably from lack of humidity, though I tried to keep humidity OK.

Is the bridge fit properly i.e. even applied pressure along the feet contact area.

As best I can tell.

Provide maybe a photo or two.[/QUOTE]
I'll try to upload some photos soon.

I understand the details will dictate the prognoses for every particular situation. While I'm interested in the health of my mandolin, I'm perhaps more curious to hear everyones thoughts on the broad implications of a flattened top in general...to any mandolin. So if it's helpful, let's assume a slightly flattened top that's been stabilized.

Thanks,
dave

[bmac]

The negative impact of a sinking or sunken top is that it could very well continue to sink, eventually making playing impossible and more or less permanently distoring the top wood. Another negative would be that it devalues the instrument financially.... Most folks wouldn't consider paying anyway near market value for an instrument with a sunken, or sinking, top. As long as you are willing to remove the back it is not terribly difficult to repair. There is a good article by Gail Hester showing her approach on a Gibson A style with a sunken top. I think it is somewhere on this site.

[sunburst]

A slight distortion of the top is normal, wood moves very gradually in response to constant stress or strain, so an old mandolin's top will often not have the exact same shape as when it was new.
The danger in more severe top sinking is that the top, and with it, the rest of the instrument's structure, can go outside of the design parameters of the instrument, so to speak, and can become unstable and lead to cracks or other damage. The vaulted top of a carved top mandolin withstands about 50 pounds of downward pressure at the bridge because of the deflection or the tensioned strings over the bridge. The vaulted arch of the top is important to maintaining the structure of the instrument under that pressure, and if the top flattens, that structural aspect is compromised.