Warping beneath the bridge...

[Oliver R]

Hello,
This issue has always been in the back of my mind (especially as when the mandolin is left unused for a couple of days you get a slight pop/crack noise if you lightly put pressure on the top under the bridge).
Anyhow, I did a first string change on it, i cant believe I have had a set of strings on for a full year! and took the opportunity to examine the top.
I found deep indentations around the feet and the top 'bulging' up in between them (as i suspected.
I have brushed boiled water around the area and it seems to have eased some of the lighter dents but I am still left with quite a bit of distortion (as pictured).
I am in the process of making the bridge full contact but how would you deal with the prospect of fitting it with the damage already done..
Cheers
Oliver

[William Smith]

I would just fit it like you normally would do, I use the sandpaper and back and forth side to side motion. I had a few F-5's like that and the full contact seemed to work-round out the dents.

[Oliver R]

Its hard to tell from the pics but its quite domed up between the dents so I suppose you would need to factor that into the profile of the base. It would be nice to be able to get the curve of the top back into a more consistent shape though..

[V70416]

Oliver,I hate to say it;but,that looks fairly normal from what I can see in the pics. Top woods are usually
pretty soft;the edges on the thin ebony bridge feet just dig in after a while.

Ihave those same kind of indentations/bulges on a couple mandos. After a decade or so,from positioning bridge,I also have scrape
marks in front and back of bridge feet. It looks ugly but I think it is reasonable wear from a necessary maneuver(due to minor shifting of top from
string pressure,temp. and humididty changes over time).

I don't think one can just leave the bridge in the exact same spot for the life of the mandolin and expect the best
intonation.

INterested to hear about how the full-contact bridge works for you.

Have read discussions on two-footed vs. full-contact bridges. From the little I understand it just depends on the
particular instrument as to whether it will benefit from one or the other. Seems worth a shot.

PS:Regarding the pops/cracks when applying some pressure to the top;I massage
my mandos once in a while like a chiropractic. I think it may help the instrument to forget that it used to be a tree.(this reminds me of the Laurie Lewis tune,"The Maple's Lament" from the album "Restless Rambling Heart" for the best rendition imho)

[Oliver R]

Sorry, I just remembered I edited out the start of my post in case it was seen to be having a go at an individual!
I totally agree with you that this is a common issue over time but this mandolin is approximately two years old and was like this when I bought it brand new!
Anyhow, as you say it gives me an excuse to see how the full contact bridge works
Cheers
Oliver

[Folkmusician.com]

On most mandolins, a properly fit bridge foot will be nowhere close to fitting if it is sitting on the top without string tension. It looks like the bridge was fit without downward force, then the top deflection caused the pressure points. The force was not spread across the width of the bridge.

The poping noises are normal if the bridge is sticking to the finish (and it would with your mandolin). The top flexes and moves under the bridge foot.

Sometimes you can fit a foot adjacent to the area it will ultimately be. Fit it right next to the dents. This doesn't always work, just depends on the top and how much deformation there is.

[Oliver R]

I have just completed the bridge base and sanded to fit, not under tension Robert (but I don’t think that’s quite as important on a full contact base).
I have it so it does have a sliver of daylight at the worst of the dips, hopefully allowing it to compress the raised hump in the middle
and smooth the curve out over time, I’m talking thousandths of inches here btw.

[Drew Streip]

I know you said you brushed boiled water over the dents -- you could try actively steaming them out a little bit more!

I've never had great luck doing that through a finish that hasn't also been chipped or cracked. It looks like you have an Eastman? I've heard that those satin finishes are fairly thin so perhaps you'd have success!

[Folkmusician.com]

I have steamed out dents with a soldering iron and damp cloth.

Oliver,

I don't do it under string tension, but push down (with hand) while sanding. For a bridge to get a good fit, it would normally be just touch at the tips with no tension. There would be large gaps toward the center. Under tension the feet will spread out giving good contact.

[HoGo]

I agree with Robert. Get smooth curve (estimeta how the top looked when new or use adjacent area) with some gap towards center that will get the bulge back under control and will load the whole area equally.
The digging and bulge is typically result of thin top, thin bridge in the center between feet or improperly fitted bridge with no pre-springing. I would probably try to steam the dents a bit if they are really deep but that is nothing for beginners (have a look at frets.com)

[Oliver R]

Thanks for your advice fellas, appreciate it!
I think I have the dents out as much as they will go, I repeatedly placed a strip of flannel soaked in boiling water and placed some weight on it to press it down ( just a brass bar) and it does seem to have started to return somewhere near normal (ish).
I have actually done as you say and left the base to press down in the middle to flatten things out (hopefully), we shall see!
The top seems fairly solid but I think it would have suffered some cracking if left to its own devices. In fact I see a hairline crack in the finish to the sound hole.
It does annoy me that the seller would not initially acknowledge the issue and sort things out but hey, sutch is life. It’s a good job I’m handy! It’s a great sounding mandolin and I will bear with it!