Cause of small depressions on lower bout

[ScaryLarry]

Hi. I just purchased this guitar what was presumably in mint unplayed condition, and indeed, is in very good condition except for 2 small depressions on the lower bout, about 3 or 4" from each other on opposite sides of the center. You can definitely see and feel them, but upon inspection the bracing seems fine and stable, and the top seems fine also.

Since I can return the guitar, I am now curious what may have caused this, and if it is a sign of more serious damage down the road.

TIA, SL

Here is an image of one of the depressions:
https://imgur.com/nlaj8gm

[charles Tauber]

If you are talking about the "dark" area to the left of centre in the photo, next to the binding, that is about where the edge of the end block would be. If the indentations are symmetric about the centreline, they are likely due to the end block being too high or low, relative to the sides, distorting the top as it makes the transition. It is possible that it is humidity related, but more likely a manufacturing "anomaly".

Whether or not it is a concern depends, in part, on the price of the instrument. It probably isn't a long-term issue, but shouldn't be expected on an expensive instrument, if it is an expensive instrument.

[ScaryLarry]

Thanks for the response Charles!
Interesting - I didn't think of the end block being the issue, but I now believe you are correct. I could not reach in to touch the end block, so I can only assume it has not become unglued. There are definitely no rattles when I vigorously shake the guitar.

As to an expensive instrument, I purchased it for $2,400 so it's not cheap and was made by Bedell in Oregon, so presumably a reputable, quality maker.

Thanks again,

SLarry

[charles Tauber]

I’d contact Bedell in Oregon to at least let them know.

I’d make sure you are maintaining appropriate humidity levels.

[Bruce Sexauer]

I often see something in that vein in my own guitars. It is probably the result of a lightly built guitar. When a top is under around .105", as many of mine are, the structure inside is liable to telegraph and be visible as distortion in the flatness of the top. I can't speak for your maker, but I have had 0 failures foretold by this phenomenon.

[redir]

I see the same thing in my guitars as well. That might be a slight more extreme case but it's hard to tell in one image too. It used to concern me a lot until I started reading the opinions of more experienced luthiers who say that telegraphing is not unusual and if anything could be the sign of a well built responsive guitar. Bruce only confirms this, I think.

But there is something to be said about too much of a good thing too.

[charles Tauber]

I agree that it isn’t uncommon to see braces telegraph through a thin top, but that might not be what the OP is experiencing. It might be.

I agree that, unless extreme, isn’t likely to cause issues. I guess it is a question of how extreme the “dents” are, which we probably can’t assess from a photo.

[printer2]

I have the same. The tail block is one piece where the lining is not, also the tail block has a lot more mass for humidity to change the dimension it. The most flexible part is the top so it moves, but not in the localized area of the rail block which is the master of its domain, at least in that area. I used to have full contact between the block and the top but have been chamfering the ends of the block to the width of the binding thickness in the unverified thought that it would lessen the effect.

[charles Tauber]

Originally Posted by printer2

... the tail block has a lot more mass for humidity to change the dimension it.

Drifting off topic...

How do you orient the grain of your tail block?

The first guitar I made, at Charles Fox's school in the '70's, was made with a tail block of birch plywood. Since then I've been making my own plied tail blocks with offcuts of spruce dulcimer tops. (I made a lot of dulcimers way back when, and had a lot of offcuts.)

I layer and glue a few pieces of spruce with alternating grain direction to a thickness of about 1/2". I've found that to be lightweight, strong and stable and have not experienced any issue with doing that. I have never have a tail block telegraph through a top, provided the block is fit properly - neither too long nor too short.

[Bruce Sexauer]

My neck and tail blocks are Honduran mahogany oriented the same way as the sides. With my construction method it is impossible for the blocks to be either too long or too short. On many of my guitars it is possible to “see” the peone in reflection off the top. Less common with Adi than with Euro.

[Howard Klepper]

You should be able to look in with a light and a mirror to see if there is a gap between the end block and the liner blocks. I suspect there is, and that the guitar has dried since it was built. It's hard to say from one photo, but there is quite a bit a "corduroy" appearing in the top around the depression, which indicates a dry guitar.

[redir]

I like to use Honduran Mahogany too and orient the blocks so that the end grain is sticking out on the sides and the flat grain is glued to the top and back. Since I build on the top the block can not be too big for the top, it could for the back I suppose. First couple guitars I made with the end grain glued to the top and back but it is a PIA to use a block plain on it when fitting the back.

I had made a few mahogany plywood tail blocks from scratch too.

[Silly Moustache]

"small depressions on lower bout" ?

Cellulite?

I'll see myself out.

[Bob Womack]

Your guitar is pining for a mate, hence the depression. Badump, tisss.

Another reason for the finish to be sunken around the grain is if it is a very thin finish. As the fish out-gasses, it also shrinks. With a thin finish it is entirely possible to have the grain ghost through the smooth top. At least that is what Bob Taylor said, back when he posted on the board when it was the Taylor Guitar Forum.

Bob

[John Arnold]

I see this as mainly the result of the top bellying, coupled with the wider area of the block glued to the top. I bevel the top of the tail block, so that the width on each edge is the same as the kerfing. It is a bit wider in the center, but nowhere is the top gluing surface as wide as the full block thickness (7/8" on dreadnoughts). A very slight angling of the top of the block (higher on the inside) can also help eliminate this.

It probably isn't a long-term issue, but shouldn't be expected on an expensive instrument, if it is an expensive instrument.

These 'dimples' are visible in varying degrees on many. many Martin guitars.