Ugly concave in the side

[viento]

Maybe someone has a helpful suggestion how I can correct this ugly mistake on the side?

I only noticed this after the glue of the bottom had cured.

I might perhaps take the kerfed lining for the top off at this spot, then spritz and slide it again over the bending iron.
Could it be straightened?
I´d like a solution for this problem...

Sorry for the blurry photo

[redir]

Something very similar happened to me on my last one. I could not figure out how that happened. Basically what I did was just carefully sand it till it was 'acceptable.' FWIW I consulted with some very respected luthiers on another forum who have had the same experience and even went as far as to say that perfectly flat sides are not the norm. But yours is bad, as was mine. Sorry that's all the advice I can offer.

Here is an after pic of mine. It looked a lot worse before. Fortunate the sides were thick enough to deal with it, to a point. And like me, since you do not have the bindings on yet, you can keep an eye on the side thickness.

[Bass.swimmer]

What about gluing a brace to the side where it's warped like that, so that way it sucks it flat?

[viento]

Thanks for your kind support!
I appreciate that "perfectly flat sides are not the norm"...

My sides are only approx. 0.08 "thick, so sanding will be only possible a tad.
But before that am going to try to make an improvement with the bending iron.
In any case, the paint will not be glossy, but matt.

[viento]

@ Bass.swimmer
Yes, I have thought of that,too. I will have a look and have a try with clamps without glue.

[redir]

.08 is already pretty thin but you can push it a bit. Curious, how do you glue on the top and back? I work of a workboard (solera) and clamp the sides to the top then to join the back I use a rubber "rope" made of tire tubes and stretch it around the guitar body.

My only thoughts as to why it happened to me was I used too much clamping force and crushed the sides (mine were at .09in thick). But I thought in time if they were crushed they would simply *deform back. They never did.

[charles Tauber]

Originally Posted by viento

I might perhaps take the kerfed lining for the top off at this spot, then spritz and slide it again over the bending iron.
Could it be straightened?

Probably not. Probably, it'll be a lot of effort for nothing.

I´d like a solution for this problem...

I'm not sure there is one.

You can try gluing side braces, as Bass.swimmer suggested. However, they'll be less effective if they don't go edge to edge. To go edge to edge, you'd have to cut out the linings to accommodate the side braces. Making the side braces slightly convex - towards the concave side - might help.

The best you might achieve could be having the sides smooth - without ripples - but concave. Sanding with a flexible pad that smooths irregularities while following the concave surface might be the best approach.

The question is what caused it and how can you prevent it in any subsequent build? Are your sides quarter sawn? Did you soak the sides prior to bending? It looks like walnut: perhaps make the sides a little thicker for future use of walnut.

Originally Posted by redir

My only thoughts as to why it happened to me was I used too much clamping force and crushed the sides (mine were at .09in thick). But I thought in time if they were crushed they would simply *deform back. They never did.

I sometimes assemble on a work board as well and have used rubber bands as you describe. One time, I crushed the one side, taking the top with it. I repaired the side, but the top was toast.

[viento]

Well, the 0.08" was made by an employee of a carpentry with a thickness sander. He processed the sides one turn too much.Both sides had to be lying on top of each other as the machine had 3mm as minimum depth. I wanted them a bit thinner than that, but it happened...
@charles: it'll be a lot of effort for nothing... you were right ;-)
I took off a part of the top kerfed linings , wetted that part of the sides and shoved it over the bending iron. I didn´t see any remedy. I let it dry clamped in the mold until tomorrow.

The sides are quarter sawn and I only wetted them when bending at about 200°C. They are of "Tineo" or "Indian Apple" of Chile or Argentina.
(if interested, have a look at: https://www.wood-database.com/tineo/)

What caused the concaves?
When gluing the sides to the bottom I had made a kind of sandwich clamped with a thick wooden board below and above. Might have been too much pressure of the clamps.

Gluing side braces will be my next try, first without glue.
I could fortify the concave region with a second inner piece of hard wood, e.g. maple. I recently saw a video of a luthier who added a second inner layer of wood to the sides.

Btw, I´ll keep this guitar for me and if it sounds good, I will try to ignore the quirks...if possible

[bob531]

In the world of cello building , ribs are strengthened usually with strips of linen not wood. The linen glued on with hide glue has a tendency to contract a little causing an outward bow to the ribs/sides.
This can also be used to get rid of concavity . I used linen strips in the two guitars i just made rather than wood side braces.
It wouldnt help in the second example/post as that looks to be behind the end block or neck block.

[redir]

Originally Posted by charles Tauber

I sometimes assemble on a work board as well and have used rubber bands as you describe. One time, I crushed the one side, taking the top with it. I repaired the side, but the top was toast.

Well that could explain a lot then. Strange thing is that this is the first time I've noticed it and it is my 65th guitar. But there's a first for everything.

[redir]

Originally Posted by viento

Well, the 0.08" was made by an employee of a carpentry with a thickness sander. He processed the sides one turn too much.Both sides had to be lying on top of each other as the machine had 3mm as minimum depth. I wanted them a bit thinner than that, but it happened...
@charles: it'll be a lot of effort for nothing... you were right ;-)
I took off a part of the top kerfed linings , wetted that part of the sides and shoved it over the bending iron. I didn´t see any remedy. I let it dry clamped in the mold until tomorrow.

The sides are quarter sawn and I only wetted them when bending at about 200°C. They are of "Tineo" or "Indian Apple" of Chile or Argentina.
(if interested, have a look at: https://www.wood-database.com/tineo/)

What caused the concaves?
When gluing the sides to the bottom I had made a kind of sandwich clamped with a thick wooden board below and above. Might have been too much pressure of the clamps.

Gluing side braces will be my next try, first without glue.
I could fortify the concave region with a second inner piece of hard wood, e.g. maple. I recently saw a video of a luthier who added a second inner layer of wood to the sides.

Btw, I´ll keep this guitar for me and if it sounds good, I will try to ignore the quirks...if possible

.08 is certainly within the acceptable limits of guitar sides.

[mirwa]

If its dipped as per photo then there is still tension in the sides.

What causes tension in the sides

Insufficent heat when bending
Grain direction / runout
Pulling the sides into shape on a mold
Shaping kerfing to one radius and clamping a top or back with a differnet radius.
Wood was too wet when bending and cupped whilst drying out

These are just some that I am aware off, pretty sure many more reasons existing for the side cupping

Run it over your hot iron a bit more

Steve

[viento]

Steve, thank you for trying to explain different causes.
I will remember all of those when I´m going to start my next built.
For this time I will accept the limitations and have stopped any improvements
except strong braces on the inner sides. I dont know if that helps but I´ll give it a try.

[kkrell]

Would a product like SuperSoft help in conditioning the sides prior to running over the hot pipe again?

(IMPORTANT NOTE: I am not a luthier, or woodworker, even).

[viento]

I guess that could work.
But I don´t know where to get "The SuperSoft Wood" veneer softener here in Germany...until now I didn´t find it in the market.