Bellied up top

[limehills]

So I just put strings on this beast, and it sounds excellent. But unfortunately it has bellied up, I am thinking it's either under braced or my top is too thin. It's not too bad at the moment but I think it will worsen. Any thoughts/Advice will be appreciated!

P.S. It has forward shifted Scalloped Adi bracing and an Adi top.

[simso]

Will definitely get worse

What is the top thickness?

Steve

[kiwigeo]

Any pics of the underside of the top showing bracing?

[limehills]

Top thickness was originally 2.90mm. not sure what it was after final sanding. I was pretty careful so I didn't take too much off it.

Here is some bracing:

[kiwigeo]

When you say the bracing is forward shifted...you mean you've moved everything closer to the sound hole? It might just be the photo but gap between end of X brace/tone bares and sides looks a bit on the large side....but maybe that's just me. Does the start of the of bellying correlate with the scalloping on your main braces and tone bars?

How thick is bridge plate. What sort of wood and which way is grain going?

[kiwigeo]

What's the top doing in front of the bridge?

[limehills]

Yes I moved everything towards the sound hole 13mm, Except the popsicle brace etc.

Here is a photo when the top was off:

there is about 10/15mm of extra material around the edges of course that got cut off after the top was glued.
And here is where it is bellying:

so between the X braces only.

The bridgeplate is about 2.5mm And made out of flatsawn heart Rimu.

The top in front of the bridge is mostly ok, it has hardly moved at all, the radius has flattened out but only slightly.

[kiwigeo]

My initial thoughts......the scalloped section in the middle of those tone bars might be a tad to long. I tend to make the scalloped and peaked segments more equidistant when I do scalloped braces.

Any thoughts from other members?

[simso]

Looks to me like a over scalloped x brace, I have never taken any even close to those shown

[limehills]

Any ideas on how I can fix it? Or should I just leave it and see what happens.

[simso]

Replace the braces, otherwise you are likely going to be replacing braces and the top

[kiwigeo]

Laurence, it looks like you'll have plenty to keep you occupied during the Covic19 lockdown

[johnparchem]

I was taught not to start the scallop before the bridge plate for structural reasons. When I shift the braces toward the sound hole I am thinking about just the X not the entire scallop pattern. The low part of the braces are right where you need structural support.

[limehills]

thanks for the responses.

Ive decided to replace the tone bars and see how that goes.

I also discovered this morning after another look that my bridge plate is too small, the back end of the bridge is on the very edge/hanging over the plate itself, so I'll replace that too. On the plus side I now have something to do in self isolation!

Stay safe

[Mark McLean]

My first build (a cedar top OM) did the same thing, and for the same reason that you have diagnosed. I definitely over-did the scalloping on the diagonal tone bars, and probably on the X-braces in the area between the X and the bridge plate. Like yours, it sounded great (an under-braced top is really responsive!) but started to belly-up at an early stage. In my inexperience at that stage I did not know how to replace the braces. I put a Bridge Doctor https://m.youtube.com/watch?v=nxJpM4xoXg0 in it as a temporary fix, which stabilized things but I wasn’t really happy with that solution. I built half a dozen more guitars and number 1 hung on a wall unplayed for a long time. Recently I got around to replacing the whole top and it has ended up pretty good after all.

[limehills]

yes I thought for my No.10 build I wouldn't run into trouble like that, guess i just proved myself wrong!

Ill post updates, just started removing the bracing, bridge plate next.

[kiwigeo]

You've got the top off? Some photos would be great as this is a job most of us will have to do at some stage. I reckon I've done around 8 re-tops so far.

yes I thought for my No.10 build I wouldn't run into trouble like that, guess i just proved myself wrong!

Ill post updates, just started removing the bracing, bridge plate next.

[limehills]

Nope I decided not to take the top off, I spent many hours french polishing this one so I wanted to try preserve the finish.

I used a finger plane and Carved the bracing off from the inside.
I did this by putting an old phone inside the guitar and live streaming it to my laptop!

And here is a photo of the bridge plate:

I definitely think it needs to be bigger.

[kiwigeo]

You're going to do a brace replacement job with the top on? Good luck with that

Have you considered how you're going to clamp up the new braces without damaging the finish on the top? All your clamps are going to have go in via the sound hole and there's only so many clamps you can jam through same.

How are you going to ensure the top curvature is maintained while gluing up the braces? Just a few things to consider.

Good luck

[ozziebluesman]

Yep I had a similar experience building a mini maton copy. It is 15 fret to the body and I had this mentality of 12th and 14th fret to the body. So I went ahead and built the neck with the 14th fret to the body and the body to suit a neck 15th fret to the body. Big issues with the bridge plate location. I cut out the old top with the jigsaw and started again. I agree with others that your schollaped area on tone braces and X brace are very low.
Good luck with it all it is not difficult to replace a top.
Cheers
Alan

[Andos]

You want to stiffen up the top without removing it and Martin has mentioned a few challenges you will have to overcome.
How about leaving the braces as they are, glue a strip of CF on the top beside the brace and another over the peaks of the brace.
A bit unconventional, but at least it keeps the top profile.

[limehills]

I am using small cedar go bars to clamp the bracing inside. As for the curvature it seems to have retained it quite well. I'm only planning on replacing the tone bars and bridge plate, I'll see how it is after that, if it's still playing up I'll do a re-top but I thought I'd take my chances.
Ill post photo updates later.

[yakka]

Did you try lighter gauge strings?

[simso]

Its really your x brace that needs replacement.

Pop the back off, then you can replace them and not damage the top at all.

Steve

[johnparchem]

I do not think changing the tone bars will do anything for you. The belly is from the nut side of the bridge rotating in. One fix I might try if I did not want to remove the top would be to sister taller braces on the over carved x-braces from the X to the finger braces on each side.
Having said that I have removed the top on a few instruments where I was unhappy with the top resonance or top structure.