12 string Sigma with bellied top

[Eugen C]

Hello

 

I live in Bucharest, Romania.

I am not a luthier, I just like to use tools and make things with my own hands.

I have read Mr. Ford frets.com and also all the discussions here and I found a lot of invaluable information and I thank you for this.

I did some minor repairs to my guitars and I repaired a broken peghead on an EKO Ranger.

Now, my problem: I bought a Sigma 12 strings from Ebay with a broken peghead that was profesionaly repaired previously. Is in very good cosmetic condition, with very litle wear but the bridge is rotated and the top is bellied.

All the braces are glued and the bridgeplate is in good shape. The bridgeplate is laminated with 4 or 5 layers, only the first layer is missing some wood between pin holes.

You can see in the pictures how much is the top bellied. In these pictures the guitar is without strings.

The action is a little too high, it can be reduced by shaving the saddle but the problem is the intonation that is sharp on all strings because of the bridge rotation.

As I can't afford to buy an expensive guitar and I like very much how this one sounds, I would like to flaten the top. And because I want to do all the work by myself, the costs and the time wouldn't be a problem. That would be also a very good way to learn.

I know about JLD Bridge Doctor but I hope to receive advice from you.

[Bob Steinarsson]

I'm glad to read this. Did you do the plastic bag trick? What is too flat? The top can't get flatter than flat, unless you change the flat bar with a convex one, so this must be a question of the original flatness of the top.

I absolutely agree with Ned. Remove the bag or whatever you have used as source of moisture and check the bracings. If one has become loose, it is important to fix it now while it is still flexible from the moisture. When it is dry, it will probably be impossible to get it back. Leave the guitar to dry, and be sure it is absolutely dry before you do anything more.

I would also install the Bridge Doctor before strings. It can now be installed with little tension. You can tighten it later if the belly appears again. I don't think it will do. The Doctor will prevent the movement of the top.

[Eugen C]

Yes I did the plastic bag&wet towel trick. I also have covered the soundhole with a plastic cover.
I know that the top must have a little arch not dead flat, this what I want to say with "too flat".
Today, after work, I will get the bag&towel out and I will check for loose bracings.

As I said, I started to make my own Bridge Doctor. Can you tell me what material is used for the piece that connects the wood block with the screw trough the bridge? I want to make one "Y" shaped to use the existing bridge screws.

Should I be worried about the bridge unglue thing? (see pictures in my second message)

[Bob Steinarsson]

Some guitars have a little arch, but many have dead flat tops. I would check this (maybe somody in this forum knows).

When it comes to the self made Doctor, I would still advice you to make a clone of the original (or buy it). This is a proven design, and you know that it works. Your y-shaped one will maybe also work, but it requires also a lot of, in my opinion, unnecessary work. I have also been thinking about making my own BDs. As rod I would use the thin rod used for small flags. At least the Norwegian ones have the right diameter.

[Eugen C]

Thank you for your quick answer.
Work is not a problem, I preffer to work more and to have a nice looking guitar.
For the rod I used a bamboo stick that it was around.
From the drawing on StewMac site, the piece that conects the wood block with the bridge seems not wood, maybe plastic?

[Bob Steinarsson]

This is plastic. I would rather have carved the whole thing out of one piece of wood.

[Ned Knepp]

Personally, I would stick with the BD design to save weight. As it is you will be adding some mass to the bridge anyway. The blocks for the Bridge doctors I've seen are very light weight. The screw goes through the bridge and into a pre-drilled plastic piece that has a long metal screw coming out of the other end which goes into the block. The plastic is fairly dense (delrin ?) which I assume is because it is under a load. I don't know why it would have to be plastic but it is a very efficient, light weight attachment. It might be possible to fabricate something like this with hardware store parts if you use some imagination and remember the pressure it may need to handle.
.
I think the dowel/rod needs to be something that won't flex too much. The end of this dowel, inside of the BD, comes to a slightly blunted point and the BDs I've seen have steel ball that rides between the dowel and the adjustment screw. Adjusting the screw pushes the rod without twisting it.

I think it is completely possible to make your own but if you haven't seen and used one, you might consider purchasing one for the first installation. I can appreciate not wanting to add another hole but it can be hidden under a matching wood plug and the design really works well without adding too much mass.

Ned

[Eugen C]

Yesterday I removed the clamps.
The soundboard is almost flat, with just a little arch.
TomoroI will put a picture with the guitar.

[Eugen C]

Pictures:

[Eugen C]

Hello again

I have finished the self made Bridge Doctor.
You can see some pictures.

For the block I used a kitchen plate (?), that used as a base for cutting meat or vegetables, I don't know the english word for it. Is made from bamboo sticks glued together. My wife broke it and she wanted to throw it away but I was quick enough to detour to my workbench :D

I also made a spruce block but the bamboo one is lighter.
The Y piece is made from phenolic material.
Tomorow I will put the strings on, I hardly wait to hear the sound.

[Bob Steinarsson]

Very nice work! Let's hope that the bamboo works good as a transmitter of the vibrations. Please report!

[Eugen C]

Report: Bamboo is very good, the guitar has a rich sound, with a lot of bass and volume.
I can say that it sounds better than before and the top is flat as it was when new. Thank you all for your advices and support :)

[Eugen C]

Hello again :)

After more than a month I can tell you that I am very glad with my Sigma and the BD I made.
I thighten the screw once, now the sounboard is dead flat.
The intonation problems is almost gone, is still a little sharp but I am very satisfyed with the sound.