The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Reply
 
Thread Tools
  #1  
Old 06-28-2018, 09:28 AM
HeyMikey HeyMikey is offline
Charter Member
 
Join Date: Oct 2017
Posts: 820
Default Belly reduction and Bridge re-glue

Here are photos of the bridge lift and belly bulge. About a nickel and quarter so 0.146 inches which is in between 2/16 (0.125) and 3/16 (0.188).

Should the belly be reduced before re-gluing the bridge or is it within acceptable range?

Given that the guitar was not very expensive, I'm considering doing the repairs myself. I' never done it, but I'm fairly handy.

I saw a product called a Thompson Belly Reducer. It looks good but at $130 seems a little pricey for limited use. A used set would be nice if I can find one. Is there another good but relatively easy DIY method for reducing belly? No, diet and exercise is not an option.

I also saw the JLD Bridge System/Doctor. I'm not crazy about drilling a 1/4 hole into the bridge and I don't want to use their brass replacement pins either, but that might be worth a try.

Looking inside I noticed that the bridge is secured by a screw/nut under each of the two MOP dots, which probably accounts for the ends still being secure. That could make it tricky to remove but I think it is manageable.

Advice, tips, tricks and other insight is more than welcome!



Last edited by HeyMikey; 06-29-2018 at 10:52 PM.
Reply With Quote
  #2  
Old 06-28-2018, 09:46 AM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 8,381
Default

"Flat top" guitars usually aren't: they have a small arch built into the top. The amount of arch changes somewhat with ambient humidity. The measurements you have provided are within a typical amount of arch for the top and doesn't constitute "bellying". Bellying is, generally, a more localized distortion of the top caused by string pull.

One of the largest structural elements on the guitar top is the bridge. When the bridge is no longer adhered to the top, it isn't providing much structural support.

Most guitars with "decorative" dots on the bridge conceal bolts. The dots can often be removed undamaged and reused. A very small chisel works to pry an edge, as can any small, sharp instrument. Once the dots are removed, clean-out any dried glue concealing the head of the bolt. Removing the bolt should be fairly easy with an appropriate screw driver and a pair of pliers on the inside to grab the nut.

From there, removal of the bridge should be easy with a wide chisel or thin bladed paint/drywall spatula. Once removed, you'll need to remove all old glue and any finish under the footprint of the bridge. You can use 3/16" nuts and bolts through two bridge pin holes, and appropriate gluing cauls, inside and out, to clamp the bridge while the glue dries.

You won't likely want or need Bridge Doctors and the like. If you feel one is needed, you can always add it after the fact.
Reply With Quote
  #3  
Old 06-28-2018, 09:55 AM
HeyMikey HeyMikey is offline
Charter Member
 
Join Date: Oct 2017
Posts: 820
Default

That's good news. Thanks Charles! The bulge does seem symmetrical and not distorted or skewed. I think I will attempt the bridge repair. I'll make some padded cauls to fit. I have a bunch of old spatulas so was going to round the edges of a couple and sand down the handles to get the angle flatter. So using bolts through the bridge pins are in addition to or instead of C clamps?

About the two concealed bolts under the dots. Do I need to remove the dots and bolts from the top as you described or can I simply undo the nuts from the inside of the guitar and lift the bridge off without removing the bolts?
Reply With Quote
  #4  
Old 06-28-2018, 10:53 AM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 8,381
Default

Bolts instead of C clamps. Make a caul for exterior use that is the size and shape of the bridge. Bolt through it and use wooden wedges between the wings of the bridge and the bottom of the caul to hold down the wings of the bridge.

The bottom of the bridge needs to be cleaned-up. Having bolts in the way makes that difficult. I'd remove the bolts and probably wouldn't reinstall them during or after the bridge reglue.
Reply With Quote
  #5  
Old 06-28-2018, 12:13 PM
HeyMikey HeyMikey is offline
Charter Member
 
Join Date: Oct 2017
Posts: 820
Default

Quote:
Originally Posted by charles Tauber View Post
Bolts instead of C clamps. Make a caul for exterior use that is the size and shape of the bridge. Bolt through it and use wooden wedges between the wings of the bridge and the bottom of the caul to hold down the wings of the bridge.

The bottom of the bridge needs to be cleaned-up. Having bolts in the way makes that difficult. I'd remove the bolts and probably wouldn't reinstall them during or after the bridge reglue.
Got it. Use the caul and wedges so similar to what that stewmac bridge caul clamp thing does.

So those bridge bolts don't provide any value once the bridge is properly glued down. I'm good with leaving them out.

Last edited by HeyMikey; 06-29-2018 at 10:51 PM.
Reply With Quote
  #6  
Old 06-28-2018, 06:12 PM
mirwa mirwa is offline
Registered User
 
Join Date: Sep 2013
Posts: 3,109
Default

Please dont use the bridge doctor.

Top distortion happens more distinctively when the bridge is not glued properly to the top and in turn to the x brace underneath.

Your bridge, looks like its holding on solely by the two bridge bolts under the pearls, this means all the top string tension is pulling at those two points only, in turn generating a very distinctive distortion.

Remove bridge, let it settle for a day or two then recheck, if its not flat enough then steam / clamp between two flat plates.

Steve
__________________
Cole Clark Fat Lady
Gretsch Electromatic
Martin CEO7
Maton Messiah
Taylor 814CE
Reply With Quote
  #7  
Old 06-28-2018, 07:10 PM
charles Tauber charles Tauber is offline
Registered User
 
Join Date: Feb 2011
Posts: 8,381
Default

Quote:
Originally Posted by HeyMikey View Post
Here's a wacky idea.
Adding the two strips doesn't buy you anything. The net forces are still the same. It might flatten the top, but also prevent it from vibrating.

Once the bridge is properly glued, and you've ensured there are no loose braces, you won't likely need any additional support. Basically, what Steve said.
Reply With Quote
  #8  
Old 06-28-2018, 08:37 PM
HeyMikey HeyMikey is offline
Charter Member
 
Join Date: Oct 2017
Posts: 820
Default

Thank you both. I appreciate the advice. I'll remove the bridge let it settle and see how it lays. No Bridge Doctor. Steam and flatten a little if needed. Got it.
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Thread Tools





All times are GMT -6. The time now is 08:44 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright ©2000 - 2022, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=