Volume 46 - Fixing a Plywood top Archtop

Written by Patrick Podpadec on . Posted in Northcoast Voice




                                           Stay in Tune

                                                                                  By Luthier Patrick Podpadec



 Well for the latest news on repair, I have gotten some new things to talk about. I had a interesting guitar come to my shop with a problem that I’m not sure exactly how I am going to approach it just yet. It is a inexpensive plywood archtop guitar that seems to have the top caving in on it. I thought that the tone bars or the bracing may have come loose because of how the pressure from the bridge is pushing the top down so far, but when I put a light and an inspection mirror in the “F” holes it looked as though the braces were fine. No cracks, and the glue job seemed to be very tight. There was some obvious altercations done to it previously though. Someone had attempted to put a “nashville tunematic” adjustable saddle on it and by doing so, decided to drill two large holes in the top where the mounting studs go. When they did this, they drilled about half way through one of the X braces. At first glance , I thought this could be where my problem lies ,but I’m not sure that it is. The braces seem very stiff, but still there is no arch to the top. The previous “repairman”? had covered the holes with a very large wood base plate to hide the holes for the tunematic bridge, which also could be some of the problem. The saddle mechanism is sitting up as high as it will go on the mounting studs, (about an 1-1/2” above the top of the guitar. It should be no more than 1”). Right now it has to be that high in order for the strings to have the proper action.  My first thought on how to repair this instrument is to raise the belly to its proper height. Being that it is an inexpensive plywood top and not a solid carved archtop, I thought it might be acceptable to add some sort of a “soundpost” similar to a violin or as a cello has in it. This, I believe will give it the needed  support under the bridge to raise the belly slightly. I have to make sure that I reinforce the area of the back where the post will sit.   If I don’t put a substantial brace there, it is a possibility that the post will just push out the back instead of the belly. I also will try to put on a wood adjustable bridge (similar to what you would find on a mandolin) that is much more suited for this type of guitar. It has a lot smaller “foot” or base which won’t push the top down as much. 
  I will put a back brace inside directly under the bridge area. It will span the entire width of the back so that the pressure that will be applied to it from the soundpost will be spread out over the whole back instead of just one localized area. It must be shaped to the exact curvature of the back so that it will not distort the shape in any way. It also must have some depth, to have enough strength (stiffness) so that it will not buckle under pressure, but not too thick to absorb too much of the tone from the top. I may even have to put two soundposts in. One under each X brace directly under the bass E and the treble e strings under the bridge. This is a “judgment call” that would be much harder to determine if the guitar was a real acoustic solid carved archtop guitar. This particular guitar has a magnetic pickup in it and is not as depended on its natural tone because of it being amplified. I know that some people will have issue with that statement, but we must realize the type of instrument and the type of repair that we are dealing with here. We are going for the “quick fix” (inexpensive) solution to a problem . The other option would be to remove the back and replace the braces with the proper arch. That of course would cost far more than the guitar is worth. This is just one of the many assorted repairs that come through my shop. I have met other repairmen that shy away from these type of problems or go about the repair the wrong way, but I seem to like the challenge and it also teaches me proper “guitar construction” I will have pictures of this repair on my website, so please take a look at www.wood-n-strings.net. Well, I will continue this topic next week, right after I  till up my garden and plant all my vegetables and rake the yard and  feed the bunnies and cut the wood and build the new shed and ……. 

                                                       Thanks Again!
                                                       Patrick from Liam Guitars/Wood-n-Strings