Pop quiz hot shot - what do you do with a finished soundboard and shaped sides? No it's not a bomb on the bus... You join them! And what happens when you join them? It's almost like you're creating Frankenstein's creature. I've tasted just a hint of the ecstasy Gene Wilder so convincingly portrayed as he succeeded in raising to life that which was inanimate. And trust me, it's altogether dizzying and excruciatingly exhilarating. So without further ado, I present to you two-thirds of a sound box!
The next step is to re-plumb the top edge. I started with a small hand plane and a palm plane, they worked well to get a good clean surface and to knock everything down to the same level. To finish it off, I used a sanding block to make sure everything was level and consistent. The final step before gluing the top is chiseling out the notches for the soundboard braces. To do this I place the soundboard on top, marked the sides, then started carving conservatively with Flexcut micro chisels. It's a little tedious, but the iterative process of carving some, rechecking with the top, carving some more, etc. makes for a good fit and the least amount of over cutting. A word of caution, it does take some finesse and a lot of patience.
Once everything fits snuggly and you're good to go, the last step is to apply the glue to the top of the kerfing and sides, smear it good, place your soundboard, then apply uniform pressure along the perimeter with your go-bars. Once it's dry, you can trim the top flush to the sides with a laminate router and flush bit and voila! It's ALIVE! almost...
So the question remains - how'd you do that??? Answer: it was a miracle like manna from heaven;) Ok, fine, I guess I'll tell you. It all begins with kerfing. I started out with reverse rounded kerfing - bad idea... I ordered the reverse rounded kerfing at the beginning of the project along with the soundboard, back, sides, neck, fretboard, and saddle stock. At that early stage I had no idea what I was doing nor what would work best. As it turns out, the reverse kerfing is not the best type to use on smaller bodied guitars.
Kerfing as it turns out is used to provide a better (larger) gluing surface for the back and soundboard. It basically makes a wide ledge allowing more contact surface area for gluing at this critical structural joint. The acoustic guitar is in essence an incredible engineering problem because it epitomizes all the classic trade-offs of weight to strength, form to function, and on and on and on. Traditional kerfing simply means that the cuts in the strip face outward when fastened in the guitar (meaning the slits are exposed to the soundbox). Reverse kerfing, on the other hand, is designed so that the cuts in the strip face the side they are being glued to (meaning the slits are against the side and are not exposed to the soundbox.
My suspicion is that reverse kerfing may provide minutely better sound quality or projection because the sound waves generated by the guitar are not broken up by the small kerfing slits since the smooth backing is what's exposed. But, as I soon found out, reverse kerfing requires larger turn radii - when you try to use it on smaller guitars it snaps far too easily. So bottom line is, I had to reorder traditional kerfing which worked a lot better.
Gluing the kerfing initially was a little disconcerting but as I became familiar with it, I found that there's really not much to it. I started with one side, trimmed a length of kerfing to the proper length, put a long bead of glue along the surface to be glued to the side, smeared it so that the amount of glue was uniform, and then started from the heal block and worked along the sloping curves toward the head block. You need to make sure you have a lot of stiff spring clamps on hand so you can clamp the kerfing along the side as you work your way along it. Don't worry about squeeze out, you just want to make sure the kerfing is a little proud of the edge and that there are no gaps with the side along it's length. If you don't have enough clamps or if it happens to break, it's ok to do it in sections. I found it easiest to actually break each side in two sections, one from the heal to the apex of the waist and a shorter one from the apex to the head block. If you want to remove the excess squeeze out once the kerfing is in place, now's the time to do it, otherwise just trim it with a chisel, plane, or sanding block after it's dry.
The next step is to re-plumb the top edge. I started with a small hand plane and a palm plane, they worked well to get a good clean surface and to knock everything down to the same level. To finish it off, I used a sanding block to make sure everything was level and consistent. The final step before gluing the top is chiseling out the notches for the soundboard braces. To do this I place the soundboard on top, marked the sides, then started carving conservatively with Flexcut micro chisels. It's a little tedious, but the iterative process of carving some, rechecking with the top, carving some more, etc. makes for a good fit and the least amount of over cutting. A word of caution, it does take some finesse and a lot of patience.
Once everything fits snuggly and you're good to go, the last step is to apply the glue to the top of the kerfing and sides, smear it good, place your soundboard, then apply uniform pressure along the perimeter with your go-bars. Once it's dry, you can trim the top flush to the sides with a laminate router and flush bit and voila! It's ALIVE! almost...
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