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Old 11-01-2019, 10:35 PM
Arumako Arumako is offline
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Join Date: Dec 2016
Posts: 25
Default Little Improvements

Thanks for the kind comments upsidedown and rockabilly69. Been making progress on small repairs and improvements here and there before closing the box and just wanted to post some updates accordingly as each of these small steps are pretty important to ensure overall functionality once the guitar is re-assembled.

As progress is made, I'm finding that both the previous repair attempts and (very uncharacteristic of Japanese builds of this era) the original build were less than admirable - perhaps built by an apprentice or a prototype? Certainly not representative of the craftsmanship inherent in typical Nardan builds.

First, the old adhesives holding the neck block and top needs to be freshened up. The joint needs to be cleaned up with thin strips of sand paper with backs reinforced by clear packing tape (if the sandpaper tears and leaves residue in the joint, adhesion will be severely compromised). With the guitar facing down, the neck is pushed down gently while glue is pushed in with a spatula and wiggled gently. Clamp down, once everything is set.

Re-gluing this while there is some flexibility in the overall assembly is important. The flexibility allows Titebond to move deeper into the joint to ensure a stronger bond. Once the side braces are installed the overall rigidity of the assembly won't allow for any wiggle.

The shape of the butt-end of the guitar was corrected when the old kerfing was removed, and this centered the tail block nicely. Of course, that means the tail piece position and strap button need to be re-positioned. The first order of business is to fill the old strap button. An old broken birch drumstick was cut and shaped like a dowel to fill the hole.

Once the glue dries the ends need to be filed/sanded down. Taking a file directly to the inside of the tail block is fine, but the outside needs to be covered with masking tape to ensure the finish is not scratched to oblivion.

Decided to use K&K's Twin Spot passive transducer pickups. Although the output levels of these transducers leave a bit to be desired, the tone and voice are pure and can be shaped with a pre-amp or mixing board. I really like the simplicity of these units. The output jack acts as the strap button as well; so a new hole needs to be drilled in the center of the tail-block. A half-inch spade bit is used. It's nice when the back is off because the spade bit can be drilled from both sides to ensure no tear-out.

Just need to be really careful and drill slowly. The density of the birch drumstick dowel/filler and the actual tail block wood is so different. After drilling the center guide hole, I realized how soft the tail block wood was. In addition, it was probably too green when the guitar was built 50 years ago, and as the wood seasoned, the shape of the block changed significantly.

Before final assembly, the back is positioned as a dry run, and the angle of kerfing is checked to ensure the fit is perfect. Imperfect areas are marked with pencil, the back removed, and kerfing filed down. This is repeated until the accuracy of the fit is verified.

Finally (for now), the bridge is shaped by fitting a piece of 120 grit sandpaper between the top and the bridge.

The bridge must be moved in exact parallel motion with the top to ensure the bottom of the bridge and the top meet flushly. Although it's simple, the process is quite time consuming. If the fit is not flush, full resonance will not be achieved. Here's another dry run to verify fit before everything is assembled.

Still got a ways to go, but making steady progress. Thanks for letting me share AGF!
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