Number 13 - EIR\Sitka Drednought -Finished

[John Parchem]

Thanks Kevin,

I am not sure why I waited before making an acoustic bridge.

I have been slowly preparing this guitar for finishing. My main concern right now is keeping the maple clean while preparing the rosewood. I have scraped the entire the back and sides and sealed the binding, purfling, back center strip with shellac. I rounded the bindings edges and re applied the shellac. I plan pore fill with z-poxy. To seal the rosewood before I really get going I plan to carefully pad on alcohol thinned Z-poxy. I should be able to create a thin enough coat that I can follow with normal pore filling coats without the need to sand off the seal coat. It might be a nutty idea, but it mimics what I do when I French Polish with shellac and I want to avoid spreading rosewood stained shellac all over.





I also made and installed two version of my hawk in moon logo. The first I made with mother of pearl and ebony. I thought that I had installed OK but, when I had it installed there was a hair line crack in the pearl going straight up from the hawks head. Also I wanted to try a black African rosewood hawk instead of the ebony to look better with the Brazilian Rosewood.







Logo one with ebony would have been Ok except for the crack. It is too small to see in the picture.



Logo two with a Black African Rosewood hawk. Still is very dark under finish but a nice match with the headstock veneer.

[Kevin in California]

I've said it before :>)
That is beautiful rosewood, and you sure are getting good at inlaying your logo.
Great work John

Kevin

[John Link]

John,

You used the Gore equation to determine the initial target thickness of your sound board. I also noticed your bracing for it was on the delicate side. Did you employ any additional empirical testing and associated math to adjust the top and/or bracing for target frequencies as you went along? Or did you rely on tap tone and other more intuitive methods?

Your comments about straight grained East Indian Rosewood are consistent with my own experience. It is strangely under rated as far as I am concerned. There were reasons Martin chose straight grained Brazilian when they built their pre-war dreads. That characteristic is not easy to find in Brazilian today at any price, but easy to find in East Indian, and at relatively modest prices too.

The insides of this instrument have the look of responsiveness.

[John Parchem]

Thanks John, I cut the braces to the drawing specification and tap tuned it from there. I basically went at it until it felt and sounded right to me. The bracing from the bridge plate back are still pretty stout. I did not use any magical equations. I did record the closed box tap tune, I am not quite sure what it means without the bridge on. The bridge will lower the top frequency a bit. The two peaks are the box or air resonance and the top resonance. I made the back non active; my guess it is the small bump around 225 Hz. It looks a lot like the D28 graph in Fig 3.2-7 of Gore's design book.

Mic lower than the sound hole

closed box mic lower than sound hole zoom.jpg (85.51 KiB) Viewed 740 times

Mic pointer at the sound hole

closed box.jpg (129.42 KiB) Viewed 740 times

[John Link]

John, When you take these readings with the mic, how do you excite the top?

[John Parchem]

John, When you take these readings with the mic, how do you excite the top?

I cut about 1/3 off of a felt sanding block and attached it to a dowel. I just tap with it around the bridge area. When using visual analyzer my spectrum graphs are averages from about 10 taps, each space a bit more than a second apart.

[John Parchem]

I have the guitar in the finish room now waiting for the second coat of epoxy to cure.



To finish off the fret board I inlayed diamond shaped pearl. Like I normally do I just glue down the pearl with a dab of white glue. With in 10 minutes it is secure enough to trace. My normal method is to just trace with a .5 mm pencil. This time I traced with my scalpel and filled in the cut with chalk This worked well enough and I started routing out the diamonds. I was switching back and forth between end mills, fine for the outline and corners and a larger one to route out the bulk. Sure I could be efficient do either all of the bulk routing first followed by the fine routing or visa versa. Instead about half through the process I looked at the nice clean cuts I made with my scalpel, deepened them a bit more and used a chisel to clear the waste. I was much happier with the fit. Also it was nearly as fast.