Hi everyone. Since my high school years I’ve had an idea to build my 8 string guitar. In 2001 I built my first guitar. It was awful. Some time ago I decided to build a new one. I started with searching for information everywhere, and I found Instructables. But I didn't find any topic about 8 string baritone hence I’m writing my own.

Step 1: Design, Materials and Instruments

I take a big piece of paper and make a drawing at a scale of 1:1. I choose a string length of 685 mm that will result in more overtones in the sound. I want to have 27 frets, that’s why the neck is longer than normal.
Why 27? Simply because it is 3^3, and it looks nice :)

I don't include all the calculations, because it is a simple math, and you should be able to calculate all the dimensions for guitar with any number of strings, just remember:

- leave 4 mm between the string and the edge on both sides of the neck.

- choose different spacings between strings on the bridge and the neck end (10 mm and 7 mm in my case). Materials:

- any hardwood from the trash. Here it is an oak, beech and birch.

- fingerboard - wenge.

- some noname pickups.

- noname bridge and head-machines.

Instruments:

- drill.

- little carpenter’s plain.

- a lot of sandpaper :)

- chisel 6 mm

- clamps and bricks

- small hummer

Step 2: Neck Workpiece

First of all I make a neck. I decided to make a neck through, for longer sound time, and it look nice.
I glue first piece together. Make cut for necks head. This workpiece I cut on axel, put inside birch board, and glue this sandwich.

Step 3: Building Body

For body I take a lot of different pieces of wood, which I collect, glue them together. In that moment I had only 2 short clamps, and can glue only one side of body. For gluing another side I use bricks.
After gluing I cut off excess with drill. Inequality remove with extra large sand paper. After I sand, sand and sand like sand-machine, and made smooth shape. I covered holes with little pieces of wood.

Step 4: Inserting Tossrods

I waited a long time for carbon toss rods delivery. I choose carbon for ultimate sustain.
With chisel I made grooves, and glue with epoxy. I did the same with regular rod, but did not glue it.

Step 5:

For fingerboard I chose wenge. I can buy it in local shop. Hard and tough wood for working.
I had to make my own DIY round-block to shape its profile. I made it with old bicycle rim, 26". My fingerboard have 12" rounding. I, actually, bought one round-block, but it was to thin, my fingerboard too wide for those round-block. In JS I calculate 27 elements of geometric progression root of 12 degrees from 2. I can use fret calculator and had same result. I used piece of metal saw 0.5mm-wide to make grooves for frets.

For hitting frets I use little hummer and piece of wood. And of course, I glue frets.

Level all frets with flat board with sand paper. After that I sand all guitar. First layer of lacquer was flaxseed oil. After 16 days of drying and polymerization I make another 5 layers of lacquer.

Step 6: Finishing

Finally, sanding with ultra thin sand paper (800, 1000, 1500 and 2000) and polish with polishing for cars.
I made electric shielding for pickup niches using copper tape. Connect all and test. I think look nice. And sound pretty nice too.