It is difficult to see all of the 3D details of the plans for this instrument without some reference photos and some explanation. Although I don't have a formal document describing the construction, here are some informal notes from correspondence with folks who built copies of this instrument from the plans. There are also some photos which show what some of the construction details look like.
Initially appeared: March 15, 2002
Last updated: September 11, 2018
This picture shows the braces glued to the top, but the bridge brace is not yet drilled for the threaded inserts for the saddle height adjusting screws. It also shows the string anchor plate glued into the body. In the plan, at the butt end of the body there are two bosses that have not been routed away when the body was hollowed. These get cut down 0.25" and a 0.25" hard maple string anchor plate is glued onto them. When the top is glued on, its bottom surface will contact the top surface of this plate. After the top is glued on the mortise for the neck joint is routed into the top. The instrument has a set neck, using a Gibson electric style horizontal dovetail joint.
The keyhole string anchor holes are routed right through the top and the string anchor plate. Here you can see both the bridge height adjustment screws and threaded inserts in the brace and, behind the brace the string anchor plate in the finished instrument.
The Gotoh battery box is mounted in the cover and the preamp in its shielded box is also mounted to the cover. Note the two holes in the cover plate that provide access to the bridge height adjustment screws. Note also the strap button mounted up a little from the centerline. This helps the instrument hang from the strap at a better angle.
The volume pot is mounted to a brass plate which is in turn screwed to the inside of the wall of the body. A very small right angle screw driver is needed to do this, as you've got to work through the upper cavity hole in the back.
The bridge is a blade of maple with a slot sunk into it for a plastic saddle. A standard piezo under saddle transducer is in the slot. After the transducer is mounted a small spacer block is glued across the middle of the slot, so that two saddles are used. This is done because the bridge blade is so narrow that its front and back walls flex in the middle without the spacer block.
The bottom of the bridge has a sheet of brass glued to it to keep the adjuster screws from penetrating the maple. The bridge sits in a slot routed through the top and into the bridge brace. After the slot is routed, two holes are drilled for the bridge height adjustment set screws in the floor of the slot, right through the brace. A hole for the transducer wire is also drilled right through the brace. After the holes are drilled the height adjustment holes are reamed from the bottom to accept threaded inserts, which are inserted from the bottom. Allen set screws are threaded into the inserts.
This instrument is sized for extra long scale (38" wound length) electric bass strings. I use regular flat wound strings as they have the mellowest tone, but this is all a matter of personal taste.
Piezo transduced basses need some eq - they are just too tinny sounding without it. You might want to experiment with the eq before you commit to circuitry. As a starting point try boosting the lows about 15dB, attenuating the mids about 3dB, and attenuating the highs about 15dB.