Bass of the Week: Karl Thorkildsen’s 7-string fretless bass

This weeks bass comes to us from a facebook post by Karl Thorkildsen.

Karl documented the construction step-by-step in this facinating forum post at TalkBass.

The basic idea of the design is like a semi hollowbody, except that it’s hollowed out to the max inside and is twice as thick as an electric to add more resonant space. Also it is a neck-thru design but there are some structural and acoustic tweaks to the way the neck goes through the body and the way the bridge is mounted in order to maximize the quality of both the acoustic and amplified sound.

This is basically an all Maple bass, but pretty much everywhere there are multiple Maple laminations with walnut veneer highlights in between. All chrome hardware. ABM piezo bridge and one Bartolini magnetic pickup right at the fingerboard. Bookmatched fretless lined (Maple) Macassar Ebony fingerboard. 34 inch scale and 7-string fretless. Some of the electronics is still TBD, so I’ll get to that in the next week or two.

I used a regular fret sawblade to cut the slots. Now I’ve taken the Maple veneer and cut pieces on a paper-cutter (don’t tell my wife). Since they fit pretty tight I then thin them a bit with a piece of 120 sandpaper. Then I mix some Titebond with water to make a thin glue that won’t try to set-up and make the veneer stick before it’s all the way into the slot. This also makes it easier for any excess to escape.Then one by one I test fit, smear glue on the bottom edge of the veneer, slip it in place, and wipe off excess glue. After it drys, I take a sharp chisel (just sharpened so it’s almost razer sharp), and trim the excess veneer off. The rest will be cleaned up with a radius block.

Someone had asked in another thread about cutting f holes. I do it the old fashioned way. Drill a hole and get the coping saw in there and cut them out, then clean up with files then sandpaper. It’s a pain but gets the job done.

Being a 7-string I’m putting in two rods. After laying out all the cuts on the neck blank I know where the truss rods belong. So I mill the slots out before moving to the bandsaw. These are hotrod trussrods so the slots are .460 deep. Angled to follow the neck sides. Also Alex wants the magnetic pickup as close to the fingerboard as possible so the adjusters will be available through slots at the very end of the fingerboard.

Ok, now we’re getting to the fun stuff. The upper and lower sections of the neck get cut out to create the opening between the body wings. I leave just over .200 which is basically the same thickness as the front and back of the body. Also it’s kept thicker where the pickup will be and where the bridge screws on. It’s down to .200 under the saddles though. Also inside the body wings blocks are attached in the same areas for the pickup area and bridge screws.

Ok, now we’re getting to the fun stuff. The upper and lower sections of the neck get cut out to create the opening between the body wings. I leave just over .200 which is basically the same thickness as the front and back of the body. Also it’s kept thicker where the pickup will be and where the bridge screws on. It’s down to .200 under the saddles though. Also inside the body wings blocks are attached in the same areas for the pickup area and bridge screws.

All and all it’s an increbile build and well worthy of the being a Bass of the Week. Head over to the TalkBass thread to see even more information and pictures from the build.