Bass Build, Volute Question (+solution!)

[Timm]

Hi everyone,

I've been reading along here on LT for a while now, it's been super helpful. Now I want to share some of my builds and also seek out your expertise.

I've built a couple of electric guitars, but currently I'm working on my first bass. It will have a Billy-Bo shape, similar to this guitar that I built earlier this year. It's a 4-string and scale length is 34".

The bass neck is already rough shaped, it is a laminated 4-piece mahogany neck with Maple/walnut/maple veneers in between the mahogany. The fretboard is Ziricote.

Unfortunately, I placed the volute a little bit too far back into the headstock (see picture below). Damned! The neck is fairly thick, 22.5mm at the nut (incl. fretboard). It is reinforced with two carbon strips 6x6mm, but they end just before the end of the fretboard. With the cutout for the trussrod nut at the headstock (9mm deep by 8mm wide) I am wondering if the transition between neck and headstock will be strong enough. It is 16 mm thick just behind the nut and 40mm wide. Oh yes, and it's scarf jointed.

On a guitar I probably wouldn't worry about it, but what do you think for a bass? How much more tension do the four bass strings put on the headstock?

 

[Timm]

So, I was puzzling my head over this during the last days, and I've come up with a solution. It might have been just strong enough as it was, but I feel a lot more confident to take this bass on the road now that I have reinforced it. Maybe this thread will be helpful for someone running into a similar problem.

Mechanically, it would have been best to reinforce it on the opposite side of string pull (on the back of the neck, where the volute is/should be). However, as it is already shaped and the neck profile is almost final, I decided to reinforce it on the fretboard side. I had a cutoff piece of Ziricote from the fretboard blank that has the continuing grain pattern of the fretboard at the nut. So I used it to fashion a top layer to go behind the nut and the front of the headstock, where the trusrrod cover would usually go.

Step 1: I cut a 3 mm deep slot with my fret saw right where the front of the nut will go. I moved the nut 4mm further down the fretboard to give the new piece more glueing area. I can easily adjust the bridge position on the body. Then I have taken a chisel and made a 12mm slope between the front of the nut and the end of the fretboard.


Step 2: I thicknessed the scrap piece of Ziricote to 5mm on one end to 2mm on the other. Then I cutout the shape of the top layer and gave it a bevel on the front so that if forms a scarf joint with the fretboard.


Step 3: Point of no return: I glued the piece onto the top of the headstock and to the slope of the fretboard. The scarf joint to the fretboard turned out fairly clean.


Step 4: The next day I sanded it flush with the fretboard sides and headstock sides and chiseled the nut slot (6.5mm wide). Wow, that black streak in the fretboard really didn't like to be chiseled In this configuration the fretboard scarf joint will be hidden underneath the nut when looking at the face side of the neck. I still have to clean up some glue residue on the headstock.


Step 5: As i have glued my trussrod access shut in step 3, I have to drill an access hole. This was super scary, because I knew that I couldn't cover it up with anything if I messed up. The material is built up pretty thick behind the nut and the strings will run low over the wood, so I couldn't put a trussrod cover on top as I usually do. I decided to go with a Fender-style access hole and drilled it with a 25 degree drilling jig made out of thick plywood. Lucky enough, it turned out very clean and I can now access the truss rod with a ball-end hex key.

Now the transition area between neck and headstock is 21mm at the thinnest point. Seems reasonable to me. I still have to figure out how to deal with the section behind the nut when radiusing the fretboard. It will probably get a little bit of a radius, too.