Ergonomic bass build "Twisted Sister"

[TFM94]

So you're not only building a torzal bass but you've also now bound the fretboard? I feel like your lutherie is making fun of my lutherie.

My lutherie would never make fun of anyone's lutherie. It's usually very polite .

The only compromise compared to a straight neck is that this one will not have blind fret slots. It's doable, but inconvenient in this case, because I would have to rout the fretboard radius with the fret slots already cut. For me that seemed like a recipe for tearout, especially with a splintery wood like wenge. I'll just cut the fret tang a bit shorter and fill the side of the slots with ebony dust and glue.

 

[TFM94]

Now I have to decide whether I want to first rout the sides of the neck using the fretboard as a template or radius the fretboard first.

I gave this some more thought and decided to do the rough shaping first. This way I will find out if the neck will spring back a little due to twisted fretboard layers and twisted binding. I'll let it sit for a few days, maybe a week, and check if it has moved. The fretboard radiusing will determine the final twist and I can still compensate for wood movement then.

I now cut the sides and the back of the neck about 2-3 mm within final size. It looks pretty rough, but that's ok. If this build doesn't go as planned, I could still use it as an abstract sculpture .

 

[TFM94]

Just a little progress today, but I'm quite pleased with it.

I cleaned up the back of the neck with rasps and files and got it closer to its final thickness, maybe 1mm oversize. I will wait until the fretboard is radiused to determine the final thickness then.

I also routed the sides of the neck with a bearing bit using the fretboard binding as a template. It worked really well in the jig, so that the neck blank is now absolutely square throughout its length. This way I can use my faceting technique to profile the neck later on. That should be very similar to shaping a straight neck.

Quick tip for building twisted necks: Leave a little square block at the nut/headpiece end. I flattened the back of the neck blank before I started routing the twist in the top surface. Since it's almost impossible to track any wood movement just looking at the fretboard, I can now check if it's straight using the back. After I removed a lot of material from the back of the neck last weekend it developed a little upbow, but nothing that a small trussrod tweak can't fix. Most importantly, the thing has not twisted or sprung back even a little bit. Yay!

 

[Gilmourisgod]

Wow. This is fascinating to watch.

 

[Durham52]

Smart thinking leaving the bock at the headstock end. I probably wouldn't have thought about doing that until it was too late, then I'd have had a "Eureka" moment when I realized, if only I had left a block at the headstock end....

Following this build is a real mind trip and more importantly an education.

 

[Gilmourisgod]

A lot of smart thinking ahead on this build, that’s where my builds go awry. the sequencing.

 

[TFM94]

Smart thinking leaving the bock at the headstock end. I probably wouldn't have thought about doing that until it was too late, then I'd have had a "Eureka" moment when I realized, if only I had left a block at the headstock end....

Following this build is a real mind trip and more importantly an education.

Thanks for the kind words everybody. It is important to plan ahead with a build like this.

The square block at the nut also has a second purpose. I use it to mount the neck in my twisted router jig. I'll keep the block for as long as possible, at least until the fretboard is radiused.

 

[Durham52]

Thanks for the kind words everybody. It is important to plan ahead with a build like this.

The square block at the nut also has a second purpose. I use it to mount the neck in my twisted router jig. I'll keep the block for as long as possible, at least until the fretboard is radiused.

Yes, at least I was smart enough to see at least some other possible benefits of keeping the block, once you'd pointed out that you left it that way, I just doubt I'd be smart enough, or organized enough, to have thought about the possibilities in the first place.

 

[TFM94]

No work on the neck today, but I made some body wing MDF templates. On my last neck-thru build, the Custom Elan-Jazz build, I used a single full body template, but now I'm trying individual body wing templates. Let's see which way is better, maybe it works equally well.

After seeing the body in full size I realized that it was very wide, measuring 14.6"/37 cm at the widest spot, so I scaled it down 5% in width, but kept the length. It should be more comfortable and also easier to fit into cases or gigbags.

I used a "poor man's spindle sander", a piece of sandpaper taped to a spraycan, which is clamped to the table with a piece of MDF to sand the inner radii. Makes me feel like a redneck. It's ok with MDF, but definitely not recommended for bodies.

 

[TFM94]

Alright, the fretboard is now radiused.

I was a bit nervous about this, because here the fretboard radiusing is the final straightening of the neck. I used the curved rail router sled from post #71 to get the radius. It's very close to 16", and I'm quite happy with the result. I routed this in paths with 2mm increments, and the technique reminded me of @Jeff Siddall 's recent fretboard CNC processes. Moving slow with high rpm and a dome bit, I didn't get much tearout, but there's some fuzziness in the wenge parts. The 2mm grooves from the individual passes are still there, I'll sand them out before fretting.

About halfway through the routing procedure:

and the finished board:

This is not on purpose, but it's great to see that the ebony binding matches the darker streaks in the wenge! This way the binding is not so striking, but it blends in very well.

The top fretboard layer got pretty thin at the edges toward the body end, but we're good.

A little problem is a flat spot around the 24th fret. It's in the middle of the board, but not very deep, probably less than half a mm. The green line is the end of the fretboard after cutting it to length.

I have four options here:
1. Ignore it. It's the 24th fret afterall, a bit of sanding and it should not be noticable. if the 24th fret sits a bit lower, no problem (I probably won't use it anyways)
2. Re-rout the whole fretboard radius a bit lower. I'm not into that idea, because it's a lot of work and there's a risk of routing through the top fretboard layer, and that would be much worse.
3. An ebony inlay matching the binding, maybe some rounded shape that blends into the fretboard end.
4. Cut the fretboard shorter and make it a 22 fret neck. That would get rid of the flat spot.

Nevertheless, I'm very pleased with the result. I've never celebrated fretboard radiusing day before, but I think a glass of whiskey this evening is justified.

Btw, this has been very fast progress compared to my usual build speed, and now that I know that the fretboard is ok, there won't be as much progress in the next few weeks. You know, work and stuff. But don't worry, I'll get back to it. Meanwhile, I'll be following the WBO finale, there's some great stuff going on.

 

[mb94952]

That is so amazing and looks so complicated. I can't wait to see it ! Hurry up. Just kidding !!!

 

[Jeff Siddall]

A little problem is a flat spot around the 24th fret. It's in the middle of the board, but not very deep, probably less than half a mm. The green line is the end of the fretboard after cutting it to length.
View attachment 4599796
I have four options here:
1. Ignore it. It's the 24th fret afterall, a bit of sanding and it should not be noticable. if the 24th fret sits a bit lower, no problem (I probably won't use it anyways)
2. Re-rout the whole fretboard radius a bit lower. I'm not into that idea, because it's a lot of work and there's a risk of routing through the top fretboard layer, and that would be much worse.
3. An ebony inlay matching the binding, maybe some rounded shape that blends into the fretboard end.
4. Cut the fretboard shorter and make it a 22 fret neck. That would get rid of the flat spot.

Nice work!

That flat spot: how shallow is it compared to the nominal fretboard level? If it is sufficiently shallow to not be obvious to the eye then I vote for option 1. You could even leave the 24th fret a little proud of the surface there and hold it with some CA to keep it secure.

 

[TFM94]

Nice work!

That flat spot: how shallow is it compared to the nominal fretboard level? If it is sufficiently shallow to not be obvious to the eye then I vote for option 1. You could even leave the 24th fret a little proud of the surface there and hold it with some CA to keep it secure.

I checked with a radius template and a feeler gauge, and it's about 0.3mm deep. The fret would hold just fine, but there is an area of the size of a thumbnail where the wenge grain pattern follows the recess and makes it quite visible. I think I'll do some sanding and see what it looks like.

 

[Jeff Siddall]

I checked with a radius template and a feeler gauge, and it's about 0.3mm deep. The fret would hold just fine, but there is an area of the size of a thumbnail where the wenge grain pattern follows the recess and makes it quite visible. I think I'll do some sanding and see what it looks like.

Yeah, definitely sand first and see how it looks. No harm in that. The 3rd option also sounds like it could be cool. I mean, lots of people put inlays at the 12th fret. Yours would be 24th so... twice as good!

 

[Matt Liebenau]

Good stuff. I believe a toast is well justified. Given the list I’d probably pick option 3 or 4, leaning towards 3 depending on how much ebony you have left and how much you really want to make an inlay.

 

[TerribleTim68]

I'd just ignore it and call it "intended fall-away".

 

[Gilmourisgod]

Leave it, I have a couple 24 fret basses and after confirming that the 24th does in fact sound.... Really high, i virtually never use it. Amazing build, some Booze in order. Maybe a Lazy Boy and some Netflix vegetation too.

 

[TFM94]

Another item in my arsenal of unconventional luthier tools for twisted necks: The miniature sanding beam.

In my previous post I mentioned that I'll sand the fretboard, and it's necessary to get rid of the little grooves left by the dome router bit. Obviously I cannot sand this with a conventional straight sanding beam. I considered hand sanding with a piece of sandpaper, but there's always a risk of creating bumps and valleys. Today I cut a sliver, ca. 1/2" from a normal 16" radius block and rounded the underside. With a 180 grit strip of sandpaper taped to it I can follow the twist and still keep the radius.

It's tedious work, because the sandpaper area is very small and it has to be replaced frequently. Also, my radius seems to be slightly flatter than 16", so I'm sanding slightly more at the edges. But it's all ok, as long as I keep it consistent. More sanding to be done.

 

[Gilmourisgod]

Slick solution. I was wondering how you'd sand that board, i guess I assumed you'd do it by hand. The trick is going to be keeping even pressure despite the physics of arms and hands. Ive had trouble sanding evenly with a full length sanding beam.

 

[RichterScale]

That ebony binding on the wenge looks amazing