Ergonomic bass build "Twisted Sister"

[Levent]

This makes me think If It's possible to mix Compound radius
Multi scale fan fret
Torzal twist
True temperament
Scalloped Fretboard
Frets would look like cut out from a curly mobius strip?

 

[Flamingo21]

Compound radius
Multi scale fan fret
Torzal twist
True temperament
Scalloped Fretboard

.

 

[TFM94]

This makes me think If It's possible to mix Compound radius
Multi scale fan fret
Torzal twist
True temperament
Scalloped Fretboard
Frets would look like cut out from a curly mobius strip?

From a technical standpoint it's possible, but obviously very complex. Router jigs will not suffice for a compound radius, sounds like a job for the CNC.

Edit: @Jeff Siddall already showed is efforts in compound radius twisted fretboards with a CNC in this post.

 

[Jeff Siddall]

From a technical standpoint it's possible, but obviously very complex. Router jigs will not suffice for a compound radius, sounds like a job for the CNC.

I have one of these planned. Well, maybe not true temperament or scalloped fretboard.

 

[TFM94]

Ladies and gentlemen of the Luthier's corner,

while I'm waiting for new dremel bits to arrive to continue with supersymmetry, I finally had some time to work on this build. It's been really quiet around here, time for some updates.

After a long break I first had to check if the neck is still straight. After fiddling around with the suspended guitar string I declared it to be straight. It's not the precision tool I want it to be, but I think we're close enough.

The first step this weekend was shaping the neck profile. How do you do that on a twisted neck? Basically like any other neck, I used the faceting method for the rough shaping and then adjusted it from there. I always find myself removing more and more material from the shoulder. I wonder if this is normal... The heel is not fully carved yet, I'll blend it in with the body wings once they're glued on.

Nex up is the volute. There's no precedence on what a twisted multiscale headless volute should look like, so I just started rasping and filing away until I found a shape I like. It is highly asymmetrical, both in outline and height, but it fits the overall style. I still need to refine it a bit and sand out some tool marks, though.

On to the fretting process. I tried to mark the fret position with a ruler and pen directly on the fretboard, but that is incredibly awkward due to the twist. I drew up a paper template instead, cut it out, taped it to the fretboard, made a shallow incision with my fretsaw on both ends of each fret, removed the templated and cut the slots from one side to the other. A bit unusual, perhaps, but it worked well enough.

The actual fretting process was similar to a normal neck. For some some frets I had to position the neck at a weird angle in the fret press, though. I undercut the fret tang on each end so that I can fill the slot with ebony dust and superglue later.

And that's it for the weekend, folks. The next steps are fret ends and side dots. I have the body wings ready to be glued on, I hope it won't be long until we see it in one piece. Stay tuned!

 

[Hout]

Wow, that's really cool neck! Amazing work!
Trying to wrap my head around leveling the frets on such a board..

 

[Videojunkie]

Wow, that's really cool neck! Amazing work!
Trying to wrap my head around leveling the frets on such a board..

I was thinking the same thing...

 

[MPU]

Wow, that's really cool neck! Amazing work!
Trying to wrap my head around leveling the frets on such a board..

Just follow the string path and blend between them. A bit tricky but not too difficult.

 

[JIO]

Just follow the string path and blend between them. A bit tricky but not too difficult.

You took the words right out of my mouth! Visually it throws you off - but the task remains the same as standard fretted neck.

 

[TFM94]

It's been a while, but finally I got a little work done on this build. It ain't much, but maybe enough for an update post.

A list of problems accumulated during this build, things that are usually quite easy, but somehow more demanding this time with this unusual geometry. I'm talking about the control cavity and the neck profile, among other things. The control cavity is challenging because the lower body wing is strongly tapered toward the outer edge, so that the standard routing method would not leave a constant thickness at the top. The ideal tool would be a pin router with the template mounted to the top of the body wing, which is then routed from the back. I don't have a pin router, so I used a router sled and a pattern bit, with the disadvantage of having to mount the template to the back of the body wing, which is at an angle. This resulted in the uglies control cavity I've ever made, but at least the top has consistent thickness. I think I'll not attempt a recessed backplate here, because later I want to radius the back of the body. The easiest way seems to be a proud, beveled plastic backplate, like a strat trem cover.

Here are some pictures of the cavity. It's not pretty, but at least it's done.

The second thing that was holding me back was the neck profile. I used the faceting method for basic shaping, but it left way too much material at the shoulder and the neck felt huge. The neck is quite thick anyway (It needs to be a bit thicker because I had to mount the TR a bit deeper because of the twist), so getting a comfortable shape was very important. A few evenings of rasp, sand, check and repeat got me to a shape that feels nice. I don't know if the profile is perfectly consistent throughout the neck and I can't check that with a straight edge, but it feels good now.

Just as I prepared the body wings to be glued on, I realized that I forgot to install side dots. I have to order some more luminlay sticks, so it's going to be a while until I can glued everything together. Until then I'll do some more fine-tuning of the volute and other details. Also I have to decide what roundover/bevel or other edge I want to have at the body. Perhaps it's a good idea to rout that before gluing the wings on. Stay tuned!

 

[TFM94]

Update time. I finally finished my list of things to complete before I glue the body wings on.

An important part of that is side dots. After I used Luminlay side dots for my last two builds, there is no going back. 3mm super blue all the way. They are large enough to see during the day and glow nicely when it's dark. So, I drilled some holes with a handheld drill. It felt a bit wonky to drill at different angles, but the exact angle doesn't matter all that much as long as the hole is positioned properly.

Then it was time, the moment we've all benn waiting for: Gluing on the first wing. I decided to glue the top one first because it is longer and harder to clamp. The bottom wing should be easier because it has the control cavity to clamp into. I temporarily attached some MDF pieces with the masking tape and superglue trick to have a proper surface to clamp to. I used some locator pins, with all these different angles I didn't want to take any chances of misalignment.

It's still in the clamps and I'll leave it there until tomorrow. The bottom wing will follow very soon. Stay tuned!

 

[Jeff Siddall]

Looks great! I agree, everything gets wonky on a twisted bass so I can appreciate your struggles.

 

[TFM94]

And, as promised, the second half is now glued on:

There is no flat surface to rout theoutline of the transition between body wings and neck beam, so I took a saw and a sanding block and did some free hand shaping. I'm still happy with my decision to ditch the horns, this way it looks a bit more mellow, and it's more compact, too! Now it even fits in my guitar-sized gigbag

From the bridge end, the body profile looks like this. I shaped the top edge of the bottom wing so that it continues at the same angle as the neck beam. Later I will round this edge to have a smoother transition.

The back of the body will have a concave carve (like a Spector), so the weirde edges on the back will disappear and it will be a bit thinner, too.

Now I have to figure out three things:
- Build a radius jig for the back of the body. @MPU and @Barticus had those in their build threads, I will use them as a template.
- I'll have to do a mockup to determine bridge height. I will have to flatten the bridge mounting area anyways, but I'm not sure how much of a recess I need.
- Figure out a good way to rout cavities (PU, bridge recess and tuner access) to the top of the body. Right now the twist continues over the body which looks nice, but there's no flat spot to mount a router template to. I guess supporting the templates with tapered strips of MDF could be the way to go.

 

[Barticus]

And, as promised, the second half is now glued on:
View attachment 5128022

There is no flat surface to rout theoutline of the transition between body wings and neck beam, so I took a saw and a sanding block and did some free hand shaping. I'm still happy with my decision to ditch the horns, this way it looks a bit more mellow, and it's more compact, too! Now it even fits in my guitar-sized gigbag

View attachment 5128025 View attachment 5128021
From the bridge end, the body profile looks like this. I shaped the top edge of the bottom wing so that it continues at the same angle as the neck beam. Later I will round this edge to have a smoother transition.

The back of the body will have a concave carve (like a Spector), so the weirde edges on the back will disappear and it will be a bit thinner, too.
View attachment 5128024
Now I have to figure out three things:
- Build a radius jig for the back of the body. @MPU and @Barticus had those in their build threads, I will use them as a template.
- I'll have to do a mockup to determine bridge height. I will have to flatten the bridge mounting area anyways, but I'm not sure how much of a recess I need.
- Figure out a good way to rout cavities (PU, bridge recess and tuner access) to the top of the body. Right now the twist continues over the body which looks nice, but there's no flat spot to mount a router template to. I guess supporting the templates with tapered strips of MDF could be the way to go.

This is crazy cool!
Great work can’t wait for the final sound clips

 

[MPU]

When you finish this bass I have to come and see it live! Very nice build in every possible twisted way!

 

[Max Bogosity]

- Figure out a good way to rout cavities (PU, bridge recess and tuner access) to the top of the body. Right now the twist continues over the body which looks nice, but there's no flat spot to mount a router template to. I guess supporting the templates with tapered strips of MDF could be the way to go.

I had a similar, but easier, problem with my 'King In Yellow' with the curved top. Separate clamping and levelling features on the template might be useful in this case too.

Another option that didn't occur to me until later is that you don't need a template at all to cut a rectangle on the typical 'sliding bridge' style router planing fixture. Just clamp stops on the X and Y rails to restrict the router's travel to the dimensions of the rectangle you want to cut. I'd want to do a few test pieces first, but I'm sure it would work.

 

[scuzzy]

beautifully done. the simplistic beauty of the wood contrast is made up for by the complexity of the design.

 

[TFM94]

After a long break once again I have made a little progress. Just a little bit, though.

I finally got to building the concave radius jig to rout the back of the body. I think I've never build so many jigs for a single build before, but it's actually something I enjoy. This jig is a really simple version of a typical radiusing jig (as seen many times here in the LC). No bearings or wheels, just MDF sliding on MDF.
Anyways, here it is in action:

Now that the back is routed, I can shape the heel. It feels a bit weird because it is thicker on the treble side than on the bass side, but I think it will get there with a bit of fine tuning.

You can still see the router marks from the radiusing process, and there is a lot of curved surface sanding in my future. Any advice on this? I'm thinking about a foam pad with an attached sanding disk on my random orbital sander, but I haven't tried it.

One of the next steps is routing the surface for the bridge and headless tuner recess. Right now the center beam of the body just follows the twist of the neck, but I have to rout a flat area for the bridges to mount to. I suppose it's time to build another jig...

 

[Jeff Siddall]

After a long break once again I have made a little progress. Just a little bit, though.

I finally got to building the concave radius jig to rout the back of the body. I think I've never build so many jigs for a single build before, but it's actually something I enjoy. This jig is a really simple version of a typical radiusing jig (as seen many times here in the LC). No bearings or wheels, just MDF sliding on MDF.
Anyways, here it is in action:
View attachment 5255125
View attachment 5255124

Now that the back is routed, I can shape the heel. It feels a bit weird because it is thicker on the treble side than on the bass side, but I think it will get there with a bit of fine tuning.

View attachment 5255130

You can still see the router marks from the radiusing process, and there is a lot of curved surface sanding in my future. Any advice on this? I'm thinking about a foam pad with an attached sanding disk on my random orbital sander, but I haven't tried it.

One of the next steps is routing the surface for the bridge and headless tuner recess. Right now the center beam of the body just follows the twist of the neck, but I have to rout a flat area for the bridges to mount to. I suppose it's time to build another jig...

Nice work!

Not that it will help you, but I created the bridge block in FreeCAD. Next step is to double check that it is at the right angle before I actually start cutting it on the CNC. I honestly don't know how I would build that without CAD/CAM so all I can do is wish you good luck!

 

[TFM94]

Nice work!

Not that it will help you, but I created the bridge block in FreeCAD. Next step is to double check that it is at the right angle before I actually start cutting it on the CNC. I honestly don't know how I would build that without CAD/CAM so all I can do is wish you good luck!

My current plan is to make a template for the bridge mounting "shelf" outline (similar to a pickup template) and then suspend that over the body with tapered strips of MDF so that it matches the correct angle at the front of the bridge (or rather where the saddles will be). Then I have to see how far I have to rout to get a flat mounting surface. If that makes the bridges too low, I could still lift them up with an inlaid mounting plate. The good thing is that there's some adjustability in the bridges so there is a bit of leeway as long as I get the positions right.