Further progress on the two-layer neck

Improvements since last post:
Saddles modified -> lower action
Transparent plastic body (styrene-acrylonitrile) added.
Two screws at the bottom side of the head end holding the two layers of the neck together.
Row of neodymium magnets in M4 blind screws for current transformer pickups.

Future improvements:
String guide - pressing down on the strings before the zero fret, since they tend to rattle.
Row of magnets for current transformer pickup in bridge position.
Screw holes making the saddles lengthwise adjustable for intonation.
Piezo pickups and amplifier.
Jacks, switches, pots etc. I plan to put the electronics on the plastic body rather than on the beam itself.

Progress with the two-layer neck

Still much fitting required, but it's playable and tuning works well. Neck tension needs attention; the two beams don't have sufficient contact at the headstock end.

Two-layer aluminium neck

Among the drawbacks of my old T-beam designs were the lack of a truss rod or similar system to control the bow of the neck.

A way to help this - but still use stock aluminium beam for the guitar - could be having a neck in two layers - an upper flat beam, tightening itself by pulling on a similar lower beam.

I hope the picture explains it, but in case it doesn't: The design uses a screw being retained by a bracket attached to the lower side of the top beam. The screw goes into a threaded hole in the end of the lower beam. When tightened, the screw will draw the top beam downwards, counteracting the pull of the strings.

With this build, I'll try if it works. The upper beam is only the length of the neck. It has frets mounted directly into it. The lower beam extends into a narrow body.

On the bridge end, I plan to mount a "stick-and-screw" tuner system. The prototype shown here works decently. I imagine, that using a brass bracket rather than the aluminium one here as well as harder steel for the screw threads will improve that.

The nut end contains a brass bar for holding the string ends, plus - on the bottom side - a bracket for the screw, that tightens the neck against the strings' pull.

Today, I cut the fret slots in a home made miter box and mounted the frets. The glue (two component epoxy) is hardening at the moment.  Tomorrow, I shall see how well it turned out.

Next steps will be making the brass bar and bracket for the nut end plus drilling the screw hole in the lower beam.

The Bobber - the black SG is further reduced

My black SG has had to go through further alterations. I am trying to see, how much you can modify a stock guitar into something ergonomic. Since cutting away is easier than adding on, i've carved a "shark bite" for thigh rest. It allows the guitar to be balanced in a classical playing position with the neck pointing upwards.

On the bass side, I carved a concave area for the strumming/picking hand. It does away with the sharp edge and makes it easier to hold the guitar.

Both were covered in damp-shaped leather, fastened with epoxy glue and copper tacks.

The shark bite made it necessary to relocate the controls, so I added a series/parallel switch mounted in a slanted copper pipe end cap. The jack enclosure is from copper tube and brass plate. The volume and tone knobs are located in what's left of the original control cavity.

The tip of the bass side horn was replaced with a brass one, while the length of the treble side horn was reduced considerably and topped off with a brass cap.

I am going to abandon the new coarse tuner system for now, so next steps on this guitar might be tidying up the headstock brass plate and remount the old high e coarse tuner.

Improved thigh support

The Lectus Testus has gotten a more adjustable thigh support. The fine-adjustment screw might be over the top... there's a limit to _how_ precisely you need to adjust it, but it _is_ a testbed (and it all is a hobby and supposed to be fun), so on it went anyway. The thigh support was twisted slightly in relation to the body of the guitar. Now it better follows the curve of the player's hip when sitting.



Also added was a treble side horn, giving the player the option of resting the guitar at his thigh in a "traditional electric guitar" style. Unfortunately, the thigh support is now in the way of the flexible outer cables that went from the side of the body to the thigh support, so they had to go for the moment. I might relocate them to the other side of the body.

The whole instrument functions nicely as a playable testbed. It has begun to develop some rust on the steel body, so polishing and bluing might be some of the next steps. Tuning is acceptable, but not extremely smooth. Filing and lubrication should impove that. If not, I'll have to use finer thread (M4 X 0.35).

Coarse tuners part 5

The coarse tuners that I made for the black SG with the Schaller fine tuning bridge were - after all - too troublesome to string and adjust. I've made another attempt, this time consisting of
- a hex screw going through the head plate,
- an acorn nut with a hole for the string and the top cut off,
- and a hex blind screw going through the top of the acorn not, securing the string against the end of the big hex screw.

All screws have been shortened and filed flat at the end. Many other tubes, screws, etc, can be used. The string is secured at the bridge end, inserted through the hole of the acorn nut.

It seems to work nicely, but I'll have to make some more and try different string gauges.

New tuner, bridge, jack and tubing

This last month I've been improving some details of the testbed guitar:

The tuner has been changed to my slider-based design. It is mounted on an angled plate ensuring that the strings have sufficient break angle over the saddles. The angle also keeps the sliders in contact with the plate. I've used six modern strat style saddles for sliders - when I get around to it, I'll make some better (and prettier) ones from brass. Using the right screw hole for securing the string ensures that the pull of the string tightens the screw. It's got more travel than I need, so I'll shorten it around 5 mm. The knurled knobs are standard DIN 466 brass knobs. I've used two for each slider so the fingers have more grip surface. They're interlocking with one another, giving great utilization of the existing space, but making it difficult to remove one without loosening them all.


The tuner works very well. The grooves and lid that you see on most other headless slider based tuners aren't necessary, as the string pull keeps the slider oriented lengthwise. When I get some tools for making fine thread (M3 and M4 x 0,35), it'll be even smoother.

The bridge is an improvement from my earlier design consisting of two saddles each holding three strings, but is a bit simpler: It is reversed, being fixed to the body in front of the contact point of the strings. This gives me a shorter overall design, allowing for the tuner to be placed closer to the bridge. 

Action is set by lifting or lowering the saddle with the small blind screws in the bottom and then securing with the big inner hex screws. Intonation is set by turning the blind screws going through the vertical flange of the saddle (they press against the big hex screws).

The jack holder is a copper pipe cap - thanks Martin for the brilliant idea. I'll use them for swithces and potmeters as well. The copper tube holds the wires, shielding them from electrical interference. The flexible cable is a piece of gear cable outer tubing back from the days when I was racing bicycles. It allows for the thigh rest to be moved and turned.

It is common among some luthiers to give their guitars a name. Since it's a testbed, and bed is called Lectus in latin, I'll call it Lectus Testus. Yes, it's rubbish latin, I know. And yes, it might actually mean something different.

Added: I just weighed it: 2,5 kg as it is now. That's not too bad.