This is looking really good, I’m waiting patiently for your build pictures of the top half of the shell 
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Carbon fiber fretless four-stringer
- Thread starter MPU
- Start date
Well something went wrong with the top. For some reason I don't know the laminate did not bond to the clearcoat. I have to brush a few coats of epoxy over the top and level sand it before I can continue fitting the top. Luckily there's things to do with the back while fixing the top.This is looking really good, I’m waiting patiently for your build pictures of the top half of the shell
Truss rod channel side beams fitted and filleted in. There’s 6mm thick acrylic strip between beams to keep the sides at correct distance. It’s also easy to aim that the channel is straight. I thickened the epoxy with cf dust from sawing the pieces and chopped cf tow. That makes the fillet strong enough so no need for laminate layer in the neck.
And the top with third leveling epoxy coat.
Tomorrow I have to test if my foam still works. It shows no signs of not working but I’ll test it anyway. I’m fitting the top before foam. I want to get as tight as possible fit at sides and also at the center beam. Neck top plate will be last as that needs to be at the right height and angle from the top.
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How are you going to do the pickup routes… I’ve never worked with CF before, does it require special cutting bits so the fabric doesn’t fray/crack as you cut it?
I’m going to route the pickup cavity with Dremel spiral cut bit. I’m rough cutting it with cutting disc. No special bits needed.
Truss rod channel trimmed to the height of the neck beam. I also got the top fitted pretty close. Some fine tuning left. I forgot to test the foam. That will have to wait until tomorrow.
I've never worked with CF but hear lots of nasty stuff about the dust and fibres that come off when you cut or sand it. How do you deal with that?
3M ventilated dust mask, long sleeved shirt, gloves and vacuum cleaner always when I'm cutting or sanding anything. Seems to work fine. Carbon fiber dust is not as irritating and itchy as glass fiber. Uncured epoxy is something to note as it's quite allergenic. When cured it's not allergenic any more that any other dust.
Agree with @MPU about the PPE listed above, plus I try to do CF work outdoors when possible so I don't need to cleanup so much mess inside. One thing to note, unless you are sanding the "end grain" of CF you are not actually sanding CF directly but rather just the cured epoxy top layer, which is basically just plastic dust and generally not an irritant. I also generally try to wet sand so there is no dust at all.
I got an idea for pickup. I have a DiMarzio J set. I can make a twin j pickup out of them in closed covers. Like Delano DJC or MEC TJ. DiMarzios are two coil per pickup. I plan on making them switchable so that I can have twin j, p, reverse p or single j configurations. Now just the wiring. I suppose I need switch for both j which switches between EA coil, both coils and DG coil and volume for each pickup. Any other wiring ideas? No need for parallel/series switching.
I have a quad-coil Bartolini in one of my fretless basses that I wired up as if it's two separate J pickups, with separate volume control for each. (Would have preferred a Blend pot, but the preamp I chose wasn't available that way.) Varying the balance between the front and back coil pairs yields some fascinating shadings of the basic instrument tone; but it's subtle, not overt.
I think the useable configurations would be series P, reverse series P and parallel both J. That would probably give consistent volume through the choices. Now you have me thinking as I have an old set of Dimarzio Js myself but probably would make a custom wood cover.
Two 3-way switches. One for the EA coils (bridge, both, neck) one for the DG coils (bridge, both, neck). Not sure how that can be wired so you get series wiring in "P modes" and parallel wiring in "J modes." You could go with series all around, but I think the tone of will be too similar between J and P modes in series.
Maybe a rotary switch for P, reverse P, neck J, bridge J, all-4-coils?
Don't know yet. I think I'm going to test each one and choose the ones I like the most. Four options may have three too many for me anyway!
Foam poured in the neck beam. Tomorrow I’m cleaning the mess. 2k urethane foam cures hard with no uncured spots like you get in 1k urethane foam in thicker places. This foam also sands easily without breaking into small pieces. I may have to do a small fill cast in some places.
This is a very interesting build and I've very curious as to how it will turn out. Thanks for sharing all the detail thus far.
I have a rotary switch, it's 4 or 5 position if I remember right. That is a good alternative if I just find out how to wire it. Last time I used one it was a nightmare to wire. Rotary switch wiring is something my brains just don't understand.
