"FiberD" carbon fiber 5 string build

[Jeff Siddall]

Just read through this whole thread. Looking forward to seeing how the neck turns out, I've always wanted to try something similar to this. I may have skimmed too fast and missed these details, but are you including a truss rod? If so, from the back? And what about the fretboard? Is that what the wenge is for? And you're gonna glue it to the top CF surface of the neck you just bagged?

Actually, I don't think I mentioned it but yes, there will be a truss rod, from the top, under the fretboard. Due to the thickness of the CF it was iffy whether I could put it under the CF and still have enough clearance to keep it from coming through the balsa on the back of the neck. Amongst all the other things I need to do is construct a CF truss rod channel since the balsa is too soft to support the truss rod on its own.

And yes, fretboard will be wenge also, probably epoxied to the CF, along with the wings. I will likely use dowels on the wings since those could be exposed to much greater forces.

 

[MPU]

I made the truss rod channel with waxed 6mm acrylic beam. I routed the channel 8mm wide, 1mm deeper than final. I wetted cf cloth strips, laid them over the acrylic beam and pressed the beam to the channel with clamps. No need for excess clamping, just enough to press the beam in the channel.

 

[Jeff Siddall]

Yikes, 9 months have gone by since I worked on this build!

I had the day off today so spent much of it working on the neck. The next big jobs were shaping the back of the neck, since it was more/less still just a giant block of wood, and final shaping the perimeter.

One of the strange things about working with CF wrapped wood is that the wood part must be significantly smaller than usual due to the thickness of the CF skin. Adding to the complication is that, to allow a flat sheet of CF running the length of the neck, I needed to make the fretboard much thicker than usual (about 8 mm or just over 5/16") so the fretboard will be a significant part of the neck contour, further narrowing the required size of the CF/wood part. All that meant calculating and marking things much narrower than what looks right:

After marking I used a cutoff wheel to cut the CF, and a jigsaw to cut through the balsa, then final shaped with rasps and files. I wore full sleeves, nitrile gloves, a respirator and safety goggles this time and thankfully no nasty itchy rash.

Here is a view during final shaping the perimeter:

Then onto thicknessing the headstock:

Started with a table saw and finished with a hand saw, then got to final thickness using rasps and files.

Then moved onto thicknessing the neck contour with the router sled:

I think I might win the contest for thinnest neck ever, at about 9 mm at the 1st fret:

After covering in CF and a thick fretboard it will end up about 20 mm at the first fret so not especially thin. However, it will be thin enough that the truss rod will need to be inset into the fretboard.

So much work yet to go, but at least a bit closer now.

 

[Jeff Siddall]

Got a few more hours in on this project and all the balsa work should be finished now. I started with marking facets. Had to use Sharpee for that given how easily the wood dents with anything as hard as pencil:

I went straight to rasp and file, no need for a flap sander with so little material to remove. It's also very fast to rasp balsa, with primary facets only taking about 5 minutes.

After removing the facets went onto blending and then level sanding. Once all that was done moved onto heel and headstock transition shaping. I was especially pleased with the headstock transition as I was able to connect the tips of the headstock into a continuous smooth curve:

Here is the finished back of the neck:

Here is a side view:

So strange seeing a neck that thin (less than 9 mm so far).

Next step: laminating the back with CF. That will be the trickiest part of this build by far, with all the odd shapes and angles, so I am not exactly looking forward to it. Time to muster some courage.

 

[MPU]

Cover the front with masking tape before laminating. This way you have a mark how far you have to sand when sanding the overlapping carbon back laminate. You could even mask the sides and back and wax the front tape before laminating. That makes easy release for the excess cf laminate.

 

[TerribleTim68]

Nope, nope, nope. I'm not even close to ready for that. I freaked out over carving a normal neck to a realistic thinness. Nuh-uh, no way!

 

[John_Nicholas]

Dang, I agree with Tim on this, that neck is super thin! I'd be afraid it would break when carving it!!

Otherwise, this is a very interesting and very cool project!!

 

[Jeff Siddall]

Regarding breaking the wood, yes, it would have been snapped long ago if I hadn't laminated the top with CF back in post 38. It's amazing how much stiffer things get when they have 2.7 mm (just over 100 mil) of CF stuck to them!

As you can see in the top photo from my previous post I clamped both the body and headstock before shaping and after that it wasn't too bad to work on. Still much less rigid than it will eventually be with all the extra CF and wenge attached, but I had no concerns with snapping anything while working on it.

 

[Jeff Siddall]

I am considering going less traditional with the pickups and instead of dual humbuckers using many single coils in various positions instead, then combining them in various humbucking ways. To do that will require a skinny but long pickup, so I decided on X5 "candybar" size pickups:

Bass Candybars - Bartolini Pickups & Electronics

Since I should be getting the pickup bobbins and magnets within the next month I figured I should come up with a cover solution. Unfortunately I haven't found any off-the-shelf covers in this size so decided to have a go at making a wood cover. I started by making a printable template that I glued to the top of the pickup as a guide for length, width, corner radius and screw hole locations. I had some curly maple offcuts which I cut slightly oversized on the table saw. I glued the template to the wood and went at it on the belt/disc sander. Then on to the drill press for a countersink and a through hole, then some hand sanding and finally a coat of oil. For an hour or so of work I thought this turned out pretty well:

I hadn't routed out the guts so I built a little jig to help with that:

It's mostly just a box made from few rectangular bits of plywood with a couple of maple "L" shaped pieces on the end to make sure the route doesn't get too close to the screw holes.

All of this is clamped from two sides with some C clamps, and then the whole thing is clamped into the bench vise so it can be routed with a palm router and a template base:

If you set the router on the outside of the jig you can see how close it is to the face of the pickup. I left a mm or two to be safe:

Done!

I will eventually need to make 5 of these out of wenge. I already wrote a G-code generator for doing pickup covers so I might try the CNC for those.

I also finished cutting and planing the extra-thick 9 mm fretboard blank. That's ready for the compound radius and fretslot work to be done on the CNC... some day when I finish upgrading the CNC that is. The remaining parts should be here in the next month or so, which is step 1.

 

[dwizum]

With reasonable wall thicknesses left, you can have room in a wood Candybar cover for a standard sized Jazz neck pickup bobbin, if you want to leave your options open.

 

[Reedt2000]

How about CF covers?

 

[Jeff Siddall]

With reasonable wall thicknesses left, you can have room in a wood Candybar cover for a standard sized Jazz neck pickup bobbin, if you want to leave your options open.

Yes, that is true, but... because this is a multiscale, and the pickups will be on a significant angle, I need something wider, about the sensing width of a typical 6 string pickup. So the current plan is to stuff these with 6 string blades, pending testing.

How about CF covers?

Yes, I could do that too, but I was thinking that since the neck-through part was already CF that wenge might add some subtle contrast. Another option I considered was a hybrid with a CF top and wenge sides. Definitely things to consider.

 

[Jeff Siddall]

Here's a render of the pickup positioning I am currently contemplating:

The one nearest the bridge is in the typical Warwick bridge location, the one beside that is in the modern Jazz bridge position, the next two are in the typical Stingray location and the one nearest the neck is in the typical Jazz neck position. Should be able to get some variety out of all that!

 

[Max Bogosity]

You could fan the pickups in proportion to the distance between the bridge and fingerboard, echoing the fanned frets.

 

[Jeff Siddall]

You could fan the pickups in proportion to the distance between the bridge and fingerboard, echoing the fanned frets.

That's true, but the pickup spacing is ideal down the centerline as it is currently. To fan them would mean the spacing would need to increase on the bass strings but also decrease on the treble strings. Since the pickups are basically already touching, the distance on the treble strings can't decrease.

 

[Jeff Siddall]

Hooray, some progress on this build. I finished the first pickup wind, a single coil blade. This was the first thing I have ever wound on my never-before-used custom pickup winder. I was fully expecting all sorts of issues along the way, but for some inexplicable reason it all went flawlessly! Here is the finished bobbin

Pretty tight, just like I was hoping for!

And, for the first time ever, the winder said "FiniShEd"!

There are more details posted on the Magnets & Copper Wire: A Pickup Building Thread for anyone interested.

Now I guess I need to finish the pickup mule to see how it sounds.

 

[Jeff Siddall]

Next up, the trickiest part of this build: laminating the back. The issue is the back is full of curved surfaces, something CF tends not to like to bend around nicely. Also, it's mainly the back layer that has to deal with the string tension -- about 220 lbf worth on this bass -- so it really should be done with continuous strands of carbon end to end.

I started with a standoff made from 1/2" fence board offcuts from the fence build earlier this month. The standoff is required so the fabric doesn't need to make a sharp bend at the board I laminate on when it wraps around to meet the front face.

Then I used the balsa offcut from the back of the headstock as a caul to resist the clamping force of the vacuum bag, and shimmed that up with an offcut of black limba to match the angle of the front of the headstock. It all looked pretty ugly but function was the only goal.

Next I taped off all the parts I didn't want the epoxy to bond to, including the sides and top. I also waxed the melamine base board so it didn't stick to that either.

Finally, I cut up 6 layers of CF, perforated release film, release ply, breather cloth and nylon bag film:

All ready to go:

Final step was to dry-fit each type of CF for this layup (plain and biaxial) around the curves. The weave can shift in these non-stabilized fabrics so it kinda works to get them around bends, albeit with a significantly distorted weave:

The biaxial actually worked best for this so I started with that on the bottom layer to get good bond to the balsa, then alternated two plain to one biaxial for the rest of the layup.

The presentation layer will be a 4x4 twill wrap done at the end. It is stabilized cloth so I will need to cut and join that layer around the curves, but the flat parts will stay nice and undistorted.

Then mixed up a bunch of laminating epoxy and went at it. There are no pictures of that process because my gloves were covered in epoxy and you need to work pretty quickly. Anyway, about 20 minutes later it was all wetted and laminated and ready for the vacuum bag. I inadvertently cut the peel ply too small, but the resin didn't stick to the nylon bag film so I think I will just skip that layer going forward. Kept it under vacuum for another 4 or 5 hours:

A day later and out of the bag and it looked like this:

I am pretty pleased with that. A few wrinkles that need to be filled and sanded but that was expected.

Left it for another day before starting at all the stuff that needs to be cutaway before I can really see what is going on. Gaah, cutting CF. Never look forward to that.

Anyway, outdoors with respirator, long sleeves, long pants and gloves on I started at it. This time I used an oscillating tool and I gotta say that worked pretty sweet. You can be precise and also trim flat along a face, which are both good things:

An hour or two later all the excess was gone and I could confirm that it as all well bonded. Success!

That really couldn't have gone better. Not sure why I was dreading this step so much!

Yup, that neck is still super thin, though now up to about 10 mm (just over 3/8") at the 1st fret and about 13 mm (just over 1/2") at the 12th fret:

It looks like it should be floppy but that neck is already incredibly stiff. Add another 8 mm thick slab of wenge on there and this thing should be plenty rigid.

There isn't much more fiber to go on so I also did a weight check: 955 g or 2.1 lb. My original predictions, back in post #10 were just over a kg (2.3 lb.) which seems pretty close.

So yeah, so far so good. There is lots more work to be done, even on the CF parts (perimeter of body and headstock, then filling and sanding, then the presentation layer), but I feel like I am past the halfway point now.

 

[Jeff Siddall]

Having finished my CNC, and a script to generate cut files to make them, I finally finished the fretboard for this build today:

This is a 7.25" radius at the nut and a 21.9" radius at the bridge with 0.5 mm surfacing pass spacing, which worked out to 153 passes and took about an hour at 2000 mm/min. That should be pretty easy to sand smooth, which makes me happy! Because I used an upcut mill there is a bit of fuzz at the top of the fret slots but that will sand off easily too.

However, before any sanding can happen I need to free the board from the blank on the table saw, which will probably wait until spring with some warmer weather. Then it needs to be side/face slotted and drilled for LED fret markers and associated wiring on the bottom side, then finish sanded, fretted, and eventually attached to the CF. Lots of work ahead but getting that compound radius multiscale blind fret slot fretboard cut was a huge hurdle and I am really happy with how the board has turned out so far.

 

[Jeff Siddall]

Next CNC job: plan and build some code to cut the LED wrap-around fret position markers. Again, with multiscale everything is at wonky angles, and for nice clean work I wanted small cut passes, so I also had to build bottom clearing algorithms and ramps into things. However, after much brain hurting and a few iterations I ended up with a version I was happy with. Here is a render of the finished fretboard with fret slots and markers:

The markers are just over 5 mm (just under 1/4") wide except for the 12th fret which is a double-wide marker. They all extend down the same amount into the board, but since it is very thick (about 7 mm at the edge) there will still be fretboard meat under the markers.

I will fill the slots with clear or semi-opaque (pending some test pieces) epoxy after mounting the LEDs to the back of the board.

 

[Jeff Siddall]

I was able to test the marker slots using some hard maple scrap and they turned out exactly as rendered. Here's a couple of the double-wide slot test cuts. I did one over the edge to see how clean the edge was, and it really couldn't be smoother:

Also, for my 6 string project I designed some new 19 mm 6-flute knobs and cut them on the CNC. They turned out great but I also did a test render of a slimmer 5 flute variant that I might use on this project instead the plain black Gotohs I have: