Walnut Scroll 4-banger - Cm#1

[erikbojerik]

Body Time...trimmed the heel and roughed the roundover. This one has a graduated roundover, 1/4" in the vicinity of the bridge transitioning gradually to 3/4" from the waist on up around the horns. This was done on a router table using 1/4" - 3/8" - 1/2" - 3/4" roundovers in turn, and smoothing the transtions by hand. There's still quite a bit more carving to do in the waists, cutaways and heel, and the scroll of course.

Here's a more realistic shot of the eventual color that the oil finish will impart (this one's just wet down with water), it will actually look a little darker than this.

Got the cavities routed on the body. With the parts now in hand, I could make spot-on MDF templates for the pickup. The control cavity rout was already cut into the template for the body.

To make the pickup routing template, I first drill the corners with a 1/4" diameter forstner bit since this corresponds pretty closely to the corner radius on the EMG 35DC pickup housing. Then I use a scroll saw to cut out the interior and clean up the edges with a sanding stick.

That gets double-stick taped to the body and the edges get cleaned up with the router (the bulk being previously removed with a forstner bit on a drill press). Pretty much same deal with the control cavity.

Here's the finished product.

[erikbojerik]

This one also has a faux pickup ring made out of wenge that matches the fretboard. I first thicknessed the wenge and taped it down onto a similar-sized block of scrap maple to serve as a platform. This shot shows the template before scroll-sawing, and the pup ring after hogging out with a forstner.

The interior of the ring was removed with a forstner, and the edges were cleaned up with the pickup routing template that I used for the pup cavity....EXCEPT that I put some masking tape around the template bit's bearing so that it cut a slightly smaller outline than the template, which was slightly oversized to permit a little flexibility in placing the pickup.

The ring was then bandsawed off, and the edges sanded smooth and square on my mini edge sander. Have to be careful here to not let it heat up too much, or the tape softens and then the pup ring starts to move.

Once it's done, I sand the edges & corners smooth by hand, then *carefully* remove it from it's maple platform with a StewMac seam separation knife, the kind the acoustic folks use for removing tops & backs. It is a VERY useful tool for separating all manner of lumber from taped-down templates.

[erikbojerik]

OK so here's how I'm doing the control cavity cover, now that it's routed. I HATE to see screws, sometimes you can't avoid them but that doesn't stop me from trying.

On the body template goes 5 small holes to locate the magnets that will be glued to the cover, lined up with 5 holes in the body where the magnets will register and stick to recessed metal screws.

So I use the template to drill the small holes in both the body and the wenge cavity cover (matches the fretboard and pup ring, of course...).

Then shallow 1/4" routs are made in the cover with a forstner bit, and 5/16" to 3/8" holes in the body to leave room for the recessed screw heads...and take up slight differences in magnet & hole positions when the cover is on.

[erikbojerik]

Oh yeah...almost forgot....rough carving is done. Still some finer sanding to do, but the essence is there.

And the back...horn carved both front & back, and heel contoured.

I know I know....screws for the neck...I'd use big honkin' neo mags if it weren't for the fact that they'd stop the string vibration dead in its tracks.

[erikbojerik]

Hehehe...pics of the next-stage progress (hand sanding) would be tré BORING!

It is, however, something new and interesting neck-wise....I am off the roadmap, no going back now!!!

This will be a surprise even to Chris, so I'll keep the lid on it until we meet up for a check of the neck's back contour.

Shhhh.....

[erikbojerik]

Fretboard is fretted. Chris is looking for low action with a light string gauge on this bass, so we went with standard-height guitar fretwire.

My goal for this fretboard is to have it, and the neck, be sufficiently level that I'll have almost no fretwork to do. The fretboard was dead level all along it's length, and underneath every string trace after radiusing. With the frets in, there was the predictable back-bow but it was pretty minimal with the binding on it (about 2 mm with the board sitting on the table). A little flexing to bite the tang barbs in a little more, and it was back to dead flat and level. So far so good.

Wait a minute...what's up with THIS?!?!

Don't look at me.....Chris told me to do it!!

[erikbojerik]

Neck is now ready for attaching the fretboard. As a reminder, at this point both the neck and fretboard have been tapered on the neck template, so their width is a perfect match.

The clamping caul is a flat & level stick of Home Depot pressure-treated pine (easy to relevel if it goes out...), with 3 StewMac radius blocks stuck upside-down to the top, forming a radiused caul that the fretboard will sit in (upside-down). I first had to thickness sand the tops of the radius blocks so that the bottoms of the radiused valleys were all at exactly the same level when flipped upside-down.

The upside-down radius blocks were covered with painters tape, and so was the fretboard except I left the tape 1/16" shy of where the glue joint will be.

To attach the fretboard I am using System 3 epoxy...the reason for this is to avoid the wetting of the neck grain with water (as happens with Titebond) which results in a bit of back-bow when gluing on the fretboard. This happens because the typically porous woods used for necks suck water from the Titebond, while the ebony/rosewood typically used for fretboards does not.....the neck grain swells at the joint, creating enough back-bow that it often requires a bit of reverse truss-rod tweeking to level out. Epoxy avoids this.

A strip of tape over the truss rod, and the epoxy goes on. Here you can also see how much fretboard I left uncovered by the painters tape...I want to see some squeeze-out, but I don't want it running onto the fretboard!!!!

Here we are, all clamped up. I left the nut slot exposed for clean-out, same for the end of the neck (where I had chopped off the last 4 frets of the fretboard......).

To return to Eleonn's question...this method of clamping up the fretboard glue-up provides a dead level radiused surface for the fretboard to sit in, and the neck provides enough of a caul that (provided you use enough clamps....I used 7) the resulting joint should not vary in thickness. I left the epoxy on the neck long enough that it self-levels, and with enough clamps I got nice uniform squeeze-out all along both edges of the neck. Schwing!!

[erikbojerik]

Here's the neck after a full day in the clamps. I put a straightedge on the fret tops...no backbow and with a feeler gauge found that the largest gap was ~0.003" in the middle of the neck, with the truss rod completely slack.

Success!

A question from Jethro in Bozeman Montana....

"What about those last 4 frets? What happened there?"

Funny you should ask Jethro...

Here's a shot of the heel-end....all 28 frets!

Aha! It's the "fretboard extension as truss rod access cover".

This idea came from Chris and I kicking back & forth some different ways to cover the truss rod access. I did some hand-wringing over it, especially with regard to using "big" neo magnets like I did on the control plate...I didn't want the neos to dampen string vibration. So I found some 1/4" diameter really thin ones (1/16" thickness). One set glued with CA onto the level underside of the fretboard extension, the other set recessed into 1/4" pits drilled with a forstner. It attaches nice and firm, and the magnets under the extension register perfectly in the holes so that these last 4 frets are still playable.

[erikbojerik]

Getting closer to Home!

I tweeked the contrast of the images to darken it up a little, but it's still not as dark as it will be when the oil goes on.

So with the truss rod totally slack, the relief at #7 was 0.003. With the strings on and tuned up to pitch, relief went right to ~1/64" when capo'ed at #12. Action is now 0.1" on low-E and 0.09" at G measured on #12, and no buzzing.

I may get out of doing any fretwork after all! But we'll see for sure when Chris gives it a test-drive in the white.

[erikbojerik]

We finally got together to give Chris a chance to test-drive the bass. Chris is an awesome player, and he put it through the paces unplugged....fingerstyle, slap, everything. He gave the bass an A+, despite receiving a nice wenge splinter from the edge of the unfinished fretboard...now we KNOW this bass has attitude!

Tru Oil here we come!!

Here's a shot of the happy owner-to-be:

[erikbojerik]

Got Semi-Hemi^TM?

Oh yeah....

Almost forgot to explain the surprise turn this build took, inspired by the work of acoustic builder Harry Fleishman. I'd always wanted to try this out, and knowing that Chris is an excellent player looking for fast action and a good neck feel, I thought this would be the perfect project to bust out with it.

It's called the semi-hemispheric fret end, otherwise known as "SemiHemi Frets^TM". The idea is to mimic the feel of the neck on a vintage instrument, in which the fret ends have been rounded down over the years by the player's hand. The edge of the fretboard is also worn down by this process, so I combined the SemiHemi frets with a "rolled" fretboard edge.

The process is painstaking, but combined with a bound fretboard (requiring undercut fret tangs) and a rolled edge, it potentially offers the ultimate in neck playing comfort. You need the width of the neck at every fret slot, and a finished fret length that falls under that width by a specified amount, so that the end of the fret doesn't quite reach the edge of the fretboard.

Rather than pressing in the frets and then working on the fret ends afterward, the process is reversed. Each fret is cut and filed to a specific length for its slot, the tang nipped from underneath both edges to account for the bound board, then the ends of each fret are carefully filed into a hemisphere, and sanded smooth with 320-600-1000 grit sandpaper, and the length checked so that it still falls within the tolerances.

Once the board is oiled, the whole works will be buffed with 2000 & 4000 grit Abralon, and each fret will be buffed with a Dremel and a little swirl remover. With SemiHemi frets, it almost feels like playing a fretless. I am very pleased with how it turned out!

[erikbojerik]

Onto the finish....here are the special tools that I use to apply a Tru Oil finish.

You basically take the little square of T-shirt, wrap it around the little cotton ball, tie it with the little twist-tie, and you have yo bad self a little TO pad. The main thing is to choose a T-shirt material that is lint-free (polyester is good) so you don't have little furry specialness in your finish.

Very important to a good TO finish is the quality of the wood prep, here everything has been sanded down to 400 grit (inspected carefully for scratches), all the dust blown out of the pores with compressed air, then the whole works wiped down with lacquer thinner and allowed to dry thoroughly.

The raw wood really drinks in the first coat, so you basically saturate it with full-strength TO, wipe off the excess, and repeat until it ceases to go in.

After the first coat cures for a day, I scuff the entire thing with 1000-grit Abralon (removing all traces of shiny surface) then apply 3 more coats with 15-minute wait in between....the key is to go THIN, way thinner than you'd need to get any kind of run in the finish. Think thin.

[erikbojerik]

Well alright! Managed to finish this one (wow...that was quick!). Here are the last of the build pics...a long way from lumber.

I did end up having to mill some fallaway into the frets above ~#17, I was getting a little more buzz than I like with my sledge-hammer right hand. :scowl: Chris' chops are a bit more refined than mine... :smug:

Laser-engraved flame maple appointments on the headstock; ebony nut and zero fret. The faux truss rod cover was designed by Chris.

Thanks Chris for prodding me to come up with some kind of name for my operation. The name came from an Argentine friend of mine (the same one who hooks me up with prodigious Brazilian Rosewood)..."Solo Rio" is a legend local to the natives in the Andean foothills of Navado Mismi where the Amazon river originates. Their story is that the Amazon is the "one river" that leads to the ocean...this apparently originated hundreds of years before Pinzon "discovered" the Amazon from the ocean in 1500.

I liked the story, so "Solo Rio" it is. Whether or not the natives ever navigated all the way to the sea is hotly disputed, there are long stretches of hellacious Class X (and worse) rapids....but the legend suggests they managed it.

[erikbojerik]

Here are some more natural-light shots (although they did come out a little on the yellow side....)

Sculpted bolt-on heel. The Tru Oil really brought out the figure in the maple and walnut both.

Rear battery cover (18V or nothin' baby!) in amongst some flame that was totally hidden until the Tru Oil brought it out.

[erikbojerik]

Here's a closer shot of the back's walnut figure

Wenge control plate:

Front: master volume

Center: mid boost/cut on top, mid freq sweep below

Back: treble boost/cut on top, bass boost/cut below

This system also has some dip-switches on the circuit board that allow you to play with some frequency tweeks....tre cool.

Oh yeah...still have to do the Straplocs. Chris is coming by to pick it up on Friday.

[Prostheta]

Great work Erik! I'm practicing making semi-hemispherical frets and using a couple of "self-bound" fretboards myself at the moment, although you make it look a lot easier with your setup. I've found that HS fret ends are a zen-or-nothing job to get right, and I find it hard to maintain focus to put as much work into the last ones as the first. Still, very worthwhile. Calipers and a fret dressing jig with a wide slot help a hell of a lot.

How does the walnut sustain? I remember opinion being polarised on it's use. I remember mention of it being used in gunstocks to reduce recoil transmission shock, which I suppose is reasonable to extend to it reducing body resonance. On the other hand, it's a popular tonewood....

Again, great work!

[Joel Rainville]

Very nice write-up, thanks for sharing!

[erikbojerik]

I've found that HS fret ends are a zen-or-nothing job to get right, and I find it hard to maintain focus to put as much work into the last ones as the first. Still, very worthwhile. Calipers and a fret dressing jig with a wide slot help a hell of a lot.

I used calipers and held the frets in a StewMac nut slotting vise backed with couple small bits of leather. Worked great. I started at about 15 minutes per fret, and by the time I was done I was at 10 min/fret.

How does the walnut sustain? ...I remember mention of it being used in gunstocks to reduce recoil transmission shock, which I suppose is reasonable to extend to it reducing body resonance.

Thankfully the bass does not have a rubber end-cap shock-absorber.

[Prostheta]

I've found that HS fret ends are a zen-or-nothing job to get right, and I find it hard to maintain focus to put as much work into the last ones as the first. Still, very worthwhile. Calipers and a fret dressing jig with a wide slot help a hell of a lot.

I used calipers and held the frets in a StewMac nut slotting vise backed with couple small bits of leather. Worked great. I started at about 15 minutes per fret, and by the time I was done I was at 10 min/fret.

How does the walnut sustain? ...I remember mention of it being used in gunstocks to reduce recoil transmission shock, which I suppose is reasonable to extend to it reducing body resonance.

Thankfully the bass does not have a rubber end-cap shock-absorber.

Hmmmm…you say that now :-D

Rubber feet either side of the bottom strap button would save a few instruments from sliding around and gaining some nice damage in a fall next time they get laid up against an amp/cab/chair/wall/table/drumkit/bar/bath/tree.

15m down to 10m when up to speed….it’s a slow process, but at least 15/10 is better than 15/1 for consistency at least!

[low end fuzz]

yess!

carl thompson is the man!

which would put you in a close second with this (ya that s acompliment)

i wsa initially upset you went for a bolt on ,but it looks outstanding, good work; aand ya fast! what was that about 10 mins!

[Xanthus]

I dig. I feel the shape is a bit electronics-cavity-heavy, but it's pretty snazzy otherwise. I'm also finding out that Tru-Oil is great for bringing out "hidden figure" in the woods. How many coats of oil did you put on? Did you end up doing a final buffing?

[erikbojerik]

10 coats of Tru Oil....the first to saturate the wood (then wipe off).

Let cure a day

Scuff-sand with 600 grit dry

3 coats 15 minutes apart

Let cure a day

Scuff-sand with 1000 Abralon grit dry

3 coats 15 minutes apart

Let cure a day

Scuff-sand with 1000 grit Abralon dry

3 coats 50/50 TO+naptha 15 minutes apart

Let cure a day, easy buff by hand with T-shirt (like, 10 minutes)

Smooth out the neck back with 2000 grit Abralon

[carousel182]

that seems pretty easy to apply. I might have to try out some tru oil on my next build. how does the tru oil feel?

[erikbojerik]

that seems pretty easy to apply. I might have to try out some tru oil on my next build. how does the tru oil feel?

It actually feels great, especially on the neck if you knock off some of the gloss with 2000-grit. Not sticky at all like nitro can be.

[carousel182]

Thats awesome. Is there anywhere that you can order tru oil online, i know you can get it at gun places in small bottles, but is there anywhere you can order a bigger bottle of it.