Saturday, November 29, 2014

Building a Lefty Short-Scale Tele Bass

I thought I'd give a short-scale bass a try, as I've been having some issues with the last joint on the little finger of my fretting hand (recently diagnosed as osteoarthritis).

As usual, there's always a problem trying to actually find lefty basses to buy, especially short-scale lefty's. So let's build one instead (hey, it's fun!).

I purchased a right-handed short-scale neck from Rondo Music, and thought I'd make a body for it.  But what kind of body?  While I was deciding, I did some work on my G&L ASAT bass and just for fun put the righty neck on it to see how it looked...


Not bad!  OK -- the decision was made.  A telecaster body!

Downloaded some plans for a tele guitar body.  Printed them out and assembled them.


Made a tracing...


Flipped it to be a lefty...


First mockup!

Working out possible pickup locations, scaled down from 34" to a 30" scale...


Purchased a block of Alder via eBay...


Used spray adhesive to glue my template to the wood...


Clamp and cut with a jigsaw!



Leave a bit of margin around the body to account for saw blade flexibility.  You can see here that the cut isn't vertical as I went around a bend, but instead it cants away from 90 degrees.


Finished cutting!


Needed some way to finish up the edges.  So decided to purchase an oscillating spindle sander (via Amazon).

The box has arrived!


And here's the sander...


Sanding and oscillating...


Checking for unevenness along the edge with my finger...


And now, time to use a router.  First, to trim off the top edge of the neck pocket so that it's flat, I use plexiglass as a bearing guide (stuck to the body with double-sided tape).


Ooops -- bearing slipped while routing.  To fix this boo-boo, l'll shift the template slightly to route this error out, too.


Router bit wasn't long enough to do the entire 1.75" depth of body, so flipped the body over, carefully repositioned the bearing guide, and completed routing on the other side (no, the spindle sander isn't running).


Creating a flat area for the jack plate.  Again, plexiglass straight-edge as bearing guide.


Body edge finished!

 

Time to do the neck pocket.  First, drill the screw holes...


Then, route the pocket using a template (from StewMac). 


The Rondo neck is slightly narrower than the standard pocket, so I used a piece of plexiglass as a bearing guide to narrow the edges, one edge at time.  Still, I wound up with a pocket that slightly too wide.  My fault!


Checking the center line...


And shimming the neck with some business cards so that I can mark the neck for drilling the neck mounting holes.

Here's how it looked.  Tuners are Hipshot Ultralites.


The righty neck needed the nut flipped for lefty use.  I had glued it in with Superglue, but then decided that it wasn't quite centered correctly.  So I tried prying it out.

Bad idea!


Fixed it by gluing in a new nut and the wood chips.


String tree installed.  Not exactly parallel to the nut, but pretty close...


Time for some pickup placement experiments before routing their cavities.  The controls, mounted externally.



I put the pickups on plastic cubes (from Tap Plastics) and moved them around over the strings.  Double-sided tape sticks them to the body for testing.


The schematic of the controls I used for my initial testing:




Mounted my bridge using calculation from StewMac's Fret Calculator.  That was a mistake, as it puts the bridge too close to the neck.  Note that the E string spring is almost fully compressed, while the G string is pretty far from the right edge of the bridge.  In fact, for this type of bridge (Fender 5-hole), the screw holes should be placed 1 inch longer for the scale: i.e. 31" for a 30" scale.


Drilled new holes further back and dowelled the original ones...


Ooops, the holes weren't quite straight! 


I'll get back to this later.  First, let's work out pickup placement for a 30" scale using numbers for a 34" scale (34" numbers from a spreadsheet I found on the web by B. Gavin).

(click on image to enlarge)

Playing around with two G&L pickups...


Let's try replacing one of the G&L pickups with an SCPB-3...



Final placement, after much experimenting.  Note -- to my ears, moving a pickup a quarter-inch one way or another doesn't appreciably change the timbre of the sound. 


OK, placement has been decided.  So let's do more routing.  First, drill the hole for the jack plate.


Route the control cavity, after first drilling holes at either end with a Forstner bit.


Routing the cavity for the G&L pickup.  I didn't have a correct template, but a "Bartolini BC, Nordstrand 4 String Soapbar Shape" template is pretty close.  Just needed to move it four times to get the entire cavity routed.


And routing the cavity for the SCPB-3.  First drilled holes at either end with a Forstner bit.  Then added plexiglass as router bearing guides.


Routing done!



Drilling holes between cavities for wiring.  G&L cavity to control cavity, check.  Bridge grounding to control cavity, check.  SCPB-3 to control cavity...whooops!

Plug with dowel and redrill.




Time to remove the paper template on the front.  Started sanding.  Hey, what's this gray stuff under the paper that's gumming up my sandpaper?  Guess what, it's the spray adhesive!


Tough to get off, but I found a jar of used solvent (thinner?) lying around.  Soaked a rag with it and scrubbed off the mess.

Much better!


I was curious how different tone-cap values might sound.  So I devised a way to test 5 different values, using a standard 5-position guitar pickup switch to select 1 of 5 cap values (1nF, 5nF, 10nF, 50nF, 100nF):


Here are the controls, yet to be wired.  Please note:
  1. Pickups are engaged by pushing-in the appropriate knob. Pulling-out disconnects a pickup from the circuit. If both knobs are in, both pickups connect in parallel to the output.
  2. The two sections of each DPDT push-pull switch are wired in parallel for reliability. You could use one section of each switch in lieu of both sections, if desired.
  3. The coils of the G&L Humbucker are wired in series, not parallel (I like it that way).
  4. Capacitance values are 1nF, 5nF, 10nF, 50nF, and 100nF, but in a 1nF-10nF-5nF-100nF-50nF pattern as the switch is moved from one end to the other. (That's the only way I was able to figure out how do it with this type of switch.)

Here's how the jack would look if I did it this way -- tone cap selector switch is nearest to the jack.


Wired up!


And assembled.  Not bad looking!  (Still needs paint, though.)




After playing on it a bit, I decided it needed a forearm contour.  Roughed out with rasp, then finished with an 8-inch rectangular steel pipe with 320 grit sandpaper taped to it.


With the contour finished...


And after playing around with the cap values, I decided to decrease the number from 5 caps to 2:  10nF and 47nF.  One of the push-pull switches will select the cap value.  And I changed the 5-position selector switch to a standard 3-position pickup selector, as shown in the schematic below:


Also, I noticed a bit of fret buzzing.  Guess I need to level the frets!  To do this, I first adjusted the trust rod to ensure that the neck was exactly flat (using a neck straight-edge notched for a 30" scale neck).


Then I marked the tops of all the frets with a black Sharpie and carefully sanding them (320 grit on an 8" beam) until all of the black has been touched by the sandpaper.


Next...because I'm using a righty neck as a lefty, the neck side dots are on the wrong side of the neck.  So I needed to add side dots on the other side.  I picked up some black plastic 2.0mm diameter rods on eBay.  To install the dots, I drilled shallow 5/64" holes at the appropriate locations.


I then put a drop of wood glue in each hole, stuck in the end of one of the plastic rods, then clipped it off a bit above the neck with a pair of diagonal cutters.  The cutters leave a bit of a mark on the rod (it looks white where compressed), so I then filed off the cutting marks, leveling the plastic with the neck wood using a small needle file.


I'd been planning to use Danish Oil to finish the body. Didn't know what tint to choose, so I picked up 3 different cans: Natural, Golden Oak, and Cherry. Tested them on scraps from the body, and frankly, they didn't do anything for me.

So on to Plan B: Why not seal the wood with a 2-part urethane clear coat? This is how I would normally treat the body (i.e. seal the wood) before painting a color base coat. Let's see how it looks.

So I picked up some cans of SprayMax 2K Glamour High Gloss Clear Coat. (This is a paint where you press a knob on the bottom of the can which releases the catalyst (or activator?) into the can and you have 48 hours to paint with it before it is kaput).


Note -- this is not healthy stuff. So I use a good respirator mask and goggles (and nitrile gloves...)


The temporary paint booth. Cheap paper drop cloth thumb-tacked to the wood above, with duct tape reinforcing the paper where the thumbtacks poke through it.


Not too bad!


After looking at it, though, I decided to go ahead and paint the body with the yellow paint that I'd had mixed at the auto paint store. (All painting, by the way, is done with rattle-can paints.)

First step was to sand the body smooth with 320 grit, dry, sandpaper, then spray with automotive white primer.


After priming it, I waited a day and then lightly sanded the primer with 600 grit sandpaper, dry. I then applied the base (color) coat. The base coat is automobile urethane paint, designed to be used in a dual-stage process in which the second stage is the application of a clear-coat over it. The clear-coat will be applied another day. First the base coat...

Here's how the base coat looked:


I let this sit for 24 hours, then did a very light sanding of any obvious "bumps" or imperfections in this color coat using 600 grit, dry, but for the most part I left the body unsanded. Here's my reasoning for no sanding: the clearcoat that I will apply actually melts into the base coat (or so it seems to me), and so I couldn't see any benefit to additional sanding, whereas there's an obvious downside to sanding, which is the potential thinning of the color coat so that primer shows through. I've had sand-through issues in the past, and this was a huge concern to me.

(With that said, if anyone believes it's better to sand the color coat when using automotive urethane paint, please let me know! This is the third body I've painted this way without sanding the color coat and it seems to work fine, but I'm no expert. Would love to learn more.)

After 24 hours had passed, I sprayed the first can of clear-coat. This is an automotive urethane clear-coat that, when mixed (by pressing a red knob on the bottom of the can), has a pot life of 48 hours.

I let this clear-coat cure for 24 hours, then lightly sanded the body with 600 grit, dry, and followed that with my second can of clear-coat. Here's the body after both cans have been applied:



And here are the spray cans I used for this latest stage of the build. All were purchased at an automotive paint store (in my case, "Jerry's Paint and Supplies," in Sacramento, CA):


Note that during all painting I wore a good respirator, goggles, gloves (nitrile), long-sleeve shirt and long pants, as some (or all?) of this paint can be pretty bad stuff.

I waited a week to ensure that the clearcoat was adequately cured, then on to sanding and polishing.

Sanding was done with the following progressive grits of sandpaper, wet: 600, 800, 1000, 1500, and 2000 (sharp corners were only done with 1000 and above).

Followed with Micromesh pads of coarseness: 2400, 3200, 3600, 4000, and 6000 (also wet).

And then lots of rubbing with Meguiar's "Diamond Cut Compound 2.0".

Not sure if this is the best way to do it, but it seemed to work. Still some very tiny scratches, though, visible on the body if I look closely. Advice on better methods is always welcome!

A couple of other faux pas on my part...

First, I'd used washers on the screws that held the body to the neck stick. One washer was a bit too large (both in size and inner diameter), and so it didn't lay centered under the screw. As a result, there's a fairly large patch of unpainted wood jutting towards the top of the body. Fortunately, the back plate just covers this. But lesson learned. Will need to figure out a better way of holding body to stick. Might just be a correctly sized washer (or...?).

With all of the wet sanding, it's important to keep the water away from the wood, otherwise the wood will absorb it and swell. In the first two bodies I'd painted (kit-bass bodies), I had this problem, and I thought I'd solved it this time by plugging the few holes I had with wax. And this worked well. But I'd removed the tape I'd used to mask off the neck pocket, revealing bare wood next to the edge of the paint, and a small amount of water was absorbed there, swelling the wood in a few places under the paint.

I was able to bring the swelling back down by heating the area with a desk lamp and then applying pressure with clamps (via a piece of wood). But there's still a bit of irregularity in the smoothness of the top near the neck pocket (most easily seen when using the body as a mirror and looking at reflections in it). A good reason to use a pickguard, as it will hide this. And next time I sand, maybe leave neck pocket masking on?

Sanding done, time to install the neck and all of the parts.

It's done!


By the way, this build is also documented on the TalkBass forum (where you can also see the commont of others on my work-in-progress).  If interested, go here:

  http://www.talkbass.com/threads/bass-build-short-scale-lefty-tele-bass.1105446/


Links to Bass posts of mine...

Sonic Blue Bass (part 1 of a 3 part series)

Mellow Yellow Bass

Short-scale Telecaster Bass

Bass Guitar Painting Jig

Repairing a G&L Butterscotch Blonde Paint Chip

G&L ASAT Bass Strap-button Extender

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