Saturday 18 April 2020

Building a 13 Course Lute, Start to Finish, 16: Shaping the Fingerboard and Setting the Action

Hi friends, and welcome back to the series. Hope you're all well, and taking advantage of the downtime caused by the Covid-19 quarantine to make the art you've always wanted but never had the time to do before. Or tidy up the house. Or do your taxes. Or read a good post-apocalyptic novel.

Here in Vancouver, it has never been a better time to ride a bicycle. The air is clear, birds are singing and the streets are snowed under with cherry blossoms. It is a strange--and in some ways, strangely good--time to be alive.

But I want to go back today to a former time, a time before the Great Hush of 2020. If you recall, I had just glued a curved fingerboard on the 13 course lute I'm building.

I've taken off the clamps, and now--a small problem. I've glued the fingerboard to the neck--but I've also managed to glue the caul to the fingerboard!

I'm pretty sure that the caul is stuck only along the edges, so as I use strips of paper towel to soften the squeezed out glue along the joint, I also try to soften it along the edges of the caul.
Eventually, I get a little impatient and gently tap some wooden wedges in from the sides. The caul comes up with a bit of damage, but it's only to the cork lining, which I can easily replace next time I use it. (Apparently, I placed a gluey thumb down on the fingerboard before placing the caul.) Note to self: cover the caul with plastic wrap!
Okay, the fingerboard edge is cleared of glue. You can see the overhang I have left to remove.
Here's a close-up of the joint. Not bad!
I make a start shaping the fingerboard down at the body-neck joint. I need to plane (very carefully) and then scrape to get the fingerboard close to flush with the belly tongue.

Getting close...
There we are. I don't use any sandpaper around this area, only scrapers from now on.
 I begin to trim the overhanging edges of the fingerboard with a standard block plane.  
The idea here is to get the edge pretty flat along its length, and pretty close to perpendicular to the mid-section of the neck (that is, to the glued line between the mahogany neck core and spruce fingerboard spacer.) Notice how I've got my left thumb hooked over the edge of the neck down by the body, to guard against accidentally whacking it on the recoil stroke of the plane.

Down by the body-neck joint, I set aside the block plane and work carefully back toward the body with a chisel (a skew chisel works well for this job.)
For the opposite side of the neck, drawing the plane toward me is the way to go.
The plane and chisel get me close, but eventually I need to start working with files.
A slight boo-boo with the file: I've chipped out a little bit of the fingerboard edge. This particular piece of ebony has quite swirly, interlocking grain, which is very tough, but also tends to chip and tear out. I need to fix this little problem before I can go on.
I add one drop of cyanoacrylate glue to a little pile of ebony dust that I've made with a file and a scrap of ebony.
I apply it like putty with a palette knife, and wait for it to dry thoroughly.
Then I can go ahead and shape the area with the file. 
Using a straightedge with a strong back light shows me how close to flat the edge is (I like to get it as flat as I can.)
On smaller areas, the file works best...
But over larger areas, a sanding block is the way to go.
That's my edge. I don't know if it's visible here, but I leave the fingerboard just the tiniest bit wider than the edge of the neck. I'll be rounding over the fingerboard edge very soon, and will use that extra half-millimetre or so to blend the underside of the fingerboard into the neck.
Right now, I try to keep the joints and edges square and tight. When I finish out the lute to get it ready for varnishing, I will take an overall approach to the whole lute, rounding over the fingerboard edges, half-binding edges, and so on, hopefully in a uniform and coherent way.
First, though, I have to finalize the action. I've already scraped flush the body-neck area, so I now need to focus on the fingerboard from about the end of the belly tongue to the end of the neck. I'm using a Japanese scraper-plane here, pulling it away from the belly.
This swirly ebony tears out so easily that at a certain point I needed to put away edge tools, and just use sanding blocks. I try to avoid using sandpaper in lute making for both aesthetic and health reasons; but sometimes, with difficult material like this, I just have to surrender to the modern woodworking world.

As usual, to check the action I have pieces of fishing line tied to each course on the bridge; I pull each one tight over a spacer at the first fret position, and then read the height at the eighth fret by slipping wooden spacer pieces under the string. The spacer used at the first fret, by the way, is 1.6mm, which represents the nominal height of the first tied fret (1.1mm) plus the necessary clearance for the string not to buzz (0.5mm).
One other thing: in the photo above, note that I have masked off the upper part of the belly with a couple of pieces of masking tape, to keep ebony dust from contaminating it.

I feel I must pause here in order to try to convey to you the exquisite boredom of the work that I'm about to describe. I don't want to rush over this part, and give the mistaken impression that it's a quick job, Bob's your uncle, and we're off to the next stage. No. This job, shaping the baroque lute fingerboard to set the action before varnishing, is, to me, the slowest, most tedious, most excruciatingly boring bit of business in all of lute making. Here is the sequence:

1. Scrape, or shape with sanding block, all, or some, or small, strategic areas of the fingerboard, in order to lower the action at the nut end and/or the body end of the fingerboard, as appropriate.
2. Carefully vacuum all ebony shavings and dust from the work area. Then wipe the fingerboard (from the body toward the nut end) with a piece of paper towel, to remove the finest dust particles.
3. Re-draw the trajectories of each of the courses as they cross the fingerboard from the body to the nut. Re-draw the positions of the 1st and 8th fret.
4. Pull each piece of fishing line for each course tightly over the 1.6 spacer at the first fret, and slip spacers of various thicknesses under the fishing line at the 8th fret, to gauge the specific string heights of each of the courses. Write these numbers down beside the 8th fret mark.
5. Take the straight edge in hand, and with a strong backing light, hold it on the fingerboard exactly on the marked position of each of the courses and sight underneath it to see where the fingerboard is high, or low. Mark the high spots.
6. Take a moment to consider a strategy in the next bout of fingerboard shaping. How far do I need to go, and in what areas? Is there a discernible pattern--for instance, is the whole central area of the fingerboard high (or low?) Can I work in a larger area, or must I restrict myself to the line of only one course?
7. Begin again at 1. Continue repeating this sequence as necessary, until the action is set, and the fingerboard well-shaped (that is, smoothly curved in cross-section, but very flat in long section.)

Sound boring enough? I don't think so. I'd like to make it more boring, but I don't think I can. You'll just have to trust me on this (or, better yet, try it yourself.)

Here's a bit of an illustration, from rather late in the process. The squiggly lines are the high areas; the numbers are, of course, the string heights at the 8th fret.
Getting the final action is a job that can take an entire day, or more, depending on how well I am concentrating. If I can, I like to bite the bullet and get it done quickly. Ebony dust is bad for my health--I have asthma, and it's become a bad trigger. I wear a face mask, long sleeved clothing, and a cloth tied over my (short) hair. Periodically I need to go to the washroom and wash my face and hands. At the end of the day, I remove all work clothing, put it in a bag, change into street clothes in an outer room, and leave, pausing only to wash up carefully once more before getting on my bike and riding home.

These are my final action numbers for a baroque lute measured at the eighth fret. 
Just a word on that--these are 'final' action numbers before varnishing only. I fully expect to have to re-shape the fingerboard at least one more time before the lute is done. Why? Well, over about the next 3 to 4 weeks, this lute is going to spend quite a bit of time in the UV light box, a warm environment; and even though I'll be running a humidifier in the vicinity, the neck, and fingerboard, will continue to subtly change shape. Not too, much, I hope... But I think I've left myself enough leeway in setting the action thus far, that I will have the flexibility to make some small corrections later on.

By the way, the distance in time between the earlier photo and this one--showing string height differences of 0.1mm--is probably a couple of hours. As I said, very slow work, for very small gains.

Okay. Enough boredom for one blog post. I'll see you all next time, for the finishing out-stage--and perhaps some foundation coats to prepare for varnishing. Stay well, and I hope to see you back here again soon.