Saturday, February 6, 2016

Violin Body

I've put in a lot of late nights recently because I want very much to work on my own instrument, but there just isn't time available to do it.  So I make time between 10 p.m. and 3 a.m.  This means some nights I only get about three or four hours of sleep, but I can do that for a while without a problem.  Eventually I kind of crash and go to bed really early one night which seems to catch me up, but for the most part the late night schedule works out.  I can focus without interruption.  (Or distraction.  When my kids are up I want to be with them, so it's better if I wait until they are all in bed.)

In any case, here is the progress I've made on the violin body I'm working on:

When last I posted about this instrument I'd finished carving the scroll, and had gotten as far as the purfling on the body.

Next up was to rough graduate the top plate, then do the f-holes.
F-holes are the sound holes cut into the top plate on either side of the bridge.  They need to be large enough to help sound escape from the inside of the instrument's body, but not so large that they compromise the structural integrity of the top.  The stems of the f-holes need to be wide enough to easily get a soundpost through.  (As a repair person I know this is essential, since I am someone who has to repeatedly do soundpost work on instruments once they are out in the world.  When I have to work with a violin where the f-holes are too narrow it makes my job more difficult than it should be, so I'm mindful not to inflict the same problem on others in future.)

Carving f-holes is tricky.  They are one of those elements of violin making where there is nowhere to hide.  You can tell a lot about a luthier's skill level by how he or she carves their f-holes.  F-holes by different makers have different characteristics, and this was my first time carving in the Amati style, so that was fun. 


You begin by laying the f-holes out in pencil on the front of top using a template.  The f-holes are positioned based on the eventual placement of the bridge, and the predetermined distance between the upper eyes.
Once the f-holes are properly laid out, you drill a few holes in them, and use those holes as entry points for the fret saw.

After the rough work has been accomplished with the saw, you do the rest of the carving with an f-hole knife, which is very long and sharp.  The challenge of carving spruce is that the summer grain is soft, and the winter grain is hard, so keeping all the cuts even and avoiding chatter takes practice.

We strive for symmetry with the f-holes, but recently I've adopted an attitude about them based on a piece of advice I read online about shaping your eyebrows:  Remember they are sisters, not twins.  I think as long as they look like they balance each other appropriately I'm not going to keep chasing every cut to try to make them exact mirror images.  I've altered f-holes in the past that I liked just because I felt I had to match something that got away from me on the other one.  Unless there is a glaring imbalance to address I don't plan on doing that anymore.
After carving the f-holes (leaving the wings attached) I graduated the top, which means thinning the plate from the inside to particular thicknesses.  (Leaving the wings of the f-holes attached at this stage helps to protect them from getting snagged by the finger planes.)
Plate graduation is an interesting process.  I have patterns that I follow, and I take frequent measurements with my calipers, but a lot of it comes down to how the specific piece of wood feels.  It needs to flex in your hands properly and the different thicknesses need to flow into each other well.  The thickest area is at the center, and on this top plate it ended up at 3.1mm.  The thinnest areas (2.5cm in from the edges) were 2.4mm.

The plate is also tuned to specific pitches, which are referred to as "tap tones."  You hold the plate a particular way and tap the wood in spots to make it resonate.  You can adjust the pitch you hear by removing more wood.  I did not get the tap tones I was originally aiming for because the electronic tuner I was using to hum the pitches into had a low battery, and I didn't realize it wasn't giving me an accurate reading until the tap tones had gotten lower than I intended.  It should be fine, though.  The plate feels good and rings well, and my teacher back in school was always adamant that you "don't hang on tap tones."  It will be interesting to note any acoustical differences between this instrument and my previous ones.

After the graduation is complete you cut the wings on the f-holes free.  (This usually drops the tap tones but then they go up the same amount again once the bass bar is in.)
The bass bar!  The bass bar is a structural support that runs under the lower pitched strings on a violin (viola, or cello) and helps move more of the plate to produce the larger sound waves in that range.  It's made of spruce, and is angled slightly askew to the grain which helps avoid cracking.  The bass bar is laid out based on the eventual position of the bridge (and is symmetrical to where the soundpost will be on the treble side).

You chalk fit the bar, which means you put down a layer of chalk along where it sits, place the bar there, and see where the chalk has touched it so you know where the high spots are that need to be cut.  Temporary cleats help you put the bar in exactly the same spot.  Getting a perfect fit on the bar doesn't actually take that long.  The part that always slows me up is adding "spring" to it, which means removing an extra amount of material evenly from each end so that the whole length of it rolls.  I made a "bass bar ring" to help keep the plate from flexing while pressing the bar into the chalk.
Once the fit of the bar is correct you have to glue it immediately.  I have a wood protector on the top side of the plate, and the bar is held in place with a pair of long C-clamps on the ends, and four clothespin clamps.
Usually you let it sit overnight to dry.  If the fit isn't exact you end up with bulges and ridges on the outside of the plate, so it pays to take the time to fit the bar well.  After it's dry you shape it until it flexes properly and the tap tones are where you expect them.
Graduation on the back plate is a little more straightforward since you don't have to deal with the f-holes or the bass bar, but it makes a mess because the tiny shavings from the toothed blades in the finger planes get everywhere.  The maple for this instrument has really beautiful flame, and it looks amazing when light shines through it.  (You can actually see how the wood gets thicker at the center.)  The middle of this plate ended up at 4.7mm, and the thin spot around the edges was 2.4mm. 

Once the back plate is finished it gets permanently glued to the ribs.
After that dries, you can finally remove the form.

At this point it always feels like things are rolling, and then I remember that I have to glue in the upper side linings, shape the blocks and the linings, and clean up all the excess glue, and things slow down for a bit while everything sits in clamps.
lots of tiny clamps for gluing in linings.
But eventually all of that is done and I can glue on the top!
It's always exciting to unclamp a violin body when it's finally glued together.  It's surprisingly light.
And this is one of the biggest fake out moments where it feels like you are mostly done and then there is a lot to do.  Besides cleaning off glue and rounding all the edges and making and installing the saddle, the purfling channel needs to be touched up.  I hate working on the purfling channel.  I kind of punted on it a few steps back, not spending as much time on it as I should have because I knew I would have to do it again anyway, but now of course I have to really do it.
The purfling channel is the scoop in the plate right along the edge where the purfling runs, and includes the little ridge that is the high point before the edges round over.  It's frustrating because it's supposed to be smooth and even, but you have to deal with the grain changing direction as you work your way around the plate, and the purfling itself scrapes differently from the wood around it.  Plus you have to do everything twice, once on the spruce then again on the maple.

And it feels thankless because it takes forever and nobody (but other makers) notice it.  Well, it's not true people don't notice it, but they don't know they notice it.  It defines the finished outline of the instrument, but not in a manner the average person could point to.  The same way someone in well-tailored clothes looks polished and put together, but if you had to say why you would be distracted by style or material or color, and less likely to give credit to good hems and seams.  The purfling channel is essential for a clean and finished appearance, but it takes forever, and when you're done it just gets taken for granted.

So that's where I am.  And I'm cheating a little with this photo because the saddle (the ebony piece at the bottom of the plate) isn't finished or glued in yet, and the corners still need to be rounded.  But I'm almost ready to set the neck!  Once that's done I will do final touch ups (including more work on the purfling channel) and I can start thinking about varnish.  Can't wait!  I've really enjoyed working on this model and look forward to doing it again.  (Probably for Quinn, since I'm doing a Strad model for Aden, and plan on a Guarneri for Mona.)  Violin making is the best.

7 comments:

  1. This. Is. Fascinating. You'll show it varnished too, right? Let us know if it's still ok even with the lower tap tones (if I worded that correctly).

    F-holes. I learned a new word!

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    Replies
    1. Varnish is considered half the process, so I will definitely show how that goes.

      (And "F-holes" always sounds to me like some kind of luthier swear word.)

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  2. Yes--hope the tap tones are okay!
    -an interested reader

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    Replies
    1. The tap tones will be fine. They are within the range, I just normally go for the high end of that range, so this will be interesting. It was mostly annoying to lose track of them because of a technical glitch! The plate is very flexible, and rings well, and the thicknesses are all within range, too. I always heard the Beckers (the most famous family of American violin makers) made their tops and even 3.0mm, and my center is a tenth thicker than that, so I'm not worried. Working on the neck set! It will look like a whole violin soon.

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  3. I was totally thinking f-holes sounded like an awesome violin swear word!! :)

    ReplyDelete
  4. Thank you for the interesting article

    ReplyDelete
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