Violin Making: Setting the Bass Bar in Fiona

One of the mysterious steps in violin making is setting the bass bar. There is much discussion about the bar tension, placement, and thickness; all factors that affect the tone of the final instrument. Also all factors that can not be changed after the top is glued on. Today I shaped, glued, and trimmed the bass bar in Fiona. Oh all the questions? The wondering? The acoustical samples and science. Every article I’ve read on “What makes the sound of a good violin?” Now I see and measure the details, someday I’ll understand or get a ‘feeling’ for the effects and results.

Tap Tone Test

I took tap frequency readings and weighed the plates prior to cutting the F-Holes, after cutting the F-Holes, after setting the bass bar, and now again after trimming the bass bar. After trimming the plate resonance frequency is at the same point as prior to cutting the F-Holes. The removal of wood for the F-Holes, the additional stiffness and trimming of the bass bare canceled each other the F-Holes to resolve to the same acoustical values.

Fiona, #6, is a bit lower frequency than Diana, #4. Diana had an F for the front plate and F# for the back plate. Fiona is 1/2 step lower with D# for the front and F for the back. This is also what Claude, #3, measured at. Fiona also weighs a bit less for each plate, with equivalent dimensions, which is expected with the lower frequencies. The wood has a little bit less density.

Continual Learning

As I build each instrument and record the resonate frequencies and plate weights. I can observe the effects as the building process progresses, as well as the final tonal effects on the instruments. The more I build, the more I understand. Right now I’m hypothesizing and observing.

There is a violin maker in the Maestronet blogs who used to work at the Jet Propulsion Laboratory, a Mr Don Noon. His tag line reads, “Making fiddles ain’t rocket science…  it’s much more complicated.”

Everyday, new lessons, more progress; the path to mastery

 Photos journey of setting the bass bar

Fiona with a fitted bass bar. The plexiglass brackets hold the bass bar in position while checking the fit. Chalk is spread under the bass bar, and then the bar is pressed into place, removed, and inspected for even chalk on the bar. Where its not even, the chalk and a little wood is removed until the bar fits perfectly.
Fiona with a fitted bass bar. The plexiglass brackets hold the bass bar in position while checking the fit. Chalk is spread under the bass bar, and then the bar is pressed into place, removed, and inspected for even chalk on the bar. Where its not even, the chalk and a little wood is removed until the bar fits perfectly.
Top view of Fiona's bass bar. The bar is placed in proportion to the center line of the top plate. The placement is close to the line of the G string, the lowest string on the violin. The purpose of the bass bar is to transmit the lower frequencies down to the larger 'bass' end of the violin's vibrating top plate.
Top view of Fiona’s bass bar. The bar is placed in proportion to the center line of the top plate. The placement is close to the line of the G string, the lowest string on the violin. The purpose of the bass bar is to transmit the lower frequencies down to the larger ‘bass’ end of the violin’s vibrating top plate.
High Tech bass bar clamps :-) You can purchase cast iron C clamps to span perfectly over the bass bar. I like to use the simplest technology that works. Stradivarius did not have cast iron spanner clamps, but then he probably didn't have rubber bands either....
High Tech bass bar clamps 🙂 You can purchase cast iron C clamps to span perfectly over the bass bar. I like to use the simplest technology that works. Stradivarius did not have cast iron spanner clamps, but then he probably didn’t have rubber bands either….
The under side of my bass bar clamps, wine corks. The corks are cut in half and line up with the bass bar. Without them you don't get even pressure, also the cork (or modern plastic corks in this case) provide a nice pliable surface to avoid denting the soft spruce.  Once done with the process, I celebrate by finding a new wine cork :-)
The under side of my bass bar clamps, wine corks. The corks are cut in half and line up with the bass bar. Without them you don’t get even pressure, also the cork (or modern plastic corks in this case) provide a nice pliable surface to avoid denting the soft spruce. Once done with the process, I celebrate by finding a new wine cork 🙂

Violin making: Rib Assembly on Fiona

The first steps in making Violin #6, Fiona is building the violin rib assembly. To get started we set the corner gluing blocks to the form and then gluing the ribs. It all sounds pretty simple until, like most things, you get into the details.

This first photo shows fitting the template over the form and marking the edges of the corner blocks. The insides of the corner blocks are trimmed and clued first, then the outsides of hte blocks. If you trim the outside, the point is so fragile that it will break when clamping in the C bouts, the tight middle rib pieces.

Fiona #6, triming corner blocks to fit the Strad violin template
Fiona #6, triming corner blocks to fit the Strad violin template

We test if the corner block is trimmed close enough by trying to hold a pencil line on the wooden block. If the block is the correct size the pencil will slip down the side rather than draw on the edge.

This next photo shows fitting the clamping cauls to the corners. A clamping caul is used to hold the exact curve during clamping. If the caul is not an exact reverse surface from the corner block, you will get gaps which are weak glue joints. Also the ribs need to fit, clamp and glue perfectly square, else the finished violin will not rest flat on its side, all four outer edges of the plates touching flat.

Fiona #6, Setting the glue cauls for the corners, top, and bottom blocks
Fiona #6, Setting the glue cauls for the corners, top, and bottom blocks

 

Once the cauls are all trimmed and fit, a test clamp assures that the ribs will fit tight into the corner blocks. The entire assembly is clamped up without glue with each corner seam checked top and bottom for a clean fit. Once everything is correct pencil lines are drawn on the sides and forms to show the exact position when the gluing starts.

Fiona #6, Testing Clamp fit of the ribs onto the Strad form
Fiona #6, Testing Clamp fit of the ribs onto the Strad form

If it doesn’t fit dry, it will certainly not fit in the rush of getting everything together before the hot hide glue starts to set.

Next Steps Trimming the top and bottom and gluing the rib assembly together.

 

The Making Violin #6, Fiona Started today

Sound Testing #5 Edward

With #5, Edward, playable in the white, I did a set of recordings for comparison to when Edward will have his varnish on. The recordings consist of a set of open string bowings; G, D, A, E and then a D major scale, and a three octave A major scale. The final recording is a tapping on the bridge, this measurement will provide a frequency ‘ring’ of the instrument independant of the bow and/or player skill required in the first set of recordings

Prior to making the recordings I tuned the sound post, moving it a bit forward and to the treble side. The slightest movements of the sound post had an impact on the sound of the instrument. The changes ranged from shrill to mellow, to nasal or hollow. The adjustments strive for a pleasant blend of these two scales; a tiche to the left, a tiche to the right, oh too far and a tiche back to the left. Once satisfied, then the sound test were done and recorded. I keep a set of recordings on every instrument first the tap tones taken when graduating the plates, then the instrument in the white, then when the varnish is first complete, then after a couple of months of playing. The scientific process of improvement; measure, compare, adjust, measure, compare, adjust then repeat.

The Start to Making Violin #6

These paragraphs were musings about the  process with finishing Edward, now on to the real purpose of this post: Starting to make the next violin!!!

The following photo shows the spruce and maple that will be planed, cut, glued, carved and scraped into a fine violin.

Raw wood for violin #5: top spruce billet, bottom maple billet, maple side pieces, and maple neck block
Raw wood for violin #5: top spruce billet, bottom maple billet, maple side pieces, and maple neck block

 

Wood for making Violin #5; Foreground is a jack plane fitted to a fixture to create a striking board. It is used to get a square, true edge for gluing.
Wood for making Violin #5; Foreground is a jack plane fitted to a fixture to create a striking board. It is used to get a square, true edge for gluing.

The first step is to plane the plate glue edge perfectly square and straight. The striking plane jig holds the plate flat and cuts square, then the movement across the blade will determine the straightness of hte edge.  The goal is to hold the two pieces of each plate together in front of a bright light. If any light shows through the seam, then it is not a good fit. Holding the plates together square or straight should show no light, then hold the edges a skew with the the top aligned with the bottom on one end and the bottom with the top on the other end. This will show a straight line, and no curve or angle in the cut. The finished edge will match perfectly creating a clean thin glue line in the finished plates.  An axiom in violin making; a little extra care early saves work later. Same as “Haste makes Waste.”