Light weight fiddle

[Roger Frankland]

My quest is light weight fiddles. I have found a lot of things do not work. A lot of this was coming up the learning curve - which I am still doing. I have succeeded in eliminating the problems of tubbyness and wolf tones traditionally associated with light weight fiddles by controlling belly arching and graduations but that caused other problems. Just to prove to myself that I could get a good sound, I built 2015-2 with more traditional weights. It sounds much better. Then 2015 - 3, better still and with a 50 gram belly. I am tthinking about shifting focus now towards a folk fiddle ... dark, responsive, very playable, and sort of light.

here is my evolution:

Slightly lighter fiddle - 2012-1

Total weight incl chin rest: 370 grams,

Specific gravity of top: .32

Thickness of top: 2.2 to 2.9 mm

Weight of top: 48 grams

Arching: 16mm

Tonal Response. Normal to dark

Very light fiddle - 2013-1

Total weight incl chin rest: 320 grams

Specific gravity of top: .32

Thickness of top: 1.9 to 2.7 mm

Weight of top: 45 grams

Arching: 16mm

Tonal Response. Unacceptably dark

High arch fiddle with aspen back. - 2014-1

Total weight including chin rest and Mech pegs: 323 grams

SG top =.35

Thickness of top. 2.3 - 3.4 mm

Weight of top: about 60 grams including 5 gram bar

Arching: 20mm with "perfect rounding" to edges.

Tonal response: harsh

Left overs fiddle. - 2015-2

Total weight including Mech tuners and chinrest - 424 grams

Belly and back with traditional arching and weights

Tonal response: brilliant - at times

Treated wood fiddle 2015 - 3

Total weight 413 grams (380 wo chinrest).

Belly is treated spruce (SG= .29). Belly weighs 50 grams, traditional arching and graduations.

Tonal rsponse is the best I have done. Clean in the low range, i.e. no tubbing or wolfs! Maybe it is possible!

Edited September 27, 2015 by Roger Frankland

[Don Noon]

My quest is good sounding fiddles.  I'm not sure why you are on the quest for lightness,

 

Some theory indicates that lighter weight fiddles should be louder, so I did venture in that direction, with very low density wood.  Even though I never came close to what you seem to be doing (lightest top ~55g with bass bar), my observation was that the high frequencies and overtones didn't gain any strength when the weight was reduced, but the lower and middle frequencies (mostly middle) did gain.  That gave a darker sound.

 

Also, with the reduced mass came reduced stiffness, with more problems with playability:  wolf notes, more difficulty getting notes started, etc

 

One other hidden issue with ultra-low density spruce is that the stiffness drops off quite sharply once you get into the zone below ~.34 density.

 

Joseph Curtin made some ultra lightweight fiddles using balsa and spruce laminations.  I played one, and didn't like it; seemed to me like it was all midrange, with weak lows and highs.  Very quick response, though.

[Roger Frankland]

Thanks Don for your observations. It is good to get confirmation of my results. My plan is to try again and to make adjustments with the arching to reduce plate response to low frequencies. I also plan to move up in SG. Do two things at once, not very scientific. This hobby is keeping my mind sharp (pun intended).

[Roger Frankland]

Now here is a really simple analysis. Let's assume that the average fiddle in the universe weights 475 grams and the average finished top weighs 71 grams (15% of the total). Then let's assume that the law of proportions applies. Voila, here's what to do:

Fiddle weight 475, top 71

Fiddle weight 400, top 60

Fiddle weight 350, top 52

Fiddle weight 300, top 45

Fiddle weight 250, top 38. Whoops, crash

[James M. Jones]

The guide lines given to me are 55-73 gms for the top. there are many variables such as arch height,high /low , arch shape, i.e long smooth rise from the edge,or one with lots of swoop. the bridge platform , round or flatter, and thickness, under the bridge around the edges in the lungs.

  I would guess that a high arch rising swiftly from the edges with a round bridge area through the c bouts should let you use thinnest graduations possible. without becoming watery and hollow sounding. Also a smaller size model, like DGU or a standard Amati , as opposed to a full sized Strad or Amati grand,would help.

 I see the top plate as a sort of complex trampoliene , It takes a ballance of forces to redirect the energy of the bouncer/bridge. to much resitance and the weight just sits there ,to little same issue.

[Don Noon]

Everything is a balance.

 

You want to go super-light?  Then you're going to sacrifice strength margin and tone.

 

Scaling things, I'm sure you know, is overly simplistic, as certain things are constant and do not scale... like string force and vibration frequency. 

 

If you really want to make a light top that withstands the static forces of the strings, the most efficient way to do that is to make the arch straight from the blocks to the bridge feet, with a sharp kink right under the feet.  That gets all of the stresses in-plane, with no bending.  Bending is the weakness of thin structures.  However, that concept would also make any vibrations of the bridge foot convert to mostly in-plane vibrations of the wood, and it therefore it wouldn't make much sound.  It's all a balance.

[skiingfiddler]

In weighing fiddles as a whole, you might want to remove the chinrest, so that comparisons from one fiddle to the next don't get skewed, unless you're using the same rest on all the fiddles.  Chinrests, like the ebony, large cup Flesch, must weigh about a quarter pound, while a small cupped, thin rest would weigh far less.

 

Also worth considering is the weight of different fittings, boxwood vs ebony, for example.  Also full sized metal tuners would skew weights, depending on how many there are.

 

But it looks like total fiddle weight is less important to you than the weight of the top, alone.

[Roger Frankland]

Thanks guys for your comments on arching. I also read D. Noon's article on testing wood and was impressed. I'm heeding your advice and moving ahead with my next build. Today I selected wood, created new arching templates, and glued together the top billets. Life is good, but the next step is a long one.

Regarding chin rests, I included its weight in my total because my goal is to create a light instrument, ready to play, and the chin rest can be a significant contributor. The chin rest on my 320 gram fiddle weighs 15 grams. I use a triple beam balance to weigh my parts so the numbers are accurate but I've had this fiddle apart three times and the weight has changed some as I've tried different things.

[Roger Frankland]

A simple arching equation.

I have been fooling around with long arching templates for my next project and came up with something which might be helpful.

My goal for top plate arching is 18 mm high with very smooth transitions. I realize that arching shape is another controversial topic with many divergent ideas, but here's mine. After messing with several freehand versions which achieved 18 mm but didn't look very smooth, I decided to start with a round arch, either making the belly round like Santa Claus or flattening it slightly, sort of like Venus de Milo. But what radius to start with? I eyeballed one and it turned out just OK. So I dug back in my memory and created an equation for the radius that goes like this.

The fiddle top length is like the chord on a circle where the arching height is a line drawn perpendicular to the chord reaching to the outer edge of the circle. For simplicity I chose a spot half way down the chord to solve the equation. The solution for the equation is:

R= (B*B+C*C)/2*B Where R is the radius of the circle, C is one half the length of the chord and B is the arching height ( not including the thickness of the wood). In this application 2C represents the length of the fiddle.

I decided to make 2C = 322mm, leaving some room at the ends for a gentle transition. I made B = 15 mm allowing for top thickness of 3 mm. My radius R then simply computes to 871.53 mm or 34.3 inches.

I went to my workbench, drew a 34.3 inch radius on my template, drew a 322 mm long chord across the radius and had it! As a refinement, I extended the tails at each end to achieve my final fiddle length and flattened the top slightly to be somewhat Venus like.

I then cut out the template, rough sanded the radius with a drum sander, and finish sanded with a rounded wood block (same radius). Took out my calipers and measured the arch height. Close enough .... 15.3 mm which will net an 18 mm arch assuming 3 mm final wood thickness! And very smooth transitions.

This same equation can be used for the side templates but the long arch comes first.

Edited December 12, 2013 by Rofrankland

[Roger Frankland]

I constructed a fixture to temporarily attach an A string to my top so I can bow it and measure both the fundamental and harmonics as I carve my top. I'm now down to a top center thickness of 3.5 mm and, sure enough, A4 is building while A5 is not. This is quite interesting to me because I really wanted to go light. Will see if the trend continues as I progress with the carving.

[DonLeister]

Rofrankland, can I ask, what is it about a lightweight fiddle that is attractive to you? Does it have to do with sound or with being easier to hold up when you play, or other things?

[Roger Frankland]

Don, sorry, I haven't been checking in, too busy staying out of the cold.

I guess there are three reasons I am trying to make a light weight fiddle (300 grams including chin rest).

1. I don't know of anyone who has done it successfully!

2. If I can do it without losing all the harmonics it should have good tone, be quite loud, and have an exceptionally long sustain... something a fiddler might have fun with but not a classical violinist.

3. Playing a light fiddle is like having a deadweight removed from your shoulder!

But this is so very hard to do. While carving my latest belly I found the point where the overtones started to disappear! I'm carving the back now, using some .37 SG aspen. Since aspen is lighter than maple, I can leave just a little more meat on the belly... Maybe.

[Don Noon]

I think the sustain would be the exact opposite... very short.  Light weight implies low impedence, thereby taking energy out of the string at a high rate.  That's how my lightest top instruments play: very responsive and quick, but very little ring to them.

[violins88]

Don, sorry, I haven't been checking in, too busy staying out of the cold.

I guess there are three reasons I am trying to make a light weight fiddle (300 grams including chin rest).

1. I don't know of anyone who has done it successfully!

2. If I can do it without losing all the harmonics it should have good tone, be quite loud, and have an exceptionally long sustain... something a fiddler might have fun with but not a classical violinist.

3. Playing a light fiddle is like having a deadweight removed from your shoulder!

But this is so very hard to do. While carving my latest belly I found the point where the overtones started to disappear! I'm carving the back now, using some .37 SG aspen. Since aspen is lighter than maple, I can leave just a little more meat on the belly... Maybe.

Are you measuring and recording M5 and plate weight of both top and back?

[Roger Frankland]

Yes, I am recording weight and M5 on both top and back. I also built a deflection apparatus to record bending moments and a playing apparatus to record harmonic content of a bowed note as I carve. For me, it is instructive to see the gradual disappearance of harmonic content as I thin the plates. To be expected, I guess.

My problem is I am now approaching conventional thickness for both top and back. Everything seems to be coming together except if I stop carving I will not reach my weight goal! Compromise? Never.

I was messing with sustain today. Time to 50% amplitude on a plucked string seems to be a tenth of a second more or less on everything I measured.... both plates and fiddles. maybe a little longer near the body resonance. Now I'm not so sure about sustain on a fiddle. Doesn't seem to matter much in my playing because the bow on the string shuts it off unless I get off the string quickly. Now if the wood continued to resonate after the string stopped that would be something but I guess that isn't going to happen. There is another phenomena. When playing in a group, other instruments sometimes make my fiddle ring. It is a glorious sensation, but I have no idea what all the interactions are. This continues to be very complicated.

[Don Noon]

Everything seems to be coming together except if I stop carving I will not reach my weight goal!

Most makers I would think have a goal of tone and playability, with weight being a distant third.  Apparently you're not one of those, and there's no reason you should be.

 

 

When playing in a group, other instruments sometimes make my fiddle ring. It is a glorious sensation, but I have no idea what all the interactions are. This continues to be very complicated.

That's one of the less complicated things.

Normally the vibrating string moves the wood which moves the air, but it can be reversed with an external sound moving the wood and making the string vibrate, if the strings have a matching frequency with the sound.  Or, if there is a structural resonance, the violin can vibrate on its own without the string being involved.  I normally fiddle around next to a table full of violins and a nearby piano, so there are many voices that join in.

[violins88]

Yes, I am recording weight and M5 on both top and back. I also built a deflection apparatus to record bending moments and a playing apparatus to record harmonic content of a bowed note as I carve. For me, it is instructive to see the gradual disappearance of harmonic content as I thin the plates. To be expected, I guess.

My problem is I am now approaching conventional thickness for both top and back. Everything seems to be coming together except if I stop carving I will not reach my weight goal! Compromise? Never.

I was messing with sustain today. Time to 50% amplitude on a plucked string seems to be a tenth of a second more or less on everything I measured.... both plates and fiddles. maybe a little longer near the body resonance. Now I'm not so sure about sustain on a fiddle. Doesn't seem to matter much in my playing because the bow on the string shuts it off unless I get off the string quickly. Now if the wood continued to resonate after the string stopped that would be something but I guess that isn't going to happen. There is another phenomena. When playing in a group, other instruments sometimes make my fiddle ring. It is a glorious sensation, but I have no idea what all the interactions are. This continues to be very complicated.

I would strongly encourage you to measure M5 and mass of the free plates. Please ready my page here.  I have had great success so far. Just my 2 cents.

[Don Noon]

I would be most interested to see the mass and M5 of the top without the bass bar, which is what I mostly pay attention to.

I have made 3 fiddles with tops in the 50 - 52g range, with taptones ranging from 285 to 335 (without bass bar).  I wouldn't go that light now, unless I was using .30 density spruce.  But that's a range where I don't think it sounds quite right.

[Roger Frankland]

Thanks guys for your comments. I can use all the help I can get in my quest.

John Schmidt: my unfinished back plate currently weighs 82 grams and has an M5 of 382 hertz. This results in a kback of 1.2. Did I do the math right? My unfinished top plate currently weighs 79 grams and has an M5 of 370 hertz. I am measuring M5 using Audacity software and the peaks are sharp and repeatable to within a few hertz. My back wood has an SG of .37 and the top has an SG of .35. The arching for both plates is very high and the radii are as smooth as I can get them. I am mindful of Strobel's graduation suggestions.

Don Noon: I stopped carving the top a few weeks ago in order to work on the back and see where that took me, but the back has been stubborn. I am proceeding carefully, trying to keep everything in balance. I am keeping my data in a spreadsheet and will share it when I finish. So far, my results with light tops have also disappointed but that could change.

I am continuing to measure the harmonics with my bowing apparatus and have been applying the technique to my back plate. Same trend, the harmonic content of a bowed string fades as the plate is thinned. I have read everything I can find about string harmonics but can't find any references about what affects their relative amplitudes. Was that the class I dropped in school? This is really fascinating.

[Roger Frankland]

Most makers I would think have a goal of tone and playability, with weight being a distant third.  Apparently you're not one of those, and there's no reason you should be.

 

 

That's one of the less complicated things.

Normally the vibrating string moves the wood which moves the air, but it can be reversed with an external sound moving the wood and making the string vibrate, if the strings have a matching frequency with the sound.  Or, if there is a structural resonance, the violin can vibrate on its own without the string being involved.  I normally fiddle around next to a table full of violins and a nearby piano, so there are many voices that join in.

Most makers I would think have a goal of tone and playability, with weight being a distant third.  Apparently you're not one of those, and there's no reason you should be.

 

 

That's one of the less complicated things.

Normally the vibrating string moves the wood which moves the air, but it can be reversed with an external sound moving the wood and making the string vibrate, if the strings have a matching frequency with the sound.  Or, if there is a structural resonance, the violin can vibrate on its own without the string being involved.  I normally fiddle around next to a table full of violins and a nearby piano, so there are many voices that join in.

[Roger Frankland]

Don Noon:

Most makers I would think have a goal of tone and playability, with weight being a distant third.  Apparently you're not one of those, and there's no reason you should be.

 

 

That's one of the less complicated things.

Normally the vibrating string moves the wood which moves the air, but it can be reversed with an external sound moving the wood and making the string vibrate, if the strings have a matching frequency with the sound.  Or, if there is a structural resonance, the violin can vibrate on its own without the string being involved.  I normally fiddle around next to a table full of violins and a nearby piano, so there are many voices that join in.

[Roger Frankland]

Most makers I would think have a goal of tone and playability, with weight being a distant third.  Apparently you're not one of those, and there's no reason you should be.

 

 

That's one of the less complicated things.

Normally the vibrating string moves the wood which moves the air, but it can be reversed with an external sound moving the wood and making the string vibrate, if the strings have a matching frequency with the sound.  Or, if there is a structural resonance, the violin can vibrate on its own without the string being involved.  I normally fiddle around next to a table full of violins and a nearby piano, so there are many voices that join in.

Don: ah yes, well said. But I'd say it is a little more complicated. If the wood is really light and "responsive" the effect will be much more prevalent, right? I practice fiddle in my den where I have a light classical guitar on a stand and a heavy Taylor Guitar on a stand. I can hear the classic guitar ring from across the room, but not the Taylor! When I was young, I sang in choral groups and sometimes I felt the music of the group resonating. Now that I'm old and tough, it never happens ..... I think it is another dimension... And another reason to make light, responsive instruments.

[Roger Frankland]

I'm stuck. Carved on the back some more today because M5 was higher than I wanted even though the graduations were about right. I took off another 0.2 mm. The plate weight dropped 4 grams to 78 grams and M5 dropped 10 hertz to 372 hertz. Problem is the harmonic content (from my bowing test) also dropped ... to the point that I don't want to go any further.

[Janito]

I'm stuck. ...

Problem is the harmonic content (from my bowing test) also dropped ... to the point that I don't want to go any further.

 

Is the tail wagging the dog?

[violins88]

oops