Balsa wood?

[polkat]

I just read a passing mention somewhere on this forum that some violin makers are beginning to try balsa wood for top plates. Balsa wood? As a kid, I remember making model planes from this stuff, and I don't recall it having any tone qualities, although it is pretty strong for it's weight. It's an evergreen I think, but any relation to the spruces/firs? One would assume it has to be graduated a bit thicker.

Has anyone heard of this, and if so, can you fill me in? Thanks.

[Tim McTigue]

As an aeromodeler, I have more than a passing familiarity with balsa, and have some doubts as to its suitability for top plates. OTOH, I suppose a "hard" grade of balsa MIGHT be somewhat suitable. I have done some carved-and-hollowed work with balsa (wing tips, cowls, etc.), and have noted it seems to have some interesting tap-tone qualities when properly thinned...

[matthew tucker]

AFAIK some makers have tried using balsa wood as bracing for very thin tops and backs, but not for the actual diaphragm.

[David Tseng]

I just bought a model sailplane (Omega II 1.8m), the leading and trailing edges are carbon fibre, only the spars are balsa. CF is stronger and lighter than balsa.

[polkat]

Thanks guys. After starting this thread, I did some research on balsa violins. Turns out that this was discussed in some detail on this forum a few years back. I've decided that, though I think such experiments are important to our craft, balsa is not for me. My interest in this came from a desire to try other woods besides spruce for top plates, but woods that would be similar in tone and workability. What have others here tried?

[David Tseng]

I've tried cypress which is very similar to spruce, but have to give up because of the strong smell.

[Lyndon Taylor]

 I have a

really good sounding fake Guarneri del Gesu with what definetly

looks to be a fir top, not spruce, its kind of thuddy when you tap

on it, and doesn't have quite the brighter harmonics but it sounds

just fine, don't assume every violin is spruce, pine and fir were

used also, sincerely Lyndon J Taylor

[kubasa]

This discussion reminds me of an article that I read in the spring.

I thought some others might be interested in seeing the article

too.

http://www.iht.com/articles/2006/11/29/hea...usic.php?page=1

[Darren Molnar]

Heres a N. Y. Times article on balsa violins.

 http://www.nytimes.com/2006/11/28/science/28acou.html?pagewanted=1&ei=5088&en=235921a7d7ee3639&ex=1322370000&partner=rssnyt&emc=rss

 Also if you root around the multi-media box you can find a

sound sample along with a strad. and a schleske.

the quality of recording sucks,though.

[DMartin]

Ok folks, send any barbs to Darren. He asked for this in the borax thread.

This is #14 of balsa experiments with #15 coming along in background. Every effort was made to avoid symmetry, regularity, and neatness. Several months ago the depth of the transverse braces was greatly reduced which was a great improvement. The tranverse braces are doubled on the inside with 1/32 inch strips.

Caliper length back plate 363mm

Max width 215mm

Will have this fiddle at the Boston Early Music Festival next week, on June 13th--carbon seminar.

Also at Oberlin in July.

[Darren Molnar]

 Doug, your awesome, thanks for sharing. For those of you who

are scratching your head I think in time we`ll see how this unusual

research translates into traditional making.

My first question [of many] is, what do the red patches signify?

[David Burgess]

The top is foam core?

Is it skinned on both sides?

[DMartin]

quote:

---

Originally posted by:

Darren Molnar

what do the red patches signify?

---

TransTint brand dye. Color without much stiffness. Influence of Mondrian perhaps?

Will quote Jeffry, "Momentary lapse....." irreversable.

Doug Martin, ready for more

[Darren Molnar]

I think the foam is used similar to the way we use inside moulds,

just to get the shape. Is that correct?

Doug, how do you get the curvature of the front and back plates?

also how thick are they ?

So do you see your process as an additive one where as you start

with a structure that is weak and add the braces and such to

support . Are the braces placed with acoustics in mind from the

beginning?

[DMartin]

quote:

---

Originally posted by:

David Burgess

The top is foam core?

Is it skinned on both sides?

---

What you see is pretty much what you got. Both plates single sheet of 1/16 inch balsa. Graduations are visible in the external braces. The c-bouts were hewn with BIGGER chips than you ever made out of a solid blocks of ego wood. Balsa is a hardwood after all! Corpus is assembled totally with hide glue, which, with a hobby iron, makes an outstanding instant glue.

Hidden items -- transverse doublers - 1/32 inch, bass bar, sound post patches of poplar plywood, some vertical stiffeners on ribs, end blocks. Only carbon fiber is the single yarn that substutes for button and the fingerboard.

Some construction photos of this and other balsa fiddles will be shown in an upcoming Guild of American Luthiers journal.

Doug Martin

[DMartin]

quote:

---

Originally posted by:

Darren Molnar

I think the foam is used similar to the way we use inside moulds,

just to get the shape. Is that correct?

Doug, how do you get the curvature of the front and back plates?

also how thick are they ?

So do you see your process as an additive one where as you start

with a structure that is weak and add the braces and such to

support . Are the braces placed with acoustics in mind from the

beginning?

---

Yes, this was made on a foam waste mold that represented the entire inside volume including the inside arch.

The plates were made of 1/16 inch planks spiled (boatbuilding term) in a manner similar to lute backs. The joints were covered by the longitudinal braces.

The intent was to have a structure to which stiffness could be added and subtracted at will without removing a plate. So far, this instrument has only undergone subtraction. Being number 14 of my all-balsa experiments, it benefits from some iteration and tragic experience. Some earlier ones were very additive.

I have been interested to find the minimum number of braces that would give sufficient control and complexity of sound. Much as I would love to say that "the braces are placed with accoustic intent", they are shot from the hip. My goal has been to gather maximum experience in minimum time (now 50 years of messing at this). I think Darnton has it right when he says in essence, "If you make a number of fiddles, they will tend to get better".

Doug Martin

[linarol]

for what it's worth that pegbox looks like it could be used to

impale a stand partner who's got his scroll in your

face while you're trying to read the music

[Darren Molnar]

I think the peg box looks pretty cool,why did you decide to

laminate the neck? What does this instrument weigh?

[DMartin]

quote:

---

Originally posted by:

Darren Molnar

why did you decide to

laminate the neck? What does this instrument weigh?

---

The neck evolved from earlier molded versions with a hollow handle. This is made with a central keel of sapele and okume plywoods with two layers of graphite and cheek pieces of white pine. Pegs are native locust set in epoxy bushings. It is no more than what seemed the most expedient way to use some materials at hand to make a neck strong and stiff in the heel as it isn't set into the block.

Without chinrest, but with strings it weighs 9 oz or 255 grams.

Doug Martin

[Darren Molnar]

doug, whats your acoustic testing set up like? What are you

measuring with? I`m looking for guidance on this subject because

right now I`m basically using my ears and the opinions of a select

few musicians that I trust. Actually I`m curious to know what other

maestroneters are using as well.

[DMartin]

quote:

---

Originally posted by:

Darren Molnar

doug, whats your acoustic testing set up like? What are you

measuring with?

---

I have been using "Mac the Scope" on a PowerBook laptop using only the built-in mike. Mostly I use it in "real time" mode with each trace retained on the screen. After 15--20 minutes of hard playing all over the board and concentrating on each resonance from every possible position, a resonance profile emerges that seems to match what I hear. I use this mode also for exploring the corpus by tapping.

Though scientists might cringe, I feel that this is a useful shop and learning tool, particularly if it is taken as an indicator subject to many pitfalls rather than definitive measurement. Many illuminating insights can be gained by vocalizing into the mike while watching the results on the screen.

In general though, I have been seeking experience that trains my senses, as my goal is to work as much as possible in "full sporting mode" without mechanical aid.

[Johnmasters]

Congratulations.. I am a believer in finding qualitative tendencies for a good reason. Measurements of exact numbers are fine, if you know what should be measured. Since we don't really know this, any tendencies that satisfy you, and that you can discover with crude measurements should tell you many things. You need only be honest with yourself. Later, it may come to you what needs to be measured more specifically and accurately.

[DMartin]

Yes, John, that's the camp I'm in.

Likewise, I looking forward to doing parametric variations with FEA models (yours perhaps?) to get indications of places to explore. In other fields, mathematical modeling has led to results not imagined by ordinary thinking.

[Oded Kishony]

Hi John, Doug,

I've been reading an old paper by Oliver Rodgers of an FEA of a violin. At the time the only way to do this was at a University, since personal computers were too feeble.

Is there modeling availbable that's been done for the violin or do you have to build it yourself?

I'd be interested in sharing some of the work and expense if anyone is willing to share and the process isn't too time consuming.

Oded