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[kraut]

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I don't have his(Weisshaar's) book--what was his remark?

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Not advocating for it, but for the record Weisshaar says on page 28, "We see no advantage in fitting a bar with tension and believe that this practice can be detremental to the instrument. Excessive tension invariably pulls the table arching out of its natural form because the mass of the bar will cause the table to conform to the bar's arch, not vica versa. The "tension" theory might well have been invented by someone who did not know how to fit a bar without tension! An equally strange theory hols that a sunken arching in the bridge area can be raised by fitting a bar with tension!"

Also for the record, the Croen/Atwood article, "Report on Bassbar Study" that was mentioned earlier is printed in the VSA Journal, Vol. XV,No.2, pp.65-92. It's an article worth reading. (Incidentally, the same issue has an article on Maestronet!)

Just for the record,

Pete.

[Michael Darnton]

Perhaps _Hans_ couldn't fit a bar properly with tension without distorting the top, is possibly more like it. Others seem to manage it just fine.

I don't have any great pix of the eyebrow--I'll look around a bit more and see what I come up with.

[David Tseng]

I have an ETX, a small Maksutov-Casegraine. Based on the price I paid for it, it is probably not that difficult to manufacture.

[Alex_E]

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Anybody who would even THINK of trying to make a Maksutov-casegraine telescope has my deepest respect. How did it turn out?

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I won't go into a lot of detail as I don't wish to hijack this thread, they're straight forward to make because of the spherical corrector lens, the hardest part was drilling a hole through the pyrex mirror.

This was done using a copper tube braised onto a shaft with the end turned down small enough to fit into a drillpress chuck, then using ordinary automotive valve grinding paste and plenty of patience, slowly drilling though it.

(With the soft copper the caborundum grit in the grinding paste becomes embedded into the copper so that it becomes like a mini "diamond" drill.)

The ground out centre is then cemented back into place until the mirror is ground, polished and corrected, then tapped out.

It was only a small one with a 4 1/4" mirror, turned out fine, I later gave it to an astronomer friend as my interest was more in making it than using it.

An interesting aside for you, looking back at some of my old notes prior to commencing it was a comparison of sagitta using the simple formula of r2/2R and the true formula of R-,/````R2-r2 (that's the nearest I can show to it with standard fonts)

Using figures of R = 29 7/16" and r = 2", the true formula gave a sagitta of only .000095570 less.

[jmasters]

All of the surfaces are spherical....... That is something that is easily done with a machine........ but to make the front corrector by hand would be a LOT of work, I would think. Certainly it would be less work to make a bad violin than a bad Mak. At least it would take less time. (yes, I know what you might respond) I have never made any optical parts, but I have read about it for years. Grinding glass for dozens of hours seems like real work. Recall that my posting was that anyone who would take this on has my true respect.

Alex has made his comment, but he did not say how much time he took, and how patient he is. I will certainly say that anyone could make a violin too. If you are afraid to make a violin, Alex, let me say that sharpening a knife is likely a lot easier than avoiding a turned-down edge on a mirror. Write my email (jmluthier@aol.com if you wish to discuss a few tricks here or discuss telescopes.)

I suppose it is just a question of where you want to spend your time. A few years ago just the glass blank would have been very expensive. Just recall that both are made in China, and that means your ETX and a decent violin are both "worth" $2000 or whatever it is.

I hope the few people that have shops on this board do not think that they are somehow special. I mean with respect to being some sort of exotic craftsman. Learning what one wants may be an issue. Being a violin maker perhaps is very difficult today because of the need to copy or reproduce. I am sure it was much easier for the early Italian makers. That at least should make for a good discussion. I suspect that "eyebrows" and other refinements are strictly for the sake of art/sculpture. So far as sound is concerned, the jury is still out with respect to reasons. So far we have a.) materials b.)correctly doing things usually overlooked c.) special treatments in finishing or treating the materials with some kind of chemicals d.)breaking in or superior maintainence over a long period of time. e.)some ideas of my own which I will not discuss at this time. By the way, I will make a comment on the eyebrows in another thread.

What makes telescope making "easier" is that the end product is fully understood. The actual practice is still quite time-intensive unless you have clever mechanised methods. Trouble with violins is, nobody wants a good mass-produced violin. There is a lot of snobbery here. Hey, this is a good topic for a new thread. Let's get it on.

[Alex_E]

The corrector lens for a Maksutov is made of soft optical glass, the blanks are usually sold preshaped and are brought to the correct thickness during the final grinding and polishing process. The main thing required is to make sure the edge thickness is exactly the same all around, to stop the prism effect.

If they weren't preshaped it would be a long task to shape them by hand.

Even I could make a violin in less time. I think.

[jmasters]

"" If they weren't preshaped it would be a long task to shape them by hand.

Even I could make a violin in less time. I think. ""

Our postings obviously passed in the mail (I edited my response, so check back). Yes, I think you SHOULD make a violin. The tolerances on working good optics are not less than those of sharpening a knife. If you have trouble with knives, either you are using bad tools or misunderstand something. Good equiptment is not expensive, at least not in the USA.

[jmasters]

"" I never supposed that any of that type of information would ever be useful in instrument making, so when you mention a parabolic shape I can picture it clearly in my mind.""

I just said the equivalent in my last posting. The violinmakers have a lot to gain from all this esoterica. Michael Darnton himself will know EXACTLY what you mean if you say the word "Hasselblad." Please take my advice and try to make a wooden violin. Knife sharpening is not such a big deal with a few concepts in mind... write me.

[jmasters]

I got a stern lecture once from Carl Becker on eyebrows etc. (I still don't do it)

Presumably you are talking of a continual rise to the edge of the f-hole. This will give a healthy look to the thickness of the plate at the f-hole in addition to sculpting the top.

But I will go back to the notion of the Helmholtz airtones and their mechanism. The amount of air mass in and around the f-hole will affect this, but I do not know how sensitive it will be to plate thickness. Eyebrows would possibly be influential in this regard. I have even read some who have said that a superior tone result from all the degrading of the edges of f-holes caused by careless post adjustments.

[Alex_E]

"Please take my advice and try to make a wooden violin"

I'm still hopeful that my possible source for some affordable magnesium sheet will come to fruition later this year, so will hold off for the time being.

I at long last had an experienced violinist play both my standard 4/4 and the "Chanot" at a Church function last night, the unanimous opinion was that they sounded very nice.

The strange thing was though that the "Chanot" sounded the best in a small room but the standard 4/4 sounded better in the larger hall.

The violinists opinion was that they both sounded just like new wooden violins before they've been played in, which of course they both are. So the $100 question is whether alum bodied violins will play in or sound the same forever.

I feel that as there is a fair bit of stress on the plates when they are tightened into their final positions that the strong vibrations running through the bodies during playing will allow the metal to stretch into a less unstressed shape, that will duplicate the same effects as playing in a wooden one.

[Alex_E]

Michael, my apologies to you for getting so far off topic from the excellent and informative information you are providing for us, in your most comprehensive tutorial on Viola making.

I won't post any more items that are not relative to the subject.

[jmasters]

I don't think that these ideas are at all off the topic. If I can make a connection, there IS a connection. The violinmaking world could use a bit of cross-pollination.

I am not surprised at what you say. Putting the aluminum under stress is not necessarily a bad thing etc. If you read Michael's discussion of a stressed bar carefully, you will note that he says that he presses in the bar until it starts to get a lot harder to push. I think he mentions that he does an equivalent thing with respect to fitting posts. What this means is that he is biasing the static loads to push everything to the edge of the linear properties of the materials. I don't know if you have even approached this with the aluminum. (I tend to doubt it).

One thing especially should be of interest to the makers. Some say that the cross-grain of the spruce needs to be brought closer in stiffness to the longitudinal stiffness in order to make a good tone. The aluminum is isotropic of course. So that should be good data for the readers.

By the way, you have a serious misconception. The worth of a violin has almost nothing to do with tone. Unfortunately, like me, you are a "science type" and tend to believe rational conclusions which seem obvious. Well, you need to understand what is going on in the violin business. But keep on truckin' and make that violin from wood. (Avoid wooden optics, however)

And why are you waiting for this magnesium sheet ?

[Jacob]

A general comment, not a direct reply to jmasters:

I have this uneasy feeling that not everybody is on the same page with "eyebrows" and the shaping of the lower wing. I'm not even sure on which page I am, but for whatever it's worth, my question to Michael was not about the hollowing of the lower wing. What I was referring to is the actual carving away of the lower wing of the f-hole apart from hollowing, so that if the arch is continued from the wing over the f-hole to the top of the belly above the f-hole, there won't be a smooth connection. Similarly, after Michael mentioned the "eyebrows" at the top, I went and had a look at all the photos I could find, and it seems that if the top wing of the f were continued over the hole, it would sort of dive in underneath the arch over the top. Looking along the surface of the top towards upper end of the f-hole, the upper edge of the hole rises above the surface of the wing, resembling an "eyebrow."

OK, if anybody could figure out what I was trying to say you can have next week off.

[Jacob]

"Being a violin maker perhaps is very difficult today because of the need to copy or reproduce. I am sure it was much easier for the early Italian makers."

I think that you are right if one can assume that the early Italian makers had a better understanding of the tonal and aesthetic principles which formed the basis of the Cremonese style, compared to modern makers. Even if one makes as exact a copy of a Strad or del Gesu as possible without fully understanding what one is doing, the tonal and even aesthetic results can be meagre. It would be much easier and faster if one had a better understanding of what one was doing instead of meticulously and laboriously copying a plethora of misunderstood detail - and then still missing some(such as the "eyebrows")which may or may not be critically important in determining the tonal result. One such example is the scoop around the edges and how, together with the arching, it influences tone. Nevertheless, it seems that the scoop is still held by some to be of no more than aesthetic significance.

[Michael Darnton]

Jacob, you have the right idea for the eyebrow, but some of what you're noticing is distortion, expecially on the E side, from arch collapse. However the idea is right--that is that the top rises a bit as it meets the upper edge of the f. Did you notice in photos how Stradivari has a little white band around the top and outside of his f-holes from the sculpting in those areas standing up and being rubbed clean more than other makers? Also, along the bottom edge of the hole where the lower wing permits the same extra access to the lower and inner edge of many violins, not only Strads?

As far as hijacking the thread--all I see is that hits on my site jumped up yesterday. My theory here is that it doesn't matter what you're talking about: as long as the thread keeps floating to the top of the list, people are reading it and going to look at the pictures. :-) However, it would be nice to come back to violas once in a while. :-)

[fiddlecollector]

Heres a pic of the right `f` hole of the 1709 ex-Hammerle.

Its shows the highlighted area Michael is refering to i think also a scoop mark at the upper eye.

[David Tseng]

The correction of upper wing was mentioned in Sacconi's book. I think the eyebrow is mainly due to the distortion from the sound post.

In all the Strads I have seen, I do not find any bee-sting at the corners. Is bee-sting a modern invention? I think Michael far surpasses Tony in workmanship in this respect.

[Michael Darnton]

Yes, Sacconi mentions cuttine down the upper wing on the post side, because it tends to go up, initially when the post is put in. The eyebrow is something definite, though.

No, the beesting isn't a modern thing, but modern makers (probably me, too) tend to overdo it. However, there are some makers, the middle Guarneris, for instance, that sometimes even dragged the purfling knife right off the end of the corner, with a flip to the inside, which fills later with dirt and is pretty remarkable-looking. Probably they were mimicing Andrea Guarneri, who sometimes put on long beestings pointed quite a bit inwards. Stradivari, and the others of his time, weren't as careful with purfling as modern makers are assumed to be. That's why Seraphin, who does an essentially modern-looking job, is always mentioned when careful workmanship is the topic.

[Victor J. Colon]

Very Nice Clamps Michael. They look like the Herdim Clamps. Did you make them ?

Vic

[Michael Darnton]

They're pre-herdim. A friend made them.

[David_Gouthro]

Any new pics Mike?

[Michael Darnton]

I'm just starting to hack on the scroll. Expect me to start a new page in a day or two.

[Roderick Quiros]

Michael, here's a question, since you're starting on the scroll/neck:

How are you determing your neck length, given that the model is an enlarged violin? Are you using a "standard" length based on what what a 15 3/4" viola should have, or are you basing it on the stop length (2/3 ratio of neck/stop)? Or are those one and the same? Or, could you be using a neck length based on Francais' recommendations on viola vibrating string lengths? Just curious, as it seems viola measurements are less "set" compared to violin measurements.

Thanks

[Michael Darnton]

First, it's actually a 16"+ viola. The "15-3/4" on the mold is my notation of the length of the upper rib.

To determine the string length, I positioned the f-holes appropriately for a Strad model, and measured the resulting stop. Then I'm applying the 3/2 rule from there. Fortunately, the resulting numbers are "proper" for a viola--for instance, I think the stop is about 223mm.

[Roderick Quiros]

Interesting. I'm wondering what you would do for a 16 1/4 inch instrument, with a 208mm stop, as the famous Maggini Dumas viola is/has. I've often wondred about the neck length of this instrument, or other Brescian instruments with less "standard" proportions, (at least by modern set-up's). By the 2/3 rule, such a neck would measure about 140mm. But by the length of the instrument, the neck "should" measure closer to 150mm. Any thoughts? I'm curious, as Brescian models seem to be relatively popular.

thanks