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Ed Glass

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    Los Angeles
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    Violins, guitars, accordions

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  1. " Grain of wood becomes less visible as coats are added" and "Fewer coats allow grain of wood to remain more visible" You are conflating the number of coats of application with final film thickness Yes, agree, but the idea is just this: For any given varnish mixture, it takes more time to apply (N+1) coats than to apply (N) coats, and (N+1) coats will result in a thicker covering than (N) coats. The trick seems to be knowing when to stop, or to continue, applying more and more varnish mix, based on the wood, ground, color(s), grain, anticipated effect on which part of the sound spectrum, and overall appearance, both at that moment and as anticipated months to years later. Hard to find any two builders who do this all the same.
  2. Wish it were simpler, but: More Coats: More time and effort Hopefully achieve final color and prismatic depth of color desired Needed when wood is very white, and darker final color desired Needed when varnish is thinner, e.g. with alcohol (spirit) or turpentine (oil) Grain of wood becomes less visible as coats are added Better control of streaking and blotching with multiple thin coats Fewer coats: Simpler and faster Less muffling of sound of true wood of instrument Less added color needed for wood that is darker to begin with Less varnish needed to achieve darker color when wood is torrified Less needed if dark understain or foundation prep was applied Thicker the varnish (less thinned), the fewer coats needed Fewer coats allow grain of wood to remain more visible More difficult to avert streaking and blotching with thick varnish Those who judge will never understand, and those who understand will never judge.
  3. 1st tried just a garage sale stereo amplifier. Not enough. Then put a preamplifier ahead of that cheap amplifier and then the combo had adequate volume. But key also is the speaker, which has to be powerful enough to deliver the [considerable] output volume needed. And BTW, don't forget the ear covers. But all that said, my experience is, as Don said, that you can get more or less equally useful information from just the tap tones alone, plus some good software. There are various software options, or you can write your own, and tailor it to the tasks of making stringed instruments.
  4. Living in a place with quite variable humidities, have had the chance to see what happens after performing assemblies under conditions of both low and high humidity (and temperature). The more unwelcomed outcomes have resulted from assembling under high humid conditions, then seeing (and hearing) what happened when the humidity dropped to say, 25% or less. Ugh. Now I use the "Rule of 65" - humidity under 65%, temperature over 65 degrees F. Otherwise, leave the glue in the can, etc., and wait. An ounce of prevention...
  5. To assume that all violins, made with different woods, different archings, different thicknesses, different bass bars, etc., etc. will respond the same to some varnishing seems kindof far fetched. But here are some generalizations based on painful learning. I once bought an unfinished guitar at a shop in Paracho, Mexico for a very good price. Kept it around and played it a while, but it was getting kindof dirty from camping trips and all that. So one day when I was building a surfboard and had plenty of fiberglass and epoxy all made up, I decided to give the guitar a new finish job and some needed protection. So I sanded it down clean and epoxied it right up. Then it was all shinny, tough, and ready for the road. You could stand on it. Only one problem - it would scarcely make a sound any more. Since then I 've built a pile of violins, guitars, and violas, and I always set them up and play them in the white first, before finishing. Almost without exception, they seem to sound "better" in the white, except maybe for higher notes in 4th and 5th positions (violin). And people always comment about how beautiful they look in the raw. But they get dirty and stain up real easy without any finish. The varnish (oil, spirit, copal, amber, lacquer, shellac, or whatever) makes them look prettier (to some), but, just like the epoxy on the guitar, detracts from the quality of sound the instruments produce. Just enough for looks and some protection, just like I started out to achieve [and grossly overdid] with the epoxy and fiberglass on the guitar. That's what has worked out best.
  6. It seems a central goal of treatment is to quickly induce the changes in many of the properties of wood that the passage of years of time imparts. Among these are changes in density, speed of sound, shrinkage, tap tone frequencies, appearance, etc. These can be measured and statistically tested before/after treatment. Data that would be nice to know for Torrefied Wood as per Stew Mac, Don's method, and other methods. Also, as wood ages and "improves", it is continually exposed to oxygen, which undoubtedly affects chemical changes and processes over the years. So why is it important, at temperatures below combustion levels, that oxygen should be excluded from the treatment environment ?
  7. Yes Don, by "strength" I am referring to what would cover "stiffness" in particular. I agree. As for applications, when CF is mentioned in the context of lutherie, my knee jerk response is to think of a dark colored, stiff sounding, not particularly nice looking instrument, nearly completely, or completely composed of the stuff, with low expectations for quality of its sound output. However, I doubt that that's the level of thinking that goes into the development of processes for using CF to optimize the performance of aircraft. When building and repairing musical instruments, where, when, and to what extent, do we often want to incorporate improved stiffness, improved resistance to warp, and other properties of CF compared to wood, with less net weight ? That's how we may find the stuff to be of interest as an adjunct to fine tonewoods. CF is available in all kinds of shapes, sizes, thicknesses, braids, polymers, etc. Interesting material.
  8. Composite CF polymers (e.g. carbon fibers polymerized with epoxy) have extremely high strength to weight ratios, usually nonisotropic strength, depending on orientation of the fibers. Hence their widespread use in aerospace (e.g. Boeing's Dreamliner), high performance racecars, sporting equipment, etc. The bottom line is greater strength, at the "cost" of less total weight.
  9. Well, what is it about carbon fiber might a luthier be concerned with? Some features are: lightweight (low density), high stiffness, no or minimal realignment with time under tension, different resonance properties than wood. So rather than thinking about building plates out of the stuff, maybe we should be thinking about what parts of the instrument could benefit, in part, from some of its properties. That is what guitar builders have done, with some very impressive results.
  10. Whether one uses a constant radius all along the fingerboard or not, scoop will be needed to try to achieve constant tension all along that string as it is depressed in different positions. This is independent of the problem of criss crossing of strings as one or another is depressed. If you use the same radius all down the fingerboard, scoop is needed: 1.) for the problem of the convex bulge as discussed above, and 2.) also for the problem of variable depressed string length (and therefore tension) as you move from nut to fret x(i), i = 1, 2, ...(24 ? or more), based on string height at nut and at end of fingerboard. Calculation of the "correct scoop" is not trivial. The bulge problem can be solved (all or in part), by using conical sections to determine, and cut, a variable radius of curvature at each position on the fingerboard, instead of using a constant radius. For example, starting with 24 mm radius at nut, expanding to 42 mm at bridge end. Some choose to use variation in radius, but still some. Can be done on lathe. Al Fisher used to do it that way. Then you are still left with the problem 2.) as above, which can be solved for scoop at each "fret" position by nonlinear numerical methods, given any desired string heights at nut and end (or other position) of fingerboard. But under either condition, the "correct" scoop will vary with desired string heights at nut and at some predetermined position on the fingerboard. Or, you can just use common sense and experience, and scoop out results that are probably about as good.
  11. Interested in tips for smoothing out the bottoms and far ends of violin/viola pegboxes. Have tried using sharp chisels, but they tend to cause tear out in highly figured wood. Have tried sandpaper on end of sticks, but not enough umph for the job really. After so much work at surfacing everything else on these things, it seems sort of crass to leave those surfaces all scruffed looking, even though they are relatively obscured after all is said and done. Am looking for better techniques, jigs, or tooling. Thanks.
  12. This seems to be an area of varying opinions and approaches. Whatever technique you choose, or develop on your own, the bottom line is to get a uniform tight fit, that you can't see light through when you hold the touching edges up toward sunlight. then there's the choice of glue... etc.
  13. Well, this sounds like too much nonsense to miss out on. Here are some bass factors: Thinner - yes but look out for wolves and that rubbish tubby sound. and what if you need the instrument to play Paginini ? Flexibility - yes but how do you objectively measure or set it ? Bass Bar - yes but everyone carves them differently. Bridge setup -yes, that too And yet another, Soundpost - how it's positioned will certainly affect timbre Plate weight, density, and thicknesses... And while playing a particular note (frequency) the nature of that sound will reflect not only its amplitude but also the width (quality factor) of that spectral peak and the other associated spectral peaks that are generated. And on and on. That's why we keep building these toys.
  14. Sorry, but formatting of tables was completely trashed in final above post from how it appeared in preview window. If anyone is interested can try a different format.
  15. Players of violins and other acoustic instruments built of wood often comment that their instruments play and sound differently when the weather, and particularly the relative humidity, changes. On Sunday and Monday May 11 and 12, 2014, a blast of dry Santa Ana winds blew over Southern California, dropping the humidity into the teens in some areas. The week before that I had just completed measurements on top and back plates for several violins, including their weights and frequency responses for modes 2 and 5. The relative humidity in shop then was about 60-65%. So with the arrival of the Santa Ana conditions, I thought it would be of interest to repeat the measurements. The relative humidity in the shop measured about 25% to 30% when the measurements were repeated. Findings are in the tables below; Table I is for the tops, Table II for backs. Table I. Tops Instrument Weight gm.s at 60% RH Weight gm.s at 30% RH Hz Mode 2 60% Hz Mode 2 30% Hz Mode 5 60% Hz Mode 5 30% Type of Wood WSBCL2Ptr 80.1 79.1 176 180 341 350 Bearclaw Sitka HEB1 72.6 71.8 181 184 352 356 One piece Engelmann DG 74.8 74.3 186 183 339 343 Old Redwood One Piece SS1 79.8 79.5 185 184 334 337 Bearclaw Sitka SS2 72 71.5 183 187 341 348 One piece Engelmann ENMA2Ptr 70.9 70.4 188 190 333 334 Engelmann Average 75.03 74.43 183.17 184.67 340.00 344.67 Change -0.60 +1.50 +4.67 Table II Backs Instrument Weight gm.s at 60% RH Weight gm.s at 30% RH Hz Mode 2 60% Hz Mode 2 30% Hz Mode 5 60% Hz Mode 5 30% Type of Wood WSBCL2Ptr 101.5 100.5 151 156 362 373 Walnut HEB1 120.3 119.7 165 168 293 299 One piece Bigleaf Maple DG 140.4 140.3 176 175 332 334 Walnut SS1 111.8 110.9 174 173 353 356 One piece maple SS2 112.5 110 140 155 353 357 Bigleaf Maple One Piece ENMA2Ptr 92.5 91.3 159 160 353 359 European Bosnian Maple Average 113.17 112.12 160.83 164.50 341.00 346.33 Change -1.05 +3.67 +5.33 All twelve (unvarnished) plates demonstrated loss of weight in the lower humidity, and all twelve demonstrated an increase in Mode 5 resonance frequencies, of about 5 Hz. Four of six tops and four of six backs also demonstrated increases in mode 2 frequencies, but the changes in mode 2 were less uniform. Longer periods of exposure to low humidity would likely result in more pronounced changes, and the fact that the woods were unfinished allowed greater exchange of water and air. Varnished plates might demonstrate lesser change with weather. Even though the changes were not dramatic, they support assertions that instruments change with the weather. Duh !
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