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Marty Kasprzyk

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Everything posted by Marty Kasprzyk

  1. One method of seeing the location of high stresses in a part is to varnish the part with a brittle coating (Stresscoat and others, US patent US3801340A is an example) which would crack and craze at the high stressed areas. Sometimes those areas would be made thicker to reduce the stress while the untracked low stress areas were made thinner to reduce the part's weight. This might help to improve violin designs. Sometimes these coatings were made from zinc and or calcium roseate which are apparently quite brittle and they a mixed with small amounts of plasticizers to adjust the amount of deformation they had before they cracked. I'm guessing that the original violin varnishes used natural rosins that were too brittle in their pure state and that various oils were added in larger amounts to prevent any cracking.
  2. Am I watching a sun set or an earth rise?
  3. For shallow curves all these mathematical shapes look nearly identical as you've shown in your plots. About 30 or 40 years ago Fred Nitchy suggested that a bent stick (spline) was used to generate the classic arch shapes and I've attached his old drawing. I bent a stick and held it in shape with Gorrila tape and placed it along side your plot to show that it also generates a very similar shape. But I doubt the Old Italian makers used this very simple bent stick method to generate their arch shapes because Gorilla tape is a recent invention.
  4. Are those Aloe plants in the background? I just read that Aloe gel is a good wood treatment for preventing termite damage. Dried aloe gel may also have some viscoelastic properties that give high damping at high frequencies which might reduce the harshness of your A and E string notes.
  5. I agree. I put the inflection point line right over the sound post position for my bent saw shape back on the violin I'm making. The original idea was to get rid rinky-dink shoulder rests but there might be some acoustical advantages too.
  6. Is there enough clearance between the chin rest and the tailpiece? It looks like the tailpiece is pushed over to the right and not centered over the end pin. The tail chord is also off center. Maybe the grooves in the saddle aren't centered either.
  7. What's a "geometric center line" ? Is this the line that connects the center point of the upper bout, the center point of the middle bout, and the center point of the lower bout? What happens if this is not a straight line when the violin is bent all over the place when taking it off its inside mold. Is it the line that connects the center of the finger board at the nut, and at the bottom plug.? I didn't realize that the center joint line the two top plate halves wasn't really the straight center line of the instrument.
  8. The f hole eyes and the fingerboard look centered over the top plate's center joint. But there isn't a photo to show if the end pin hole is also centered on the plate joint.
  9. That seems like a good understanding of what a violin is supposed to do. It might be helpful to get some opinions on how long a violin is supposed to last. I've heard somebody say there are only about fifty great Strad violins in still in use so it would be nice to be able to make a violin sound that good and last that long. On the other hand maybe the other ones which died early even sounded better. I hope (as a retired mechanical engineer) that my instruments last a little longer than me so I don't have to witness their demise. So as I get older and older they can last shorter and shorter time which allows me to make them lighter and lighter which makes them louder and louder to make up for my hearing getting worse and worse.
  10. Have you considered taking a vacation?
  11. William Fulton wrote an article "Bending of Violin Top Plates: a Hypothesis" that is in the Journal of the Violin Society of America, Volume XI, No.2, 1991, which describes his method for bending half plates which are subsequently glued together for final shaping. Others have reversed the order and first glued together thin plates which are then bend into an arch shape with heating and steaming. They use (used?) polyurethane glues such as Gorilla glue for their glue joints because it could survive the heat and moisture in bending process. I had planned to do arching experiments with bent plates to see what the optimum arch height was for wood shaped this way rather than carved. The starting point was glued flat thin plates and I was going to higher and higher arches in 2mm increments. But I was satisfied with my first violins and violas made with flat plates and I never completed the experiment. I've found the only downside of using flat plates is that nobody else likes them.
  12. I think the paper towel wrapped around the bridge will affect the sound more than the bridge feet fitting.
  13. Maybe we should try to duplicate great violins a little faster. If the famous violins we like so much have saddle shape creep deformed arches like Don's CT scans show then maybe we should make an undeformed arch to start with and then quickly creep it into the deformed shape if you don't have the patience to wait 300 years. So I suggest putting your new violin with tensioned strings into your kitchen oven with a pan of water and then leave it until you get a Strad Titian, or DG Plowden shape or your favorite. Sort of like sticking a fork in it to see if it's done.
  14. Adopting pets or children doesn't make financial sense either.
  15. Do you want an instrument to sound good today or 300 years from now?
  16. I'm beginning to think (new for me) that the minimum bowing distance to the bridge is important--the closer the better for getting a highly expressive instrument.
  17. Other epoxy materials come in various setting times (1min, 5min, 1hr. etc.) and they rate their strengths on the labels. The slowest hardening ones are listed as the strongest. It's only a guess on my part but the slowest ones might also be the hardest and most wear resistant ones too.
  18. I'm now using only spruce--fine grain and quarter sawn. The clear epoxy top surface coating is about 0.4mm thick and adds about 5g to the weight. I could dye the wood black or add black coloring to the epoxy but I like the natural color and grain of the spruce wood better.
  19. The player is no Dumbo. He has a masters degree from Juliard and I suspect that he is one of those rare people at the tail end (intended pun for this discussion) of the distribution curve that have perfect pitch hearing. I'm also a rare by having totally imperfect pitch and can't tell one note from another without looking at my electronic tuner. So the after length pitch is very important to him but not to me.
  20. He claimed the silk winding at the string's end makes the 1/6 length ratio not quite right for a 1/6 pitch ratio. The exact string after length pitch must be important to him. I didn't tell him I thought he was nuts.
  21. I've experimented with fingerboards made from ebony, zebra wood,curly maple, mahogany, Sitka spruce, and paulonia in descending order of density to reduce weight. I've mentioned before that I use a thin coating of clear epoxy bar top finish to get a hard wear resistant surface without adding much weight. I doubt it will ever wear enough to need resurfacing. But if it does, the grooves could be easily filled with more epoxy and sanded smooth.
  22. Should I use two sound posts--one for each bridge?
  23. I'll try two bridges to see what happens.
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