catnip

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  1. Doesn't look like "thin" layers of varnish... just 7 layers of varnish. If you weigh the instrument before and then after varnishing you will have a meaningful number regarding your varnishing technique... ie sanding does remove some weight.
  2. Sometimes before I close the box I measure the inside arch of the back and top especially if it is a new model for a first approximation for the cutting the sound post angle. I have made a plastic gauge that allows me to easily measure the cross arch position for the sound post. Although not necessary this just gets me closer. I record both the top arch and bottom arch then I draw a tangent line at the appropriate point then measure the angle(s).
  3. Those C counter forms look quite promising. Pliant structures that bend! If you are interested here is more:
  4. I remember years ago a luthier friend showed me one of his violins that he spray-finished with auto grey metallic enamel paint. In any case the violin had a muted sound which could have been the result of the final coating or more likely overly thick graduations.
  5. F-holes are done so now it time for the bass bar. I was able to cut 6 bass bars (3 from each side) from this generously wide billet. So the bass bar and the top are from the same billet. After chalk fitting the bar I also like to do two visual checks: one is the track left by the bassbar and the other is a visual check from both sides. After removing the temporary studs the first approximation is done with a chisel
  6. Here is a discussion initiated when I first started.
  7. Any consideration given to angle "x"? From some observations I see x = 40 degrees for the lower bouts and about 35 degrees for the upper bouts. On another note when tracing the outline overhang with a washer the corners ended looking too long. I like to reduce them about 2 mm. I draw the reduction curves by eye.
  8. Here is information about the D Lashof book in question. He was an active member here from around 2000 - 2008 but now is retired. An ebook version is available. David was very helpful when I wanted to make my collapsible molds regarding a method of using thin 4 mm aviation plywood. I found that 4 mm aviation plywood is very expensive and not readily available so I ended up routing 3 mm slot in standard 1/2" (12 mm) plywood. None the less he was very helpful. Here is how you can order directly from him. here or https://violininformation.webs.com/
  9. I have Magic Probe v4 and it came in useful especially to measure assembled violins to see if thinning the the top would be a productive tonal improvement before removing the top or to diagnose the "tubby boxy" tonal quality if the assembled violin's top plate was too thin.. The contour plot is a quick useful visual reference that can be used in discussion with other luthiers. I was looking for a Magic Probe User Group where luthiers both guitar makers and violin makers could share their setup techniques and more importantly their Master files which have the map locations, the outline and the exclusion areas such as f-holes. As with any software program there are anomalies that could be avoided in discussion with others. The software does not come with a written guide ( I wrote my own) but the web site has video tutorials as to how to use it. It is not so useful for a maker where plate measurements can be made directly with a thickness caliper. My interest in contour plots was renewed when MikeC posted his contour plot using Excel which can plot color values based on cell values and based on the cell locations. Although usable it was a bit crude which is why he pursued H Pulhar plotting software. Since I will be remotely tutoring a 2nd year Calculus student whose professor says Matlab will be part of the course I decided to "learn" Matlab by connecting it with something useful such as violin contour maps from xyz data. Matlab is extensively used in Vector Calculus and Differential Equation courses and is made available through the university site. Octave on the other hand is freely available and is a clone of Matlab. You can check out my programming diversion here Here is my Octave (Matlab) experimental program with my comments. It was written to contour plot a back but the output had some visual "island" errors. Here is the output for a top I am currently working on. Maybe this will help you get started and then you can share your program and results
  10. It depends on which eye is dominant. The C bout "eye" or the Lower bout "eye". The winner gets to finish the curve.
  11. The top came in at 59 gm with reasonable flexibility. Since this is a Cannone model it is only fitting that I use Guarneri f-holes. It was really difficult to get a clean image of the Cannone f-hole. I had to "snip" the image from a rare photo; open it in Xnview to adjust the black and while levels. Save and create a flipped image then import it into Photoshop so I can use the "ruler" to measure and adjust the image to an average 78 mm f hole length. Print out an acetate and a paper copy. I am not used to carving Guarneri f-holes ... they just look too long and angry in general and specifically the Cannone f-holes. I have made a start and I will slowly adjust or modify them a bit.
  12. Just a follow up on matlab (or octave) programming experiment. I measured the top I am currently working on with my magic probe and found that the "white region" error was in my datafile or at least how matlab (octave) handles the data. Also, I found out that the probe is not meant to work on free plates since it must be held ... so 3 hands are needed. Also the probe data is created using (0,0) as upper left corner but graphs it correctly using (0,0) as the lower left corner. Matlab (Octave) graphs the matrix data as written so if you have any horizontal asymmetry it will be flipped. This can be fixed mathematically. The problem in some books that show grad patterns is whether it is an inside grad pattern or outside grad pattern. Makers assume inside patterns but measurements on historic violins (assembled) are taken on the outside. Here is the current top with a bit of asymmetry.
  13. Another detour. I am learning to use Matlab / Octave because I will be tutoring a student in a Differential Equation course this semester in 2nd year Calculus. What better way to learn Matlab than connecting it with violin making. I want to see if Matlab can plot a graduation map of the thicknesses of a violin back from a data file. I have a data file of maybe a couple of hundred points x y z format. The x y is not only the 2D outline of the violin plate but also the locations of where the thickness measurements were taken. z is the thickness of a violin plate in mm. I have followed an example of how to read the data into a matrix and how to reshape the data for the contour plot. Also I am using a color scheme that represents what you would see if you hold the plate in front of a strong light. In programming the level of complexity can be seen by the levels of indentation used to format the program. Three levels of complexity is taught in a 1st programming course and up to 5 levels in an advanced course. Sub routines or functions are used to reduce complexity. Matlab (or Octave the free version clone of Matlab) reduces this problem to just level one because of all the powerful built-in functions (or procedures). Here is the program with my comments to get you started if you are interested in exploring this option. And if you are successful maybe you can share your code also. And here is the output. There is a small error in the output. I am not sure why there are white bands dividing the back into 3 regions. Now its back to graduating the spruce top.