Kae

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About Kae

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  1. Looks neat and smartly designed! Is the steel piece in front of the plane blade meant to do sideway cuts?
  2. D Dennis, congratulations on the success of the scheme you've developed and good luck on your on going quest. BTW, I am curious why double-string-length line is called double-string-length line?
  3. Kae

    Bending iron

    Thanks a lot, Conor!
  4. Learned something. Thank you! Actually I tried boinking my ruler yesterday. ( I didn't know how Rene Morel's demonstration was like so I used some imaginations.) It's a good exercise and worth trying. For me I felt the vibration, and the coupling. So real and I can start to think about what might happen in a violin. Very Zen as described by Violadamore. Some people learned by experience while Some other people learned by insight.
  5. Thank you! It's my pleasure that you like it.
  6. Hi Julian, I have a stupid question. Mixed with cooked oil, does the varnish request sun light (or UV box) to dry? Does it mixed well with alcohol and resin?
  7. Jerry, could you name a few demonstrable facts, or phenomena that catch your attention based on your experience in sound post placement and fitting. It would be so valuable for beginners like myself. For example, in the earlier thread, you pointed out that moving the bottom of sound post sometimes means to it couple to a stiffer or softer back ( due to the thickness variation of plate where the post sits.) It was so educating to me! At least it gave me some clue about how things might work. Things like that initiate some thoughts, and that's good enough, I think.
  8. Kae

    Bending iron

    "A little at a time", and "inching around" sounds straight forward and reasonable. What is the shape of your iron? Because I found it difficult to bend inch by inch with the bend iron I have. Do you have a special shaped iron, or there are some tricks involved? ( The one I have has a flat oval shape.) Enlighten me if you will.
  9. Aha! The first sound post I cut happened to sit in a place like that. I couldn't help but put it there for it was shaved too short due to my inexperience fitting skill. ... about the optimizing "breathing action" stuff, I suspect it could make some sense. Intuitively, I think putting sound post more off-center might allow more relative motion between the plates...
  10. Yes, and I feel blessed, too.
  11. Dear all, Thank you for your comments! As a beginner in violin making, there are still lots of things that I want to explore, and lots of things to learn. Your encouragements really mean something to me! Thanks again!
  12. 15 5/8 inches viola project (-continued) Fitting and test drive- I strung up the unvarnished viola on last Christmas eve. At that time, I didn't have a viola bow yet, and I played it with a heavy violin bow in stead. How did it sound? I would say not bad! Varnishing- On this viola I used commercial products- OldWood varnish and ground . Casein/borax solution was first applied to size the wood. It swelled the grains so I scrapped it down and applied once more. I must have scrapped too much after casein sizing and the spruce apparently absorbed too much ground liquid (OldWood A/B fluid). OldWood refractive ground as the 1st layer followed by 2 layers of clear varnish, one layer of colored varnish, and 2 layers of clear varnish. No rubbing between layers ( for I had to get everything done before my daughter's string quartet competition ). .... layer by layer, in and out the UV box .... ... and its done! The Music Competition- This viola came out of the UV box just in time for my daughter's rehearsals and the national final this March. She played this viola in the competition, and her quartet won the first prize. So my job was done!
  13. Yes. If you press deep in and close to a fret, the string is elongated by your finger. Hence the tension increases according to Hooks law. And this additional tension results in a higher pitch. And now the vibrating system between saddle and fret has a higher tension. Given the increased tension, which is now a fixed value, ( the string length and mass) we can derive its equation of motion accordingly. Unless you pluck really hard, the frequency is given by the formula we see all the time. Note that the addition tension is not resulted from the transverse vibration of the string, which we always assume small or you'll get an unstable pitch.
  14. I found something on Wikipedia about plate theory. https://en.wikipedia.org/wiki/Plate_theory I went through it with my hazy eyes and thought it might be relevant to what we care about. In this theory plate of finite thickness is discussed. Vertical deflection as well as in-plane motions are considered here. There is a screen capture of the out come equations. Just want to point out that the "external stress load" indeed takes a part in the differential equations. Unfortunately, the chance of finding a closed form solution is unlikely for such messy stuff. It seems that simulations or experiments are the only ways to go any further. We all know the stiffness of wood has a major influence on violin resonance modes. However, has anyone ever discussed the stiffness of string on its vibration frequency. I guess the answer is no..... Shouldn't that be as strange as what Don has found? <<<<< Where is k, the stiffness of string? ...... Furthermore, when we strike the violin box and we hear sound. But what happens if we pluck a lose string?.... As what I recall back from college, when we derive equation for traveling waves, the amplitude is assumed small so that the string is not elongated so that Hook's law is not considered. The only restoring force comes from the applied tension. That's why we don't see the stiffness of string in vibrating string equation. We neglect the effect of spring force, and we are happy with the results. For the case of violin resonance box, the stiffness of the wood alone produced enough restoring force. ( Not like string where the stiffness alone does nothing.) And according to Don's experiments, the effect of stress from the strings is negligible and "static forces swamped by the stiffness of wood" is a probable explanation. And I have some theory add to it: Curvature of plates plays an important role in my discussion and the external stress load need not to be small. Assume the deflection is small so that the concave part remains concave and convex part remains convex during the vibration cycle. And let's assume the stress load is pressure, eg. a squeeze from the outer edges. Applied stress result in a force which tries to make a convex part more convex, and vice versa. In the upper cycle the plate has a larger convexity then equilibrium, and in the lower cycle the plate has smaller convexity then equilibrium. However, the externally applied pressure tends to increase the convexity all the time. Therefore, half of the time the externally applied stress acts agains the restoring force and half of the time the stress acts with the restoring force. The time to complete one cycle of vibration is the sum of the time the plate stays in the upper cycle and the time in the lower cycle. The former is prolonged by the applied stress and the latter is shortened by the stress. We can expect increase and decrease to complete half cycle cancel each other to some extent. This would make the mode frequency insensitive to the externally applied stress. I am not here to prove anything, but just try to find some mechanism to explain Don's experiment results. Experimental fact is fact. You can't argue with it, but the video is really fun to watch! ...