nathan slobodkin

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  1. So reading the article David posted I don't understand if the preferred vibration frequencys of the bridge are transmitted to the top of the instrument making those frequencies louder or If the vibration of the bridge means that energy is used up moving the bridge in those frequencies and thus reducing their contribution to the motion of the top. Also as usual we have the paradox that while lowering the mass of the bridge should raise it's frequency that is negated or surpassed by the loss of stiffness which lowers the resonant frequency. i've been cutting bridges for years according to directions like "cut here to make the sound more open" but really have no idea of what is happening in terms of the physics.
  2. Don pretty much hit it on the head. The kerf thickness is negligible compared to any wandering or cupping of the blade which can easily happen either through inexperience or an underpowered saw. The thin kerf blades tend to not clear chips well and therefore slow down in the cut causing no end of problems. With my little Delta saw a 5/16" 6 hook blade seems to work best and I can cut cello ribs or one piece violin backs without much problem.
  3. The fiddle is trash but this is an interesting neck set. Was this a through neck which has been modified and reset? A transitional neck of some sort? Seems like the neck was set first before the top went on.
  4. Argle, I don't think the complex shape of the bridge is just for looks . The standard shape and that of cello bridges as well, allows no direct transmission of vibration between any string and the top of the instrument. All vibrations have to involve the whole bridge. David- Any references to some of the studies on bridge vibration? Didn't that Icelandic violin maker (Johannsen?) do quite a bit on this?
  5. Just curious. Are Jacob and Jerry married? They certainly sound like it.
  6. Checking my notes on the Pickering lecture (VSA 1988?) Norman referred to the bridge as a "high pass filter". I didn't understand it then and still don't so if any one can explain that I'm all ears. As regards Venturi effects of vibrations in wood. I am familiar with the increased velocity of fluids moving through a funnel but don't believe vibrations in a solid would act the same way. Again, way past my level of scientific education.
  7. Yeah. I do saw the heel free from the button and then use a short, thin chisel made from a saw blade to split the part that can't be sawed. There should be a warning label on those necks with a shouldered dovetail (terminology my own). This illustrates the need for standardized best practices of building and restoration. If you have a "better" way to do something that you don't publish it could result in big problems down the road when it needs to be repaired.
  8. Thanks Jacob. This is slightly different than what I was tought which is to saw down the side of the neck with a thin saw leaving the neck and back untouched but cutting the rib and block to the full depth of the mortise leaving only the end grain joint of the neck to break out. I then fit and glue shims on the sides of the mortise and the edge of the top so that the neck can be reset.
  9. Jacob, I assume you are sawing along the edges of the neck and separating the button before breaking the glue joint at the root of the neck?
  10. Don't have actual numbers and not sure it could be measured but in my fairly knowledgeable opinion the dove tail provides most of the strength. I used to set a minimum of a dozen necks a week for several years and would test the joint on each one by picking up the instrument by the neck (cellos included) before gluing to make sure the neck didn't move in the joint. Also there is absolutely no way that the neck can move in a well fitted joint due to wood expansion other than a small rise in pitch which can be easily allowed for. The glue is to make sure that the neck cannot slide up in reverse of assembly which would of course loosen the whole thing and to make sure that the neck cannot compress the softer block wood which would also provide some possible play in the joint allowing it to eventually loosen. If you were to make this kind of slightly angled dove tail joint in metal then even a couple of thousandths wider at the bottom of the joint would make it impossible to remove without sliding it back the way it went in. In wood if the glue holds everything in assembled position then the only way it can come loose is for the wood to actually break. Any space in the joint allows the possibility that the glue will shrink or fracture causing failure. Likewise if the joint is starved in some way so that the glue doesn't hold. Otherwise there is no way the joint can loosen other than wood failure which certainly can and does happen especially if given some kind of abrupt percussive shock.
  11. Wait a minute Jeffrey. We don't want this guy thinking the violin neck joint is the same as on a guitar. Yes it is a dove tail. No, it is not the same as most guitars because the guitar usually has a shoulder up against the ribs and a much more acute angle to the dove tail. For those who don't know what a normal modern neck joint on a violin looks like how about looking it up in any of the standard violin making texts.
  12. Absolutely no reason to make Back, ribs and scroll of the same wood except if you like the look.
  13. The reason I said guessing is that I really don't know. Perhaps Don could weigh in on this. I remember an interesting lecture Norm Pickering gave on bridge function and will check my notes when I get a chance.
  14. I am amazed that any one can get so worked up over the definition of a dove tail joint. My own understanding of the term dove tail is any joint where a tenon is wider at the bottom of the mortise than at the top which even if very slight adds considerable resistance to the tenon pulling out. The standard shouldered dove tail such as used on case work or drawer fronts is obviously going to be very strong because it would require large chunks of wood to be split off the mortised member in order to come out even if the glue should fail. The glue in that case is only to keep the joint from sliding apart in the reverse direction that it was assembled. On a violin neck the dove tail is so slight and the mortised member i.e. the block so much softer than the maple of the neck that if the glue fails the neck can compress and or break the wood of the block and come out often taking the button with it. While the button is unlikely to hold the neck by itself in the event of glue failure in the neck to block joint I am sure that it does help to strengthen the joint against normal nontraumatic forces. I have seen necks put in without the dovetail which lasted a long time due to good fitting and strong glue but which eventually failed when I think they might very well have held had the extra strength of even a slight dove tail helped resist rotation of the neck in the joint. I also just wrote in another thread about having once finished carving the neck and button of a violin and then while varnishing realized the neck had never been glued after final fitting and was in fact held only by the slight dove tail and a tight fit. It is hard for me to imagine that it would not have loosened while being carved if it had no dove tail at all.