Don Noon

Members
  • Content count

    8204
  • Joined

  • Last visited

  • Days Won

    3

3 Followers

About Don Noon

  • Rank
    Using tools without supervision
  • Birthday 03/20/1952

Profile Information

  • Gender
    Male
  • Location
    Carlsbad, CA
  • Interests
    Acoustics
    Violin construction
    Varnish
    Old-time fiddling

Recent Profile Visitors

25837 profile views
  1. Bridge Rocking Motion and Leverage

    If you're concerned about longitudinal compression waves along the grain, then yes. But the important stuff is bending waves in thin plates, both along and across the grain, which are completely different from compression waves. The speed of sound in water is over 3000 mph, but somehow surfers don't make sonic booms.
  2. Why mortise the neck?

    A few things that went by where I didn't get around to commenting... -Strength of endgrain glue joint vs. other types: as long as the endgrain is filled with glue by sizing, and not wicked dry, the glue joint should have the same strength. However, usually one is comparing the strength of the joint vs. the strength of the wood, and in the endgrain case, the wood is very strong, and the joint will fail before the wood splits off. With crossgrain or tangential glue jobs, the wood is far weaker, so the impression might be that the glue is stronger. -Structural analysis of a glue joint: probably pointless. I think that the preparation and execution of making a joint are such big factors, you'd just mislead yourself by doing this. Far better to do testing. -General observation about making a mortise: everyone seems to be just thinking of string tension and how to resist that, and the surface-glued joint with a button would seem to work fine. More worrisome would be lateral loads on the neck, which don't happen in theory but certainly do in real life. Even suspension cases don't do much to protect the neck joint if you drop it, or if you ship or baggage check it where it gets sorted by one of those automated karate chop machines.
  3. Neck Overstand

    ... or the effect of the hours (or days) between playing, and the difficulty in accurately comparing the two. Not only that, but presumably the free tailgut length shortened by 3.5mm as well, which I have found to be an even bigger change.
  4. UV LED

    With that fast of a cure, what happens if the varnish has some thinners in it? Do you have to use varnish with no thinners?
  5. kiln dried wood

    I only am giving my guess about what the upper limit of shrinkage might be; it could be a lot less. Unless there are precise records over time on the measurements, I don't know how you'd ever tell. Perhaps old form dimensions might give a clue, if you could ever be sure which exact form was used on a particular instrument.
  6. kiln dried wood

    Going by torrefied wood as being the limit of the change, I'd say no more than 0.05 mm, or slightly over 1%. Using the same criteria, the width would shrink too, by about half the rate, or about 1.5 mm for a fiddle that started out 207 mm wide.
  7. Minimum top thickness at sound post

    Two problems with this idea: 1) If more load was being put on the wood by the strings, then the the tension of the strings would have to be higher too... a significant pitch change. I have never noticed that. 2) Longitudinally, wood doesn't expand or contract much, if at all, with humidity changes. Spruce is especially stable.
  8. Importance of grain direction on maple backs

    Why would anyone want a giant pile of wonky-grain ribs? Maybe for varnish test samples.
  9. Neck Overstand

    Your dimensions assume that the base of the triangle is the top/ribs interface... but the string end at the nut doesn't necessarily like on that plane. Close, yes, but not exactly. Hmmm... actually, I made a similar mistake in my previous calculations for the arch height required to change string angle by 2 degrees. I fixed it. Keeping the overstand fixed introduces a bunch more problems, as the neck angle changes and the endpoint of the string at the nut moves all over the place.
  10. A pleasant surprise

    The best part of making violins (or whatever) is when they do their job well.
  11. Neck Overstand

    The other thing is: what does it take to get that 2 degree difference? If you start with a 16mm arch and 158 degree break angle as a starting point, and keep the bridge, overstand, and saddle the same, you'd have to have over 3.2 mm difference in arch height to get that 2 degrees... or 12.8mm arch on the low side, or over 19.2mm arch on the high side. Now THAT would be significant, I'd say. So, it looks to me like normal geometry and arching will just end up very close to the same break angle all the time. For anyone who likes to run the numbers, this is a very handy triangle calculator here to avoid having to remember the formulas and all that stuff. (above numbers are edited... determining the parts of the triangle are not so simple; I ended up using a computer graphics model of the violin geometry rather than trying to figure the appropriate lengths for the triangle sides)
  12. Neck Overstand

    50 pound string tension at 158 degree break angle figures to 19.08 pounds downforce, roughly. Changing the break angle by 1 degree would change the downforce by 4.5%, or ~.86 pounds .
  13. kiln dried wood

    The only times I have had cell walls collapse, it was in the process of removing the free water, and usually combined with elevated temperature. Loss of bound water definitely does cause shrinkage, but as yet I have never had cell collapse from that. Just my experience, not necessarily what happens to others. On the topic of end checking, the reason for coating the ends is to slow down drying (and shrinkage) at the ends, which is the cause of the checking... but with the proper schedule of kiln drying and humidity, it seems like you could do the same thing to minimize the checking. Air-drying, where it is more difficult to control the conditions, might need the end coating.
  14. Mold Material

    I glued some thin maple shims onto the MDF with really strong glue to prevent that problem.
  15. Mold Material

    That looks a lot like my first form, now a bit over 9 years old. I just got it down off the shelf, and it seems to be fine (although I only used it once). Varnished, and I never got it wet. It actually seems pretty nice... maybe I'll use MDF again some day, although I wouldn't use it for a fancy collapsible form.