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Posts posted by MikeC

  1. I'm not satisfied with positioning yet either.   Using the placement geometry I seem to get some asymmetry so I cut out my drawing and folded it half thinking my plate was asymmetrical but it's pretty darned close to perfect symmetry so my drawing must be off some even though I was careful in drawing it.   I think I will have to move the F's around some to make them work well.   I need to print out an F template or trace from the Titian poster.  

  2. Something interesting I noticed while playing around with the F hole positioning.   The distance of the upper eye from the center line is a golden section of the distance of the lower eye from the center line.   Maybe I'll do some pictures later to show that.   

  3. I think that violins made on the same form would be close enough in size and shape that they could use the same F hole positioning.  So Strad could make one drawing and just use dividers or compass settings from that to do both sides.   Maybe use a different drawing for each form.  

    In this image I'm sure most of us are familiar with I noticed something in the dots that are hard to see since this isn't a good quality image.  If you enlarge it and look carefully there is a mirror image of the side.   I'm not sure what the significance of that is but it's there.   I darkened the dots to make them more visible. 



    Strad F hole geometry.png

  4. 19 minutes ago, Andreas Preuss said:

    In my view this is the Stradivari system. The difference to the original Cremona system is that he works from the outside to the inside. This has the advantage that if the outline gets distorted, what was usually the case withbthe baroque construction method, the f hole on the opposite side could be adjusted to the eye as sitting in the right place. (A sort of clever cheating)

    Only working like this the distance from lower f hole lobe to the c bout border is, within working precision, the same. DG did not use this system and therefore the distance to the c bout border shows bigger difference left and right. 
    (just my interpretation from measuring f hole positions on quite a number of full size photographs)

    Accordingly you find on Strads that the bass side f hole sits in the right position on an overall geometric scheme and on the treble side it is always as much off as the distorted ribs. (Not very much though, but it made me scratching my head until I found Strads clever way of cheating) 

    Hi Andreas thanks for your comments.  I have a couple questions.   When you say the difference to the original Cremona system is that he works from the outside to the inside.   What is the alternative?  What is the 'original Cremona system'?

    You say DG did it differently do you have any idea of his method? 

    my outline is a little bit distorted that's why I had to scrap my first drawing and start over.  Marking the center line more carefully but still the center points for the F holes are off slightly one side vs the other side.  I may have to cheat a little bit Strad style.  :)  

  5. I'm no expert so take my advice with a few grains of salt.   Try going thinner,  get down to 1mm.  I seem to remember reading that DelGesu went even thinner than that in the tightest part of the curve where it glues to the corner block.  

    for a bending iron I use an iron pipe clamped in a vice and heat it with a propane torch so I have no idea what temperature it is but a drop of water on it will instantly vaporize.  When I put the rib to the iron I can feel it soften and start to bend.  If it starts feeling stiff I'll wet it again, make sure the iron is still hot enough and then bend it some more vs. trying to do the whole bend all at once.  

    I do the smoothing and scraping on one side while the rib is still flat and then do all the planing and thinning on the other side which will end up being on the inside of the finished instrument where tool marks wont be seen.  

  6. Attempting to layout the position of my F holes using the old Cremona system.   Lower hole center is where the golden section intersects the triangle which is one third the pin length.  Upper hole centers is a radius of the hypotenuse of 1/4 the triangle height and positioned in from the C bout sides radius 1/4 the triangle height.   Compass points on the C bout edges can either be from a radius of the hypotenuse to 1/4 height or from half the base length, there's not much difference either way.    Is that confusing enough?  heh.  I made a few mistakes and restarts along the way.  


    F Hole Positioning.jpg



  7. He says,  quote "and now we can see what is called the dichromatic quality of the famous Cremonese varnish".  So he seems to be implying that this is an old Cremona instrument.    If it's French or German or whatever it is,  I like the effect.  





  8. I think what you're seeing in these photos are thin film interference.  https://en.wikipedia.org/wiki/Thin-film_interference

    There is a video Kevin Lee luthier where he is doing some cleaning of what he claims to be an old Cremona violin.  At the end of the video showing the varnish at one angle it's golden in color and at another angle the thin red varnish appears.  It's a very nice effect.  

    Attacking a Strad with steel wool.. really?  heh  but seriously skip to time stamp of about 44:45 and check out the dicromatic effect on the ribs.

    Does anyone know what instrument this is?  





  9. 1 hour ago, David Burgess said:

    Oh, a "Swiss bridge".

    "Before shooting the apple off his son's head, William Tell practiced, using a violin bridge, and sometimes cheese, so as not to waste fruit."

    yeah I bought some swiss cheese recently but had to return it.  There was something wrong with it.  It was full of holes.   


  10. On 9/4/2021 at 9:36 AM, uncle duke said:

    So I believe I have the small diameter circle figured out in regards to the three rings that are drawn on some violin outline plans of yesteryear.   I realize some others have to and are asking "what about the other two"?  I'll get to them eventually.  I'm really asking myself why though.

    I have a copy of all the drawings and hoping a translation of Bagatella may have some info on the circles although I think that you have already gone through that one.   What little translation I've done so far I have the impression that he viewed the circles as the central thickness of the back plate but I'm not sure of that.   We know from maps of Strad and DelG that the actual thickness is farther up in the C bouts but what about Amati?  I haven't seen any thickness maps of Amati instruments.

     Maybe the Librum segreti will have some info on the circles.     

    45mm?  The copies of the drawings I have don't have a scale for length so I'm not sure of the diameter of the inner circle.   If the drawings are a general guide to design then the concept could be used for any size instrument which means the circles could vary in size.   It wouldn't be hard to size one of the drawings to a standard violin size and then measure the circles.  


  11. 22 minutes ago, Mike Atkins said:

    Indeed! My next violin will be my first too! ha! The things I learned from the sort-of-first disaster was really invaluable though.

    Have you seen any of Davide Sora's videos on youtube?  I highly recommend them.   I learned a lot watching those and from hanging around here on MN.   

  12. Thanks!  I guess you could technically call this my third build.  But the first was way back around 1980 and was not good, then a year or so later I put together a partially pre-carved kit so it was just ok.    Fast forward three or four decades and I consider this to be my first real violin.   :)  

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