francoisdenis

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Everything posted by francoisdenis

  1. That's also my idea and it is also a pragmatic way that we all still use. - First you define the main dimensions - Second you draw the outline If you bound this two steps in one - the process can apparently, be more efficient but...it fails to describe accuratly the reality and it becomes too stiff The way you define the main dimensions and draw the outline is another different seperate question. About the first step: measurements People use the words "proportion" and "ratio" in an inapropriate way. Actually they speak of two different types of measurements which both are based on ratios 3/4 means "I have 3 parts of a quantity that I had divided in 4" and 10 cm means "I have a 10 parts of a quantity of 1 meter that I had divided in 100" Both of these systems of measure that I call "relative or metrologique" have avantages and disavantages and people are not aware of that. The relative system progressively disappeared after the Renaissance for political and mathematical reasons, and we find now only historitical traces of it. At the end the question is: " which one of this two types of measurements have been use by the carftmen at the time of Amati? " The answer can't be a question of belief, it is a question of historical documentation and these one is clear enought (and encourage Marty and others to read it ) The use of relative measurement is a very serious working hypothesis. About the second step: drawing outline They are many way to draw outline and it is a rather boring topic as soon as you understand that its definitely stop to be a crucial point if you considere a two steps process. Anyway, .if you defend a system you must, at least, be able to understand how it works. Kevin, David and I have all noticed that a correlation existed between radii of the arcs drawing the outline and some main mesasurement (the Vesica is the most famous example of that). For Marty his ellipse proposition is also proportionaly connected to the main dimensions of the form he want to draw. Every system having is own logic. With some effort, you can check if a form follow a system or another. What seems complicated to me with the Marty's proposition is that the dimensions don't seem to be fixed first . I have only experimented it once but the dimensions were done before the outline. Few nails in a board and that its! Very efficient it is true , and I made some arching template that way too. But Martys system works differently I understand a kind of variation the "guardener ellipse".... May be Marty could tell me if the proportionnal schem ( I mean the correlation between the position of your thumb and the ratios) observed match the attached drawing I have attached.
  2. thank you for the info you deserve some water to your mill
  3. Only a way to trace line nothing more...and further more not the easiest to manage if you want to pay attention to the dimensions Really do not understand what you want to demonstrate.? do you want to explain that ratios than we all observe are made by chance ? The measurements come from the process is it your idea?
  4. Dear Kevin, I go back to your Strad guitar shape solution I did the drawing following your measurement The drawing on the right side is how the guitar is asymmetrical and on the left in red is how your proposition really match In regard with the asymmetry we can consider that the measurements of the radii tangency to the UB and LB are 1/3 of the width at this place And ratio UB/LB= 4/5 and MB/UB = 4/5 could be OK . But it remains some other pbs and I would like to know how you solve them -How do you find the position of the maximum width of the upper part ? -How do you find the position of the minimum width of the middle part ? - There is two straight lines to connect the upper and the lower bout they are missing at your solution
  5. I notice that you avoid to answer to my simple question.... at least you agree now that guitars with corners have existed (even in Japan of the sixteenth century!) and that it is smarter to manage certain variations of measures with corners rather than without.
  6. yes, the plugged and bowed vihuela, which later originate the viol and guitar families the point is to understand that the instrument can be played both way , the raison why the viols keep their frets here is the type of form we get if we have to keep a guitar shape with these dimensions do you like it Marty? I like the first japonese guitare 1590
  7. The guitar shape has been used long before the guitar existed so...may be it's enought to distinguish the "guitar shape" from the guitar itself. Further more, the "guitar shape" is itself a symmetry of the "luth shape" Corners allow to play more freely with the surfaces and dimensions that's enough to suggest their use when it become fashionable to play the luth with a bow (just adding a secondary hight bridge) from the very beginning, bow, higth mobil secondary bridge (and later soudpost) are 3 accessories that change a pluged instrument into a bowed instrument. Great period of intensive research for the instrument making
  8. II remember that you said in previous post that you were using a set of ratios anyway....could you explain which difference do you made between measurement and proportion?
  9. OK, It seems that the author of this thesis quotes a paper of ROMANILLOS, José Luis: "The vihuela makers of Toledo, 1617", in American violin making. The quarterly journal of the guild of american luthiers, n. 32, 1992. who himself quotes another research published by françois Reynauld "The Toledans luthiers in the sixteenth century" in: Toledo and urban expansion in Spain AA. VV. Collection of Casa de Velázquez nº 32,1991. In my memory, the original text (in french) of Francois Reynauld says that the candidate must know how to draw shapes without the help of paper template only with the straight edge and the divider. It is not quite the same thing but it remains an interesting detail. What is clear is that in Toledo at the beginning of the seventeenth century, instruments makers had to master the art of drawing. Too bad people who claim the opposite ignore this remarkable document ... PS / With all due respect, I suggest you stop republishing with insistence the same drawing - I think the community has understood your position and the content and interest of your proposition.
  10. Can you document that ? What is your reference?
  11. Dear Joaquim When we use a 1/2 ratio, familiar mathematics condense several concepts into one expression. 2 is here a reference quantity (denominator) which is used to calculate the unit fraction. It means that this quantity contains the 2 parts and that we will use this part as a measure of another quantity which in the ratio 1/2 is the number 1 of the "numerator " ( the one which count). In summary, in what we call an A / B ratio, we measure a quantity B with respect to another taken as a reference (which is B ) meaning that B being divided into "n" parts A equal x of these parts (of B). This ratio is therefore a "relative measure" and not a "proportion" stricto sensu. For the Ancient, proportion means that an identical relationship exists between three terms (like A / B = B / C for the geometric proportion) For a proportion exists between 2 terms it is necessary that the third term equals the sum of the first two. In the example that you give of the relation of 3 and 4 we have the third term equal to 3 + 4 = 7 In this this specific case, the relationship between 3; 4; 7 is not strictly speaking a proportion but rather an "analogy" one could say an "almost proportion" of the harmonic type. (We are using the expression "section" to express that we consider we have 3 terms like A+B=C) The sequence of numbers having between them this most known analogical relation is that of the geometrical type which one calls "fibonacci serie" 1-1-2-3-5-8-13 one calculates that in fact 2/3 = 0.666; 3/5 = 0.6; 5/8 = 0.625 etc. are values that are more and more analogous. To go back to your question, the old ratios were more explicit and said what to watch and therefore understand. So the ratio of 1 to 2 is the ratio of twice; the ratio of 3 to 2 is "sesquialtere " literally "which exceeds by half" etc. Thus exercised eye knew where it have to look at to understand the measure exactly as the exercised ear of a musician hears the intervals of music.
  12. Dear David Marty and Kevin Whether it is David, Kevin or myself, we agree on a geometry based on the circle. Kevin supports the idea that the dimensions of the form are dependent on the integer measures of the circles. For me, the conditions of Kevin's solution are a great simplification but also a constraint that leads to approximations that do not stand up to the fine analysis.But it is also true that it testifies reality that I will evoke supra. David and I consider that the geometry of the circles (outline) is managed by relative measures (ratio). This is a very likely proposition because historically very well documented but also because it allows the flexibility of the dimensions. David retains only the rational relations but for my part the irrational values are also part of the story (the measurements of the only technical drawing of an instrument are based on the approximations of the measure of the diagonal of the square, a proof that it should not be forgotten!) Marty limits himself to the use of integer ratios and considers that the form is a free construction. Free hand drawing has always existed but it is a difficult technique. Painters who have been able to represent violins without error are very rare. The grids were very consistently used to imitate a reality and not create it. That's, I think, the idea of David's previous post. There may be one point that could make us agree is the fact that the guitar shape precedes the violin form. But, the question "why corners" comes up. I propose 4 answers - they allow to use shorter woods - they give more freedom in the choice of dimensions in the short and ample format because they make it possible to overcome the problems of tangency. - they reinforce the rigidity of the structure - they correspond to the flamboyant style still in vogue at the time of his invention The validity of answers 2 and 4 and crucial for our discussion
  13. Take care ! french like cooking snails
  14. And actually , it is not OK, again, if I study this new example from this other guitare the outline is in red (let me know if you disagree with the accuracy of the outline) The better match for two identical circles is this and that is the VP is this and even if we take account the asymmetry of the outline as you do ; It doesn't match I think that it is a question of method: What I do -First whatever is the quality of the doc I take the outline as accurately I can -second I study the asymmetry -Third I take the mesurements of the framework -fourth I try to find the best fit for the radii -fifth I take the measurement of the radii Doing that way I rarely come across a real VP It is what I noticed a long time ago (but I don't say that the VP as not been used)
  15. OK Kevin... .... except that it is not the same guitare! (time to change your glasses Could we return to the first one to continue to study your proposition please?
  16. that the way a VP fit to the outline That is what I measure It is what I see- In this case the VP is only an approximation why not...It can be discuss but it is what accuracy means the real radius is smaller for the ratio W/L = 0,609 ...something between 3/5 or 8/18 close to.. Same remark for the upper part; the VP looks to me like a rather rough approximation
  17. Ok , so we agree VP is only when: -the measurement of the radius a third of the width -the circumference pass through the center of the other circle
  18. Hmm, I feel that the spirals are coming soon ....
  19. Yes, a straight line is a good alternative (if it is not too long ) I was just trying to pick up some of the Marty's ideas
  20. Don't be surprise Kevin , I pay attention to what you say (and as you don't share your metrological measurements- I can do the job) As I said, in my previous post, simple relationship (often matching musical ratios of a scale) were frequently used Two questions on the Strad 's guitar which ratio do you used for the radii of the lower bout ? what would be the ratio W/L for you? About your proposition for the MS 368 where do you see a VP?
  21. Dûrer recommand to use the most convenient way... In this case I will define the main measurements (format 8 x 13, etc....) then, used one or may be 2 or 3 circles (not more) and a rasp or a strip of side to connect every think. And also, I would try to improve my knowledge of this form . Did copy somebody else? Can I find this shape elsewhere etc.. Most of the time is more constructive to search the similitude than emphasis the differences more constructive ..and unfortunately less obvious - differences are what we all trend to see in first to reinforce our specifity and identity
  22. Hi John You are completely right, i was travelling away and I did a mistake confusing 202 mm and 200,2 mm Anyway it is a proof that agreement to the measurement is prior to any discussion. because we are all making mistakes which lead to wrong conclusion- Possibility of a double check is a necessity When I wrote the traité de lutherie, I surrounded myself with four luthiers chosen for their hight competences and their complementarity. They had in charge to ask me all the most embarrassing questions they can about the solidity of the method. This publication is due to the critical participation supervision of a team. I confess to having a lot of trouble when very affirmative conclusions are delivered without data communication. To assert, like David do, that no irrational relationship appears, requires to have access to the measures to serve as the basis for this judgment. But this is not the case - no control possible but in conclusion, many certainties about the nature of the "tradition" and "classissime of Cremonese making". Other details puzzle me. To speak of Vesica pisci 4-5-4 is an abuse of language - it does not exist of other VP than 1-1-1 and furthermore, looking closely (on the Strad forms) radii measuring the third of width and making a real VP is very rare- the middle part of the « VP » is often a little bigger or smaller. The radius going up from the maximum width to the lower block of the corner is rarely equal to half of the width etc.. Of course, all is a matter of accuracies…Is the evidence of that based on a work carried out 25 year ago are still up-date ? Tech means evolved so much that it should be possible to deeper on that. --------------------------------------- Drawing a series of tangent arcs having simple relationships like 1- 1/2 - 1/3 etc .... is one of the first things we think about and test starting to be involved in drawing violins. These types of series have been used extensively in the past because they are pleasing to the eye and… it works also for the violin shape! There is definitely something to dig there...:) More than 50 years ago Euro Peluzzi published a proposal based on this kind of principle which shone by its simplicity. Unfortunately, the problems begin when it comes to compare this simple Peluzzi principle to fine observations. Peruzzi do not use a real VP but he keep the idea of tangency between the "C" radii and the bottom and top ones. Once again the fine observation reveals that the latter is the exception much more than the norm. Unfortunately to be convinced of it one must look closely without trying to force reality into one's wish. Thus the proposition of tangent circles, as K. Kelly do for the Titian, reveals limits of accuracy that can not be considered satisfactory (at least for me). image 2 image 3 Once again the millimeter measurements data (or the content of the Amati digital code) capable of convincingly tracing the Strad forms are not given. Still, we speak here only of a limited number of forms of violins! What becomes of this simplicity in the face of the diversity of viola, cello viola da gamba etc ....? The answer is simple - each new example will introduce an extra exception and "everything gets complicated". Explanation is may be here more complicated to grasp. It's a question of pure logic; more parameters are dependent on each other more a process can be simplified but the more it becomes rigid. When we look at the outline of Kevin's proposal for the Titian we can see that the shape is not fluid without corners (image 3). Corners are needed because they are a solution to the complicated and inelegant co-management of tangencies and surfaces problems. Thus, the corner is a decorative element that makes tangential disconnection very useful for giving flexibility to the shape in connexion with the surface. We all know that bowed and plugged instruments start to be made carved in one piece of wood, outlines being done from a template. We observe that this types of instruments evolve from a guitar shape to a one corner shape then, a two corners shape. These evolution can easily be explained by the use of a unique template of guitar shape where corners come naturally to manage smartly the problems of tangency when the format is changing. As David emphatically reminds and I agree, the use of ratios is the only way to give flexibility to a geometric process. there would also be some answers to give about Marty's theory. Evidence to say with certainty that this method was not that of Strad exist and worth it to be studied but this post is already too long may be another time
  23. The accuracy needs parallèle line easy to draw with a square any makers could do that without effort i have a long experience of that
  24. Sorry but the process need to be clarify to me in the ratio 4 to 7 4 is the real width and 7 the implied length of a design which lead to the real length which is 5 mm shorter that the implied one?