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MikeC

Critique my contour map please

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I see some issues but would like other's opinions.  Here is a back I'm working on and this is the first time I've tried drawing contours on one.   Too pinched in the C bouts maybe?  Too flat in the wide parts of the bouts maybe? 

contour map back.jpg

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I wasn't careful about getting a set height for the lines.  Maybe I should do it over.  I need to make a better contour marker.  Edges are 5mm.  Since the lines are not an equal distance in height then it may be misleading.   I'll redo it tomorrow.  

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The value of these contour lines is mosly in determining symetry when you’re fine tuning your shape. They’re kind of meaningless otherwise without more information in my opinion. That’s what I use them for.

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5 hours ago, Jim Bress said:

I have a marking gauge, but don’t really care for it. Sticking a pencil in my drill press works better for me. 

I never thought of that. Good idea. 

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Peanutty is a good description I think. Seems like the value in this is not only to get symmetry but also to get an idea of where you may be going wrong or right in the arching.    

Here is a better picture.   I made a better marking gauge and marked it on one mm increments starting at 5mm and ending at 15mm

I think it's pinched in too much in the C and maybe too flat in the outer parts of the bouts.  I'll continue with this one but next one make it less peanutty!  :) 

Any suggestions on how to improve this one?  or just leave it as is? 

 

contour map back.jpg

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I found this interesting image in another thread.  Looks like it's ok to have somewhat of a waist in the C bout area but not as much as I've got

 

contour maps.jpg

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Pencil in the drill press is awesome.  That is what I do too!

My method is to rough in using templates and leave the plates about 1mm too  thick except at the very edge.  Then I Mark the bottom contour and slowly remove material to locate the contour where I want, keep it symmetric, and make it smooth.  There is usually a lot of fussing needed around the C bout and points.   The bottom contours take awhile.  

Then I do the next contour up, at about a 20mm spacing.  Now I go through the same process, thinking about where I want this contour relative to the first, with special attention to slowly shifting the contours from one level to the next  to pull out the peanut.

Avoid cutting material where your arching templates go.  You are only trying to create smooth contours between your arching templates.  I mark the arching template lines on the plate and avoid cuting there except to improve template fit.

Go slow and be neat. A divot can never be replaced and leads to a flat spot you will see every time you pick up the violin.  Oblique lighting and scrapers finish the process.

Remember that taking material from one side of the contour moves the contour in that direction.

For you, first thing I would remove small amounts of material to smooth the contours you already have - eliminating the bumps and waves.  Mostly it looks pretty smooth already. The flat spot in the lower right may not be correctable.

Take more material off the upper corners to spread the contours closer to the edge.

Likewise take some material off the shoulders and hips to bring the lower contours closer to the center and lessen the peanut. Go slow.  It is hard to adjust the peanut after the fact, and the grain can be uncooperative. 

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The 1690 Tuscan seems more normal to me than the 1780 Mailand shown in the moire pattern above.  The 1780 seems kind of triangular rather than rectangular

 

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36 minutes ago, Shunyata said:

 

Thanks for the advice.  I've been working on it some more this morning trying to adjust some to reduce the peanut effect.   I used templates traced from the Titian Strad poster.  Apparently  I need more practice!   

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Does anyone know how to produce those moire patterns?  Or does it take expensive specialized equipment?  

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17 hours ago, MikeC said:

contour map back.jpg

no wonder you all lost the war.:ph34r:

  What you could try is to make the templates using the pin and disc method.  Then cut out the templates as straight as possible, run a straight edge along the bottom of a template and measure up in milimeters the height to wherever you placed your ruler.  Place a mark on the template. 

  Measure from the center line of the template to the other side and place another mark.  Now you have two marks that are the same height and distance from the center line.  Get the outer edge height to what you think may be right first.

  Divide the maple plate in half lengthwise, scribe the line crossways that denotes the widest part of the lower bout and place your max. height of that area where the two lines meet - that mark can be a contour line start/finish spot too.

  Make at least five templates with at least five contour lines per each side of each template.  Template two and four can have two marks per height measurement denoting the contour that appears going inwards - makes it easier to draw with the two marks.

I start out by making the lengthwise half template with the predetermined heights first and then add the five template works afterwards.  Connecting the dots is all it is.

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Sorry I didn't see the back first time I looked.  It's there.  Even the back looks remarkably like the top.    What do the number mean in the sidebar?  are those millimeters height above the surface?  

 

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17 hours ago, uncle duke said:

no wonder you all lost the war.:ph34r:

  What you could try is to make the templates using the pin and disc method.  Then cut out the templates as straight as possible, run a straight edge along the bottom of a template and measure up in milimeters the height to wherever you placed your ruler.  Place a mark on the template. 

  Measure from the center line of the template to the other side and place another mark.  Now you have two marks that are the same height and distance from the center line.  Get the outer edge height to what you think may be right first.

  Divide the maple plate in half lengthwise, scribe the line crossways that denotes the widest part of the lower bout and place your max. height of that area where the two lines meet - that mark can be a contour line start/finish spot too.

  Make at least five templates with at least five contour lines per each side of each template.  Template two and four can have two marks per height measurement denoting the contour that appears going inwards - makes it easier to draw with the two marks.

I start out by making the lengthwise half template with the predetermined heights first and then add the five template works afterwards.  Connecting the dots is all it is.

If you mean the war of Northern aggression,  we let y'all win out of kindness and hospitality.   :D    

Thanks for the advice.   What do you mean by pin and disk method?   

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55 minutes ago, MikeC said:

  What do you mean by pin and disk method?   

The other topic about inflection has a method for making your own templates for help shaping the outer arching.  Make a 32mm round disc out of something thin, poke a hole thru it at 6.5mm from the center for starters.

Assuming you have no templates, you are in a hurry or want something less time consuming than making templates then the easy way for templates is to find some on the internet, resize them if needed and carefully trace them from the monitor screen. 

I suppose this could be done with just rectangular strips of paper also instead of templates.  The idea is to make both sides of the plate even looking.

 

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