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Shunyata

How does this arching look?

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I know everyone has a different way for handling arching.  I use four templates to set the lomg arch and the arch at the shoulder waist and hips.  Then i slowly work the contours.  

I would appreciate any comment on the contours below.

PhotoPictureResizer_200704_115518885_copy_734x1305.jpg

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I usually find after a first pass that I've left the sections between templates too bulgy.  It's hard to choose how to fill in the missing information sometimes when you consider the number of possible routes. 
What you've got there looks pretty good to me.  Out of curiosity, why do you use just three cross-arch templates rather than the standard five?

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It seems to me that the higher level curves are too angled when they cross the central fifth between the C. I would prefer a more straight course, a bit more as seen in this image (not my arching, just a picture found on the web to give an idea, I don't know what the numbers mean) :

1341452808_Curvelivelloback.thumb.jpg.3d3a9d039477f4ab03478dc3bdace787.jpg

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I learned with three templates from the Bruce Ossman book - it seems to work for me, although it leaves a lot of room for misinterpretation, hence my posted question.

I had specifically wondered about straightening the contours as Davide suggests.  Structurally, straighter courses will be less rigid than the contours I am using.  I wonder what the tonal consequences are?  Mr. Noon?

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The central arching should be mostly convex, almost semicircular,  down to the edge of the scoop or concave portion of the arching. And, going by the contour lines in your pic, the cross arch lines at the upper and lower bouts would normally coincide with the widest part of the arching.

 

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12 hours ago, Shunyata said:

I had specifically wondered about straightening the contours as Davide suggests.  Structurally, straighter courses will be less rigid than the contours I am using.  I wonder what the tonal consequences are?  Mr. Noon?

I would say that straighter would be less stiff transversally, but stiffer longitudinally. But as Don Noon would say, the situation is more complex, it is difficult to separate things analytically,  and this is probably an oversimplification.

Tonal consequences? It depends on how these stiffnesses combine with everything else, even more complex...

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20 hours ago, Shunyata said:

I know everyone has a different way for handling arching.  I use four templates to set the lomg arch and the arch at the shoulder waist and hips.  Then i slowly work the contours.  

I would appreciate any comment on the contours below.

PhotoPictureResizer_200704_115518885_copy_734x1305.jpg

They look nice but I think you should erase these lines before you varnish it.

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19 hours ago, Davide Sora said:

It seems to me that the higher level curves are too angled when they cross the central fifth between the C. I would prefer a more straight course, a bit more as seen in this image (not my arching, just a picture found on the web to give an idea, I don't know what the numbers mean) :

1341452808_Curvelivelloback.thumb.jpg.3d3a9d039477f4ab03478dc3bdace787.jpg

My archings are becoming more barrel shaped as I progress, which tracks with the straighter lines in the C bouts. I think often people do a more peanut-shaped arch for their first few fiddles, like myself. 

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1 hour ago, Nick Allen said:

My archings are becoming more barrel shaped as I progress, which tracks with the straighter lines in the C bouts. I think often people do a more peanut-shaped arch for their first few fiddles, like myself. 

I agree that most first attempts give a more peanut-shaped arching.

I can't comment further on this, since I have always used oblique lighting to assess arching shapes, and have almost no experience using altitude lines for that purpose, aside from "correction" of plaster molds.

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The surface shape of the arching at the Cs, above the inflection point, is strongly anticlastic. That is it bends away on one axis and forward on the other. That is a difficult aspect of arching for any aspiring luthier to handle, or even for any experienced maker who is aware of it.

 

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As a quick followup...  I paid attention and found that as I blended the purfling scoop into the rest of the plate (using oblique lighting to gauge smoothness or the curvature) I was naturally removing wood from the shoulders and hips to create the barrel profile others mentioned.  I haven't drawn new contours in, but I bet they would look very much like Davide's graphic.

Oh, and gratitude to Davide for his plate shaping videos!  I don't use the exact same method, but his instruction has helped me "grok in fullness".  (Ant Robert Heinlein readers out there?)

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Any arching shape doesn’t mean a lot until the channel reaches it’s close to final depth. A nice looking arch with a 4+mm channel might end up being a too full looking arch or a bumpy arching curve if you don’t blend it carefully enough.

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Thanks for the heads up on the dangers of peanutting. It seems like this is something you can check roughly with a ruler while you are doing the arching. I assume this also applies to the front?

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Peanuts aren't necessarily a bad thing though. It just depends on the model.  
Brescian instruments and late DGesu's look pretty peanutty..

LateDGArching.thumb.jpg.d4cfb770f4b17095713183c2440c9273.jpg

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38 minutes ago, J.DiLisio said:

Peanuts aren't necessarily a bad thing though. It just depends on the model.  
Brescian instruments and late DGesu's look pretty peanutty..

LateDGArching.thumb.jpg.d4cfb770f4b17095713183c2440c9273.jpg

This violin (canary bird?) has indeed a rather full looking arching. But it isn’t quite as full as on this photograph and not all del gesus are shaped like that. 

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