Creating a G mold - advice critque


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1 hour ago, plasterercaster said:

On a more practical note, you don't seem to have any holes for clamping the c ribs,

That is because the classical method used a different way to glue the C bouts.  They used a wooden dowel with a caul wrapped or tightened with a cord using a very neat "boy scout" knot... not usually shown in violin making books.

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23 minutes ago, catnip said:

That is because the classical method used a different way to glue the C bouts.  They used a wooden dowel with a caul wrapped or tightened with a cord using a very neat "boy scout" knot... not usually shown in violin making books.

I know, there are holes for the dowels on classical molds

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4th mold I finally have something that’s more correct but not very pretty. 
Thought I’d post my first two molds for a good cringe / laugh.

“Some people show you how to do it. Some people show you how not to do it.”


Maybe on the next ones I’ll make them look pretty as well.

But for now I’ll be on to the next miss adventure. I’ve at least found three ways not to make a mold.

If you have more advice on the molds I’d be happy to hear and feel free to comment.This won’t be my last mold by a long shot.

But For now some rib stock is calling my name.

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10 hours ago, CaseyLouque said:

If you have more advice on the molds I’d be happy to hear and feel free to comment.This won’t be my last mold by a long shot.

Is this an artifact of the photo or are the lower part of block recesses not 90° with the centerline? If so this could give you problems when you have to separate the ribs from the form.

Immagine.thumb.png.f941a01b39ffc88c26c08886e546275d.png

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4 hours ago, Davide Sora said:

Is this an artifact of the photo or are the lower part of block recesses not 90° with the centerline? If so this could give you problems when you have to separate the ribs from the form.

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Seems that you are correct i Reviewed the SVG i used to make the mold as well .

Seems that the corner blocks are extended beyond 90 Degrees and to copensate i squared them off and dug it in made it no longer square to the center line.

figure 1. Shows block squared.

Figure 2 where it should be based on the second box.

Figure 3  shows my original drawing has a 95 degree angle.

 

So should i correct the mold and drawing to match the box in figure 3 and decrease the angle from 95 to 90?

Or leave it at 95degrees?

image.thumb.png.b37d098c7885d4be46c1daa4c4cb974c.png

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1 hour ago, CaseyLouque said:

Seems that you are correct i Reviewed the SVG i used to make the mold as well .

Seems that the corner blocks are extended beyond 90 Degrees and to copensate i squared them off and dug it in made it no longer square to the center line.

figure 1. Shows block squared.

Figure 2 where it should be based on the second box.

Figure 3  shows my original drawing has a 95 degree angle.

 

So should i correct the mold and drawing to match the box in figure 3 and decrease the angle from 95 to 90?

Or leave it at 95degrees?

image.thumb.png.b37d098c7885d4be46c1daa4c4cb974c.png

The notches are not meant to be square. The obtuse shapes helps when it comes time to detach the blocks.  

This also applies to both end block cutouts.  The sides of those notches are meant to be obtuse. AND, the bottoms of those notches aren't supposed to be unbroken.  Drill a few holes straddling those lines before cutting them.  This way you have a few pry points when its time to separate the blocks from the molds.

The horizontal lines etched on the classical molds connecting between corner notches are also not random or pointless.  These help guide you in restoring worn notches later on, in working the corner blocks, and they document the radii for the mold's outer corner circles.

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12 hours ago, CaseyLouque said:

Seems that you are correct i Reviewed the SVG i used to make the mold as well .

Seems that the corner blocks are extended beyond 90 Degrees and to copensate i squared them off and dug it in made it no longer square to the center line.

figure 1. Shows block squared.

Figure 2 where it should be based on the second box.

Figure 3  shows my original drawing has a 95 degree angle.

 

So should i correct the mold and drawing to match the box in figure 3 and decrease the angle from 95 to 90?

Or leave it at 95degrees?

image.thumb.png.b37d098c7885d4be46c1daa4c4cb974c.png

Drawing 3 is correct, I would adjust the block recesses on the form by bringing it back as on the drawing. To do this I would glue new pieces of wood to the form so as not to widen the block recesses too much, respecting the heights (distance between the two horizontal lines) which are important to determine the point where the curves change from convex to concave on the outline, and the curve of the block itself. (see David Beard previous post).

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Glued in some slivers of wood cut and filed them.

I pasted the bottom half of template onto mold.

traced mold on paper to draw and plan corners for mold.

They now lineup.

Wanted to draw up corners based off this mold if something looks incorrect please comment.

I plan to eventually make metal corners based off the finalized drawing.

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6 hours ago, CaseyLouque said:

Wanted to draw up corners based off this mold if something looks incorrect please comment.

I plan to eventually make metal corners based off the finalized drawing.

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Your corners seem a bit too long and skinny to me, there is also some disproportion between the size of the upper and lower corner blocks. The height of the upper block (distance between the two parallel lines on the original G form) should be 25.5 mm and the height of the lower block 24.5 mm

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9 hours ago, Davide Sora said:

Your corners seem a bit too long and skinny to me, there is also some disproportion between the size of the upper and lower corner blocks. The height of the upper block (distance between the two parallel lines on the original G form) should be 25.5 mm and the height of the lower block 24.5 mm

Shortened and made some corrections. 
Found out my kitchen table isn’t level so moved to my glass drawing desk.

They were indeed to long.

I took some measurements and included in corrected drawing.

Took picture with better device.

unfortunately I seem to have gotten corn dog grease while helping with the 4yr old. “C’est la vie”

Hopefully this looks better thanks for looking and posting.

1FFB4D09-364E-40BA-AFF1-F066522195B2.jpeg

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15 hours ago, CaseyLouque said:

Shortened and made some corrections. 
Found out my kitchen table isn’t level so moved to my glass drawing desk.

They were indeed to long.

I took some measurements and included in corrected drawing.

Took picture with better device.

unfortunately I seem to have gotten corn dog grease while helping with the 4yr old. “C’est la vie”

Hopefully this looks better thanks for looking and posting.

1FFB4D09-364E-40BA-AFF1-F066522195B2.jpeg

Better, but the top corner is still too sloping down. It seems to me that the edge overhang from the ribs you are using is also too narrow, which still makes your plate corners look skinny.

Of course, these are only aesthetic factors and we could discuss them indefinitely without coming to conclusive things because they depend on personal taste, there is no absolute good or bad. So I only speak for myself, in the drawing below I show you a sketch I made to set my corners so you can visually realize what I mean, which is better than any description in words. Also, you may not like my corners, so you are free to make yours however you like. Moreover, these are only indicative sketches that I made just to get an idea, then what will come out in the real violin is always slightly different (a bit longer or shorter, wider or narrower, more curved or flatter, and so on). In fact, even the top corner I drew is still a bit long and too protruding, and the lower one a bit too short:),drawings are only preparatory and never definitive. Something to keep in mind is that in the drawings you always have to deal with the pencil trait which is deceptive to the perception, instead of in the real work where you have to deal with sharp edges of wood without the thickness of the pencil trait. It's different.

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