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1 hour ago, Nick Allen said:

Is it at all possible to impregnate the wood with some kind of binding agent?

This would be the idea. I think even normal hide glue is not bad. With an after treatment of formaldehyde it becomes absolutely water resistant. This might be actually a better idea than amber varnish.

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So next is the bending of the top plate. 

Below I made a diagram how I developed the main idea.

The Michetschlager Brescian arch interpretation drives the wedges in between the two plates in a perpendicular direction to the grain. This makes the corners lift up when not clamped firmly. (diagram 1: circled areas)

Therefore I came up with the roof fold idea. When wedges  are driven in between the two boards in diagonal direction the thing becomes a little bit easier. The  problem here is that the deepest dip at the C bouts is lifting up too much. (diagram 2: distance to point A)

From there I thought it would not make a big difference to bend the center part of the roof in a concave curve and finally round of the folding line (green dotted line to get closer to the violin arching there too.

When finished my two bending boards looked like this (photo) The pencil lines are at the same height and follow (more or less) the inside rib line. With a 7mm thick board the glue surface of top and lower block will be big enough when the underside of the bent plates is trimmed into one plane. there will be as well enough material at the c bouts to carve the cross arching at the c bouts. 

 

 

 

 

 

新しいビットマップ イメージ.jpg

Roof fold diagram, bending top.jpg

image.jpeg

image.jpeg

Edited by Andreas Preuss
Add pictures, calrify the meaning of point A in diagram 2)
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8 minutes ago, JacksonMaberry said:

You are suggesting the Cremonese bent their plates?! Brace for impact haha

I rather tear down the defense myself right away.

It can't be because the grain at  both block surface areas runs inside the arch and restorers would have seen that since long. Secondly you can't really use one piece tops with this method. Thirdly  bent plates are usually recognized at the weird grain direction along the center line.

It was just that when I finished the mould I thought,  if you try to make a completely round center line things get a bit complicated, so the flat zone just comes naturally out (like in Cremonese instruments?)

 

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8 hours ago, Torbjörn Zethelius said:

I suspect that we would see less diversity in Cremonese archings if they were bent. No?

Yes, you are right Torbjorn. This was a kind of joke.

Cremonese archings were not bent, but carved for the reasons I explained above. For a while I was thinking about a half bent procedure, but this is a kind of getting too complicated.

For me it is interesting in the super light violin  project to look into new wood working techniques.  What I find intriguing here is that one can think and develop a technique where the bent curves depend on the material used. This means that the wood tells me which shape it wants to have.

Lets say you have a soft plate and a rigid plate and bend it not with clamps but with weights, then in theory the curves a soft plate should get a higher arch than a rigid plate which is desirable. Then any calculations are not necessary, the wood tells me what shape it wants to have.

In the end we work with wood and I got a kick on everything which explores the properties of this wonderful material.

 

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9 hours ago, JacksonMaberry said:

[...] depending on the parameters of the arching, it is possible to bend a one piece top using technologies that would have been available in the late Renaissance. 

It is your turn to show how this works, Jackson!;)

Last night I was thinking about that, too.

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1 hour ago, Andreas Preuss said:

It is your turn to show how this works, Jackson!;)

Last night I was thinking about that, too.

As soon as I have a moment to put together a demonstration, I shall. Just to tease you, I'll say that it requires an apparatus similar to what you'd find in a lute makers shop, as well as a common household chemical known to the early Arab alchemists. 

At any rate, I hope I can sit down with you and chat someday. We seem to share a number of interests within violinmaking.

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43 minutes ago, JacksonMaberry said:

As soon as I have a moment to put together a demonstration, I shall. Just to tease you, I'll say that it requires an apparatus similar to what you'd find in a lute makers shop, as well as a common household chemical known to the early Arab alchemists. 

At any rate, I hope I can sit down with you and chat someday. We seem to share a number of interests within violinmaking.

Would be my pleasure.

 

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16 hours ago, Andreas Preuss said:

Yes, you are right Torbjorn. This was a kind of joke.

Cremonese archings were not bent, but carved for the reasons I explained above. For a while I was thinking about a half bent procedure, but this is a kind of getting too complicated.

For me it is interesting in the super light violin  project to look into new wood working techniques.  What I find intriguing here is that one can think and develop a technique where the bent curves depend on the material used. This means that the wood tells me which shape it wants to have.

Lets say you have a soft plate and a rigid plate and bend it not with clamps but with weights, then in theory the curves a soft plate should get a higher arch than a rigid plate which is desirable. Then any calculations are not necessary, the wood tells me what shape it wants to have.

In the end we work with wood and I got a kick on everything which explores the properties of this wonderful material.

  

I can imagine that a bent top would have less creep. You could even make a super thin two ply top. I wonder how that would work?

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5 hours ago, Torbjörn Zethelius said:

I can imagine that a bent top would have less creep. You could even make a super thin two ply top. I wonder how that would work?

two ply? Do you mean two layers glued together? Would be interesting, but with spruce it is not so easy. I was thinking about a japan paper reinfoircement too, just like the ribs.

However, if I can manage to do just the natural wood strength, I'll be happy.

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On 5/31/2018 at 10:43 AM, JacksonMaberry said:

Just to tease you, I'll say that it requires an apparatus similar to what you'd find in a lute makers shop, as well as a common household chemical known to the early Arab alchemists. 

 

My guess is ammonia and a mould (on the same principle as the bent strips for a lute back)

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29 minutes ago, JacksonMaberry said:

That's right! Though I have my suspicions that the ammonia doesn't do that much. My next try will be to do the same with just an extended warm water soak.

There is a You tube about bending wood with ammonia. For spruce it seems to work but not as dramatic as for certain hard woods: There is somewhere a demonstration of bending a maple strip into a knot!

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3 minutes ago, Andreas Preuss said:

There is a You tube about bending wood with ammonia. For spruce it seems to work but not as dramatic as for certain hard woods: There is somewhere a demonstration of bending a maple strip into a knot!

That's true! I think I've seen the same video. I first learned of it through Bruce Hoadley's books. They are using anhydrous ammonia though, which is a very different beast from what I can buy in the store. Anyway, please forgive the digression. At some point I will write to you personally and ramble about my nonsense. 

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10 hours ago, Andreas Preuss said:

two ply? Do you mean two layers glued together? Would be interesting, but with spruce it is not so easy. I was thinking about a japan paper reinfoircement too, just like the ribs.

However, if I can manage to do just the natural wood strength, I'll be happy.

Yes, I meant two layers glued together, like plywood. Imagine a belly with the year rings going transverse.

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7 minutes ago, Torbjörn Zethelius said:

Yes, I meant two layers glued together, like plywood. Imagine a belly with the year rings going transverse.

But you would need to do that over a mould which has the arch shape, or not? 

You can bend maple to any shape you want, but spruce is more difficult.

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