Cloth linings on cello ribs


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Let me suggest another idea.  Purchase high strength paper from an artist supply house and use this instead of glue-soaked cloth.  One example would be the Japanese mulberry paper which uses large wood fibers.  You can layer or laminate this for additional strength.  

It is also more attractive.

Mike D

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Thanks for the very interesting question, A.B., and to Guy and Melvin for the interesting photos.

Melvin, by "natural" linen do you mean what is also known as airplane linen, an unsized, unbleached, very fine but super tough linen? This is what I mean: http://talasonline.com/Airplane-Linen

Since this linen when used on airplanes was of course "doped" with varnish, this leads me to ask Guy and Melvin if they ever apply a thin coat of varnish afterwards? Presumably not, since cellos are seldom called upon to endure freezing temperatures, rain and the Red Baron.

Conor, I believe silk has a piezoelectric quality— maybe you're on to something.

Dwight, I think the Renaissance/Baroque equivalent of fiberglass was chopped hemp and glue.

The reference to Kevlar is also interesting. What about gluing linen between two pieces of very, very thin wood? Baroque carbon fiber anyone?

 

Dave

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Having used both linen and silk rib reinforcements both of them accept hide glue well.  I tear to size, fray ends slightly, then soak in glue.  After applying I tend to cover the exposed side with plastic wrap  and let dry for a full day.  The next day remove the plastic and clean up excess glue squeeze out  and let dry further.  Even the silk seems to shrink some and is quite tough.  Linen upholstery webbing comes in handy when working on bass ribs.  It comes in various widths and thicknesses.

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On 2017/03/14 at 10:10 PM, Alchemia succini said:

Thanks for the very interesting question, A.B., and to Guy and Melvin for the interesting photos.

Melvin, by "natural" linen do you mean what is also known as airplane linen, an unsized, unbleached, very fine but super tough linen? This is what I mean: http://talasonline.com/Airplane-Linen

-snip -

Hi All - about 40 years ago I was flying sailplanes. Being a good engineer I naturally gravitated towards the maintenance side of the club's equipment.

The wings of the ASK13 required recovering and the resident experts told me to buy and use unbleached calico. I asked for the specs of the material and was met with blank stares. I proceeded to do a data search and found the US Naval specs and compared them with those of the locally produced product. To my absolute dismay it appeared that we had been flying with totally underspec. material - "unbleached calico - rags; for the use of". I approached the half-dozen or so mills in the country and asked for the spec of the material that they wove. None of the available materials complied.

Every year our club packed every flying shaped object into trailers and made a pilgrimage  to a the Goldfields Gliding Club at Odendalsrus - some 800 km north. There I was soon talking with their maintenance guy about my problem. He couldn't couldn't understand why I was wasting my time - just order the material from the manufacturer. That sounded pretty obvious - until he mentioned the cost!!!

I swallowed and almost decided to just follow the lead of our club's "experts" and go the cheap and nasty route.

Fortunately OD's maintenance guy showed me a sample of the "right stuff".

I burst out laughing - I recognized the material immediately - hadn't I had my 25 year old down-filled sleeping bag remade only a couple of years before?

A quick check revealed that the cloth used to make duvets exceeded the specifications for aircraft covering material in all respects.

So for what it's worth, reinforce those cello ribs with duvet material and be happy that the cello will then have a safe limit of 4G positive, 2G negative at 140 kph and at least 200 kph when being played straight and level.

cheers edi

 

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6 hours ago, Conor Russell said:

Mind you, I wouldn't turn my  nose up at calico. It's  cheap because it's unprocessed. It's  fineŕ than canvas, but very very strong. It takes glue very well and is easily torn into strips, which can then be cut to length. Silk doesn't tare without losing its shape. 

Hi Conor - quite right - we had been flying on calico for decades with no problems.

However wise engineers take good care of their necks. If a glider crash results in a fatality, our CAA inspectors would have been looking very carefully at whose signature appeared in the maintenance logs. It's in the nature of safety regulations that many of them are signed off in blood.

The duvet material wetted out OK and being a  finer weave than calico, we used much less tautening dope.

Back to ribs - I recommend that you tease out 4 - 5 strands of warp and weft at the edges of the patch - results in a much neater looking job.

cheers edi

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Since most cloth can be torn along the grain or weave relatively easily, unless the cloth has a special ripstop weave,

I believe it is essential for strength to glue the reinforcements in

with the grain or weave of the cloth at a 45 degree angle to the wood grain.

From what I can see neither of the examples pictured above seem to have been done in this way.

I believe this was illustrated in the Sacconi book drawings of cello rib reinforcement.

I have also found that the hot water of hide glue can cause some shrinking of the cloth which

can add enough tension upon drying to warp the ribs so I always run the my linen through at least one hot

water wash cycle in the washing machine to pre shrink it.

 

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24 minutes ago, donbarzino said:

Since most cloth can be torn along the grain or weave relatively easily, unless the cloth has a special ripstop weave,

I believe it is essential for strength to glue the reinforcements in

with the grain or weave of the cloth at a 45 degree angle to the wood grain.

From what I can see neither of the examples pictured above seem to have been bone in this way.

I believe this was illustrated in the Sacconi book drawings of cello rib reinforcement.

I have also found that the hot water of hide glue can cause some shrinking of the cloth which

can add enough tension upon drying to warp the ribs so I always run the my linen through at least one hot

water wash cycle in the washing machine to pre shrink it.

 

I lined a set of cello ribs last week like that. It has the added bonus that the threads don't fall out of the weave at the edges and so are much easier to handle neatly.

I heat up an old waterstone in the glue pot and put the cloth on it to spread the glue. It keeps it warm and fluid while I put glue on the rib. 

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48 minutes ago, donbarzino said:

Since most cloth can be torn along the grain or weave relatively easily, unless the cloth has a special ripstop weave,

I believe it is essential for strength to glue the reinforcements in

with the grain or weave of the cloth at a 45 degree angle to the wood grain.

From what I can see neither of the examples pictured above seem to have been bone in this way.

I believe this was illustrated in the Sacconi book drawings of cello rib reinforcement.

I have also found that the hot water of hide glue can cause some shrinking of the cloth which

can add enough tension upon drying to warp the ribs so I always run the my linen through at least one hot

water wash cycle in the washing machine to pre shrink it.

 

The whole point to adding the cloth is to build in the tension you are trying so hard to abolish.

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11 minutes ago, Jerry Pasewicz said:

The whole point to adding the cloth is to build in the tension you are trying so hard to abolish.

I could understand wanting to induce  a little tension when reinforcing a crack on a relatively thick plate but what is

the point of inducing tension to large separate areas of undamaged thin ribs ?

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21 minutes ago, donbarzino said:

I could understand wanting to induce  a little tension when reinforcing a crack on a relatively thick plate but what is

the point of inducing tension to large separate areas of undamaged thin ribs ?

Because they are thin and undamaged.

The tension of the cloth strengthens the ribs dramatically, and sets up a positive curve toward the outside where a damaging blow is most likely to come from.  It further allows the rib to remain flexible in compression.

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7 hours ago, donbarzino said:

Since most cloth can be torn along the grain or weave relatively easily, unless the cloth has a special ripstop weave,

I believe it is essential for strength to glue the reinforcements in

with the grain or weave of the cloth at a 45 degree angle to the wood grain.

From what I can see neither of the examples pictured above seem to have been done in this way.

I believe this was illustrated in the Sacconi book drawings of cello rib reinforcement.

I have also found that the hot water of hide glue can cause some shrinking of the cloth which

can add enough tension upon drying to warp the ribs so I always run the my linen through at least one hot

water wash cycle in the washing machine to pre shrink it.

 

Hi Donbarzino - gluing in the cloth with the weave at 45 degrees to the grain gives you  a patch that is 40% stronger than when the weave is square to the grain.

This is because with the weave square to the grain only half the threads are spanning the break - so the strength will be proportional to 50.

With the weave at 45 degrees to the break both the warp and weft of the fabric is brought into play and the strength is now proportional to 2 x Cos 45 x 50 = ~70 - which is ~ 40% stronger.

cheers edi

cheers edi

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I used Japan paper on the ribs of the super light violin because the maple ribs are only 0.5 mm thick. I glued it on the entire surface and the linings on top. It's light and made the ribs pretty rigid. 

To know which reinforcement is best I made a crush test with silk, paper, and Japan paper to find the most suitable material. 

I didn't test linen because it is relatively thick from the beginning in comparison to those ultra thin ribs.

i would assume that on cello ribs linen works better than Japan paper.

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One reason i like silk is that it's thin and very smooth.

Another is because it's insect resistant. Occasionally, I come across instruments that have been attacked by beetles especially along glue joints. You'll see tracks running around under the linings, blocks and bar, and under patches in the ribs. I think that the less glue there is lying around, the better. And it seems too, that the beetles like to lay eggs in fissures and rough surfaces. Silk, because it's strong, smooth and thin, might I hope, guard against infestation.

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13 hours ago, edi malinaric said:

Hi Andreas - and your results were?

cheers edi

Edi, The test itself was by far not scientific. I glued the materials to a rib piece 0.5mm thick let it dry and then just twisted it with my fingers slowly flexing more and more. The silk reinforced  piece somehow cracked pretty easily. The Japan paper reinforced piece was somehow more flexible and needed more twist to finally break it. Normal Paper was similar to silk.

Maybe silk can be stronger when the threads run diagonally at 45 degrees.

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2 hours ago, Andreas Preuss said:

Edi, The test itself was by far not scientific. I glued the materials to a rib piece 0.5mm thick let it dry and then just twisted it with my fingers slowly flexing more and more. The silk reinforced  piece somehow cracked pretty easily. The Japan paper reinforced piece was somehow more flexible and needed more twist to finally break it. Normal Paper was similar to silk.

Maybe silk can be stronger when the threads run diagonally at 45 degrees.

Hi Andreas - thank you.

If you ran a test - that's being scientific.

We might discuss the degree of precision in the measurement but we have the results from a test. QED.

That's the trouble with tests - they lead one on and on and.... and so we learn.

Have I now tempted you to do a silk 45/45 test?  :-)

Just to be technically correct - the orientation of the silk will not change the strength of the silk at all. However the properties of the laminate will alter.

cheers edi

 

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On 5/20/2018 at 2:19 AM, edi malinaric said:

Hi Donbarzino - gluing in the cloth with the weave at 45 degrees to the grain gives you  a patch that is 40% stronger than when the weave is square to the grain.

This is because with the weave square to the grain only half the threads are spanning the break - so the strength will be proportional to 50.

With the weave at 45 degrees to the break both the warp and weft of the fabric is brought into play and the strength is now proportional to 2 x Cos 45 x 50 = ~70 - which is ~ 40% stronger.

Most fabrics are much more stretchy on the bias, than straight across the weave, and I'm not sure this is desirable when reinforcing cello ribs. Even straight across the weave, one direction will usually have less resistance to stretching than the other, and I orient the strongest direction at 90 degrees to the rib grain.

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6 hours ago, Jerry Pasewicz said:

Edi,

   I think you should take into account the shrinking of the linen into your strength calculations.  The reasoning behind the shape of the strips is at least in part for the added strength due to this shrinkage.  

Hi Jerry - in this case there were no strength calculations. I just showed that if one orientated the fabric 45/45 you had a joint that would be 40% stronger.

Shrinkage, no-shrinkage won't change that at all.

Model aeroplanes - we misted the tissue covering with water to use the shrinkage of the tissue to tauten the covering and get it smooth.

Fabric covered aircraft - the same.

In both cases we then applied a "dope" coating to tighten up the unsupported tissue/fabric panel. It's a characteristic of the dope that it shrinks as it dries and does the tautening.

Hide glue does the same.

New thought: Maybe the fabric just serves to hold a thicker layer of HG against the rib and its that thicker HG layer that supplies the major "shrinkage" effect across the rib.

cheers edi

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4 hours ago, David Burgess said:

Most fabrics are much more stretchy on the bias, than straight across the weave, and I'm not sure this is desirable when reinforcing cello ribs. Even straight across the weave, one direction will usually have less resistance to stretching than the other, and I orient the strongest direction at 90 degrees to the rib grain.

Hi David - it's not so much "more stretchy" - it's just that "on the bias" (strictly it's at 45 degrees to the warp and weft) the movement of the threads relative to each other allows the material to conform to compound curves.

Once the thread are encapsulated in a matrix you are dealing with another material.

Normal fabric is usually the same warp to weft.

However the directional property of the material can vary between warp and weft depending on...

i) the number of threads/inch in each direction.

ii) the material properties of the threads in each direction.

For instance glass, carbon or kevlar  cloths used in laminating a multi-layer panel can feature layers from 50/50 warp/weft (equal properties in both directions) to 90/10 (usually referred to as uni-directional). This allows you to tailor the end-panel  very closely to the applied loads.

cheers edi 

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2 hours ago, edi malinaric said:

 

Once the thread are encapsulated in a matrix you are dealing with another material.

 

Agreed, but in my testing, it was the hot glue component of the matrix which failed before the fabric (at least as far as I could tell, looking at it under a microscope).

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