Cello rib reinforcement with linen


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I have a fairly beaten-up old cello in my workshop at present. It has a hand-written (on the wood) inscription reading "J. W. Hodgkinson Nottingham October 1926"

It has mutliple rib cracks (the repair of which is the reason why it is in my workshop). The ribs are more or less 1.35mm in thickness. The cracks are in the upper bouts, although there are some repaired cracks on the lower bouts. The lower bouts have been reinforced with continuous strips of linen, presumably when the repairs of the old cracks were undertaken. The linen covers the entire rib area between the linings of the lower bouts, but don't overlap onto the linings, corner blocks or end block.

Considering that Stradivari (and presumably other classical makers) used "intermittent" linen strips to reinforce the ribs, I assume that there must be a reason why he (they) didn't just cover the entire rib with a continuous piece of linen.

Or to put it differently: what kind of drawback or impending disaster should one expect for a continuous strip of linen covering an entire section of rib?

And one other issue - although the top is quite stout altogether - 6mm in the area between the f-holes - it is collapsing. From the overhangs it is clear that the top wasn't replaced where it used to be originally after the previous repairs. These repairs probably were undertaken more than 50 years ago. Consequently the ribs and rib corners aren't true all round - the bouts bulge outwards in places, and the rib corners lean inwards in others. I have a suspicion that this is what is causing the top to collapse - or not?

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I can understand using linen in new construction to help prevent cracks, but after the crack is there is it really the best choice?

Oded, my reading of Jacob's post is that the linen is only in the previously repaired lower bout, not where the new cracks are.

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I use linen to reinforce certain types of rib damage and have for decades. I believe I posted photos showing this many moons back... It has properties that allow hold a crack closed without over-stiffenting, but I'd not use it to fully line a rib.

Using it in mass (full rib) would concern me for a number of reasons. One specific one: I'd be concerned that one would get some distortion (puckering or pulling) of cracks due in part to the results of such a large % of the surface being covered in the stuff... distortion similar to what one might see when using velum to reinforce top cracks.

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We do a lot of bass repair. The attached pictures are pretty typical. We used to use linen, but switched to Dacron because of its strength and stability, and have been having good results with it. When the ribs are in tatters, there's not much else we can do. We get lots of basses in, like this one, which have been repaired with cross grain wood strips, but they often come loose due to wood movement.

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Uhh...Melvin...somebody like that...please help...

Hi Jacob..I am not a restorer so.when it comes to repairs and restoration I'd rather refer the question to someone like yourself or Jeff who seemed to sum it up for me....What I have seen of original linen rib re inforcement in old Cremonese is 5x7cm blocks of linen placed between the linings at equal spacing enabling thin ribs to be bent easily and be strong once being fixed in this way with not too much problem in the life of the maker..where I have seen originals there is often a shear point at the linings requiring repair or buckling....if the linen had extended over the linings it might have been OK. I'd not want to see it over a whole rib....I'd not really think of linen for repairing distorted cracked ribs....but I do think it can be useful for small studs and often use it in that way in my new making....AS well as mimicking where I saw it on ribs with a slight modification......Oh I just saw Conor's post above...Like him, I get my textiles from Charity shops...

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We do a lot of bass repair. The attached pictures are pretty typical. We used to use linen, but switched to Dacron because of its strength and stability, and have been having good results with it. When the ribs are in tatters, there's not much else we can do. We get lots of basses in, like this one, which have been repaired with cross grain wood strips, but they often come loose due to wood movement.

What type of glue are you using for that? I've used small patches for various thin area repairs on violins, and I'm using a museum quality, reversible PVA glue. Weisshaar recommends staying away from hide glue for overlays, because of the possibility of attracting insects that would feed on the glue. The PVA remains flexible, and is reversible.

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We used to use linen, but switched to Dacron because of its strength and stability, and have been having good results with it. When the ribs are in tatters, there's not much else we can do. We get lots of basses in, like this one, which have been repaired with cross grain wood strips, but they often come loose due to wood movement.

Do you heat-shrink the Dacron slightly?

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I once used papyrus to reinforce ribs a la Strad. It worked quite well and has lasted twenty years so far without incident.

I found the papyrus at an art supply place (Pearl's).

For rib repair of simple cracks, I fist glue up the crack, thin the rib then double it (maintaining apx original thickness) with new wood orienting the grain in the same direction as the rib.

I would also consider using Tyvek, partly because it has no orientation or fibers, is light, very strong and not prone to rotting or decay.

Oded

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What type of glue are you using for that? I've used small patches for various thin area repairs on violins, and I'm using a museum quality, reversible PVA glue. Weisshaar recommends staying away from hide glue for overlays, because of the possibility of attracting insects that would feed on the glue. The PVA remains flexible, and is reversible.

We just use hide glue. Wet the cloth & wring it out, apply the glue to the rib surface, lay the cloth on the glue and squeegee the air bubbles out. Best to work in sections & keep the surface warm. It seems like we've always got an old bass or cello with shredded ribs, have done for years, and we've seen no negative effects. No doubt you get a little bowing of the ribs due to differential expansion / contraction, but if so, it's not noticeable, and hasn't created any problems yet.

Do you heat-shrink the Dacron slightly?

You can get Dacron (polyester) to conform to compound curved surfaces with heat, as do canoe and aircraft builders, but we don't, since the ribs are simple curves.

Bear in mind that these repairs are being done on "working" instruments, not highly valuable antiques. Usually it's a 100 or 150 year old German instrument where the cost of the repair makes sense in relation to the value, or replacement cost, of the instrument.

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Michael,

Where did you get the Dacron from ?

Thanks.

Dacron is just a brand name for polyester. It's used for making sails, covering aircraft wings, and canoes, and for making clothes. I don't recall where we got our supply, but knowing how things work around here, we probably just got some 100% polyester fabric of a suitable weight at a local fabric store. Can't swear to it, but seems likely.

It doesn't need to be particularly heavy. Ribs mostly get damaged mostly by being pushed in, and the tensile strength of polyester on the inside gives the repaired ribs very good resistance to further damage. Silk and Tvek seem like viable choices as well, but we haven't tried them yet, and probably won't as long as we don't have problems with our current methods. How do you say "Time is money" in Latin?

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  • 2 weeks later...

Kevlar would be super strong but hell to work with. Repair materials need to be easy to work with ... and also to remove.

On basses and cellos I use artist's grade linen canvas, unbleached, and i use strips overlapping the linings a little as i don't want to create a weak-point by stopping the linen at the linings. I pull out 4-5 threads from each edge so that the edges feather nicely into the rib instead of making a ridge. When glue is dry I sand edges lightly to kill any rough spots then paint on more thin hide glue to seal.

I've been toying with the idea of sealing the linen/glue reinforcement with shellac. But have not done this yet.

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We do a lot of bass repair. The attached pictures are pretty typical. We used to use linen, but switched to Dacron because of its strength and stability, and have been having good results with it. When the ribs are in tatters, there's not much else we can do. We get lots of basses in, like this one, which have been repaired with cross grain wood strips, but they often come loose due to wood movement.

I'm interested in the ribs too but is it common on old basses not to have the f holes cut all the way to their eyes like in your photo?

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