The role of using linen in repair ?

I know the practice is widespread, but I am not sure what I think of it, because I happen to know that the force of the shrinking of drying hide glue is sufficient to literally pull the surface off of plate glass, so it seems potentially dangerous... though I have done it occasionally.

 

From what I've read here it's critical to use pieces of reasonable size to mitigate fabric shrinkage as the glue sets up.

My personal experience is limited to using small denim cleats on a stubborn crack spruce cleats couldn't stabilize, which worked like a charm.

 

I know Gerard Samija is very serious about using linen in crack repairs and reinforcing. Too bad he doesn't stop in here much any more... I'n sure he'd have lots to say on this subject... IIRC, he told me linen has been used for a couple hundred years in luthiery and is a very stable material - especially compared to vellum or parchment. He's used it in a couple repairs he's done for me and I have yet to have any problems at all with them.

 

I have seen linen used inside ribs where ribs are not flat enough for longer patches across the grain or over the top of longer cross patches. Sometimes as linings over quite large areas when the ribs are thin, old and brittle and have been punctured. Only once I saw a "pocket" over each end of a recently replaced bass bar.

 

Yes, indeed, but sandwiched. Would he also use it in a sounding top & back?
Many thanks for that link!

Linking into the balsa instruments discussed by Ham, a student luthier built a polystyrene cello a while ago.

 

Here's a picture of my Juzek's top when Arnold Schnitzer and Kieran O'Hara had it off last fall. Looks like linen up against the new bass bar.

Or maybe denim?

 

Wery interesting...I just missed the chance to waste months of my life restoring the ruin of a Prague Juzek that had the ugliest bass bar crack I've ever seen. I was considering linen rather than spruce cleats. Perhaps one day we shall know, for Science.

 

As expected, Arnold and Keirin's work looks great!

Kungfu, it is a huge step in the development of a journeyman luthier on the day that they finally learn to say, no thank you, I'll pass on that one. Just because you can do the work does not mean you should; I'd rather spend those three months on my mountain bike than on another wreck of an old bass!

Linen or similar woven materials are not the only answer, but they do represent a very effective tool that can work well in situations where things get complicated and difficult- grafting the ends of bassbars, adding extra stability and reinforcement to cracks that run along the linings or in tight corners around the blocks. It opens up a lot of additional options

The work that Jim Ham does is interesting, but I feel a completely different subject matter. I believe the original post was questioning using linen as an external reinforcing structure with repairs and restoration work. Jim uses a three layer laminate of external maple, an middle layer of loose weave silk, and then the other outside layer of maple again laid up in a vacuum system. That is a different application and an attempt to address the constant issue of solid bass ribs breaking and the challenges with materials, both structure and acquisition. There is a detailed article on his process in one of the recent back issues of American Lutherie. I've been to several of Jim's workshops and he presents a convincing argument for the ribs, so much that I have been working on my vacuum system all week and doing a series of prototypes. So far I can't comment on the tone or how I like the structure, but visually, the ziricote and carbon fiber laminates I have been making are off the charts compared to what you are used to seeing. A couple more months and I'll show them off; gotta take them to the destruction lab and see how the numbers look....


j.
www.condino.com
www.kaybassrepair.com

 

Howyou gettin' oily African hardwood to stick to CF? This I gotta see.

And transmission received and understood about journeyman experimentation. I didn't expect it would work, but I wanted to see what would happen, and that repair strategy was reversible with a steam iron.

 

I'm just lookin' out for you- I've got a dozen lifetimes worth of project offers I don't want to work on, but only room for one lifetime of those I can accept! I saw a couple this week that almost sent me into a panic attack before I got the words "no thanks" out- fight or flight moments. Multiple broken top plates, old repairs, a failing soundpost puncture AND a house fire survivor; hundreds of hours of work just to wind up with a fragile old burned up piece of junk; then I heard, "Well, you know they brought Lafario's bass back to life..."

Ziricote is pretty dry and it comes from central America. I'm still working out the details, but I've got that giant roll of carbon fiber that showed up a couple of years ago leftover from a prototype racecar body that allows me endless experimentation with no wallet pains, so much that I'll likely make a top or two out of it soon, just to use up the excess. I've been trying to see if I can get it to work vacuum bagging a destroyed scroll and pegbox- sort of a complete exoskeleton wrap like a giant sci fi space bug, but so far nothing I'd show off in public. I just started a new project with the folks at Dragnplate / Alred carbon this week that should yield some VERY cool new carbon fiber nerdiness....more later....

 

Indeed, I too feel that laminates are a completely different subject matter. But very interesting. And yes, sandwiched laminates are used in ultra light guitar tops (if I remember correctly: spruce veneers over synthetic honeycomb, glued w/ epoxy), but I am not aware of anyone doing similar in strongly arched DB tops (hence my question in #7). It might be promising though, possibly having more potential than the heavy CF.

 

Durr. I really should try sleeping...

 

Not necessarily with silk or linen, more like Nomex, as outlined for instance here. Or maybe there is something else. It might address the issue of long-term stability of the conventional tops, and offer new tonal opportunities. It might also be very difficult to get it right.

 

Double layered nomex tops are not uncommon in the modern guitar building scene. While they do have some interesting qualities, I've played probably 100 of them and never once did any excite me like a simple red spruce and mahogany 1937 Martin D18; the gold standard for acoustic guitars.

 

For guitar, Nomex sandwiched 'double' tops have been around by now for maybe 10 years, but so far I'm not aware of any application in the violin group. Taste & excitation levels are subjective, yet the biggest problem IMO is that this outstep approach does not allow tuning in a conventional way. Hence: difficult to get it right.

 

David here's one I did last week; a ply bass, I reshaped the thick bar and I put a linen pocket over each end to distribute any stresses over a wider area of plies. I did this because elsewhere on the bass, the plies were starting to separate in spots.

 

This was the subject of a lengthy discussion in Bill Merchant's shop the other day when I was there. A young Masters candidate from the Manhattan School of Music had brought in her ~1930 Czech with a bad lower bout rib split. Bill was talking about silk/cotton vs linen and tendency of linen to shrink when drying pulling the crack apart. He seemed to be indicating that silk doesn't shrink while it was drying. He had a plan to do this repair without removing the top. I'd love to stand around the shop and watch that.