Tone wood pairings top and back

[John Bertotti]

Is there a particular pair you prefer and for sonic reason? I ask because as many questions as I have asked about my quilted redwood I still haven’t used it. Now I wonder if nice maple would be appropriate or if the qualities of curly redwood would benefit with a different back and side wood choice. Any thoughts welcomed and appreciated. I have curly flame maple on hand and ready to go but if something else would be better then I’ll need to find some. I also have plain cherry black walnut and Bubinga on hand and dried to around 7%. The maple has been inside here for 21 years the cherry for five as with the black walnut and the Bubinga 1 full year give or take a few months. I am tempted to try the Bubinga it isn’t figured but has that nice color.
Thanks again.

[Bill McCall]

Curly/quilted or figured redwood can be quite brittle. I would be cautious and careful. I like all of your back/side material.

[Jim Garber]

Post pictures so we can at least comment on the aethetic pairings. I would thik it very exciting after you get other opinions, that you will venture into unknown territory and perhaps find some miraculous tones from whatever you decide. BTW what sort of instrument are you planning to make with this pair of woods?

[John Bertotti]

Thanks, guys. Apologies for bringing this up again. I just hesitate because it is the only piece I have and I have read horror stories of how difficult it is to use. But we have to move forward at some point. I also think it is large enough for a larger instrument. The A and F shapes are small on the surface. So maybe I should make something larger. Any thoughts on that are welcome. Here is the Redwood next to a piece of maple almost as large. The rest are just 4/4 planks although I do have some 8/4 cherry none of it is figured except the Maple. Bubinga, Black Walnut, and Cherry are planks as well. And the Redwoof is 9/4 thick.



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And the planks

[John Bertotti]

Looking at thart piece of maple it may preclude anything larger than an A or F becasue of some defects.

[John Bertotti]

I wonder as I have never handled an octave mandolin. Is the body physically much larger? Perhaps I should hunt down some plans. Ornjust blow up some I have for F or A style mandolin.

The picture of the maple I realized is actually the back side of the split. I just noticed the cut marks at the knot and v look at the bottom each piece is the outside of what was cut I think.

[GaryDavis]

FYI - I built an unconventional version of an F5 (violin edges, violin varnish) for my first mandolin and used figured cherry for B&S and sinker redwood for the top. Cherry neck. I'm not a musician at all but my luthier was impressed with the tone right off. I say go with your gut and try again if that is not to your expectations.

Gary

[Berto Boy]

That is some beautiful curly redwood but I would never put it in the top of an instrument. The criteria for string instrument tops has always been the stiffest wood with the smallest mass, thus spruce most of the time. For mandolins and guitars, quartered grain maximizes the stiffness/weight ratio. The curl in that grain is going to undulate between the top and inner surface of the top, compromising stiffness. I suspect you'd need to carve it thicker than standard to compensate for that.

Redwood and cedar already are softer than spruce and tend to yield a warmer, sweeter tone, albeit quieter than spruce. I think I would resaw that redwood and use it for tops in small cocktail tables. Just my 3 cents.

[John Bertotti]

I know some have used it successfully. If possible I will make it work.

[Dave Cohen]

Spruces are. not in general stiffer per unit densities than redwood or western red cedar. In fact, the better numbers usually go with redwood and western red cedar. For some data and comparisons, check out Daniel W.Haines' paper in CASJ, Vol 4,.No. 2 (Series II) (Nov., 2000), pp 20-32. Also check in American Luhterie (several issues, for papers by James Blylie. In particular his paper in AL #128 (Wiinter, 2016), pp 58-64), in which he showed how to measure the Young's (aka Elastic) moduli for your wood samples in your own garage without any special tools. Blylie only measured the longitudinal moduli, but you can modify things a bit to measure the perpendicular moduli, which your DO need to do. The overall flexural stiffness of a piece of wood goes with the square rood of the product of the longitudinal and perpendicular (i.e., cross-grain) moduli.

That said, the problem with curly (and other figures) redwood, and with all curly and quilt figure woods for that matter, in not their Young's moduli, but the fact that their moduli of rupture decrease abruptly where the grain goes oblique to the surface of your plate. That's where the "brittleness" comes in. So I would second the caution about using the curly figured redwood & etc., for top plates.

Finally, several people have pointed out the fallacy in assigning "tonal" qualities to particular species of wood, e.g., Sunburst, others. and even myself. So the answer(s) to the OP's question(s) reside in simple measurements of the densities, longitudinal moduli, and perpendicular moduli of your wood samples. You don't need to make the most wonderful measurements in the universe. Two significant figures is usually good enough, because when you do make those measurements, you will find that the variations of properties WITHIN species, let alone between species, are great.

[John Bertotti]

I cleaned up the edges getting bark and some grey soft spots out, once to solid wood it seemed tight. I had to use an exceptionally sharp blade, it is very stringy and can catch the tip! I’ll assume that is normal for redwood and curly like this. It is wide enough to get two 1” thick pieces. The carving process might be tricky because of how stringy it is. This is going to take quite awhile I think.

[CarlM]

I run Western Red Cedar 20 percent thicker than spruce. That is based on the difference in modulus to get the same stiffness. It was either Marty Jacobson or James Condino said they ran redwood even thicker though I do not remember by how much.

[Dave Cohen]

I've had redwood with densities like 0,56 g/cm3, and other pieces of redwood with densities like 0.28 g/cm3. You might be able to treat samples with such disparate properties the same, or you might have to treat them completely differently. But if you just automatically make every redwood plate 20% thicker than every spruce plate, you're gonna be in for a lot of disappointments.

If you measure the longitudinall elastic moduli of several pieces of any given species of wood and plot those moduli vs their respective densities, you'll get a roughly linear plot, albeit with a lot of scatter. But if you try to do the same thing with their perpendicular moduli,, you will see that those moduli are "all over the map". That is telling you that any two wood samples with similar densities and longitudinal moduli MAY OR MAY NOT need to be carved to the same thickness. Why? Because of something I posted earlier. Graham Caldersmith showed in 1974 or so that the overall flexural stiffness of a plate depends on the square root of the product of its longitudinal and perpendicular moduli. So if you measure both the longitudinal moduli and the perpendicular moduli for your wood samples, multiply the longitudinal modulus of each sample by the perpendicular modulus of that sample, take the square root of those products, and finally plot those products vs their respective densities, you will have a plot with a lot of scatter, but roughly linear. So determine the best fit straight line by least squares. Then, you will have the data points for some of the samples BELOW the line, a few ON the line, and some ABOVE the line. The sao=mples with data points ABOVE the line have a relatively higher than average ratio of overall flexural stiffness to density. You can even put data points from different wood species on the same plot, and you will find that the variationWITHIN a given species is bigger that the variation BETWEEN species. So the generalizations about WRC,redwood, and spruces might work for two particular samples, but be completely off for any two other samples.

So what does it mean for the luthier? Regardless of species, you will need to leave lower density samples thicker to start with, while higher density samples can be carved somewhat thinner. The samples with data points above the line, when carved to the "right" stiffness, whatever that is, will have that stiffness at a cost of lower mass, and they will generally be more responsive. Conversely, the plates with data points below the line, when carved to the same "right" stiffness, will have that stiffness at a cost of higher mass. They will generally be less responsive. That's not all there is to it, but it's a start.

[John Bertotti]

Seems to me a jig set up to measure deflection might be very useful. Caver thicker, finish the inside carve, mount in the jig and sneak up on the outside carve until the finest of movement is recorded. I’m not sure that’s the proper way to do it but in my head it would keep me from making a fatal mistake that would implode the first time I string it up. Do this before bracing is added I would guess? Honestly I don’t know. But it’s a plan I can wrap my head around.

[Dave Cohen]

Don MacRostie (sp?) already published his plate deflection method in American Lutherie. You can look it up on the GAL website, www.luth.org. It's a good and helpful method. The only problem for most of us is that he carved his plates to match their deflections to those in the plates of some highly regarded vintage instruments. So, what do most of us use as a point of reference if we don't have access to those vintage gems? Another good and widely available method is that developed by James Condino. In essence, he glues sacrificial linings to the OUTSIDE of his ribsets with CA glue, bandsaws his plates slightly oversize so that they can be screwed to the outside linings with small screws. Then he carves until he is satisfied with the result, removes the screws, removes the sacrificial exterior linings, and is free at that point to glue the plates permanently to the ribsets and conventional interior linings.

Both of those methods address what the OP is asking about. The only problem I have with them is that they depend on either a wealth of previous experience or on access to rare and/or unavailable vintage instruments. You often see luthiers (including on this site) say something like "Build a hundred instruments and (only) then you will know what to do". You may have noticed that wood is getting more expensive by the month (or faster?). Lutherie woods, especially tropical species, but also properly prepared quartersawn domestic species, are a precious and diminishing resource. So it seems anachronistic and wasteful that we have to waste a not insignificant amount of that precious resource on making less good instruments until we finally get to the point where we can intuitively go through the motions to make a quality instrument. And that is a particularly acute problem for the amateur luthier who has a satisfying day job and has no plans to make it big as a custom luthier. Seems to me that a beginner hoping to make a good instrument for him/herself should be able to access information that will enable him/her to make an instrument that'll (s)he will be proud of. And the information necessary to do so is already in print.

The only other problem I have with both the MacRostie and the Condino methods is that they don't address the differences in densities (which I addressed in post #13 above) between individual wood samples. That is only a minior quibble though. When you remove material from a plate, you are both decreasing the stiffness (lowers plate frequencies) and decreasing the mass (raises plate frequencies). Ignoring mass is only a minor problem, because the stiffness decrease is much greater compared to the mass decrease. So decreasing stiffness wins out over decreasing mass.

So do yourself a favor. Read the Blylie article in AL #128, and start measuring the densities and moduli of your wood samples. The jig described is simple and can be made from scraps of anything (plywood, mdf, osb?). Once set up, the measurements will take only minutes apiece. And don't forget to go slightly beyond Blylie and prepare cross-grain strips for measuring the perpendicular moduli. Unsure about the calculations? PM me.

[j. condino]

Thanks for the mention Dave.

I always try to point out that Dave is the first person who showed me a removable back design for a mandolin at a GAL show around maybe 2009. We may not always agree on everything, but I have tremendous respect for his work as a builder and as a scientist. I'll make a public apology to him for over reacting towards some of his ideas in the past.

His mandolin had nylon screws on the inside area of the plate so you could remove the back rapidly. I liked the idea but wanted to be able to use the final plate on a working instrument. None of my customers were willing to accept screws or holes, so I moved the screws and the linings to the outside of the rib garland. That way they can be tested and manipulated, but when all is done, the holes are removed and the plate can be used on a standard mandolin. I do not use CA glue for any of my process in building mandolins, guitars, or double basses. Everything is assembled with hot hide glue.

I also use a test rig for the mandolin plates, consisting of a rib garland and a neck. All of the plates go on that, they get manipulated, then they get removed and glued on the final rib garland. The whole purpose is because every system that I was shown prior relied upon me having a huge data base or access to a lot of instruments, generally using a numbers based approach. I've also spent some time at the Oberlin Acoustics workshops, which I highly recommend to anyone interested in a science based approach to building instruments. I LOVE math and numbers and have a decent education using them, but I never found this a successful way to make mandolins.

The main feature of my system relies on being able to manipulate the plates, tonebars, and aperture dimensions prior to final assembly while strung up to tension using my ears and half a century of being a very active gigging musician to dial in the voice that I'm looking for. Numbers are great, well done computer models are good, and attractive imaging are nice. My end goal is a kick @$$ LOUD versatile mandolin for aggressive group playing situations, where my ability to play and hear the results are the most important metrics. Your results will likely vary from mine. There are several threads that detail the method and the results here, as well as having been published in American Lutherie, & demonstrated at GAL conventions + the ASIA Symposiums to about 800 people so far.

I've seen enough failures in curly redwood over the years that I would not build a mandolin top using it, even though every single time I look at it I'm intoxicated by the beauty....

Building a mandolin is so much more than just the top & back tonewood pairings that regardless of materials every builder will likely have a different outcome regardless of their individual choices and every player will sound different on the same mandolin.

Every time I've tried to make major changes to my builds, they always seem to sound exactly like me playing the mandolin...! If you have some wood that speaks to you and a desire to try it, carve a few plates. It is just a little mandolin; quite easy and fast on the scale of things. I constantly experiment with mandolins, the time to build is relatively fast and the cost modest. I dream of being able to make the same experiments for my double basses, but the 50 hours to carve a top and the sometimes $750 per top set is prohibitive!

[Dave Cohen]

My apologies for the CA attribution. I thought I remembered you writing that you put the temporary exterior linings on with CA glue. That should remind me to give myself a swift kick in the backside for posting off the cuff from faulty distant memories.

I also agree about admonishing the OP to forego using the curly redwood for a top plate. I have a few pieces of the stuff. I did the Blylie test on a sample strip of it a year or so ago. No matter how much I decreased the load weight, the strip kept breaking at the points where the curly grain went oblique to the surface of the strip. So I made the rest of it into some simple but pretty end tables to go with my great room sofa. The only way I could see using that stuff for a top plate would be to use it as the thin exterior membrane with some lattice bracing which would provide most of the structural strength and integrity. And I'm not even sure it would hold up in that configuration.

[John Bertotti]

I have put off using this for a decade or more and it seems the general consensus is don’t use it. Perhaps I’ll use it to make a solid body bass with maple neck through. Or as head stock veneers or other projects but it seems I won’t use it for an instrument of any kind of hollow nature. Thanks! I have a nice piece of spruce awaiting use. I’ll use it instead.

[j. condino]

Good looking spruce.

Do you have a vacuum press? The curly redwood might be a good candidate for a layered guitar top with something like very stable red spruce underneath. Maybe slice off a set or two and I'll mock one up here and test that out. You could keep the bling, but also combine the aspects of multiple woods. Done well it becomes an engineered material; not so well and you get cheap plywood....

I'll be giving a big workshop on vacuum laminating at the Guild of American Luthier's nerdfest this July in Tacoma. I do a lot of it, all the way up to the big basses, especially with the ribs.

Even knowing what I do, every time I look at your redwood photo, I get distracted and start thinking- Maybe I need to hit up John and see if we can make a trade. That's the problem with bling- such a distraction from what you actually need. Curly redwood, "the Tree", et cetera. I've built with all of them, yet my personal instruments tend to be basic looking but sonically & structurally sound. Last week someone brought in a dreadnought guitar made from back & sides of "the tree" ($3500 cost!), a ton of shell inlay, and a master grade top....all made with modest skills that only produced a modest guitar yet with a very high expense....

[John Bertotti]

I do have a vacuum clamping set up but I have not tried laminating for a top or back. I’ll have to give it some thought.

[John Bertotti]

For projects, I just use Titebond to laminate pieces. But for a top what adhesive should be used? I have hide glue but that seems, in my mind, not the best choice. Am I wrong?

[peter.coombe]

I have some curly redwood, and look at it occasionally. Have been looking at it for around 20 years! The thought had crossed my mind to use it with lattice bracing and CF, but that is venturing way into the unknown so I am still looking at it occasionally.

[John Bertotti]

That big chunk I have is very very light it also was tearing out very easily just taking the bark off the edge. After that my desire to carve a top out of it diminished greatly. Having never done a laminated top I might take the plunge. CF crossed my mind and make an arched top not carved but having only built one instrument with an induced arch I find myself doing the same thing, looking at it but not progressing. I think I can convince myself to give it a shot because if it doesn’t work out I’ll can probably save it and still use it as a head stock veneer. That’s my hopeful side speaking inside my head anyway.

[sunburst]

For projects, I just use Titebond to laminate pieces. But for a top what adhesive should be used? I have hide glue but that seems, in my mind, not the best choice. Am I wrong?

Laminates are usually done with some kind of glue or adhesive with a long open time so that things can be placed, aligned and pressed without having to worry about glue setting up too fast. That usually means resorcinol glue or other (usually) two part adhesive that cures chemically rather than by evaporation. It can also be hot hide glue if the work and work area are heated to near or above 95 degrees so that working time is only limited by evaporation of the water in the glue.

[John Bertotti]

If I can use hide glue I might try. I also have titebond original 2 and waterproof on hand and some two part epoxy finish. But I have a room I heat to 100 F when Inuse the hide glue. That has always worked well for me. Thanks!