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Well, just to chime in with what the experts say...

Plucked strings give you a limited amount of horsepower to work with. Small engine=light car. If you want response, both volume and treble, you want to make the top as light as you can while still being stiff enough to withstand the torque of the bridge.

Stiffness in a top or a brace goes as the cube of the thickness, and directly as the Youngs modulus of the material. Twice as thick for a given Young's modulus yeilds a top that is eight times as stiff.

Suppose you take a piece of spruce that weighs 20#/cu. ft., and a piece of maple that weighs 40#/cu.ft. Suppose also that the Young's modulus is proportional to the density: the maple is twice as 'stiff' as the spruce (this will tend to be broadly true, I believe). If you normally use a spruce top that is .120" thick, then you'll have to thin the maple down to .060" to have the same weight. But the maple will only be 1/4 as stiff as the spruce at that thickness: (1/2)/\3 = 1/8 times twice the Young's modulus.

If you think about it, the ratio of Young's modulus in two materials would have to go as the _cube_ of the density ratio in order for them to yeild the same top weight. Note that this assumes the same structure: if you use the rosewood as a skin on a honeycomb construction you could probably make a very light top of rosewood. But that's cheating with a whole 'nother technology.

Bottom line is that those Olde Boys knew what they were up to.   

Okay Alan can you give your best recommendations for dalbergia latifolia thickness on a top, based on what you know? I'd appreciate your input on general thickness for the top and bracing.

Like JFrench, I have been biting my virtual tongue because I've want to suggest that this is very likely a bad idea but I don't want to squash creativity in any way...



But as Al suggested, Indian rosewood (although lower density than some other Dalbergias) is just too darned heavy for a top. Spruce works well as a top because it is very strong for its weight.

Now this unit will certainly work to a degree, but I'm willing to bet a nice light, stiff spruce top that it sounds lousy as an acoustic instrument. It will just take too much energy to drive that top at any reasonable thickness...

But if it is intended as an "electric-acoustic" then make the body 2" thick and install a nice pick-up and let her rip!

I hate writing this!

Nah, hey guys, lighten up, if it doesn't work out acoustically, then Walter is only out a couple of grand. And just think of all, not only he and I learn, but everyone else, too.

Thanks, Bruce

Less than that, if it doesn't work (I doubt it will) then all you have to do is fit a new spruce top, all that you have lost is a little time and a EIR top. If we don't experiment we stagnate.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Now you got Walter shaking in his flight jacket . Where it may work the best might be on an accoustic bass. but never the less if you are going to go though with this Bruce, Than give it you all and I am sure it will sing.MichaelP38407.4454398148

Ah, perseverance despite good sense and reason. Good on ya!

Well.... still, I don't think there is anything to be learned from this, except that Indian Rosewood is too dense and heavy to use as a soundboard.

Or perhaps it will be good practice for replacing a top, which as Colin stated is probably the worst case scenario.

Also, back to the original post - I have not seens or heard of a maple top being used successfully, used yes - but not successfully.

I don't want to rain on the parade or anything, but while experimenting with materials is good (I'm considering replicating the Torres Cardboard back/sides guitar experiment actually), there is little or no possibility of this being anything more than wasted materials and time - and I can't believe more people aren't speaking up to say as much, especially since the point of this forum is to help each other out.

I am going to go out on a limb and say I interpret Alan's post to reinforce my opinion of this.

At any rate, feel free to prove me wrong, and I look forward to seeing the result (it will be a pretty guitar surely), and wish you the bets of luck with it.

Best wishes,
Joshua French

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Instagram: @jfrenchluthier
Web: https://www.jfrenchguitars.com/

Okay Walter, I give up. These guys are right.

Well.........perhaps they are. But the thought was interesting to discuss. Thanks guys for all your info and input.
WalterK   

What!!!!

You can't give up now, send that dang wood to me Dickey and I'LL do it just to see what happens

Man what a letdown, I wanted to see what would happen, it would at least be a wonderful show piece....

-Paul-

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-Paul-

Patriot Guitars

I'm not going to venture a guess as to a 'best' thickness for a rosewood top: as far as I'm concerned there is no 'best'.

Luthiers have been doing experiments for a long time, and the more I poke around in this field the more I think they've _all_ been tried, most of them once or twice in a generation. Luthiers are also really good at stealing each others good ideas: look at how fast the Torres pattern took over the Classical guitar world. From this I'd guess that anything that isn't really new technology (like carbon fiber or Nomex) has probably been tried already and found wanting: if it was any good we'd be doing it already. This is why I'm always a little suspicious of radical 'new' ideas that are going to revolutionize lutherie: they're tatamount to saying that all the guys that came before us were idiots, and I don't think they were.

In this case physics backs up experience: there are logical reasons to suspect that a rosewood top would not be very loud. That's not to say it wouldn't have a good tone, but when was the last time anybody asked you for a quieter acoustic guitar?

If you want to make a rosewood topped guitar that's cool. Let us all know how it turned out. I think that's one of the advantages we have: the failed experiments of the past tended to get buried (out of embarassment, most likely), so we don't know about them until we dig them out of some attic someplace. With modern information sharing we can at least find out for sure what doesn't work. And if it _does_ work then you get to watch all of the theorists scrambling to figure out why and wipe the egg off their faces! :)

Alan,

You bring up many excellent points. To expand slightly - In the guitar making world, we have a couple hundred years of trial and error, which is a wonderful type of grass roots science, that have led us to the current designs. The psyche of the average guitar maker nowadays though, tends toward so much freedom and blinding enthusiasm that all that is really happening is reinvention of the wheel. In most cases, anyhow.

Liam Romanillos told me that while his father was gathering the monumental amount of information he did for his book "The Vihuela de Mano and the Spanish Guitar" (which is a reference work) that he saw nearly everything being tried nowadays tried in the 1800s, including double tops of some sort.

In terms of strictly "traditional" classical guitars, the Torres guitars I've been able to see, hear and handle have been absolutely unbelievable instruments, and his work is not trumped by any maker to date (not even Hauser). But from what I can tell, and what I've read and been told by people who have more experience with original Torres instruments - is that aside from his basic system, there is nothing remarkable about the instruments design wise. There is no secret in there, no trait that if found out would allow another maker to make an instrument of equal quality... there is nothing but the intuitive and common sense of the maker utilizing a design to its fullest potential. The man made a wonderful sounding instrument out of carboard of all things - talk about having the cards (materials) stacked against you.

There is just something that defies design or materials, and that is why we all make such different instruments. It would seem that in making guitars, 2+2 never equals 4.

If any of us could achieve the kind of common sense in constructing musical instruments that Torres had, we'd have nearly the same impact as he.

Best wishes,
Joshuajfrench38407.7674768519

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I once worked with an engineer who worked in a shipyard in WW II where they built destroyers. These were pretty standardised little ships, designed to go fast. One of them turned out to be much faster than anything they had made before, and the Navy wanted them all like that. The yard measured everything they could, and went through all the build records to see if they could figure it out, with no luck. Finally they took the thing apart and measured all the parts of the engines and boilers: still nothing out of the ordinary. When they got it together it went exactly the same speed as all of their other boats.

Something like that is a fluke: there's a reason for it, but you can't pinpoint it because it only happened once. With Torres it's not a fluke: he made great guitars again and again. It wasn't the wood, because that varied all over the lot, and it wasn't some 'magic' in the design because we've got all the data on his designs. It was in the way he knew how to change the design to match the wood.

Since it wasn't a fluke we should be able to measure just what it was that he did. The trick is, of course, to figure out what to measure, and how. That's not always so easy. For one thing we can't exactly cut those guitars up to measure stuff. For another, it often happens that the important thing is not some absolute number, but a relationship, and it might take a while to figure out what needs to relate to what else in what way.

For example, the thing that seems to matter with tops and sound production is the ratio between the top's vibrating area and the mass. A small, light top can put out more sound than a bigger heavy one. So, one way to go with the rosewood top might be to make a really small guitar, and use a thin top.

I think that at some point we'll learn the 'secrets' of Torres and Stradivari, and they will turn out to be, as Joshua says, pretty much 'just' common sense. Would that common sense were more common!

It really boils down to what sound you want to hear. Rules-of-thumb have been proven right and wrong many times over, depending on the skill of the luthier.

How about this: A rosewood top with a spruce or cedar back? Richard Schneider used redwood for his backs (though to be fair, he'd have probably scoffed at this idea!).

One of the sweetest-sounding guitars I've ever played was made with ladder bracing. It wasn't very loud, but its voice was incredible!

Remember, whatever you do, it's gonna sound like a guitar!

Carlton

Walter, I spent the money already. Would you mind visiting my website and picking out something with Englemann, Cedar, or one of the other Spruces?

I've considered the idea of building an all-rosewood concert size ukulele. I even doodled up a concept drawing. The design calls for a one-piece top and back set bookmatched at the head, with a single continuous strip of rosewood bent to form the box. Who knows, maybe I'll get to it one of these days.

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D..

That's pretty tight, as my twelve year old would say.

Dennis, nice rendering, looks like you have thought it through. I hope you don't mind me posting the link-through to the pic.

What are you building currently?

I'm still thinking of a six string with a rosewood top. I have the perfect set for this guitar. And I have a set of K and K pickups in case it's as quiet as a pin-drop. I just gotta try it. Luthier dies of boredom, .... not on my tombstone.

I've been wanting to do a uke, maybe it's time to get some plans and do a side project. Better hurry up Dickey or I'm gonna beat ya to it!!

I also want to do a parlor at some point, but I think a uke would be more fun, just cause it's so different. No molds, I'd just build it free-hand....

Anyone know where to get good uke plans??

-Paul-

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-Paul-

Patriot Guitars

What little time I've had for fun lately has been spent catching up in repairs and making replacement parts. Haven't even had time to cruise the boards. Serves me right for taking in all these wounded orphans.

Lots of good sources for plans:
Elderly Instruments offers several choices.
The Guild of American Luthiers plans detail the Martin tenor uke.
And Hana Lima 'IA School for Ukulele Making offers plans for conventional and Kasha braced versions.

I haven't seen any of these plans, but I trust the sources.

Back on topic, building in a pickup sounds like a sound idea! That sets aside the issue of volume and leaves you free to play with the tone. I wonder if this is one of those guitars that would also benefit from incorporating some variant of the JLD Bridge Truss system into the design? It surely works for Breedlove Guitars.

I'd think that the additional support from the truss, and maybe an oversized bridge patch, would allow you to use the combination of a scary-thin top with light bracing.

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D..

Hi Dennis,
Thanks for the post reply...interesting concept about the bridge support!!
I must have seen that support product on Stewmac a hundred times and didn't realize what it was used for.
Thanks for your insight and help.
WalterK