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Just curious as to how many are building flat top guitars as opposed to those with a slight dome or radius. My first two I built without a radius mainly because it was easier to glue and assemble in the GO bar deck. I am now investing in some radius dishes and plan on trying a 28ft on No 4. Aside from the advantage of resisting humidity changes better , what are the benefits /differences tone wise and structurally.
By the way I'm quite happy with the tone I am getting, but am keen to know how it might shift. I realise this is a very general question but would welcome any opinions or insight in relation to this.

Thanks

Craig

Hi

How would you say it looks? From what I have seen if perfectly flat, they can actually look 'concave' - an optical illusion created by the way we view the board?

I would suspect that 'dome' provides strength - based on school physics!

I am building a "Flat Top" Ditson right now.... as in No Radius.
I have to say... Clamping the top onto the body was easy.

My last build had a 1/16" dome on it (I won't claim it is radiused....)

There are Many builders out there who build true "Flat Tops" -- in fact, you can get a Flat Top from R Taylor.

John

Kevin Ryan and Jim Olson both make true flat tops. There are also some builders on the forum that do, though I'm not sure enough of my recollection to name names

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Truly flat top builders are a minority. But with names like Olson and Ryan in there, it's a very select minority.

Count me in with Kevin Ryan and Jim Olson...which will be the only time in my life I can be included in a sentence with those two.

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The first two guitars I built were flat tops...I found two problems with them...The fingerboard ext had too much of a drop off on it and the area around the sound hole had a tendency to slightly sink inwards over time.....Using a radius is the only way to go for me. There is no difference with the clamping,same procedure.....Larry

I had the same problems as Larry. Still, there are folks out there who do it and are happy with the results.

Building on a radius requires some adjustment in voicing. IMHO, the top tends to tighten up a bit when glued in a radius. But I don't think it's a tough adjustment to make and I've experienced gains in structural stability.

I still own a 00 sized guitar I built in 1978 with a flat top. It now has some sinkage in front of the bridge, and a slight dome behind. It was built with a thin top, and light braces. Other than the look, it has needed no adjustments, not even to the saddle.

The tone tells all, though. Great volume, but less sustain, sort of a Gibson "thump".

I think it takes more experience and skill to build a true flat top than one with some arch.
Even a "flat top" has to be built with a slight dome, to avoid caving.

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Mario has noted he has built with a flat top on occasion. One comment I do remember him saying and I now paraphrase him is it had a distinct tone and try it you will like it. I don't know how often or circumstances he does this or even how many he has done. He was just responding to a post of this question several years ago. I was in a shop back in 02' for awhile and they built with flat top. Trouble was they also did a flat back and ran into big probems with humidity then seperating the back and then eventually the top. I finally convinced them to do at least the back and they had no probems after that.

Not a lot do, but those who do (The pro's that is) are highly respected and have been doing so for well over 25 years each.

I do, because those guys do. And if it works for them, it works for me.

Is that vague enough for you

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Never have more vague words been spoken, Rod.

We are now awaiting "True enlightenment"

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After playing some of Dave Whites guitars and falling in love I'm seriously thinking of using his radii of 13' for the top and 10' the back they have huge projection better then most guitars I've played including a couple of hand built ones. Though looking at luthiers suppliers list 15' for the top may be better for those who wish to avoid the custom radius charge

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I learn more from my mistakes than my successes

OK, just because I'm feeling rather ornery, I'll

I personally don't believe the hype about the dome top resisting humidity changes better than a flat top. Wood moves with changes in humidity regardless of the fact that there is a dome or not.

Build two guitars, one with a dome, one flat in the same humidity controlled shop, now take those same guitars to Minnesota in the middle of winter when the RH has dropped down to 20%. Both of those guitars will show significant top failure and the dome will not have resisted the change in RH any better than the flat top. It's wood after all.

Look at a 15' domed back. I've seen it on guitars that I've made and now the owners don't have humidity control like my shop. I recently had one of my guitars back in the shop to help the owner re-humidify it as the back was almost flat and there were two cracks in the back, which were not previously there. Funny enough, the top was still slightly arched only from the pull of the strings as it was built a true flat top.

IMO, the dome allows more for of a tighter sound and the claim that it's stronger (as the load from the strings is in the opposite direction as the strength of the dome) is hype IMO.

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I love conflicting opinions! No better way to get folks out of the closet.
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There are advantages and disadvantages to both styles. The fact is a domed top will have more ability to move with humidity than a flat top. When humidity causes shrinking a domed top will have more wood to absorb the movement. If the change is severe enough it to will shrink to the point where the top will cave in.
Flat tops are in the minority and they do have a different tone than domed. Again it depends on what the builder is looking for. If you are looking for the Martin sound , you won't get it from a flat top. Some gibsons are flat tops and they have that old bluesy tone.
Most flat tops are often ladder or H braced. Still when it comes down to it the best way if you don't believe something is to proof it out and build one. I have learned more from those experiments than reading posts about them. One thing that you will learn is what the humidity can influence to a top. If you glue up a top when the RH is say 40% this will make the top more stable that if you glue one up when the RH is 60%. I don't glue tops up over 55% RH. Builders in Arizona will have different issues than a builder in Florida
john

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My first guitar was built with a well-respected builder who, incidentally, builds with totally flat tops. And that guitar turned out great! But, being skeptical, I wasn't convinced. So I asked Kevin Ryan this exact question - which was, of course, related to "why" he builds with a flat top, and not a radiused top like the vast majority of other builders. His incredibly polite response, and I'm paraphrasing very, very closely:

I believe the tone is better with a flat top. Radiusing the soundboard just doesn’t make enough sense to me. The soundboard should move freely in both directions and with a radius, I don’t think it can. I know I am in a lonely minority with this. But if a guy builds like everyone else, his guitars will sound like everyone else’s too. Trust your instincts. There are a lot of myths in the luthier world!

So there you have it. It isn't that I don't believe in radiused tops, it's that I've never found a good reason not to believe in flat ones. And with builders like Kevin Ryan and Jim Olson, arguably two of the premier builders in the world today, essentially confirming that belief, I'll keep building them flat until my experience says otherwise.

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John, when you say that you won't get the Martin sound from a flat top, do you mean the "current" Martin sound? As compared to a very vintage sound?

My understanding (speaking of pre-war methods) is that Martin built their tops on a flat workboard, and glued the braces, which had a very slight arch, by springing them down at the ends. This did induce a stress, but not so much an arch, to the top.

I have seen the picture of a Martin work board that did have a slight dish, but not a spherical radius. In fact it was much like a classical workboard with the dish on only part of the top. I understood that it was not typical of their workboards.

I have no actual knowledge about this, other than what I have gathered over the years by reading what others have written and spoken about.

My own experience of building two "dead flat" top guitars, a dread and a "00" is that they do have less sustain than my others that are arched.

I'm wide open on this discussion. I'm only 57 and still have a lot to learn.

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There are a lot of opinions of this but from what I saw at the factory they use a radius. I own 2 old martins an 1880 and 1909 and both are radiused. The only flat topped martins I see in my shop are usually dried out and redome when humidified. I also have an HD28 ( domed ) a D35 ( domed ) a 000-28EC ( domed ) I own 7 martins all are domed but 1 and that one is a backpacker.
john

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John, I'm a bit ignorant so please forgive my question.

Do you think the two older Martins you have, the 1880 and 1909 have developed a dome from 100+ years of string pull? Or where they in fact made with a dome?

I often have wondered about the pre-war guitars and whether they are domed only because of the pull of the string over such a time or because they were made with a dome.

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Rod, I think what you're overlooking is this. The shortest path between two points is a straight line. If your lower bout is 15" and you build with a dome the top is in fact more than 15" wide. If the top is dried, it will shrink, which will flatten out the dome rather than splitting the top.

It's not that domed wood will resist movement, just that the design allows for movement before splitting.

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David White, Toronto

"All my favourite singers can't sing."

I am, of course, concerned with humidity and it's effects on my guitars, but I am more interested in the methods of bracing a top as it concerns the resistance to bridge rotation, and it's affects on tonal quality.

I have for a long time pondered a bracing scheme where the top is braced flat behind the bridge, and arched in front of the bridge. It should be obvious what I'm invisioning, in terms of rotational resistance. If more load could be carried by the braces, the top could be thinned more with tonal issues in mind, than structural ones.

A ladder-brace scheme would be workable, but I'm not willing to give up my X yet.

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I've built guitars side by side to compare flat tops with radiused tops. I've also done several consecutive tops on the same test body to compare. All else being equal, domed tops are stiffer and resist bridge torque better. And even when the two different styles show similar deflection at the bridge, they sound different. In talking to Jim Olson, he described domed tops as sounding "strident" to him and from my experience, I'd say that's as good a descriptor as any. Given relatively conventional construction, I'd say flat tops favor a warmer sound and domed tops favor a more strident sound.

But that's certainly not the end of the discussion. I've heard a couple of heavily domed tops that sound plenty warm (but I have yet to hear a flat-top sound particularly strident). It's a complex puzzle and doming is just one part of big equation so it's hard to make broad generalizations.



I get that logic but as soon as a domed top starts to shrink, it is under tension too and ultimately it's the tension that splits things. Is a flat top really under more tension given the same circumstances? That's one of those issues that can be argued up and down with anecdotal evidence thrown in for good measure but I'd love to see a controlled test.

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The funny thing when talking about wood shrinking from loss of humidity is the simple fact that we usually glue two pieces of wood together in various grain directions. The X-brace at an angle, most lower tone bars at some angle as well as the finger braces. Then there is the bridge plate, usually perpendicular to the tops grain direction as well as the bridge.

To boot, they are all of different dimensions and sometimes different species, thus changing at different rates one from the other and at different grain angles as well.

How can we really say that a small amount of doming or arcing can greater resist changes in humidity with all those factors coming into play. Oh, then there's the creep of the glue we shouldn't forget, if the glue creeps that is.



OK, so I did the math (actually laid it out in CAD) and do you really want to know the difference in length of the arc on a 25 FOOT radius versus a straight 15" line? OK, here it is. The length of the arc with a 25' radius having a 15" chord is 15.0016". This is not a typo. The difference between the two is only 0.0016". I'd pretty much say that was negligible David.

I mean the dome on the top on a 25' radius is only 0.0938" off the horizontal plane. We are really talking about a small amount of difference between flat and radius'd. And it only gets closer as the dome radius gets larger, like 30' for example.

I agree that the dome helps combat the rotation of the bridge, but by how much really? This can also be accomplished by the bracing layout too.

Nope, I can't be convinced that such a small amount of dome is better than a flat top to combat changes in humidity. If that were really true, why do we see and hear of guitar backs caving in and cracking from lack of humidity. Heck, they have a smaller dome radius, they should be stronger right

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Some builders choose to build with a flat top because they don't see or hear the benefits of a top with a
radius built into its structure while others build with the arc built into the structure of their tops because they
do see and hear the benefits. There are plenty of younger....or at least newer to the craft of lutherie....builders
who choose to do one or the other because some of their favorites do it in a particular way and for no other
reason.

There are good reasons that are pretty obvious to those who use a radius and the discussion can't be a valid
one when one side comes from a preference that is arrived at because of someone else's experience, research
and trial and error investment. Very valid offerings have been made in defense and explanation of both methods
and it comes down to a choice by builders on an individual basis...whether they're actually doing one because
they've invested the hundreds and hundreds of hours necessary to prove it or because their favorite builders
have.

The prewar Martins were actually engineered and constructed with a radius in their tops so the radius that is
present in them today is not the result of years of string tension, although it may have increased a bit over time
as a result of it.

One of the most common and repeated things to see in American consumer mentality for many decades is
the equation of generated perception of value or quality with a product's, feature's or method's actual quality.
You have to find out for yourself if one is better than another by investing what is necessary to do so. Until
you do, you're just buying one side of the discussion over another as a result of this kind of perception effect.


If you're a builder, pick a method that you or your favorite builder has arrived at for whatever reason, but don't
dive into the futile advocation of it as the best or right way to do it in favor of another or one that you have discovered
to work best for you in establishing good tone and integrity in your guitars. It's a moot point of discussion since
so many great guitars have been made using both methods.....actually, I'd venture to say that many more guitars
have been built with tops with various radii and flat perimeters with bracing that creates and maintains a radius
or arch than there have been with completely flat tops. We need to remember that when we claim that one is right
and the other is wrong or one is proven and the other is not we are dismissing the countless hours and many years
that builders on both sides of the fence as wasted time.

R & D through research, prototypes and experiments are invaluable as they serve to be and prove themselves
to be the very best teachers for a student of any trade or craft. What works...works and what doesn't...doesn't
and those are the sort of lessons that research and development efforts teach us as we pay close attention to
the differences between instruments built using variations of construction, materials and methods.

I just chuckle when these discussions come up now....and then look back on the many prototypes and related
documentation of their outcome that I've compiled over the past few decades that helped me to arrive at my
methods and, like a lot of other builders, I've tried it all.



Regards,
Kevin Gallagher/Omega Guitars