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I've used a 25' radius on my guitar tops for a long time. As an experiment, I made a guitar with no top radius at all. It came out well, with perhaps a touch more power in the bass. But it's hard to form convictions with a test group of *one*.
So I'm wondering if there are opinions on this type of construction?
Successes? Failures? Did it work for you? What were/are the noticeable differences to your ear?
Whatever you can share will be much appreciated.

Thanks,

Steve

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Hi Steve.
I did the same thing, wondering about it.
I remember years ago doing a flat top that cupped when the weather changed, in my pre-sealed-up-shop days, so I was a bit wary of it.
3 guitars ago I did a flat top and it sounds good, and has a "loosness" to it that I like. I think it has what sounds like "age" built in.
I've done 25'r for most, but am going to flatten my bracing to 35'r for the next while. I think building here on the Gulf Coast, I need to have at least some arch, as the responsible thing to do.

As an aside, I wish you could have seen the Madagascar RW dread that I just shipped.

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Haven't actually built completely flat yet Steve, but I'm planning a build that way currently. Of the ones I've played the true flat tops seem to have a little something more in the bass and perhaps missing a little sparkle in the trebles, so that what I'm hearing.

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Jim Watts
http://jameswattsguitars.com

I only build truly flat tops Steve.... no radius on mine.

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I use flat tops on smaller bodied guitars.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

I always used a radius on my tops. Martin also uses this same set up. Many will tell you they love them. This is an individual liking. If you have higher RH swings a slight radius may help avoid cracking . There is nothing wrong with a flat top .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I want to say that some of the big Canadian builders don't use a radius, I'm pretty sure Grit Laskin doesn't or didn't. Also, Somogyi talks about it in one of his books, but I don't recall exactly what he says.

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Matt Jacobs

"Don't tase me bro"

The idea behind a radius is that it can handle humidity swings better, although there are many fine builders who build flat. As far on tone goes, I think it's hard to generalize because it's part of a system. You might carve your braces a little differently in each case and wind up in roughly the same place.

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Randy Muth
RS Muth Guitars Website
RS Muth Guitars Blog
Facebook Fan Page

Steve: Have only built one flat that was truly flat and that was years ago. So I'll give some thoughts on using a dome which you no doubt all ready know.But for discussions sake I'll ramble a bit. The bridge on a guitar is pulled up on the tail end and pushed down on the sound hole end. Some folks use a dome to build a stiffer top. I think yes and no. The area behind the bridge gets no support from this dome and may even be weaker than a flat top but the area in front of the bridge is much stronger by what I think of as "the egg shell" effect. Those who have tried to crush a raw egg between their palms will get what I mean.Think this allows us to build a bit weaker(less weight,less stiffness) into that area of the X brace.Hopefully this translates into a better guitar. Think this also helps to prevent the top from going into an "S" shape as viewed from the side and sometimes happens on weaker flat tops. Of course the other big benefit of the dome is a bit of protection from RH swings.Guess you'll have to build a few flat tops Steve and let us know the results. Good luck and take care.
Tom

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A person who has never made a mistake has never made anything!!!

This subject intrigues me. On the OM I'm working on, I ended up using a 28' radius on the lower bout of the top.........then "sprung it" onto a flat rim. I'm hoping this will flatten the perimeter of the lower bout for a nice monopole adding power/bass and leave a radius around the bridge to maintain the stiffness a dome shape creates in that area.

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Formerly known as Adaboy.......

When you build with a flat top, how do you handle the neck angle issue?

John

I think you can get away with no neck angle at all, and here is the whole beauty of it.

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Build log

I build a taper into the rims from the soundhole to the neck.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

In the case of older martins the top was figured at a 1 1/2 degree , today the neck angle is applied to the sides and the top has a double facet , the top and the angle from the top of the sound hole to the neck block
john

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I built my 2 guitars with a spline radius from the upper bout to the waist, and flat from the waist down. My thinking was to give it just enough curve that it will not fold in the detrimental direction. I did an elevated fingerboard to deal with neck angle. The older of the 2 is only 5 months old, and so far nothing looks funny. Small body guitar, decent bass, trebles are not too bright which works for me.

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Gentlemen, thank you for your replies.

David & Jim, interesting observations about the sound of your guitars.

Peter, it's hard to argue with your success, isn't it?

Woody, your direction is intriguing, and for me brings me back to a question--do you do that in the hopes of enhancing the bass in your smaller guitars?

John, thanks for the input...always good to have the Martin perspective.

Matt, thanks mate, and go find the quote!

Randy, that's what I'm hoping!

Tom, ramble on. Appreciated. But you're putting the burden back on me, aren't you? Clever....

And Darryl -Comfy, the geometry problems are just as intriguing, and those comments are also welcomed. The idea of faceting the sides down a degree or so from the soundhole makes sense.

Any other thoughts or opinions out there?

Thanks again,

Steve

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Thanks to all who responded to this.

So I take it from most of the answers that the top isn't really built flat but has a facet to handel the neck angle. Am I understanding that right?

John

How about Olson and Ryan? Don't they both build flat tops?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

John, if you lay a straightedge on the area between the soundhole and where the neck attaches, this area needs to be flat and be at a pitch such that the straightedge is elevated above the soundboard at the bridge. The amount of this depends on the action desired, the height of the strings above the soundboard desired, the thickness of the fingerboard, and the compliance of the soundboard etc. This has nothing to do with the sides. The angle the side makes with the top has to do with the neck angle you wind up with. So this pitch has to be built in either using a radius top, sanding the upper bout sides down a little, sanding the top, etc.
In the end you need to know where that straightedge needs to land. Hope this makes sense.

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Randy Muth
RS Muth Guitars Website
RS Muth Guitars Blog
Facebook Fan Page

I love this repeating thread, every 6 months... up next glue!!

I'm beyond biased as to building with it (a totally flat top), my favorite guitars are all "flat."

Hey Waddy, Yes. At least Jim does and 1350+ guitars with no "top splitting due to humidity swings" can't be wrong.

And John P, The Neck angle is built into the top on his guitars (Jims) which sets the right saddle height but also removes any fall away from the 14th fret on. There is a specific process to build the necks to the body, it's nothing short of genius, and his stuff is perfect.

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Todd Lunneborg
http://www.tlguitars.com/
http://www.fretboardjournal.com/

After building about 30 domed guitars I just built a true flat top, my last one finished a few months ago. To be honest it's one of the best sounding guitars I've built to date. There could be many reasons why I suppose but it's the same wood, same body shape and depth as a lot of my other guitars. I will be building more true flat tops in the future.

It actually has me wondering about true flat top classical's as well but I'm afraid to go there.

I think, and I'm no expert, that flat topped classical guitars can be fine, but are somewhat less responsive than domed tops under some tension. With only about 100 lbs of tension in the strings, it may not give enough to fully tension the top wood into it's optimum sweet spot. On a steel string, you have twice the string tension, and it pulls that top into a dome, no matter what, when it is tuned to pitch. They're only flat when at rest with no strings attached, right?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Well, this is becoming fun to check back in on. Thanks for all your input.
And, even if this is a repeat topic, it seems like one that weighs on several minds, no?

What got me really thinking on this is an upcoming fan fret guitar.
Moving the X brace around to catch both edges of the bridge was a concern.
One leg of the X would fall under the treble side of my bridge just fine.
Ah, but the bass side of the bridge will be swung back far enough to miss the other leg--in its normal configuration. So--I thought of swinging one leg of the X down to catch that straying bridge. That will work, but it shifts the intersection of the X off of centerline.
Now, if the top is domed, that means that the apex of the dome will also be off center, which might cause problems with the action. Maybe I'm making a mountain out of a mole hill, I'll grant. But, the idea of a flat top gets around this problem altogether, and since this will be a baritone guitar, it just might benefit acoustically from the flat top.

Does this make sense?

Steve

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From Nacogdoches...the oldest town in Texas.

http://www.stephenkinnaird.com

Oh please tell us the "specific process" that he uses.

John

Hmm...
If it's a radius would it mattter where the x's intersect? Follow me? If they are following the arc of a sphere, the apex will be in the center of the available real estate between the edges of the rims, regardless of where the x's cross. Imagine a picture of the earth from afar. Now put an arrow pointing straight down over the polar ice cap. The arrow represents the apex of the dome in between your rims. Now play the game where you spin the globe to find out where your next adventure will be. The arrow stays fixed in space as the apex between your rims, but the ice cap is free to go wherever you spin it. The apex is still beneath the arrow.
Well..how very convoluted. Perhaps I should get back to work!