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Just curious.

As far as I know, no. I had this discussion with Woody B when I was concerned about noting having a jig to brace my tops top a radii. He advised a flat top is fine.

Do you mean....

-Does the top have to have a radius?

-Can you bend straight braces into a domed top?

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I'm asking does the top have to have a radius.

Nope. True flat-tops can work just fine.

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But humidity control when gluing up is even more important than with a domed top. (at least it is in my mind). I brace and install my flat tops at a strict 37% RH. I do the same when using a dome, but I don't think it's quite as critical.

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Woody, how much doming do you get in say 50-60%? It should normally pull up a little...
Do you still feel the need for a neck angle with a true flat?

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I'm sure it changes but I've never checked it. The top pulls up a little under string tension too. I use a ~1 degree neck angle, and slope the ribs from the position of the UTB toward the neck to make this happen. I visualize the string height at .625" above the soundboard at the bridge, but it ends up right at .550" after stringing up, and toneriteing. I don't know how much of the .075" comes from string tension, and how much comes from a humidity induced dome.

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

You can build a true "Flat Top" as woody says... In fact, Ervin Somogyi recommends it for Beginners in his book... It sure makes tooling and geometry easier... Your "Workboard" is just a sheet of Particle Board!

Just think of it as a "Radius Dish" with an infinitely large radius....

My #1 was a true flat top... Sound is really nice -- I like it a whole lot.
Neck set was fairly easy -- I just set the neck with a straight edge across the body joint... No angles... Fretboard and bridge lined up just fine....

I do plan to build some more "Flat Tops" like this in the future....

Thanks

John

I'll add Jim Olson uses flat tops, as does Charlie Hoffman, and many others.

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

FWIW I never built a true flat top until my last one which I completed a bit over a month ago. I don't know the reason behind it, same materials and body shape as many others, but I swear to you it is by far the very best sounding steal string guitar I have ever made! I'm keeping this one for myself

Wow, how things have changed around here. There was a time that if you just mentioned building flat you would get your ... ah never mind. It's good to have so many flat worlders around here so I can ask my flat flattop questions. Like, can you build flat and not have the area in front of the bridge go concave?

You can build with an arch on the top without needing much in the way of jigs. I remember grumpy having a video which shows his arching technque which is as slick as it gets. Maybe someone has a link to his video. If needed I do something very similiar and can link in some photos.

You can arch the top and glue it to nearly flat rims, (I would add a bit of slant from the waist to the neckbock to help with neck angle issues but there are other solutions for that too.

Even if you don't want flat rims, It's easy to make a simple tool that will help measure the arch. And you'll need something to help with the back arching because I don't imagine that you're building the back flat. Are you ?

John

NO

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

Oh come on, Tom, you can't just answer a question like that!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Newbie question,
When you refer to "flat top" are you saying you don't put any radius at all on the top? I'm just at a point with my current guitar where I'm ready to radius the top (was going to use 50' ). What would be done differently?

Newbie question part deux,
You mentioned lower room humidity for gluing flat tops. If I build at 45% or so, are you saying the top will dome automatically? Even if it isn't radiused? Will this affect the instrument when finished?

Waddy: My one typing digit it tired today....!!!
Tom

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

Yes a truly flat topped instrument, no arch radius in the bracing. That's what I did and I will definitely be doing it again. It's only slightly easier, radiusing braces is a 5 minute job. I did it after reading some comments from posters in this forum, just wanted to try it and I am very pleased with the results. As it is right now there is a slight arch from string tension so I guess it ends up being arched. I did make my X-Brace a little bit beefier just incase I was loosing a lot of strength by not arching.

Oh and the back is definitely arched.

There are plenty of flat top builders out there, and some, Jim Olson, are pretty successful. The main difference, aside from the construction, is the sound.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

If you build at 45%, then as soon as it goes below that, it will start to go concave. Woody's level of 37% sounds good, so it's fine down to there, and will dome outward a bit at higher levels. I guess it is sort of an auto-dome

And from all I've read, I'm guessing that the reason that a lot of beginner flat tops sound good is because the dome makes it a lot stiffer. So by going flat and using similar thickness, it will be less stiff, and thus less overbuilt.

I have mine sprung into a dome by clamping curved braces to it (Cumpiano & Natelson book), and glued to level sides. Peak is 1/8" higher than the rim, and centered between the bridge and X intersection. We shall see if I run into any geometry problems when attaching the neck, but just eyeballing it, it looks good. I guess the main problem would be if the part of the top under the fingerboard extension doesn't continue in line with the neck, when angling it for .5" saddle height.

Waddy, I'm trying hard to put into words the tone of my flat top but words escape me. What can you say about the tone of a flat top versus one with an arch? My flat top has an incredible sustain, that's the first thing I noticed.

I build CGs but I'd love to put up a small 12-fret pseudo-00 steel for myself with the least possible effort. Probably Spanish neck and no truss-rod as well just a chunky ebony stripe in a stiff Cuban mahogany neck.

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Build log

I don't know if i can put it into words either. It's just, well................different!

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Yes you can. You can use the humidity induced arch (but isn't that a domed top?) as Woody suggested. I've built 15 or more that way and all have been very successful. You can also build in the more traditional manner and make the X fairly stiff above the bridge and scalloped below.

Or, scandal of scandals, you can let it go a bit concave.

No, it doesn't look great. Yes, you may have trouble selling it due to the misconstrued but widespread notion that any concavity above the bridge is a sign of imminent collapse. But indeed, guitars can be built that way, sound great and be structurally sound. In fact, I recently saw a classical from a very well respected builder that was dramatically and intentionally concave. It sounded outstanding and appeared to be stable.

As my grandma used to say, there's more than one way to skin a cat.

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LOL... In one of Somogyi's interviews -- he talked about building some Concave top instruments on purpose..... Said they sounded great.....

If you take careful measurements -- it seems like *EVERY* guitar with a non-tail piece (glued on) bridge bellies a bit behind the bridge and sinks a little bit in front of the bridge.... I think the "Dome" shape makes it less obvious... and if you carefully build your bracing, it spreads it out over a larger area.... but if you measure it with a dial indicator... it is there...

My description of the sound of a "True Flat Top" is Older or Warmer.... That's the best words I have for it....

Thanks

John