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Does anyone build with a flat top instead of with arched braces ?Been thinking about this for a while now and may try it on my next build and would be interested in hearing from anyone who builds this way.Thanks Roby.

Many of the modern ladder braced builders do - Haans and Todd Cambio at Fraulini for example.

Ed

I do. I believe the consensus is that it gives you a little more bottom end.

Steve

My tops were cylindrically arched at 10', both ladder and Larson X brace.

Guessing it won't give you much leeway with humidity swings.

Martin uses 52' ---- R. Taylor Models flat or 65' radius. If you understand the neck set geometry it can be done. The actual surface area of a slightly domed plate is larger than the perimeter of the rim which helps to make it more tolerant to humidity swings.

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I've built a few flat tops on smaller size guitars. When lightly built they do "pull up" some from the tension of the strings, which creates a slight dome in the top.
If you decide to try this, my advice would be to brace the top under lower than normal humidity conditions, otherwise you might have the top go concave if the humidity gets too low (indoor winter humidity levels).

I believe Jim Olson and Kevin Ryan also build flat.

It's sort of impossible. Either you arch it yourself, or you brace in lower humidity and it will arch on its own when brought into normal range. Or if you brace flat in normal range, it will go concave and then crack if you don't babysit it all the time.

But I do use a flat perimeter (straight jointed sides glued to the soundboard with dentellones), and that probably makes some difference in tone compared to doming it.

+1 Exactly.

One super old fashioned way is to clamp up the top with HHG in a hot room next to the wood stove. If the top has been in there a while, it be very dry, and when the braces are glued on flat a slight arch will be induced when the assembled guitar body is brought back into normal humidity.

Two things.

Does not the hot stove method described produce a concave on the cross braces?

Are we all on the same wavelength regarding the definition of a cylindrical top? I have seen cylindrical meaning the wings are lower than the center seam; and I have seen cylindrical mean the very bottem edge is lower than the bridge.

In my book, transverse. Longitudinally, mine were flat.

My resonator, L-00 & Parlor guitars have flat tops.

Mike Franks
www.mjfranksguitars.com
www.facebook.com/mjfranksguitars

I like the look of the non-flattop. It's harder to coordinate the neck angle. But you never have to worry about concavity issues. I want to change mine from 25 to about 35 feet. Boost low end. But my last bunch at 25 feet have pretty good low end. I know for a fact I would not like the look of a truly flat top... that's just me.

This is a good question, one new builders should pay attention to.

Mike

Thanks for the replies, the main reason i asked this was because it would make it easier to calculate the neck angle when sanding the angle on the upper bout area of the sides i.e. you wouldn't have to compensate for the arch of the top at saddle position (is there a formula for this?) All the best Roby

Hi Robin: Often it's the case that we talk about a 1.5 degree neck angle but that's just an approximation and misleading in the sense that all necks need to be individually fitted to the specific body anyway. This is the neck fitting stage and unavoidable in the process of building a guitar.

There are tutorials in the toot section of the OLF specifically shinning a light on fitting necks AND there are methods of building that also flatten the upper bout or reduce the radius to help the fret board extension sit flat and even fall-away slightly also in the toots section of the forum.

You might want to read these and see if that helps get ya where you want to go.

Yeah, I just checked and on the first page of the toots section are two tutorials by me that I think might help you out. "Flattening the Upper Bout" and "Fitting a Neck" both need to be read together in my view to start to understand the relationship of the neck, body, bridge, upper bout, etc and how we can manipulate them all to get us that nice neck angle.

Every guitar I've built are built with the flat top design. I use 0.75* angle from the front of the soundhole to the front of the body.

There are many high end builders who built this way, Jim Olson and Kevin Ryan being probably the most notable, with Charlie Hoffman being another.

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Not that I have done it personally, but wouldn't putting an arch of the required radius in the UTB achieve exactly the same end result, with less effort, as sanding the slope from the soundhole to the neck block?

Yup there are lots of ways to get to where you want to go (and even more ways to mess it all up nicely too... ). Some builders do just this Murray, build in their desired radius to the UTB and it's usually a very shallow radius. The last two that I built I did this way and it worked well too.

Flattening the upper bout though only takes a few minutes before the pencil lines drawn on the linings in the waist area start getting sanded off. IIRC this goes very fast, likely 2 - 3 minutes tops with 80 grit on the flat surface. If it took any longer I would have been doing it another way....

Anyway what's important is that we all find something that works for us, gets us to where we want to go, and does not require much in the way of unnatural acts.

I use the Luthier Tools Neck Jig, Gen II. With it, you put the body in the jig and use a reference bar & dial indicator to tilt the body until the neck angle is transferred to the tenon routing table. When you cut the tenon, the neck angle will be built in. And if that sounded confusing, just try reading the instructions that come with the jig. None the less, that's all there is to it. There still is some block sanding to do after the cut, but it comes out amazingly close. I promise, once you understand the principle, its easy as pie. Flattening the upper bout where the fretboard goes is critical to avoid the dreaded hump. But as Hesh said, that's pretty easy too.

Hesh ,do you only arch the x brace? And Rod have you had any trouble with this concavity issue that has been mentioned?

I radius the X brace, finger braces, and tone bars but the upper transverse brace I leave flat except for the last two that I built and mentioned above which I imparted something like a 65' radius to try it out and that worked well too. When I used the very shallow radius on the UTB I did not get as much fall-away of the fret board extension as I would prefer, .010 - .015 measured at the last fret by the sound hole but I still got some fall-away, just less.

Back in the day on this forum one poster was critical of a flat UTB indicating that it may go concave someday. The last couple dozen guitars that I built my upper transverse braces had .020 carbon fiber laminated/sandwiched in the UTB making it super rigid with no flex at all so this concern never bothered me.

There is a third possibility that I know of too and that is a UTB with a shallow radius that the center several inches, under the fret board extension is flattened. This gives the UTB a bit of radius, more strength likely from the radius, but a flat area for fitting the fret board extension. It eliminates any need to hollow out the underside of the extension because the guitar top has a shallow radius.

Nope. I've got a guitar out in Toronto, been there through last winter and it's doing just fine.

My suspicion is that this isn't an issue. We'd hear all about it from the 1500 Olson owners out there if it were.

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"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

I also build flat, with no issues of "concavity" (is that a word?). Just fixed a crack in the BACK of one that lives in Toronto with appalling dry winter heat, but the setup on that guitar has remained virtually unchanged for 6 years. FWIW, I also use a Spanish heel, another violation of most North American building wisdom.


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