is a "flat-top" really flat?

[pete nardo]

I am building my first acoustic kit, a stewmac triple-o, under the tutelage of a local luthier. he insists the top must be dead-flat; "that's why it's called a flat-top"

so when sanding the top-side kerfing and neck block, he used a flat sanding stick, rather than one with a 1&1/2 degree wedge on the end, as stated in the instructions.

Im under the impression that the 1&1/2 degree taper in the neck block, as well as the radiused top X-braces are meant to result in aprx. 28 degree radiused top?

it's an academic question now, as the top's been glued on, but should i be concerned?

I appreciate your thoughts. This is a great forum; and I look forward to contributing more. I'll post some pix of the build, when I figure out how to.

Regards,
Peten

[deadedith]

Pete - I raised this issue a couple of months ago and it provided for a stimulating discussion, at the end of which two luthiers dueled to the death and the rest of us were too depressed to think about suicide.

Okay it was not that bad, in fact I learned a lot from the pro's and advanced amateurs I rely on in this Forum. I will let them weigh in on this; if you use the 'search' feature with the words 'flat top' in the meantime you can get up to speed.

Please keep us up to date with this - and ask as many questions as you can, it's good for all of us.
DaveB

[kencierp]

Well I almost agree with your Luthier friend. At the factory Martin uses braces contoured to 52’ almost flat and the rim is sanded essentially flat with a 1.3 degree slope from the sound hole to the neck block. Here are some more details

http://www.kennethmichaelguitars.com/ne ... angle.html

Many builders however, have built Martin style guitars using angled sanding bars and abrasive covered radius dishes. Which in fact has more to do with getting the neck set to the correct "cooresponding" angle to the rim -- I suggest that you read the links above.

[tippie53]

the term FLATOP came about during the hey day of arch tops . I was trained at martin and the angle is 1 1/2 degree that is sanded into the sides and with a top radius on the braces of 42 but it is semantics as the top is glued up flat. When under load the top will have a 1/8 inch dome. When you think about it , once the braces are glued on to the top you have made a hygrometer. The top will move with the changes of RH.
Now many use a 28 foot disk to create a 1 1/2 degree angle . It really doesn't matter as long as your process works for you . Martin uses all kinds of fixturing and jigs to build a guitar. It is after all a production plant.
the only place were a single person will actually build a guitar is in the custom area. here they guitars are made the old fashioned way . all by hand. Even the necks are hand carved in the custom area.
it is nice to see the old jigs put to use .
I agree that this can be a can of worms as some people are very adamant about their opinions. When it comes down to it there are more ways to build a guitar than you can shake a stick at.

The Stew Mac kit is one that you need to follow the instructions with the kit. They are different from martin kits and making it flat will not get you the action height you need.

check out this link for setting up side geometry
http://www.youtube.com/watch?v=QYHPCeVRUA4

[kencierp]

To your original question -- is a "flat top" really flat. The answer can be a definite yes -- the very expensive R Taylor models are advertised exalting that feature. http://www.rtaylorguitars.com/Woods-Bracing-04.aspx Some boutique builders are trending back to flat tops as well. One caution about using a perfectly flat top is that the soundboard must be dried and stable – Taylor bakes its soundboards. A slightly domed top is actually a fraction larger in square area then the perimeter of the guitar so if it shrinks from lack of humidity it will be able to contract a bit. On the other hand a sound board that perfectly flat has less margin for error (its has just enough square area to cover the perimeter) so rather than sink (reverse belly) it will tend to pull itself apart and cracks can occur.

[tippie53]

Ken is correct on the taylor without a doubt .Again it is what you plan on using. Martin , while called flat tops , are not totally flat.
Many builders go for flat so if that is what you want go for it . I do think it is fair to say that they will sound a bit different as flat tops will disperse energy a bit different than a domed one. Gibson I think are also flat
Find what works for you and go that way. There is no one right or wrong way . Ken and I have different philosophies in building , that doesn't make either one of us right or wrong . I think that adds to the discussion and information that is available here .
I bet Ken and I both have flattened a thumb with a hammer at least once , Does that mean a framing hammer hurts less than a finish hammer ?
You know it is gonna hurt when the thumb nail turns black within 10 seconds.

[pete nardo]

thanks for the input guys; very informative. I find it interesting, and reassuring, that there's more than 1 way to do a flat-top. R. Taylor is brilliant for marketing different flat top options; I wonder if other luthiers will follow.

Tony, my teacher has built over 40 guitars. He seems to know what he's talking about. You can check out his youtube videos under hot strings guitar shop.

John, how does the stew mac kit differ from martins? are you saying I may have a problem with the action? I'm assuming there's ways to compensate for this my adjusting neck angle and/or the bridge height?

Regards,
Pete

[tippie53]

Stew macs techniques don't translate well with the martin. You have to be careful Martin uses a countoured side and stew mac tapers theirs.
Just take your time and think if it makes sense. When in doubt ask here .we are all here to help

[hummingbird]

John, what's the difference between contoured and tapered? I have a "practice kit" from Jim Hall which consists of pieces from a Martin kit. I may need to know this.

[tippie53]

Jim used the contoured , that means the actual geometry would match the spherical dome on the back. Tapered is , just that a straight line from the tail to neck. There would be no spherical match on that .