Top and Back domes or radii..necessary?

[nnickusa]

I've got a little idea kicking around in my head for a gujitar. Want to make one that's all my own....

Here's the question:

What effect positive or negative would flat top and back have to a steel string? I'm thinking thin bodied, and hope to get some jazz sounds out of it, and add a neck-mounted pick up, but I don't know if it'd be worth the potential waste of material

Any help would be appreciated...

[charangohabsburg]

Hi Nick,

Completely flat plates are much more prone to cracking when the guitar at some point in its life experiences dry climate (which sooner or later will happen), Additionally, a domed top can be made thinner to withstand the string pull respectively bridge torque, e.g. you'll get a lighter top at the same rigidity, which makes a more responsive and louder guitar.

[nnickusa]

Thanks Markus. I knew there must be a good reason, and those are both good ones....

[woodrat]

Whilst in the UK last year I went to visit the makers at Brook Guitars in deepest darkest Devon. They had an interesting take on it. They build dead flat tops in an extremely dry room and they puff into a sight dome when they are in the real world (ie...higher RH) ....not the way I build but another point of view and one that works for them...

John

[Allen]

Truly flat tops also have the tendency to sink. Even a little will be very noticeable and not a good look at all, not to mention the structural and geometry problems this presents.

[woodrat]

I think the high end Taylors that are called R Taylors have a 65 foot radius on their tops....that would be very subtle but still domed....yet another point of view. I use a 30 foot radius myself....

Cheers

John

[Paul B]

Totally flat tops can look like they've sunk in the middle even when they are still flat. Some kind of optical illusion going on there.

Adding a dome gives the top another axis in which to move in response to humidity changes.

[charangohabsburg]

To make the confusion complete: lutes (some lutes?) have a sunken top (=reverse doming) built in by purpose!

[Dominic]

Whilst in the UK last year I went to visit the makers at Brook Guitars in deepest darkest Devon. They had an interesting take on it. They build dead flat tops in an extremely dry room and they puff into a sight dome when they are in the real world (ie...higher RH) ....not the way I build but another point of view and one that works for them...

John

Martin guitars used to do something similar. But they had quite good control over the work environmet..
Cheers
Dom

[simso]

I think the high end Taylors that are called R Taylors have a 65 foot radius on their tops....

Yes they do, but as you mentioned its still quite a noticeabley domed top.

[kiwigeo]

To make the confusion complete: lutes (some lutes?) have a sunken top (=reverse doming) built in by purpose!

This lowering of the central section of some lute tops is probably done as a crude from of relief to stop slapping of the strings against the top. Along the neck, relief is normally provided by dialing in a slight posotive raxke and also using progressively thinner guage tie around gut frets up the fingerboard. The "reverse doming" (not really a true doming as the axis of the lowered section of top runs across the instrument only) is achieved simply by deforming the belly of the lute by squeezing it between your arm and stomach and then running a block plane along the central section of the last ribs of the belly. All done by eye and with no measurements supplied on plans.