Official Luthiers Forum!

Thanks everyone for weighing in on this one. It really does make me want to hurry up and build one with a dome just to compare.
My first instrument had this concave look but unfortunately was not an optical illusion. Not realising how important the relative humidity was in the building of the instrument and particularly with a flat top, I glued in anywhere from 40% to 60%. Not recommended. I learnt a valuable lesson and was much more careful with this aspect of my second build.
Larry I sanded a slight ramp into the rims forward of the soundhole. This seemed to do the trick. Getting the neck angle correct was another matter.
Very interesting Bill
Thanks Kent that is good info. Do you think that the strident sound diminishes as the instrument ages?
Thanks Kevin for your voice of experience here .

Regards

Craig

Rod,

Remember that scene in "Crocodile Dundee" when he's walking the New York streets with his girl and some punks pull a knife on him. His girl says "Give them the money, they've got a knife" and he says "Nahh . . . that's not a knife, THIS is a knife" and proceeds to pull out a bush knife? Well you're dead right, 25', 28', 30', 40' - they're not a dome, they're all flat tops

Kevin's spot on - different builders choose and then work their magic.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

The above post states the facts better than I can. The one thing I am going to add to this discussion is this , Shape built into the top will influence the stiffness . That is a fact and depending on what you are looking for in your build . Each style has it's following but the market demand is looking more for the domed top than flat.
As for top stress , once you glue on the braces to start a stress process . As the wood is in constant flux from humidity and temperature the plates work against the braces. This does build up stresses within the system. In essence we are building hydrometers with the cross grain gluing.
john hall
blues creek guitar

_________________
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 have always believed that the benefits that I'm taking advantage of by building a top with a
radius built in are more created by the tension that is generated by the structure and not by the
additional top width offered by its having to traverse the arc spanning a chord rather than being
stretched across the chord itself.

Regards,
Kevin Gallagher/Omega Guitars

Kevin's post is very educational. The shape of the top will incorporate stiffness. A dome is stronger than a flat surface. These are engineering facts. Using an implied shape can do much for influencing tone and volume. Like Kevin I have done many experiments until I learned what these influences can do for your guitar.
Lets face it , we all hear things a little differently and we all have something that we want to hear when we build a guitar. A process when established and followed will get you repeatable results .
john hall

_________________
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 believe this is what John Arnold does on his guitars now.

_________________
Jeremy Douglas

On some guitars I build with arched X bracing and a flat rim. All the other bracing is flat also. This gives a slight rise in front of the bridge and I believe stiffens up the area below the sound hole. I leave a little more wood below the bridge and I think the "flatness" of the top in this area keeps things from becoming too stiff.