MIMF

Is there a longitudinal arch in the tops of these guitars?

I'm assuming the Vienna style Hauser guitars have very little transverse arch in the top. What I can't see is a longitudinal arch in the top. There is a pronounced longitudinal arch in the back.

Everyone I ask says these guitars have no longitudinal arch in the top.

I've never seen one, but I am building a guitar now from a plan of a 1828 Stauffer. Dimensions of an instrument in a museum. The back does have a 10mm longitudinal arch. The guy who made the plan said that he put in a 2mm or so arch below the sound hole, implying that the original was probably flat.

This is a bit different, as it has an elevated neck that is adjustable, and is at about a 3 degree positive angle. The bridge is very low, but string clearance over the body is no concern at all. The force vector diagram is very different from a classical design.

Curved backs and flat tops is probably what they did; like long hoods and short decks in the 60's car styles.

Do modern classical guitars have much arch in them?
Do Hauser's survive with dead flat tops?
I don't know.

I recently built tops for two Early Romantic guitars. One is traditionally braces, with added 2mm arch carved into the bracing of the lower bout, the other is a five fan braced top, domed 3mm in the lower bout, for a guitar increased from 11.75" to 13" lower bout. The larger guitar will have a 24.75" scale. It's what I have besides 650mm in scale templates, and I had a nice, full 13.125" one piece maple back plate I didn't want to waste. Sometimes we design for what we have, hence the ukulele.
So, a dome may change the sound, but the guitar is ladder braced. I don't think it will greatly alter the character. On later model Hauser I guitars, the arch of the top dome was carved into the bottom of the bridge and pressed into the top with clamping, I'm told.

The back on the Stauffer has a very slight 2-4mm cross arch. 3 bars on the back and 4 on the belly. There does seem to be some thickness tuning on back and belly. The belly is thicker, 3-3.5mm at the bridge. I started the Stauffer simply because the wood was just wide enough for it. Sometimes violins get higher or lower arches because the stock was or wasn't there!

Ken Nagy wrote: ↑Sat Feb 27, 2021 4:45 pm The back on the Stauffer has a very slight 2-4mm cross arch. 3 bars on the back and 4 on the belly. There does seem to be some thickness tuning on back and belly. The belly is thicker, 3-3.5mm at the bridge. I started the Stauffer simply because the wood was just wide enough for it. Sometimes violins get higher or lower arches because the stock was or wasn't there!

That makes me wonder if Strad built with a flatter arching than Amati because he didn't have thicker stock.

Most of the early guitars I have, appear to have flat tops, but Hauser who was building much later may have done something different.