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For the classical soundboard, how much doming? Where is the peak of the dome located? I thought I knew but it seems the more I read, the less clear it is. For example, here is what I’ve gleaned from several books:

Cumpiano: Fan braces are glued flat. The soundboard dome is created by shaping the glue surface of the lower cross strut using a smooth-curve template of 1/16-inch offset in a 10-inch span. This works out to a 16.6ft radius. The dome feathers gently up into the soundhole and down toward the bridge.

Sloane: similar dome method and location to Cumpiano but the amount of arch pre-carved into the lower cross strut is unspecified.

Middleton: The fan braces are glued while pressing into a 2.3m (7.6ft) radius dish with the peak of the radius centered 15mm to 25mm from the bridge going toward the soundhole. It is expected that there will be spring back of about one half which would result in an approximately 3.5mm dome (about 15ft radius).

Doubtfire: Dome location and method similar to Sloane and Cumpaino, with the fan braces being glued flat and the lower cross strut pre-curved by 2mm (10.8ft radius), additionally, the upper cross strut is curved slightly at 1mm (21.6ft radius).

Bogdanovich: 25ft radius dome with the apex centered in the lower bout. (The lower bout section is also tilted.) Braces are glued while being pressed and clamped against the dished workboard. He pre-shapes the gluing surfaces of the fan braces and cross struts prior to gluing.

Courtnall: Dome is created by pressing braces into a dished solera. Fan struts are left flat along their glue surface. The harmonic bars (cross struts) are pre-curved to match the shape of the solera dish prior to gluing. The solera dish is 2mm deep centered at the bridge and feathers into the soundhole area and toward the periphery of the lower bout. This works out to approximately a 17ft to 19ft radius depending on the where it feathers out.

I’m interested in hearing what folks here have found to be their most successful doming amount and location for the classical soundboard and method for creating the dome. Thanks for any feedback.

Joe

I am using a 25' dish in a solera with a raised lower bout. I also was under the impression that Cumpiano got a dome in his top by supporting the perimeter of the lower bout on a piece of 1/8 poster board or cork or something, then the fans were pressed in to create the dome, even though it wasn't supported by the solera, except at the edge. I could be wrong. I read the book, back in the 90's then again in 2006, but have not looked at it since. I have a bit of a preference for the overall method used in the Courtnall book, though it has many holes. The one thing you have to come to grips is that whatever you choose for your dome, you'll have to adjust your neck angle to adapt to the dome. Generally the apex of the dome is near the center of the lower bout, where the bridge attaches. In my case, and in Bogdanovich's case, there is a bit of drop off between the sound hole and the apex of the top, that is created by the raised lower bout. In that case, you pretty much have to do the math to make sure everything will fall in the right spot. As to which one makes the best guitar, it's hard to say. Hauser only used the bridge to pull his tops into a dome, otherwise he built pretty flat - maybe a slight curve i the TB below the sound hole. Lots of good guitars made in every possible way.

_________________
Waddy

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Sound Clips of most of my guitars

Thanks Waddy.

I had to go through Cumpiano a few times but I interpreted his use of the cork shim as being used to stabilize the edge of the soundboard during installation of the ribs while allowing clearance for the dome. His photo of the fan braces being glued show the soundboard lying flat against the workboard without the shim. In the online book update he says he has since dispensed with the workboard shim and hollowed out the workboard directly under where the arched lower transversal is expected. The hollowed section extends and is feathered up to the soundhole area and down towards the bridge location. So I guess if he uses the same procedure of gluing and clamping the fan braces against the workboard, the workboard now being dished, the fan braces would be sprung a bit in their upper sections.

Does the raised lower bout make fitting and attaching the ribs more difficult?

Joe

Joe,

Fitting the ribs for the tilted lower bout isn't too bad if you do it the way all of us followers of Jose Romanillos do it - keep the rib edge straight, and trim the top so that it fits within the bent ribs rather than having the ribs sit on the top. For me, that meant building the Bogdanovich forms (which just happened to be what I was reading at the time, and which goes down the route of having the tilted soundboard), and then cutting 2mm off the dished elevated addition to the form so that the sides would fit in and rest flat against the original flat surface of the solera, with the elevated dish then sitting inside the form. The top then fits inside the sides as well and rests fully on the form. This pretty much means that you have to use the individual dentallones to join the sides and top.
I would not want to have to fit the sides to the top the way Bogdanovich describes it.

The solera that Courtnall describes works perfectly well for a top that is flat around the perimeter and domed towards the center. I've built 3 Rodriguez copies and 2 Reyes copies using that approach. Works perfectly well. I would hate to slot a fretboard the way Courtnall describes - what was he thinking?

_________________
Jim Kirby
kirby@udel.edu

How much doming?, where? and how to achieve?

Just completed 2 classicals last week ('37 Hauser bracing) with Cumpiano, Courtnall, and Bogdanovich open and on the bench.....I went with Courtnall mostly....(my first foray into classical guitar building)...

How much doming?? a few mm's, where? mostly under the bridge. How? IIRC, I radiused the fans but not the closing bars..per Courtnall....?

Good luck and thanks to OLF classical builders for inspiration and advise......

Find a method you like and go for it....there's always the next one, and the next, etcetc...

Thanks Jim. Romanillos’ style is appealing; I’ll have to give it some thought. Does it require a mold or can the ribs be held in place using individual well-placed solera blocks?



Doug - Thanks for your input. You didn’t mention the amount of doming you used. Are you happy with the sound? If the two guitars were made following the same design, do they sound similar?

Joe

In my early days I used what you describe as the Doubtfire method ie. fans glued flat and the doming being created by the curve of the lower harmonic bar.
That was before I made a Solera. Presently I press form the struts - what is considered to be the traditional Spanish (or rather Torres) method. My dome is a touch over 2.5mm, centred around the bridge. Lower harmonic bar is curved, the upper bar is flat.
In his 'higher grade' guitars Torres used continuous kerfed linings, glued to the pre bent sides before he assembled the box. I use solid linings but the principle is the same: the seating edge of the sides and linings have to be shaped to fit the dome of the soundboard. That does make assembly a little more complex. Using individual blocks (Peones) is a little easier, although I find it somewhat tedious.
I don't use a mould (as such) but simply glue little tabs of spruce around the penciled outline on the soundboard.
As Waddy has already stated: many different methods. They can all be made to work.

Jim. The Courtnall method of fretting (IIRC) is used by the vast majority of Spanish Guitar makers. No big deal if you are accustomed to doing it that way.

A solera with blocks works equally well - check out Waddy's builds, which are well documented. (links in his sig above) I just decided to try a mold, for whatever (possibly misguided) reason

_________________
Jim Kirby
kirby@udel.edu

Sorry to disappoint Joe but there really is no unanimity on this question. Some are flat on the perimeter with a slight arch. Some are flat perimeter with a slight dome, some are highly domed with a 5mm "drop off" in the perimeter at the end of the guitar. Some are completely domed with sides profiled accordingly and I've recently seen some with the top domed away only on the treble side of the fretboard extension to improve access.
For many years I used the flat perimeter and arching method and then moved to the higher doming (with "drop off") after taking the Romanillos course several years ago. These approaches all can be made to work quite well though to take full advantage you should be adjusting the top thickness and bracing depending on which you choose.
Here is my Solera/form, You can see the pattern of the doming (roughly from the back sound hole edge to the butt of the guitar and the periphery "Drop off" extending from the beginning of the lower bout curve around to the butt. Radius in this area is about 25'.
BTW, I've now segmented the form so that the pieces can be adjusted.

I agree with David, at least on his comments in general. I choose, not saying it's right or wrong, to keep the outer perimeter of my lower bout flat, which imparts somewhat of a recurve in the top at the edges. I believe, but can't prove, that the added stress has a direct impact on responsiveness of the top, though I could easily be wrong. I was once before! As to the Solera, I use blocks and not a mold. Somewhere Filippo has pictures of his solera and blocks, and his is really nice. Mine looks like this. Here you can see the raised lower bout, and how the side fits the perimeter of the top.

Here is the solera. If you look close, you can see the level edges around the spruce, raised lower bout.

This was the solera, made from the Courtnall book, before I found out about the raised lower bout thing.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Joe- amount of doming? A few mm's (2.5-4??), per Courtnall....Solera is per Courtnall (don't recall exact numbers).

Happy with sound? Ecstatic!! harmonic resonance? on treble E sustains...like rubbing your fingers on a crystal glass rim...soundboard is crazy alive....

Guitars sound very similar....I do not plan to make any major bracing modifications if using same soundboard woods...linings are solid (paulownia).
Guitars woods are similar except necks (alder vs. walnut)...need more time to determine any noticeable tonal differences from necks, besides possible sustain...they're still breakin' in. Gimme a month....

Waddy - Good next to last picture! I was wondering about that. I have my elevated portion of the lower bout more or less radiused out to the edge, and was just wondering if I was going to be able to glue in blocks without compensating for the slight tilt (i.e., greater than 90 degree angle) at the top and side joint. Now I think I should sand a flat border around the lower bout to make sure that the 90 degree angle on the blocks actually fits right?

(Previous fiddling with the blocks and the sides and top in my form suggested that it wasn't enough of a difference to worry about?)

I am hoping to close up my first Romanillos style body this weekend. I've been away from actual construction too long - a year now.

_________________
Jim Kirby
kirby@udel.edu

David -

Looking at your solera and form, is your solera dished (domed) slightly close to the sound hole as well as being elevated in the lower bout?

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Jim Kirby
kirby@udel.edu

Yes. Scooped out a bit through the first layer of the birch ply as you can see just behind the sound hole area and then it transitions first to the single layer and then to the doubly built up area of mahogany around the lower bout.
The actual top profile of course becomes the positive shape created by the negative of the solera.

David
How are your braces fitted to the top ?
Pre-curved or bent to fit--like in a go bar deck ?
I use a solera very much like yours-the # 1 brace is almost flat
(need a bit of a dome to help with dry weather )
the # 2 has a 25' radius .
The fans-so to speak are glued on in the go bar deck(25') without
any pre- arching.
My sides have a flat heel to butt line .
The highest point of the top comes right under the bridge.
I believe after fixing& examining many classicals that this is the best place for that to be.
The bridge will pull the top up .
The area behind the bridge will lift more over time then the shape you build it in.
The radius and the brace shape will keep the area in front of the bridge
from caving in if done right.
But tone will not suffer ,but be better because of this
careful doming & bracing.



Mike

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Mike Collins

Thanks for that additional info David.

Here's my present example of the top-inside-the-ribs build, in (gasp!) WRC (sorry guys, customer request.)

_________________
Jim Kirby
kirby@udel.edu

Thanks everyone. The discussion and pictures are very helpful and very much appreciated.

Joe

Just keep in mind that how you set the doming, and how much of it you use, significantly affects you neck angle! Some minor adjustments can be made during setup of the saddle height, but not much. If your neck angle is out, everything is out.

For a top that is flat and all in the same plane: If your dome is higher, the forward neck angle will be low, if the dome is low, then the neck angle will be higher. I find, as a general rule of thumb, that if I add the dome and neck angle and the sum is 5mm, then I am in the right neighbourhood

If you build with the tail dropping as described above, then your bridge height and neck angle calculations will need to be adjusted. This style of build drops the bridge height while keeping the doming. Basically the whole domed area is tilted so that the area between the soundhole and the bridge is flattish and the are behind the bridge continues the dome.

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Expectation is the source of all misery; comparison the thief of joy.
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Thanks Douglas. I see that Courtnall uses a 2mm dish and 3mm neck drop in his solera design for a total of 5mm. It sounds like any spring back in the press-formed dome is expected to be negligible?



Ok, so if I understand correctly, tilting the lower bout in effect lowers the dome apex so a steeper neck angle is needed to compensate. What are the main benefits of a tilted lower bout? Does a steeper neck angle make the neck/body join trickier?

Joe

There are many ways to skin the cat. I also taper my fingerboards, and taper more on the bass side, so that brings the neck angle back down. When I made my Courtnall work board, I used his suggested neck angle and doming properties. Then when I made the lower bout adjustment for the Romanillos style build, I checked out all the variables, and realized with a tapered finger board (7 mm at nut to 4 mm at 19 on the bass side) that I would have to adjust the neck angle up(on the solera) and not down. Many ways to look at it, but you can't leave out details. I just added cork at the nut end and midway to the 12th at 1/2 the thickness. The biggest advantage of the tapered fingerboard is more level strings to the top, though it's still not a flat saddle.

The neck angle is pretty negligible at the join. Most don't allow for it, but just cut the slot at 90* to the plane of the neck, then let the sides adjust. It's not noticeable. However, there is no problem with making the adjustment in angle if you prefer.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

What Waddy said.

You would do well to spend a little time with some large paper and a sharp pencil drawing out the various options in profile. When you see it laid out graphically like that everything "clicks" and starts to make sense.

Once you've got a handle on the geometry, make some decisions about how you want to build your guitar and draw it out full size: include the dome, neck angle, fingerboard thickness, bridge/saddle heights, fret heights, and string clearances. Sounds like a lot, but its not really. And taking an eraser to a pencil line is a LOT less work that trying to re-work something that is not lining up right on the guitar build!

As long as your build is getting you close enough to refine things in the final setup you'll be OK, but you DO want to be close enough to do that.

_________________
Expectation is the source of all misery; comparison the thief of joy.
http://redrivercanoe.ca/