estebanana -> RE: Next 19th c. Spirit guitar (Sep. 19 2023 7:29:42)
Custom making another plantilla on late 19th c. lines. A bit wider than the Calle’ model. I can’t even say how happy I am to be getting these requests.
Wow such an interesting question. The Occam’s razor answer is fast: my customer wanted a smaller body than a normal guitar. ( normal: lower bout width of 14 to 14-1/4”) . But the customer wanted to work in metric units, so he told me the small Calle’ model I make was too narrow in the lower bout, and the full size guitar was too big. He gave me the Goldilocks Dimensions, 340mm lower bout width.
I worked with those dimensions and that he wants a 630mm scale length. First I drew a center line down the paper and use my collection of plantilla templates to rough in a guitar that would fit those dimensions. At the same time I was thinking a lot about the bridge and the bracing, but that’s a separate issue.
First I try to make a beautiful outline, then I try to get the upper bout large enough to get as much air volume in the body as I can for a small guitar. After I have a rough plantilla drawn in I erase and redraw until all the lines feel blended and flowing. I like certain things, a feeling of uplift, a narrow waist, slightly flat bottom… it’s a thing you do by eye after lots of looking at many guitars.
Once I got the plantilla looking correct to my eye, I thought about how it would work with the bridge design I will use. Once that’s drawn in I decided on the bracing based on recent patterns I’ve been using and have a feel for.
At this point I start thinking about aiming at F# for a main air resonance ( lots of controversial stuff and infinitesimal details can be said about resonance modes most of which I don’t think about. I think there’s something to the saying ‘analysis paralysis’ ) I think for these smaller lighter Spanish style guitars making them with thin plates and ribs is important to keep the air resonance low. Even my small Calle’ models have surprisingly low main air resonance for their size.
Ok why is that important? It’s important because you don’t want the main air resonance to match any open string or couple that resonance between the back and top. This produces real resonances that beat together, but do not decay at the same rate. All that is bad news. I don’t worry too much about it. It becomes more critical when making more modern style guitars with thicker backs and ribs and lots of top bracing.
I think about the bridge first, the plantilla width and shape, the placement of the sound hole and the scale length. Once all that sifts into place, the transverse braces above and below the sound hole find their places by virtue of being near the sound hole. Then after all that I think about a brace pattern. Most people design around a brace pattern and the other elements fit in to the top bracing scheme, I feel that is backwards and counter intuitive. Probably a result of so many makers simply copying store bought plans without making the model themselves over the years by trial and error.
People say they want to build a certain brace pattern by a certain maker, but probably that maker arrived at the brace pattern by setting up a whole bunch of other ideas first. At least that’s how I see it.
Does that answer anything?
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