Ok, let's talk about design aspects. If you find something that I write here that is in error, or needs more thought, please don't hesitate to comment. I really know nothing.
The first is how does a guitar even work. It has the same basic range as a cello, yet it has much smaller belly and back plate area; it has shorter strings; it is no wheres near as thick in the ribs, so the internal volume seems like it is less than half of a cello. How does it give any sound at all?
When I read that a cello has the same range as a guitar I was surprised. It sounds MUCH deeper than a guitar. The guitar is written on the G clef, but it sounds an octave lower. It doesn't really sound an octave lower, does it? A low E on a clarinet (which is actually, low D) doesn't sound almost an octave higher than a low E on a guitar, does it? It does, but it doesn't seem like it. At least not acoustically. With amps, yes. Even when a cello is played high up on the fingerboard by the body, it has a much lower sound than something that I imagine coming from the seventh fret of a guitar.
Volume wise, the cello drowns out an acoustic guitar. It isn't even close. I found that a cello can play at from 85-111 decibels. A guitar will top out at 80. Top out. The strings on a cello have about a 27 5/32" scale. About what a baritone guitar would be. Since a baritone goes down to B or C, that makes sense. The 4 strings on a cello give 120 to 130 pounds or so of pressure combined. The high bridge on a cello translates more of that tension to the belly. Using 125 as an average, and a 153 degree string angle, 58 pounds goes to the belly, leaving 67 pounds to be counteracted by the with the grain strength of the spruce top and the neck. Many of the arch tops I've looked at, (On line, I've never actually even LOOKED at an archtop in person, let alone held one) have a shorter 25 inch scale. Why? I don't know. The six strings have a wider range of tension; maybe 160-190 pounds. Let's call it 175. The angle I have drawn up for the archtop is 175 degrees. That gives us 46 pounds on the bridge, and 129 pounds pulling on the top and the neck. So the guitar has almost twice as much tension pulling on the neck. No wonder they want truss rods. But notice that the pressure going on the body is about 20% less than what is on the cello body. But also remember that the guitar does not have a soundest to help hold up that pressure. Does that mean that the guitar belly actually has to hold more? How much more? 50% or so?
Now consider the body size. A cello is about the same width, but it is much longer. Deflecting it at the bridge seems like it would be easier. The smaller body of a guitar would make it inherently stiffer. The cello has very deep sides. That gives it a huge volume, and that is where it's deeper voice comes from. I can't find anywhere what the A0, or the breathing mode of the cello is. For an acoustic guitar I found that it can be from 80 to 150 or so. Steel strings at the lower numbers. Classicals were higher. Anyway, the guitar low E might, or might not have any support from the body itself. The main difference is that the guitar is strummed or plucked, and the cello is usually bowed. The cello gets continual energy from the bow, and the guitar has to save the string energy, and effectively transmit it to the body. The body of a guitar seems like it needs to be extremely resonant. At the same time it has to be quite strong.
As far as to the tuning, free plate tuning, combined with weight, seems like it just gets you close to some general stiffness guide. I usually get the inside finished, and then get the outside close, and tune it after it is glued to the ribs. I noticed very little mention of actual notes in doing a lot of web surfing. But what I did find seems to be that the guitar plates are done pretty much the same as a cello. To me, that seem like they would have to be thinner. Wouldn't they? We'll find out. For a picture today I give you a Guadagnini guitar. It's labeled an Anacleto Guitar. What does that mean? He was the grandson of probably the third most famous violin maker G.B. Guadagnini. I will make this guitar as if G.B. was around, and saw what the boy was doing, and put his take on it. I'm still leaning toward the baroque neck joint at the headstock. Should be fun.
I plan on using the parallel bracing design. That should work for the lengthwise string tension. Cross arching, combined with the cross catenary curves on the inside should give the cross arch stiffness. That will be the next post.
When I read that a cello has the same range as a guitar I was surprised. It sounds MUCH deeper than a guitar. The guitar is written on the G clef, but it sounds an octave lower. It doesn't really sound an octave lower, does it? A low E on a clarinet (which is actually, low D) doesn't sound almost an octave higher than a low E on a guitar, does it? It does, but it doesn't seem like it. At least not acoustically. With amps, yes. Even when a cello is played high up on the fingerboard by the body, it has a much lower sound than something that I imagine coming from the seventh fret of a guitar.
Volume wise, the cello drowns out an acoustic guitar. It isn't even close. I found that a cello can play at from 85-111 decibels. A guitar will top out at 80. Top out. The strings on a cello have about a 27 5/32" scale. About what a baritone guitar would be. Since a baritone goes down to B or C, that makes sense. The 4 strings on a cello give 120 to 130 pounds or so of pressure combined. The high bridge on a cello translates more of that tension to the belly. Using 125 as an average, and a 153 degree string angle, 58 pounds goes to the belly, leaving 67 pounds to be counteracted by the with the grain strength of the spruce top and the neck. Many of the arch tops I've looked at, (On line, I've never actually even LOOKED at an archtop in person, let alone held one) have a shorter 25 inch scale. Why? I don't know. The six strings have a wider range of tension; maybe 160-190 pounds. Let's call it 175. The angle I have drawn up for the archtop is 175 degrees. That gives us 46 pounds on the bridge, and 129 pounds pulling on the top and the neck. So the guitar has almost twice as much tension pulling on the neck. No wonder they want truss rods. But notice that the pressure going on the body is about 20% less than what is on the cello body. But also remember that the guitar does not have a soundest to help hold up that pressure. Does that mean that the guitar belly actually has to hold more? How much more? 50% or so?
Now consider the body size. A cello is about the same width, but it is much longer. Deflecting it at the bridge seems like it would be easier. The smaller body of a guitar would make it inherently stiffer. The cello has very deep sides. That gives it a huge volume, and that is where it's deeper voice comes from. I can't find anywhere what the A0, or the breathing mode of the cello is. For an acoustic guitar I found that it can be from 80 to 150 or so. Steel strings at the lower numbers. Classicals were higher. Anyway, the guitar low E might, or might not have any support from the body itself. The main difference is that the guitar is strummed or plucked, and the cello is usually bowed. The cello gets continual energy from the bow, and the guitar has to save the string energy, and effectively transmit it to the body. The body of a guitar seems like it needs to be extremely resonant. At the same time it has to be quite strong.
As far as to the tuning, free plate tuning, combined with weight, seems like it just gets you close to some general stiffness guide. I usually get the inside finished, and then get the outside close, and tune it after it is glued to the ribs. I noticed very little mention of actual notes in doing a lot of web surfing. But what I did find seems to be that the guitar plates are done pretty much the same as a cello. To me, that seem like they would have to be thinner. Wouldn't they? We'll find out. For a picture today I give you a Guadagnini guitar. It's labeled an Anacleto Guitar. What does that mean? He was the grandson of probably the third most famous violin maker G.B. Guadagnini. I will make this guitar as if G.B. was around, and saw what the boy was doing, and put his take on it. I'm still leaning toward the baroque neck joint at the headstock. Should be fun.
I plan on using the parallel bracing design. That should work for the lengthwise string tension. Cross arching, combined with the cross catenary curves on the inside should give the cross arch stiffness. That will be the next post.
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