Classical Guitar Top Questions

[Diane Kauffmds]

I have a couple of questions about classical guitar tops.

1. I've noticed several plans where there are no bridge plates. Are they not necessary? Would think that a plan with 7 fan braces would give sufficient support for a typical tie-on bridge, but is it better to have a thin bridge plate, or does it really matter?

2. Is there a reason why most classical bridges are made of rosewood instead of ebony? Is there a tonal reason for this?

Thanks

[johnnparchem]

I have a couple of questions about classical guitar tops.

1. I've noticed several plans where there are no bridge plates. Are they not necessary? Would think that a plan with 7 fan braces would give sufficient support for a typical tie-on bridge, but is it better to have a thin bridge plate, or does it really matter?

2. Is there a reason why most classical bridges are made of rosewood instead of ebony? Is there a tonal reason for this?

Thanks

1. The arguments go both ways for a bridge plate or not. Most respected Classical guitar builders do put in a bridge plate, usually spruce as there is no need for a hardwood plate. I use a thin bridge plate.

2. There is not as much energy in nylon strings so the mass of the top is very important to the performance of a classical guitar. On a classical guitar it is easy to get bass but the trebles are often weak. Ebony is a lot denser than RW and the difference in mass makes a difference. It will lower the resonance of the top and attenuate the trebles.

[Diane Kauffmds]

Thank you John. I need to replace a top, so I'll use a spruce plate and IRW bridge.

[Danl8]

Until John mentioned plates in his post above, I didn't even know they weren't exclusive to steel string guitars. I would argue that a bridge plate is useless on a spruce top and possibly useful on cedar. The early makers (Torres et al.) didn't use plates. They also used gut strings. I guess with the advent of 26+" mensur, high-tension strings, maybe there is a place for plates. I've thought about doing a Bouchet-like lateral brace, but probably will never experiment with that either.

[Diane Kauffmds]

Well, I this is my idea of a classical top. I replaced the top on a guitar left to me by my husband's late daughter a few years ago, before I built any guitars. But, it vibrated 2 notes at once if not fretted precisely on a fret. I never found the cause.

So, I'm replacing the top again. It's nice engelmann. I don't have any plans, so I studied bracing patterns I saw on the internet and chose the traditional Torres fan with 7 braces.

I thinned the top to .110, but with further sanding, it is .085-.090" thick. The soundhole reinforcement is about 1mm thick. The bridge plate is 1/4" wider and longer than the bridge, but is only 1.5mm thick. It's also made of engelmann, cut crossgrain to the top.

All of the bracing, except the transverse braces are 1/4" wide and about 7mm high. I may have over done the transverse braces, but they looked substantial to me in photos. Both are 1/2" and right now 5/8" high. I'll take a lot off when I peak them, leaving height, but taking a lot of bulk.

Comments are welcome.

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[Danl8]

Looks perfect to me.

The trans braces on the top are exactly right. IMHO, I would shape but not lower. I am currently following a measured drawing of a 1923 Domingo Esteso. He used 5/16" x 0.5" transverse and 1/4" w x 1/8" tall fan bracing. His top thickness finished at 0.09" to 0.078" tapering towards the edge. BTW on the back, braces ranged from 0.5" to 0.75" tall (center of middle where the arch was biggest).

[Diane Kauffmds]

Sounds like I need to decrease the height of my fan braces. Otherwise, I'm okay. I've already shaped the transverse without decreasing the height.

[Danl8]

Sounds like I need to decrease the height of my fan braces. Otherwise, I'm okay. I've already shaped the transverse without decreasing the height.

I should add that on the Esteso (and many others) the fan braces have a 'tent or roof' shape, peak in center with angled sides that go down about half the distance from the top of the fan brace.

[Diane Kauffmds]

Sounds like I need to decrease the height of my fan braces. Otherwise, I'm okay. I've already shaped the transverse without decreasing the height.

I should add that on the Esteso (and many others) the fan braces have a 'tent or roof' shape, peak in center with angled sides that go down about half the distance from the top of the fan brace.

I understand. I made this shape on all of them after I decreased the height. I installed the top and binding. I'm in the process of fp.

Thanks for your input. It helped a lot!

[Diane Kauffmds]

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