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Here's a basic question: Given that the top on a classical guitar is domed just like the top on a steel string guitar, why is it that the neck angles up relative to the body?

Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

S classical top isn not domed anywher near like a steel string. It is typically domed only in the lower belly of the lower bout from about the bridge to near th tail block and the string tension is far less so it has far less pull on that area.

Try this:
Make a side view drawing of a guitar body, with a bridge on it. Make a side view drawing of the neck with the strings, and print it out on a transparency. Now, pin the end of the strings to the top of the saddle, and play around a bit with the neck angle. What you'll find is that you can tip the neck up as far as you like, but you can only tip it back a little before the top of the fingerboard touches the top at the edge. Note that in general this has nothing whatever to do with how much or where the top is domed so long as you're not trying for a particular 'overstand'( distance of the figerboard off the top). Obviously, as you tip the neck upward, you'll end up with more overstand, and most likely have to fill in some space between the fingerboard extension and the top.

The up angle of classical guitar necks is probably one of those traditional things. Early guitars wre made like lutes, with the fingerboard surface being an extension of the flat surface of the top. When they started adding a thick fingerboard on top of the neck it made the bridge too tall, so they tipped the nut end of the neck up, rotating the whole thing around the 12th fret, to get the saddle back down.

This poses a problem: with the neck already angled up, it is all that much more likely to pull up under tension over time. Since the tradtional Spanish construction has the neck and heel block integral you can't just pul the neck and reset it when the action gets too high. One solution is simply to use a really thick fingerboard, and plane some off at the nut end when it's too much of a problem to play easily any more. The thicker fingerboard, of course, would tend to make the saddle higher off the top, so you need to tilt the neck up a bit more. And so it goes.

.....or, simply build the top as a dome, just like a modern SS guitar, and make the neck angle DOWN a little.

Dave F.

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Cambrian Guitars

"There goes Mister Tic-Tac out the back with some bric-brac from the knick-knack rack"

It might not be as easy as that, as the action on a classical is so much higher than a steel string. String height at bridge is in the 12 mm range, and you don't want it getting too close at the sound hole, which is where all the finger action takes place. If you use a full dome, you'll get closer at the sound hole. I even have a bit of a problem with that in the design I have been building. I can be 11 or 12 at the bridge, but only be about 10 at the sound hole, the way the lower bout falls away from the waist.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I tend to keep the neck angle on the same plane as the top and use a thicker fret board that I taper down to the last fret. I taper a bit more on the bass side. I built a few bolt on classical guitars that had an up angle but I think I am going to start building with the Spanish heal again. As was mentioned before if you use a thicker fret board then 40-50 years down the road when I am dead and gone some luthier can set the neck back with a refret. Depends on the customer too. I had one customer that wanted a nylon guitar with a thin neck both in width (like a steel string) and thickness with low action so I built that one up more like a steel string guitar. But typically I set Nylon action high, 5/32nds over the 12th fret on the base side.

This is more interesting than I anticipated.

Sorry Alan, but I don't fully understand your first paragraph:



When you say: "...touches the top at the edge.", edge of what? And when you say: "...distance of the fingerboard off the top", do you mean the whole fingerboard extension over the body or are you talking about the maximum distance if the extension is at an angle to the body? Sorry to be slow on the uptake here.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Interestingly, Richard Brune' told me that the modern set up of the classical guitar is strictly a 20th century development which arose from the desire of players for more volume and a clean tone with agressive playing.
Many 19th century Spanish guitars, especially those of the tablao style (a heavily arched type used in Flamenco cafes) had a zero neck angle and were played with the resultant low action.

Pat Hawley wrote:
"Sorry Alan, but I don't fully understand your first paragraph"

Hmm; it's hard to think of another way to say it, and I have not yet been successful at posting graphics on this list.

We're trying to get two things to come out right here: the strings have to be a certain distance above the neck to be playable, and the saddle can't be too high or too low off the top. So it's useful to think of the neck with the strings on it as one system, and the body and bridge as another. Of course, we know that the strings have to be stretched between two fixed points, but we can suspend disbelief for a few moments by making a drawing of each system, the neck with the strings floating above it, and the body with the bridge in place. Then you pin the two drawings together at the top of the saddle so that the strings are properly 'stretched' between that and the nut.

Now you can pivot the neck-and-string drawing around the point that represents the top of the saddle. Note that, no matter what angle the 'neck' makes with the 'body', the action height and saddle height off the top are 'correct'.You could even make the strings pull straight up on the top, and things will still be where they 'should' be for playability, as long as the top holds up. OTOH, you'll quickly find that there's only so far you can tip the neck back before the fingerboard, and even the strings, hit the edge of the top. There is a wide range of workable up angles, but not much leeway in terms of back angle. It really all becomes quite clear if you make the drawings.