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I'm going to do my first ever slotted headstock. My solid peg heads are 15 degrees and I know some use a smaller angle than that even on those. With the slotted peg head, it seems the string break angle would be greater because the strings wind below the face plane of the head.
What's your preferred angle?

I use 10 degrees for my slotted headstock and 14 for my standard solid headstocks.

Josh

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Josh House

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due to the lower tension of nylon or perhaps gut, i would think a greater break angle would be in order, but you didn't specify. just speculation. wish i had a way to measure my nylon "collection" at the moment.

I'm so sorry….I'm making a slotted head acoustic! Forgot to mention that important fact:) Thanks for the replies.

I am using 7.5 degrees on my current classicals, which gives a string break angle of ~10 degrees. Plenty.

Pics here.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Just to clarify, I believe Beth is asking about steel string slotted headstocks as opposed to classical. Is that corect Beth? I think that is what you were trying to get at with your last post.

Josh

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Josh House

Canadian Luthier Supply
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House Guitars - Custom Built Acoustic Instruments.
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That's correct, Josh. I forgot that important detail in my OP:)

The point is, if 10 degree break angle works on a classical, it will work on a steel string, too, because the higher string tension on a steel string results in a greater seating force of the string in the nut slot.

Apologies if that wasn't obvious.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

If the results I got on looking at bridge break angle hold for the nut (and I don't see why they would not) even ten degrees of break is probably more than you 'need'. Here's one way to think about it...

If you are trying to get the most possible sound out of a string, the way to do it is to push the string down as far as you can and release it so that it's traveling exactly 'vertically' with respect to the soundboard plane. This is because the 'transverse' string force is the most powerful signal the string makes, and driving the top 'vertically', so that it acts like a loudspeaker cone, is the most efficient way for it to produce sound. Naturally, there is a limit to how far you can push the string down; once it touches the fingerboard you're done.

If you look at the string in the 'time domain', that is, track the shape of the string over time, you'll find that the 'kink' you made at the spot where you pushed it down runs out toward the ends of the string at a certain speed, which is the bending wave velocity of that string. After a certain time had had been a triangle shape just before you released it is truncated: the point is chopped off and there's a flat there. The string goes from having two straight sections joined at the kink to three straight sections, joined at two kinks. The initial angles at the ends remain unchanged: no information about the bending of the string can travel up it faster than the speed of the bending wave, so the ends of the string take a little while to find out that you've let it go.

When the kink reaches the nut it reflects back down the string. The small 'down' angle of the string at the nut (remember, you pushed it down) is replaced by an 'up' angle. If there has been no loss of energy from the string, the 'up' angle at the nut will be the same as the original 'down' angle the string made at the bridge. So long as that angle does not exceed the break angle, the string will remain in contact at the nut

So how much of a 'down' angle can you put on the string? Well, that depends on how far you push it down, and how close to the bridge you are. If your action is 1/8" at the 12th fret, then you will bottom out on the frets if you push the string down by 1/4" at the bridge. As you move out away from the bridge it gets easier to push the string down by any given amount, and you bottom out with a smaller deflection. I found that, for me, deflecting the string downward by more than about five degrees when I pluck it is a lot of work, and unlikely to happen in real life. YMMV

That being the case, a five degree break angle at either end ought to suffice. In my bridge break angle experiments I used a minimum of six degrees, and that seemed to be just enough: it's possible that the string did hop off the saddle top at the initial pluck, but it was hard to see of hear any evidence of that.

I hope this makes sense: there are animations on line showing the way a string moves, and you can look it up in a number of texts, such as Fletcher and Rossing's 'Physics of Musical Instrumets', or (of course) the Gore/Gilet books. This says nothing about the need for slots in the nut to keep the string from moving sideways under pushes from the left hand, of course. It's interesting to note that Benedetto, in his book on archtop making, uses a six degree break over the bridge top, iirc.

Back to the Bat Cave Robin.

Thanks, Alan! I'm happy to say that I followed almost all of that. I got the basics and appreciate the information, Alan! I'd like to see a guitar with a 6 degree, because I wonder if it would look unusual, being so much straighter than what I'm accustomed to seeing on a steel string. I'll probably close in on 10 degrees, but now I won't worry if my actual angle comes in a little lower than that (I'll be free-handing this one through the bandsaw because I haven't made a 10 degree cutting jig like the one I have for 15 degrees (and might not if my free handing skills are improved over the past few years).

Thanks to all, Beth

you may be able to "get away with" super shallow headstock angles, but i think there is a reason why guitars through the past few centuries are steeper than 6 degrees. some people play aggressively; if you snap an open string(by pulling up with the strumming hand) there is a risk of the string coming out of the nut slot if the break angle is insufficient. also, the risk of rattling at the nut is increased the shallower the angle is
with a 3x3 tuner arrangement, of course the D and G strings will have the shallowest angle, so they will be the strings to worry most about

Ny, I agree with that. I don't need to push the envelope, and it sounds like 10 degrees will be a nice compromise between the super shallow and the more acute of the typical solid peg head.

Not 6 degrees but 7.5. Likely as close as you're going to see (without checking out Leo's work).

Classical, but you can see how the strings "dive" as they head for the rollers. Steel string rollers are typically smaller diameter, so you'll get even more "dive". There's probably just enough length of straight lines showing to put a protractor on. For more pics, follow the link in my previous post.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

As with so many things on the guitar, there's a balancing act going on. More break angle gives you some insurance against the problems that nyazzip points out, but at the cost of greater friction through the nut slots. This can exacerbate any tendencies for the strings to 'grab' in the slots, and make tuning more difficult. Polishing the slots (I use rottenstone and a wet piece of cotton string) helps there, but you have to be careful to not round over the slots at the fretboard end, which causes buzzing. There's no free lunch.

Martin uses 15 degrees for both slotted and solid headstocks. Works for me.

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John

...which just goes to show that you can use more head angle than you need. Look at lutes!

Some Baroque Guitars used as little as 10 degrees. Effectively less because the strings were wound on friction Pegs, above the surface of head plate.
Providing you have half depth of the string in the Nut slot, it works.

The minimum I've used is on my Strat. No string trees, no problems.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I wonder; does the angle of the headstock relate to the scale length? Would a very short scale [classical] guitar benefit from an increased angle?

I'm sure one could run a spurious correlation:

Fender, not much angle, 25.5" scale

Martin, 15 degrees, 25.4", 24.9" scale

Gibson, 18 degrees, 24.75 scale

Lutes, ~80 degrees, 23" scale (to suit the purpose!!)

To answer your question: No
To ask a question: What prompted you to ask?

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Like the inlay on that Arnold.

Thanks, Trevor, I just wanted to be sure that I wasn't missing a trick on my current build. I shan't be cutting the neck for a week or two so I'm trying to get all my questions in early! I thought maybe a greater angle would make up in some way for a lower tension... I'm still trying to process an awful lot of the information I've read about guitars so I need a bit of clarification here and there! I just can't wait to get my hands on your book, I'm like Johnny 5 in Short Circuit: "Need [guitar] input!"

The tension on the string is a function of the string itself (material, diameter), the length, and the pitch. Any two steel high E strings .012" in diameter at pitch will have the same tension at a given scale length. That's physics.

This gets confused when people mix up 'compliance' (how easy it is to fret the string: low effort = high compliance) and 'tension' (the actual load on the string). A lot of players simply call them both 'tension', but they're different things. For example, one of those high E strings would be much harder to fret if it was twice as far off the fretboard, even though it's no 'tighter'. Strings made of stiffer material are often perceived as 'tighter' at a given tension. I'm not sure if anybody has sorted out all of the variables there. Aside from action height, it's likely that relief affects compliance. Back string length can be a factor: if the tuners are a long way from the nut, and the strings slide easily in the slots, it probably reduces the change in tension as you push the strings down, and increases the perceived compliance. Some people argue that 'soft' terminations; a flexible top or neck, make a difference. Break angle at the bridge and nut are also thought by some to be important, with more break angle seen as making it harder to fret the strings. A lot of this is stuff that could be resolved by some experiments, although you can't always count on people to believe data either.

I suppose it depends on who the data is from! I'm happy to take your word on it!

I suppose I have been conflating tension and compliance. My aim is obviously to make this guitar as easy to play as possible. I'll be giving her the lowest action I can. The headstock is going to be as small as I can get away with, still yet to plan it exactly but I'm ordering single tuners so as to set them closer to each other. I guess that means I won't have the long back string length to give extra compliance.

I've chosen extra hard tension strings because I though standards would be too loose at this scale, even up at open G. Maybe I need to re-investigate that. DennisK very kindly tested a classical capoed at about 480mm and then tuned to E for me... Maybe I'll have to ask if he can do the same up to open G and see if the strings are still floppy [I don't own a classical - not made one before]. That should be a decent indication, shouldn't it? (I need to choose strings ASAP so I can make the dummy neck)

I did find on my last guitar that the saddle break angle affected compliance. And relief. I'm slowly experiencing first hand all these things I've read about!