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Assessing Classical Neck
I think I understand steel string guitars enough that I'm a little confused by what I'm seeing on a '70s Conn Classical C-300 with what I believe is my new favorite neck joint (pics are of another, not mine).
Action is 4.5mm E and 3.5mm on e, which is a bit high even for a classical, but there's enough saddle left to be able to restore 4mm and 3mm pretty easily, but that's not how I do things (though I should). In checking things out, I found a straightedge laid on the frets hit below the bridge top (at least 1/16"). I then realized that the fretboard was not in a plane - the 12th fret is a rocking point - pressure toward the headstock and the straightedge is raised off of the soundboard frets, and vice versa. Using the straightedge on the soundboard frets (meaning, the straightedge is not touching frets 1-11) and the straightedge hits farther down the front of the bridge (maybe 1/4" total). I also used a notched straightedge (slots for frets so the straightedge lays on the fretboard, not the frets), and the neck was dead flat (no relief) from frets 1-12, but then was up in the air above frets 13-16 (not touching) due to the 12th fret rocking point. No truss rod on this guitar. What do you think is going on with this guitar's body and/or neck that provides a rocking point at the 12th fret, with a flat neck from 1-12? If the guitar was folding up, I'd think the fretboard wouldn't be flat from 1-12 - it'd have a bit of a curve. If the body was folding up (neck stays straight), then I'd think the soundboard frets/board would be pushed up to complete the curve as the soundhole folded in on itself. I should note the guitar plays and appears fine - no bulges or raised areas, belly is nice and flat. Of course I'll likely reduce the saddle to lower the action a bit, saving the reset for later, but I'm curious if anyone can shed light on that I'm seeing. |
#2
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Some people and majority of manufacturers, put the frets into the fretboard whilst its not attached to the neck.
Once you attach the fretboard to the neck, the fretboard sits up in the air over the body, traditionally a clamp is used to pull it down and clamp to the body, we call this in the bizz as fallaway. Classical necks join the body at the 12th fret as well rather than acoustics which are traditionally 14th, hence the hump happens at the 12th, I personally fit a fretboard to the completed neck body join, then level it again and then fret up, gives a perfectly straight neck. Steve
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE |
#3
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You say "once you attach the [pre-fretted] fretboard to the neck, the fretboard sits up in the air over the body" - why is that necessarily so just because the board was fretted before being glued to the neck? If the fretted board is glued to the neck (and the extension is then glued to the soundboard) after the neck is assembled to the body, why doesn't the fretboard run in a flat plane, assuming the neck angle is correct? I'm afraid I'm just not seeing why/how the pre-fretting makes the difference, but I'd like to understand, so thanks for your patience. In thinking more about it, inserting the frets first to an unmounted board would seem to create a backwards bow, as the fretboard was forced into a gradual reverse curve by the frets' insertion. Forcing that now-curved board to be flat again for the glue process to the neck would seem to apply some backwards pressure on both the neck and the soundboard, but is that potentially enough force to result in creating the rocking point at the 12th? I wouldn't think so, given the stoutness of the neck, but I suppose it's possible. In the meantime, I'll read up on fallaway. Thanks Steve |
#4
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The top of a guitar is basically a flat surface, the neck is set into the body at an angle to allow the strings to rise up to the bridge and saddle.
The fretboard continues along the same plane as the neck, then is pulled down to contact the body When a non fretted board is fitted to the neck and body, it is then planed flat and fretted afterwards, so fallaway does not exist On a well fretted board, no backbow is introduced from the fretting process, the tang hooks barely add any compression, for compression fretting, we will use say a 24 thou wide tang into a 23 thou wide slot, which will induce backbow.
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE Last edited by mirwa; 04-23-2018 at 07:30 AM. |
#5
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I'm not quite sure what you are describing but the way I build them, the neck actually has forward angle. The straight edge along the frets on my guitars comes probably about 1/16th below the bridge as well. 4.5mm certainly is high action though.
How thick is the bridge? |
#6
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But, assuming the final neck plane is perfect without tension, isn't it unavoidable that a strung-to-tension neck will have a slight forward bow, thereby eliminating the usefulness of using a straightedge to assess neck angle, since it won't lie flat? |
#7
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As you point out, the "traditional" - as opposed to the modern "cross-over" - classical guitar is not simply a steel string guitar with nylon strings on it. Traditional classical guitars aim for about 11 mm vertical string height from the top to the bottom of the strings at the bridge. This is achieved, traditionally, by having a less than 180 degree neck angle - call it "forward" or "negative" - as opposed to typical steel string construction that achieves its 1/2" or so string height at the bridge by having a greater than 180 degree neck angle.
Likely, what you are describing - two planes in the fingerboard - is as Steve described, fallaway. On more expensive instruments, the much greater amplitude of the nylon strings was dealt with in a few different ways, one of which was to contour the playing surface of the fingerboard from nut to sound hole, so that the fingerboard was not "straight", particularly on the bass side. |
#8
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Doesn't sound like it.
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Last edited by charles Tauber; 04-23-2018 at 08:25 AM. |
#9
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Start with a quarter sawn block of wood for a neck 2 inches wide by 1 inch thick, put some strings on it and no way in the world is it going to move from the tension of the strings, now start shaping it into a neck, as we remove wood for comfort we also remove strength to combat strings, at one point the remaining wood is not strong enough anymore, so now we fit a truss rod or compression fret. Bowing of the neck is subjective to wood grain, wood type, neck profile, fret fitment style, fretboard material, trussrod etc etc etc. Steve
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Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE |
#10
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E String is 1/2" (12.7mm) off top Exposed Saddle measures 1/8 in middle 5/32 on E and 7/64 on e. I think there's enough room for me to take 1mm off to reduce the action to something more acceptable, say, 4mm E and 3mm e (which I understand are pretty typical measurements for this type of guitar). Do you set yours up lower than that? If so, to what? Does your straightedge run along a flat/consistent plane? Or on one of the slopes of a fallaway? If the latter, which slope gives you the 1/16" mark? |
#11
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I'm very surprised at this guitar's sound - very rich bass and clear/distinct trebles all in one box. Very light construction means you feel every note. Probably doesn't sound that great as you move up the board, especially with the current intonation compromise (hight action), but to my rookie ear, it's enjoyable. |
#12
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I've jsut not experienced that and in fact as you get closser to the saddle frettign notes up higher on the neck the angle the string makes from the fretted note to the saddle is greater which means you are less likely to get buzz anyway/ So I just don't really 'get' the concept of fall away. I like to see a straight shot from the nut to the end of the fretboard, relief notwithstanding. Personally I like my classical guitars set up with what I call concert action, 5/32 under the low-E down to 4/32 under the high. It produces the loudest and clearest notes and that's the way I like it. A lot of players however are willing to give up clarity and power for ease of play. So it's purely a matter of choice. Your bridge thickness sounds about right. It also sounds like you have some room to play. If the saddle is out 1/8th in the middle then you should have plenty of room. I'm guessing your fretboard is arched but that doesn't matter even at the ends you have room. |
#13
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I also don't seem to have the neck joint I showed in the pics above. Mine's a higher end model and it appears to use some form of modified Spanish Heel joint. Mine does not have the heel bolt, or the full block under the fretboard extension for that sliding dovetail joint shown. But, neither does mine have the full "U" of the typical Spanish Heel. Instead, mine has a half-a-"U" from under the extension to the back, where it stops. Any idea what kind of joint that might be? If it helps, mine's supposed to be a copy of a "Jose Ramirez 1A". |
#14
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That is the traditional "Spanish heel" arrangement. There are lots of variations including dovetail and mortise and tenon arrangements that use a similar shaped interior block. I use the "U" shaped block with a dovetail joint. I used to use a Spanish heel/non-joint arrangement with both classical and steel string guitars. I don't anymore. I see no advantage to it - unless one is building entirely with hand tools - and some disadvantages.
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#15
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