Neck relief on an 8 string classical.

Discussion of all aspects of multi-string guitars, namely those with 7 or more strings.
johnparchem
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Neck relief on an 8 string classical.

Post by johnparchem » Fri Aug 28, 2015 11:53 pm

I have been working on an 8 string that I retopped. After it was all put together I noticed that I was buzzing on the 6th string fretted on the third or forth string when plucked hard. I have the action at the 12 fret set to 3.5 mm. No problem open or at the first fret. I spent some time getting rid of the buzz but noticed there was a whole lot of relief on bass strings. I pulled the frets and found that while the first 5 strings were close to where I would have them around .2 mm, the bass strings were close to .5 mm of relief at the 5th fret. When leveling the fret board it is really easy to see that the relief was carved in as I can see a dish.

So two questions, could the excess relief been causing the buzz? and What would be a good relief for the 7th and 8th string, strung to a A and a D? I decided to quit sanding until I had a better idea of where to go with this.

Thanks

Jeff Highland
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Re: Neck relief on an 8 string classical.

Post by Jeff Highland » Sat Aug 29, 2015 10:08 am

John,
A typical scenario if a guitar has excess relief, is that the saddle will then have been lowered to achieve a desired 12th fret string clearance.
The nut and lower frets play clearly because the frets in front of them are falling away, but once you get past the point of maximum relief, you are climbing out of a hole.
Like you I would be looking for around 0.2mm under string tension for good clarity and playability over the whole fretboard.
Guitar building and repair at Caves Beach, Australia

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Tuomas Kourula
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Re: Neck relief on an 8 string classical.

Post by Tuomas Kourula » Sun Sep 06, 2015 4:46 pm

Hi John! I've built an 8-string guitar, and although I can't give you an exact measurement for the relief, I can say that the thick & heavy low A and D strings definitely need more relief than the normal bass strings of a 6 string guitar.

Of course it all depends on how hard you play, but I find that 3.5mm at the 12th fret is pretty low action even for a normal 6 string.
of the guitar, by the guitar, for the guitar

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mikfik
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Re: Neck relief on an 8 string classical.

Post by mikfik » Mon Oct 10, 2016 3:43 am

Neck relief is a subject that few people really understand. In order for it to work correctly (allow extra room for vibrating string to travel) the relief would have its largest dip at the 12th fret. This is where the plucked string follows the largest arc. Since our guitar's neck joins the body at or about the 12th fret this is not practical. As long as the neck has NO backbow, the only thing relief gives us is higher action around the 6th fret (where the dip is greatest). Try playing a guitar with action set to 3mm and a dead straight neck and you'll understand what I mean. With a straight neck the guitar feels wonderful and intonation improves because the distance the string travels when fretted is constant and linear all the way up the fretboard.

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Steve Ganz
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Re: Neck relief on an 8 string classical.

Post by Steve Ganz » Mon Oct 10, 2016 5:21 am

johnparchem wrote:I have been working on an 8 string that I retopped. After it was all put together I noticed that I was buzzing on the 6th string fretted on the third or forth string when plucked hard. I<snip>s
(Italics are mine)

I don't understand what you wrote. Do you mean: You were buzzing on the 6th string fretted at 3rd or 4rd fret (not string?)

If that is what you meant, this may be relevant.
I've built several 8 strings. In my experience no more relief is required for the 6th string.
Steve

johnparchem
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Location: Seattle, Washington

Re: Neck relief on an 8 string classical.

Post by johnparchem » Fri Oct 28, 2016 1:28 pm

Steve Ganz wrote:
johnparchem wrote:I have been working on an 8 string that I retopped. After it was all put together I noticed that I was buzzing on the 6th string fretted on the third or forth string when plucked hard. I<snip>s
(Italics are mine)

I don't understand what you wrote. Do you mean: You were buzzing on the 6th string fretted at 3rd or 4rd fret (not string?)

If that is what you meant, this may be relevant.
I've built several 8 strings. In my experience no more relief is required for the 6th string.
Yes I did mean fret. Ultimately I pulled the frets on this guitar, leveled the fret board and refretted. All of the buzz went away. The pull of the strings provided enough relief to play buzz free.

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Steve Ganz
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Re: Neck relief on an 8 string classical.

Post by Steve Ganz » Fri Oct 28, 2016 6:28 pm

John, thanks for closing the loop and confirming.
Steve

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