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How to calculate fret positions

I hope I am posting in the appropriate place, I am in the process of building a 3 String cbg and I Want to fret the neck. I have seen necks with 14 frets which should be what I will need. It will be tuned GDG, and I want it for slide, with some 3.string chords as well which is why I want to have frets. I have the wood for the neck, which is oak 2x1 inches and 36 inches in length. I am fitting a brass nut which I will make.
So what I would like to know is as its only 14 Frets, do I have to shorten the neck, and also how to calculate the fret positions. I am planning to fit a hard tail adjustable bridge.

I was an engineer by trade, and now retired, and this will be my first build, I would be so grateful for any help and advice in this regard.

Thanks In Advance

Phil Hale

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Permalink Reply by Michael Fred Johnson on March 9, 2016 at 9:54am

I wonder how on earth did luthiers manage before the advent of online calculators and computer print outs

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Permalink Reply by Tom T on March 9, 2016 at 10:01am

A lot of slide guitars?

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Permalink Reply by Lane Martin on March 9, 2016 at 10:07am

Templates. Lots of templates.

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Permalink Reply by Moritz Voegeli on March 9, 2016 at 10:13am

... constructing the fret layout with compass and ruler as described on this forum... another approach were instruments like viols and ouds, fretted by means of movable wrapped-around and tied-on gut frets, positioned by ear.

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Permalink Reply by JL on March 7, 2016 at 3:09am

Since you are an engineer, I'll tell you that fret layout is an inverse power series with a ratio of the 12th root of 2.

I do my own fret calculator with a spreadsheet

scale / ((2^(1/12))^Fn)

where Fn is the Fret Number, 0=nut, 1=first fret, 2 = second fret, 3 = 3rd fret, etc. this gives the pre-compensated bridge to fret lengths.

scale - (scale / ((2^(1/12))^Fn)) if you prefer to put the 0 end of the stick at the nut instead of the bridge.

I do my layouts in centimeters because I have not yet found an SAE ruler with decimal inches.

fret calculations are based on idealized strings, just like the law of gasses are based on idealized gas. since real world strings have actual physical properties, the bridge saddles get adjusted away from the nut to compensate for that, giving the bridge a slant where bigger strings are compensated more than thinner strings.

on my spreadsheet I put the scale in A0 and in all the formulas I put $A$0 instead of 'scale' so that I can recalculate the whole set at once. that makes it easy to put the 0 mark of the ruler on the box about where I want the bridge and play with the numbers to see where the nut, 12th, and 17th frets end up.

I try to do at least 17 frets, to allow 1st position fingering an octave higher.

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Permalink Reply by Philip Hale on March 7, 2016 at 3:39am

Thank for your response.

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Permalink Reply by Eric Davis on March 8, 2016 at 12:16am

There are several fret calculators online, which you should be able to find via Google. Personally, I use WFret. WFret is a free program that can be used to calculate fret positions and also print a template. I don't remember where I found the download, but again, a Google search should find it for you.

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Permalink Reply by Philip Hale on March 8, 2016 at 4:12am

Yes wayfinder I like the look of this myself, but please tell me, as my printer is only A4 how does it cope.

Take Care And Thanks In Advance
Phil

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Permalink Reply by Lane Martin on March 9, 2016 at 4:35am

Fretfind2d (http://www.ekips.org/tools/guitar/fretfind2d/) lets you save a pdf in A4 size instead of letter (8.5" x 11").

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Permalink Reply by Philip Hale on March 8, 2016 at 4:17am

Yes thanks for this Eric, I managed to get it loaded, but just a quick query, as to how my A4 printer will cope with the length.
Thanks for the info on wfret.

Regards Phil

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Permalink Reply by Eric Davis on March 8, 2016 at 4:52am

Philip, When the template is printed, the frets are divided into two parts (on my printer). You simply cut out the template and attach the two halves with tape, or just align the second half to the last fret of the first half when marking the fret positions on your fret board. When I mark the fret positions on my fret board, I use the first half of the print, then line up the first fret of the second half with the last marked fret from the first half.

Also, you might want to print the template and print the chart, then check the fret lines on the template using the the measurements on the chart.

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Permalink Reply by Philip Hale on March 8, 2016 at 5:32am

Thanks for that Eric sounds good.
Just got to decide on the best width for the neck of the 3 string
bearing in mind the strength. Will probably post and ask.
Thanks again and best wishes.
Phil