Converting 14 fret plans to 12 fret?

[Gingerninja]

Hello all
Having built dreds and OMs I am now looking at a 00. I would like to build a 12th fret body join rather than the 14th fret on my plans. I am looking for some advice on what changes need to be made to the plans, so far I have considered:

1) Moving the sound hole further back
2) Moving the x brace back the same amount as the sound hole and increasing the angle of the x brace a very small amount and therefore adjusting the braces accordingly
3) The length of the neck will obviously need to change!

Are there any other factors I need to consider? Will the thickness of the neck at the 1st and 9th fret be the same as a 14 fret? Will the fretboard have the same dimensions?
Thank you in advance for any responses
Alan

[Rudy4]

You'll find that most plans also show a significant differance in body length between 12 and 14 fret versions. When I was working up a new design the general information I could find stated that simply re-locating braces and physical placement if components could be a bit of a dice roll as to what results would be.

Can you not find a "standard" 12 fret 00 or similar to work with?

Here's my recent small body that's in between an 0 and an 00 with a slightly shortened scale length, including the full plan if it helps you make any choices. It's a 14 fret slot head all mahogany and it's proved to be a great little guitar.

https://www.acousticguitarforum.com/...d.php?t=579732

[phavriluk]

Depends what kind of 12-fret guitar OP intends to build.

One kind of 12-fret redesign stretches the upper bout 'north' so the body extends to the 12th fret. Guitar total length doesn't change. Bridge position and soundhole don't move.

Another 12-fret concept moves the fingerboard 'south' so as to join the body at the 12th fret, requiring relocation of the bridge, bracing and soundhole. Gjuitar gets shorter by however much length is associated with the shorter neck losing two frets. Not unknown for that variety to lose the 20th fret. The soundhole location and bracing location and angles all change. The bridge plate, too, is on the move.

[Gingerninja]

Originally Posted by Rudy4

You'll find that most plans also show a significant differance in body length between 12 and 14 fret versions. When I was working up a new design the general information I could find stated that simply re-locating braces and physical placement if components could be a bit of a dice roll as to what results would be.

Can you not find a "standard" 12 fret 00 or similar to work with?

Here's my recent small body that's in between an 0 and an 00 with a slightly shortened scale length, including the full plan if it helps you make any choices. It's a 14 fret slot head all mahogany and it's proved to be a great little guitar.

https://www.acousticguitarforum.com/...d.php?t=579732

That's fantastic thank you. If I hadn't made the template and most of the mould I would have used your plans. You are right I could buy some 12 fret plans but they don't look much different from the plans I have so it seems a bit of waste, or it might be that i'm being a bit tight. I have downloaded your plans, which look really good, and will cross reference against what I'm doing, very helpful thank you!

[Gingerninja]

Originally Posted by phavriluk

Depends what kind of 12-fret guitar OP intends to build.

One kind of 12-fret redesign stretches the upper bout 'north' so the body extends to the 12th fret. Guitar total length doesn't change. Bridge position and soundhole don't move.

Another 12-fret concept moves the fingerboard 'south' so as to join the body at the 12th fret, requiring relocation of the bridge, bracing and soundhole. Gjuitar gets shorter by however much length is associated with the shorter neck losing two frets. Not unknown for that variety to lose the 20th fret. The soundhole location and bracing location and angles all change. The bridge plate, too, is on the move.

thank you for the reply. I'm looking at the second concept as i'm not too keen on the way the elongated upper bout looks, just my preference. I have moved the bridge plate too and was considering possibly losing a fret. I have gone for a shorter scale 629mm (24.75 inch) and think it will still be fine with 20 frets though, but either way isn't a problem, I may just have to change the order in which I normally build though.

[Rudy4]

Just to throw another thought out, you could also consider a 13 fret "Nick Lucas" style guitar...

[John Arnold]

I measure the neck thickness at the 8th fret on 12 fret necks. The width can be anything, though the original Martin 12 fret dimensions were 1 7/8 nut, and 2 5/16 at the 12th (either 2 5/16 or 2 3/8 bridge spacing).
Martin's intent with most of the original designs was to have the X braces intersect the lower corners of the bridge. This includes all 12 fret models and 14 fret models with forward bracing. The X angle is usually around 98 degrees.
I would shift the soundhole less than the bridge, resulting in a 19 fret fingerboard. I just like the aesthetics of that proportion on 12 fret guitars.

[Gingerninja]

Thanks John, really useful information.

[phavriluk]

I wound up applying John Arnold's dimensional adjustments on my own in the past - - - drawing the guitar out on paper and fiddling with the fretboard and soundhole. Same results, they look natural to me. Fretboard (19 frets) stops at the top of the soundhole, more or less. Bracing angles fiddled, too (wound up with 98 degrees) to get the braces to complement the bridge and bridgeplate. Nice to see my messing around confirmed by an expert.

[Howard Klepper]

If you have access to back issues of American Lutherie (the GAL publication), I wrote a short article on how to position the X brace in Issue#126 (Summer 2016) that you might find useful. It's in the "Questions" section.

[Gingerninja]

Originally Posted by John Arnold

I measure the neck thickness at the 8th fret on 12 fret necks. The width can be anything, though the original Martin 12 fret dimensions were 1 7/8 nut, and 2 5/16 at the 12th (either 2 5/16 or 2 3/8 bridge spacing).
Martin's intent with most of the original designs was to have the X braces intersect the lower corners of the bridge. This includes all 12 fret models and 14 fret models with forward bracing. The X angle is usually around 98 degrees.
I would shift the soundhole less than the bridge, resulting in a 19 fret fingerboard. I just like the aesthetics of that proportion on 12 fret guitars.

Compared this against my modified plans and I’m happy with what I’ve produced. I think my x brace angle is 97 degrees rather than 98 but that’s fine. My building skills aren’t advanced enough to be that accurate anyway!

[Gingerninja]

Originally Posted by Howard Klepper

If you have access to back issues of American Lutherie (the GAL publication), I wrote a short article on how to position the X brace in Issue#126 (Summer 2016) that you might find useful. It's in the "Questions" section.

I haven’t got access unfortunately but I’ve had a good look at the website and it does seem a great resource so currently thinking of joining.