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 Post subject: Building a 12 string OM?
PostPosted: Sat May 14, 2016 4:20 pm 
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Cocobolo
Cocobolo
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Joined: Sat Aug 08, 2015 1:36 am
Posts: 351
Hi

Thinking ahead to next build and fancy a 12 string to keep for myself

After extensive Internet searches I can't find any plans for a 12 string OM size guitar which is the size I really like

Has anyone built any 12 strings and if so I would be very grateful for any info regarding bracing and design to help the guitar last under all that tension

I have plans for a 6 string OM, is it possible to use them and adapt the bracing?

Also would it be wise to use a shorter scale to reduce a bit of tension.

and any other tips please

Many thanks


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PostPosted: Sat May 14, 2016 8:47 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
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First name: Ed
Last Name: Bond
City: Nanaimo
Country: Canada
Focus: Build
Status: Professional
Yes, you can adapt a six string plan to accommodate a 12 string. The top and bracing will simply need to be about 60% stiffer (combined) than your usual 6 string that you build. This is fairly easy to accomplish if you collect data from your builds to use as reference points.



These users thanked the author meddlingfool for the post: cablepuller1 (Sun May 15, 2016 12:20 am)
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PostPosted: Sat May 14, 2016 8:48 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
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First name: Ed
Last Name: Bond
City: Nanaimo
Country: Canada
Focus: Build
Status: Professional
Oh, and yes a shorter scale can help a bit to keep the tension down, and can also help to 'warm up' a 12 string which can often be a bit bright...



These users thanked the author meddlingfool for the post: cablepuller1 (Sun May 15, 2016 12:20 am)
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PostPosted: Sun May 15, 2016 12:14 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Dec 14, 2007 3:21 pm
Posts: 3439
Location: Alexandria MN
A guy brought a Collings small bodied "0" sized 12 string into my shop last year. I made a tracing of it. It was super cool and sounded great.

http://www.collingsguitars.com/0-12string-series.html

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.



These users thanked the author Terence Kennedy for the post: cablepuller1 (Sun May 15, 2016 12:20 am)
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PostPosted: Sun May 15, 2016 1:13 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Thu Nov 04, 2010 1:46 pm
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First name: Freeman
Last Name: Keller
Focus: Build
Status: Amateur
Cable, building a 12 string involves answering a whole bunch of questions, starting with tuning and string gauges, scale length, body size and bracing, and a few minor dimensions (nut width, bridge spacing, pin hole layout......).

I own a very nice old Martin D12-28 and have built two others, including an OM sized short scale and a long scale ladder braced (Stella clone).

Image

I built the OM specifically because I wasn't satisfied with the balance on the dread - I am a finger style player and tune down a couple of steps - the dread was just too boomy. I spent quite a bit of time poking around in other 12's (Guilds, Taylors) before I build the OM - some of the design is based on my observations of these guitars. Here are the basic specs

I used a short Martin scale (24.9, in fact it is a Martin neck). If I was going to do it again I would go a little longer (25.4) because I do tune down to D using light gauge (0.010 - 0.042) strings. If you are going to tune to concert 24.9 should be fine.

Top is Sitka and is 0.125 thick (a little thicker than usual, Taylor does this). Bracing is 5/16 non scalloped with a third tone bar (again, Taylor uses three tone bars, my Martin dread is 5/16 but only two bars). Obviously a bigger bridge plate. The guitar is about 8 years old and the top has held up nicely. In contrast, my D12-28 is 35 years old and has developed a bit of a belly.

I did make the body a little bit deeper - that of course means that the guitar won't fit in a standard case and I had to have Cedar Creek make a custom case. Expensive and long delivery, the Stella needed one too.

I used a dovetail joint and the neck angle is fine, however I'm using bolt on necks on everything now (including the Stella clone) and would certainly do that on the next 12. I also used a Martin bridge with the octave pin holes closest to the saddle - you will find arguments for both configuration (note that Martin changed their minds with the Grand J-12 and put the primaries closest to the saddle). I used mini Grover tuners - they are fine but the big chrome washers that come with them are butt ugly (btw - I did make a drill jig for six tuners on a straight sided paddle head - if you want to use that shoot me a message).

Here are a couple more progress pictures

Image

Image

Image

Image

Am I happy with the guitar? Lets put it this way, the D12-28 almost never comes out of its case.



These users thanked the author Freeman for the post (total 2): Colin North (Mon May 16, 2016 7:36 am) • TimAllen (Mon May 16, 2016 12:12 am)
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PostPosted: Sun May 15, 2016 1:28 pm 
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Cocobolo
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Joined: Sat Aug 08, 2015 1:36 am
Posts: 351
Freeman wrote:
Cable, building a 12 string involves answering a whole bunch of questions, starting with tuning and string gauges, scale length, body size and bracing, and a few minor dimensions (nut width, bridge spacing, pin hole layout......).

I own a very nice old Martin D12-28 and have built two others, including an OM sized short scale and a long scale ladder braced (Stella clone).

Image

I built the OM specifically because I wasn't satisfied with the balance on the dread - I am a finger style player and tune down a couple of steps - the dread was just too boomy. I spent quite a bit of time poking around in other 12's (Guilds, Taylors) before I build the OM - some of the design is based on my observations of these guitars. Here are the basic specs

I used a short Martin scale (24.9, in fact it is a Martin neck). If I was going to do it again I would go a little longer (25.4) because I do tune down to D using light gauge (0.010 - 0.042) strings. If you are going to tune to concert 24.9 should be fine.

Top is Sitka and is 0.125 thick (a little thicker than usual, Taylor does this). Bracing is 5/16 non scalloped with a third tone bar (again, Taylor uses three tone bars, my Martin dread is 5/16 but only two bars). Obviously a bigger bridge plate. The guitar is about 8 years old and the top has held up nicely. In contrast, my D12-28 is 35 years old and has developed a bit of a belly.

I did make the body a little bit deeper - that of course means that the guitar won't fit in a standard case and I had to have Cedar Creek make a custom case. Expensive and long delivery, the Stella needed one too.

I used a dovetail joint and the neck angle is fine, however I'm using bolt on necks on everything now (including the Stella clone) and would certainly do that on the next 12. I also used a Martin bridge with the octave pin holes closest to the saddle - you will find arguments for both configuration (note that Martin changed their minds with the Grand J-12 and put the primaries closest to the saddle). I used mini Grover tuners - they are fine but the big chrome washers that come with them are butt ugly (btw - I did make a drill jig for six tuners on a straight sided paddle head - if you want to use that shoot me a message).

Here are a couple more progress pictures

Image

Image

Image

Image

Am I happy with the guitar? Lets put it this way, the D12-28 almost never comes out of its case.

Freeman

Thankyou.. the info is great and you can't beat advice from someone who's been there and done it

I'm a few months of starting anything yet so have lots to think about
Freeman wrote:
Cable, building a 12 string involves answering a whole bunch of questions, starting with tuning and string gauges, scale length, body size and bracing, and a few minor dimensions (nut width, bridge spacing, pin hole layout......).

I own a very nice old Martin D12-28 and have built two others, including an OM sized short scale and a long scale ladder braced (Stella clone).

Image

I built the OM specifically because I wasn't satisfied with the balance on the dread - I am a finger style player and tune down a couple of steps - the dread was just too boomy. I spent quite a bit of time poking around in other 12's (Guilds, Taylors) before I build the OM - some of the design is based on my observations of these guitars. Here are the basic specs

I used a short Martin scale (24.9, in fact it is a Martin neck). If I was going to do it again I would go a little longer (25.4) because I do tune down to D using light gauge (0.010 - 0.042) strings. If you are going to tune to concert 24.9 should be fine.

Top is Sitka and is 0.125 thick (a little thicker than usual, Taylor does this). Bracing is 5/16 non scalloped with a third tone bar (again, Taylor uses three tone bars, my Martin dread is 5/16 but only two bars). Obviously a bigger bridge plate. The guitar is about 8 years old and the top has held up nicely. In contrast, my D12-28 is 35 years old and has developed a bit of a belly.

I did make the body a little bit deeper - that of course means that the guitar won't fit in a standard case and I had to have Cedar Creek make a custom case. Expensive and long delivery, the Stella needed one too.

I used a dovetail joint and the neck angle is fine, however I'm using bolt on necks on everything now (including the Stella clone) and would certainly do that on the next 12. I also used a Martin bridge with the octave pin holes closest to the saddle - you will find arguments for both configuration (note that Martin changed their minds with the Grand J-12 and put the primaries closest to the saddle). I used mini Grover tuners - they are fine but the big chrome washers that come with them are butt ugly (btw - I did make a drill jig for six tuners on a straight sided paddle head - if you want to use that shoot me a message).

Here are a couple more progress pictures

Image

Image

Image

Image

Am I happy with the guitar? Lets put it this way, the D12-28 almost never comes out of its case.


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