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What are the considerations in making a 12 string & joining the neck at the 12th fret? What scale. I want to use a
000 B/S I have
MM

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Mike McNerney

Lots of variables there.

For a 12 fret join, it's the same as for 6 string, make sure the braces are in the right spot.

For a 12 string, it's the same as for a 6 string, make sure your top/bracing combo is stiff enough to handle the tension increase.

You can do many different scales. I've come to prefer 25", as it's just a little easier to play and mellows out the 'jangle' a bit.

Mike, do you have an "under the lid" pic of the last 6 string soundboard you braced?

Also, do you plan to sell the 12 string when you're done, or keep it for yourself?

Nigel
www.nkforsterguitars.com

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nigel

http://www.theluthierblog.com

I can see the sense of a shorter scale length for a 12 string, to reduce the string tension a bit.

Super long scale (26.5) small body (000) 12 fret ladder braced 12 string. Strung with cables and tuned to C or C#. Monster



Same guitar on the right with a D12-28 (24.9 scale) and an OM sized 12 string (25.4 scale). The OM is tuned to D, I've always been sorry I didn't make it a 12 fretter



Edit to add - whatever size and scale you decide on, make sure it fits in a standard case. I've had to order two custom cases for odd ball 12 strings, the red lined one above for example

this is for myself. I don't really understand if I join at the 12th fret does the sound hole move too along with the bracing of course, and what scale would I use. I have a pic of the 000 bracing but I don't know how to reduce the file in order to include. it's a completely normal one however.

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Mike McNerney

Keep in mind that most guitar tops are actually stronger than they need to be. What limits how thin and light you can make them is not strength but stiffness: tops might fold up but they seldom break from string tension if they're well made. Stiffness in the top or a brace goes as the cube of the thickness/depth. Making the top 25% thicker, and the bracing 25% taller, makes the whole structure almost twice as stiff, but only adds about 25% to the weight (you need a bigger bridge and bridge plate, so that adds some weight). With something like twice the tension and only 25% more mass, you can really make some noise. The first 12-string guitar I made after I realized that was an absolute cannon, and it has held up fine.

The sound hole moves down a little. You want to have 19 frets, so the top of the hole has to be a couple of (short) frets further down from the edge to allow for that. Making the upper bout longer than you would on a 14-fret will help keep the hole in the proper location, slightly above the waist.

The thing that limits the scale length on a 12 is the octave G string; if it's too tight you tend to break too many. Piano tuner's have a rule of thumb that strings ought to be at about 75% of their theoretical breaking stress. This allows for things like wrapping the string around the tuner shaft, and still keeps the tension up enough to give good tone and intonation. Iirc, at a 25.4" scale length the octave G will be at something like 85%T; high enough that you're going to be replacing them more frequently than you might like. Going to something like 24.9" helps there, and also helps move the hole back up if you don't want to lengthen the upper bout.

Other things to consider in designing your 12 string:
Be very careful in planning the shape and layout of the headstock. Traditional layouts like Martin or Guild have the strings really crowded up together and tending to run into each other. Obviously it is possible to get it right, but it is easy to stuff it up. If you look at the shape used by Seagull, or even (aghast) Ovation you can see that they are a lot more sensible. OK - I know people often want traditional, not sensible, but it is something to be aware of. For the same reason I would avoid a slotted headstock on a 12er. But if I could make one like Freeman's long-scale Stella I might reconsider that rule (nice one Freeman).

You might also think about the option of using a 6-pin bridge (2 strings per hole). I haven't done it myself but have seen a number of examples of this and it allows a smaller bridge and bridge plate, less clutter, fewer holes drilled through to weaken the top, and it looks cool (but non-traditional!)

" I want to use a
000 B/S I have"

If you use the plan for the 12 fret OOO you won't have to make too many changes. The position of the soundhole, bridge, and braces will work out fine. I think the longer body also improves the sound.
I've build long scale (25.4) guitars with a high G tuning and haven't had problems with the strings breaking. But I use a tuner and just bring them up to pitch - breaking pitch seems to be right around A above high G.

I've seen the 6 pin bridge, is it as simple as it looks 2 strings in 1 hole?

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Mike McNerney

"I've seen the 6 pin bridge, is it as simple as it looks 2 strings in 1 hole?"

I've used 2 strings in one hole bridges for some double strung tenors. The holes need to have string slots splayed out similar to what is done on 2 hole\4 slot violin tailpieces but not as pronounced slots. Also use unslotted pins.

Some considerations

- before you start think about how you will tune the guitar and play it, what sound you are looking for, what string gauges and tensions you will be working with, what you like and don't like about other 12 strings

- most 12 strings are designed for string tensions of, say 200 to 250 pounds - thats about 150 percent of a sixer, not double. Your choice of tuning and strings will help you pick a scale length that will work.

- since many players like to down tune a couple of semitones consider longer scales to keep the tension a bit higher. If I down tune too much with 12 guage "light" strings (often 10's) it can get kind of muddy sounding

- a 12 fret 12 string is just like a 6 string, the scale length locates the bridge which locates the arms of the X. Sound hole is kind of dictated by the X and the end of the fretboard. Bracing needs to account for the 150% tension - maybe a slightly thicker top, slightly wider or taller braces, not scalloped or minimum scalloping. Twelve strings often have three tone bars and a bigger bridge plate. Don't get too carried away, my D12-28 has the same 5/16 unscalloped braces as some D28's.

- six pin bridges are fine, a bit of a hassle if you break just one string. Remember that the balls have to sit neatly on the b/p and apply some side pressure to the pin, just like a six string. You will want to ramp and slot the bridge. I've built with 12 pin bridges - then you have the decision of which strings to put "forward". Again, there will be some ramping to keep one string from running into another pin head. Look at existing guitars for ideas

- consider a wider than normal saddle - at least 1/8 - to give enough material to compensate each string of each course

- get your tuners and think about the head. Mini tuners work fine (but don't use those butt ugly big washers like my OM). Frankly, if I was building a 12 fretter I would make it a slothead just 'cause they are so cool. Make a good drilling jig for whatever tuners you use

- if you decide to build a stupid long scale guitar with a tail piece make sure you can buy standard string that are long enough. I literally do not cut anything off the 6th and 7th strings on the Stella clone

This is handy - the 12 string stuff is at the bottom

https://www.tapatalk.com/groups/theunof ... pFU2aNIi1s

Michael - I was asking the two questions for a reason. It would be handy to see how heavily you braced your last 6 string. Some people are over bracing their guitar tops. Folk then "beef up" the bracing for a 12 string when actually there may be no need at all.

If you're making a vintage style 12 string, yes a slot head looks good. But they are a pain when it comes to changing strings. 12 times. For a more modern guitar with a normal head, I'd suggest either Hipshot open gear tuners or the smaller Gotoh 510s.

Yes, make sure the guitar will fit in a case. So draw it out. If there is space, consider a 14 fret. They are easier to sell if the time ever comes.

If it is your first build, or you're on a budget, you can buy decent ready made 12 string bridges on eBay. They are usually beefy enough for you to reshape them into something a little more individual. I would also recommend routing a 5mm wide saddle in the bridge for better intonation.

Bracing - just draw out your own pattern based on the one you have. Don't worry too much about moving a brace a few mm one way or the other. It's common for even experienced makers to obsess over this sort of thing, but it's remarkable how little difference it makes. Over bracing will make a far bigger difference. Making the top too thick or too thin will make a far bigger difference than opening or closing the X brace a little or shifting a brace 5mm.

If you're making a more traditional guitar, I'd highly reccomend Hans's book.

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nigel

http://www.theluthierblog.com

Mike- Here's my post of a 12-string triple-O that I built with a 24.9" scale. Maybe this will help in thinking about your design.

viewtopic.php?f=10101&t=48565

Haans has built many Stella 12's - Leadbelly and Barbecue Bob. In his book he says he makes the tops .16", and he also installs a doubler between the X and the UTB - about .06 if I recall - and a couple of small braces there too.

Ed

Ed, most folks here don't want to build a Stella type 12 string because they don't like the "jangly" sound, don't want the long scale, don't understand the heavy strings and don't want to tune down to B or A.
I would say that .16" won't work for the instruments they want to build either.
They would rather build a rosewood, resonant, ringy, light gage, tuned to pitch Martin style instrument with the X brace type sound.

Here's one I made a few years ago. 12 fret neck on a small jumbo body, 380mm / 15" wide so a similar size to an OM. The last 12 string I'd made was about 40 years before so I was really starting from scratch. I wanted 12 frets and also went for a slightly short scale, 635mm / 25". I generally beefed things up compared with what I normally do, 3mm (0.12") spruce front, X-Brace from 18x7mm (0.7x0.3"). I slightly closed the X and moved it a bit away from the soundhole so as to get the right relationship between the arms of the X and the bridge. The little braces just south of the soundhole and behind the bridge plate are additional to my usual bracing as is the reinforcement over the join.

I thought the bridge position looked slightly odd on the body shape but otherwise was pleased with how it turned out. It seems to me there are two ways of looking at a 12. Either go large - and I've done one of those since, a long scale monster - or go with the naturally jangly sound of the octave stringing. This one was the latter as you'd expect with a smaller body, I thought it worked out very well and it's gone to a happy owner.

When I made this one I took note of a very helpful piece Alan Carruth posted on MIMF some years ago. Thank you very much for spreading the knowledge!

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"There is hope in honest error .... ". Charles Rennie Mackintosh.
http://www.ianchisholm.co.uk

Here are 3 twelves showing 3 different scales: L/R, 23", 25.34" and 26.5". All have Heavy strings, but the strings vary to keep tensions quite similar across each set.



While I do love the Stella on the right for it's huge sound, my favorite is the Prairie State 23". It has a very big sound for such a compact instrument. Box is 16" at the lower bout, and 17" long. Strings are .070"-.012" and is tuned to B.
Here is the laminated X/ladder bracing for it:



Back is white oak, and peghead sports special Stay-Tites with mandolin plates. Note how compact the peghead is for the size of the instrument.



Here's the front, back and a close-up of the top.







The important part of building a 12 string is getting the tensions right across the strings. You can almost expect to be changing out individual strings till you get it right for the tuning you want to be in.
Just shows you that anything is possible...