Yr 12 major project (12 string flattop acoustic)

[Noah Trickett]

So, to cut a long story short, I've been making my first ever guitar, and i'm stoked to have gotten as far as i have.
It's all completed up to attaching the bridge.
My question is pretty straightforward i hope

I know there is going to be a very large amount of pressure on the bridge, trying to tear it off and up towards the neck due to being a 12 string, but if i put 6 of the strings into it as normal with pins, and the other 6 (say every second string) through a trapeze tail peice, will that even out some of the pressure? i know it will still have the same bending pressure on the neck? but the bridge coming off is what i'm most worried about......and i figured it will at least halve (or maybe more due to the downward force through the tailpeice) the pressure on the bridge.......or am i completely wrong? hahahahaha this is just an experiment, and if it works i'll be very happy. i thought i should ask some 'old hands' as it were before i do it

cheers i hope it wasn't too hard to understand :/

P.S i'm not ridiculously worried about intonation and a 'perfect' sound, as this is just a first go. so a working guitar option is fine

[Rodger Knox]

There is quite a bit of stress on a 12 string bridge, and the strength of the joint depends on how much gluing area there is. Most 12 strings with pinned bridges have larger bridges. So, if your bridge is a little larger than a 6 string, you're probably OK, provided you are able to fit the bridge to the top and get a good glue joint. How large is your bridge?
I've never seen a 12 with 6 pinned and 6 in a trapeze, but the idea will work. It could be a bit tricky to get enough breakover angle to the tailpiece without getting too much to the pins. I suspect it would sound different, but different isn't always bad.

[Mark Swanson]

I'd be worried about the break angle too. Since this is your first guitar, why make it harder? By doing that type of bridge, you'd be making a lot of extra work and fuss, and the chances are 50/50 that you will not get it right. So my advice is just to do it one way or the other, and be safe about it. Just glue the bridge on, if you do it well you won't have a problem. remember the KISS principle!

[Freeman Keller]

I have built two twelve strings and own(ed) a few more. One of them was a pinned bridge, one a tailpiece guitar (it was also ladder braced in the style of the old Stellas). Some comments:

1- Depending on how you string and tune it, a 12 normally has about 50 precent more tension on the top (225-260 pounds) than a sixer (165-185) - not twice as much. With commercial 12 strings you will see everything from no changes in top or bracing (Martin) to thicker top plates, heavier braces and possibly the addition of a third tone bar (Taylors). Other than a larger bridge and bridgeplate my D12-28 has exactly the same bracing as an unscalloped 5/16 D28. Most of these guitars have pretty standard dovetail or bolt on necks (Guilds have two truss rods but that doesn't change the neck joint.

2 - When I built my pinned bridge OM sized 12 I made the top slightly thicker than standard, used unscalloped 5/16 adi braces and added a third tone bar. I typically string it with mediums (12's) and tune down two semi tones. It is loud, balanced finger style guitar and has suffered no problems in 5 years.

3 - Tailpieces are ideal for non X braced guitars like the old Stellas because they do not rotate the top. The do have a different sound - Todd Cambio who builds both style says they are less complex sounding. You need to notch the saddle like an archtop to set string spacing. A true 12 string tail piece (12 slots) is available from National Resophonic - but for your idea you could use a standard six string one. The one in the picture below is long scale, strung with 13's and tuned to C. It is common for them to go even lower with heavier strings.

4 - Your idea will work but I think it would be a real hassle to set up, get the intonation correct, set the break angle so that one set of strings does't over power the others - I would seriously recommend one or the other (pinned bridge with lights tuned down or a tailpiece for all 12 strings). The easiest thing would be to start with a tailpiece (it will mount with the strap pin hole) and see if you like the sound. If not, you can add one set of pins (I would recommend the primaries), see if you like that, then drill the other set if you don't.

Good luck, post some pictures, here are my three

[Noah Trickett]

Unfortunately i probably wont have time to try out the tail piece and then the pinned bridge :/ As it is due soon but from what you're all saying it would seem that if i do glue it properly it should hold. Contrary to all the stories on the internet i've been reading about 12 string bridges :/ haha Lucky i asked the people who have made them before. I'll try the 'normal' pinned bridge

Thank you very much I'll try to upload some pictures when it's done

[Rodger Knox]

Freeman's photo shows the difference in size between a "regular" bridge (on the right with the tailpiece) and a 12 string bridge (the other 2).
It needs to be a little wider to make room for the pins anyway. By the way, I've got a '67 Gibson B-25 12 that had been converted from a pinned bridge to a trapeze tailpiece when I got it. I converted it back about 10 years ago and it's been fine. I do keep it tuned down two halfsteps to D.

[Ron Belanger]

I'm with Freeman, I would recommend using a pin bridge only or a tail piece only. On my 12s, I've built 2, I thin the tops to almost the same deflection I use for my 6 strings. My X brace and tone bars are maybe 1/16 in. taller and about 1/2 the taper I normally use. Of course I use a larger bridge plate and bridge. I use Larivee style bracing and add an extra brace just below the bridge plate

[Freeman Keller]

Here is a closer view of the bridge and tailpiece on my Stella clone



Note that the break angle is very shallow, that is one thing that makes the heavy strings work (the tension is all anchored to the end block). Remember that if you do a tailpiece guitar you set the string spacing with grooves in the saddle just like an archtop. That makes it tricky to intonate each string but it can be done.

If you do a standard pinned bridge you need to make the belly part deep enough for the staggered rows of pin holes (however there are a few old 12's out there that have both strings under one pin). There is a debate among 12 string players whether to put the primaries or octaves closest to the saddle. The space of the course is set by the pin locations, however you can tweak that by ramping the pin holes. Here is the pinned bridge



If you do a combination of pin and tailpiece you will have grooves for one of the strings, probably not for the pinned one. That will make them different height at the strumming location. The will also have radically different break angles - I'm going to think that the ones going to the tailpiece will have much less drive to the top.

Yes, 12 string bridges do lift, but as I said in my first post, lots of them are built too lightly in that area and lots of people tune them too high. Do a good glue job, slot and ramp your pin holes, use moderation with your strings and tunings and you'll be alright.

[Freeman Keller]

There is an article in the latest Fretboard Journal about David Crosby, and he discusses the D18 that he converted to a 12 string. He even did a little "scalloping" with a pop bottle and some sandpaper. It has two strings under on pin, basically D18 bracing (Crosby says that lightly braced guitars sound much better) and was the basis for the signature model that Martin built.

[Tim Allen]

I would agree that using either a regular glued bridge or a floating bridge with a tailpiece makes the most sense, and add that a properly glued bridge should hold 12 strings just fine. That said, in Volume I of Dan Teeter's "The Acoustic Guitar," a well-known 1970's book on repairs, he discusses his use of a 6-string tailpiece and a 6-string bridge on Mexican 12-string guitars. In those days, we used to see Mexican-made steel string guitars with classical style fan bracing. It was bad enough with 6-strings; 12-strings really pulled themselves apart. Teeter writes: "The six and six arrangement relieves the rotational stress and the combination gives the guitar the sweetest harpsichord-like sound." So, the idea has been thought of before, and apparently works. Presumably, though, you're not dealing with a weak brace arrangement.

[Noah Trickett]

Soooo.....after all this time i'm finally done and marked! and i couldn't post pictures before now because it would be publishing images which is against the rules. But now i can! So here's the results. Bear in mind, i do realise there are many many things that could have been better, and would have been done much differently by a luthier, but for a first guitar, it plays, and sounds ok (intonation an incy bit sharp) so done with no afore knowledge, and just the opinions of my woodwork teacher, here it is. Feedback is appreciated

[Freeman Keller]

Looks darn good to me - would love to see a few more pictures, including any of the bracing. Scale length, materials, finish, how are you stringing and tuning it? I think you can be very proud.