Twelve String Plan

[ozziebluesman]

Hello to you all,

I have had a request to build a small bodied twelve string guitar. A 24.9 inch short scale with a lower bout about 15 inch has been mentioned.

Does anyone know of a commercial plan available or have any of you forum members built something similar and can give me a few tips please?

Thank you

Alan

[kiwigeo]

My dreadie 12 string was basically based on a vanilla 6 string dreadie with addition of an extra tone bar across the lower bout and 12 pin bridge. Nothing much else was different from the 12 string.

Craig will no doubt chime in and talk you into doing a 6 pin bridge.

[Shane Woonton]

I'm finishing just such a beast. I've used my own plan drawn originally from the dimensions of a Santa Cruz "H" model. If memory serves me correctly it's 14 5/8" across the lower bout. I've gone with 25.5" scale and will be using a 6-pin bridge (as per Martin's comment). Sitka top, Honduran Mahogany B&S. Should have it strung up in about 1 - 2 weeks.

Biggest questions I had was where to go with bracing and top thickness, balancing the additional tension with the smaller body size made for a bit of an experiment. I ended up going with two tone bars and was inspired by pics of Kevin Ryan's new 12-string to try something a little different with the X. So far the box is sounding good. I'll let you know when I get it strung up whether or not my experimenting has paid off.

Cheers,

Shane

[Craig]

I don't have a plan for a 12 Alan , but my thread here will hopefully be of some help :


viewtopic.php?f=25&t=60

As you can see , my design included a 24.9 scale with a 13 fret neck. Not only makes it good to play but also saves a little stress on the neck.
I'd also recommend making the neck plenty wide enough at the nut so as not to have all those 12 strings too close together . 1 15/16 " in my case and I think that should be minimum.
Include a wide saddle (5 mm.) so that you can compensate every string. This in itself, will make it head and shoulders above other 12's you may have played .
A shared 6 pin bridge not only means a smaller footprint , but also less weight . It's a tidy set-up too without strings nudging neighbouring pins.Here's a link to a tute I did on making such a bridge:
viewtopic.php?f=5&t=354

anz201.jpg (59.02 KiB) Viewed 8267 times

My first link will show you the bracing I've used . Note the A Frame bracing supporting the headblock. Again , to help handle the extra stress of a 12 string. The first lower face brace is positioned fairly close in to the bridge area




Be careful when designing your peghead . Draw it out to scale so as to not have strings running into other tuner posts :

zed31.jpg (83.96 KiB) Viewed 8267 times

[Nick]

When I get around to mine shortly, I plan on using the 'small jumbo' shape which is a 15" lower bout size & only a slight variation on my '000' based design that I already use (which meant only a subtle change to my 'spare' mold ) & I was just going to add the third tonebar, pretty much steal Craigs ideas

[kiwigeo]

Compensation can be a challenge. I managed to f**k it up first time around but eventually got it sorted with help from Craig.

[ozziebluesman]

Thanks to you all for your comments.

Craig: Beautiful 12 string and thanks indeed for the links.

Shane: I would be very interested to hear you comments when your latest project is strung up.

Jase the guy wanting this particular guitar has said he would like ten strings only with the fourth an fifth string tuned in unison as a drone. It is similar to the setup John Butler uses. Tuning will be CGCCGC and a capo used if he wants to play in D or concert pitch.

So I'm thinking of using the Stew Mac 000 plan which uses a 25.5 inch scale and 12th fret to the body. I think a six string bridge as per Craigs idea would be ideal with the fourth and fifth string holes designed to take a single string.

Do you think I need to use an extra tone bar with this design?

Also is there a way of calculating how much tension will be placed on the top with the guitar tuned to CGCCGC using 56 46 36 36 17 15 thou gauge strings?

Thanks again for your input.

Cheers

Alan

[Craig]

G'day Alan, In some cases, ( Lower tuning , light guage strings etc )it would seem 12 stringers ( or 10 ) don't need any extra bracing as the tensions are probably no higher than a six.
The danger here is that some time in the future ( when you're not around ) someone is going to string it up differently ,not knowing it was designed for very low tensions . ...... That, would be a bloody shame .

[jeffhigh]

Our own Graham Mc Donald's string tension calculator would help
http://www.mcdonaldstrings.com/stringxxiii.html