MIMF

OK, so... I have aGretsch G5265 Jet (Bass VI tuning) with a broken neck
I decided that I want to make it a 12 string (doubled 6 string eEaAgGdDbBeE)
I reshaped the body

Made a neck laminate out of Black Limba|Walnut|Black Limba
Going to use Wenge for the fret board and pen blank plastic for the inlays (Compound radius 10"/12")

ABM 2412-C 12-String Tunematic Bridge(String Spacing 2 1/16")

BLACK TUSQ XL, PT-1568 Nut (47.63mm 1.875")

Bass Strings through the body in Ferrules and the high strings on the bigsby
Planet Waves Tuners

Any comments?
Anything I'm overlooking?

Looks like a lot of fun. One thought - all those tuning heads are heavy. Without a long upper horn on the body getting it to balance well on a strap is going to be a challenge. As sketched, it might end up mighty neck heavy.

My big concerns are the usual layout sort of stuff. First, layout your scale length, neck to body joint and bridge location. 12 strings require a lot of compensation (my acoustic saddles end up looking like buzz saw blades) so spend some time calculating your string gauges and tension.

Look carefully at that bridge. Can you get the courses close enough and still have enough spacing between courses? Most people like the courses to fan out very slightly from the nut but still be close together so you pick both strings. Also, as a 12 string player I would find 2-1/16 darn narrow but again, figure out what you like.

Once you've got the neck laid out calculate the width at the body joint (lay out your bridge and nut spacing plus the string offset from the edge of the f/b. Make sure that will fit the pocket on your body.

Do a side view drawing of your body, ToM posts, pups to calculate your neck angle. At typical tunings 12 strings have about 150 percent of the tension of the equivalent 6 string (not double) - take that into consideration for neck design, truss rod, etc.

Make sure that your ToM will have the proper radius (most are 12 inch) when you extend your compound radius f/b to it.

Will a Bigsby work with a knife edge saddle? What will it sound like when you only bend the octaves?

Consider small light weight tuners - I have had good luck with mini Grovers on my 12 string acoustics.

Your tuning chart seems to indicate octaves for every course. Most 12 strings have the top two course paired. Make sure you know how you are going to string and tune it (particularly if you are going to use a premade nut).

Post pictures (and clips) when you finish.

You could put a headless 6 string guitar tuner block on the back side under the tailpiece and lighten up the headstock somewhat.

I wouldn't worry too much about neck and headstock weight - remember this was originally a bass. Most 12 strings do alright with normal or mini tuners. Obviously you need to do some layout there too - you don't want strings to foul on adjacent tuners.

You could always do like Rickenbacker with their (rather weird) combination of slot and paddle head tuners - personally I think it is much easier with just one kind (I've built slot headed 12 strings, they are a pain to restring).

Speaking of Ricks, almost all acoustic and many electric 12s have the octaves on the even numbered strings - Ricks have them on the odd positions (counting up from the floor). Your nut is "normal" stringing - if you want the Rick sound you'll have to reverse the courses.

Last hassle with an odd ball guitar is always finding a case to fit. I'm guessing this will fit the old bass case, but worthwhile to think about that as you do the design.

Oops. Just reread the original posts... when I commented about tuner head weight I was thinking this was going to be a twelve string bass. Like those good old eight string monsters, but with four extra courses. I didn't realize this was making the jump from bass clef to treble.

It appears to me that You will be able to use guitar tuners with all strings except the low E and A which must have wider slots.

But anyway - You do already have the appropriate tuners on the broken neck. Would it be possible to use Schaller compatible buttons on those tuners? Then use a 2nd guitar set which should be ideally identical except of the slot for the strings in connection with the small buttons. That would make it possible to place the tuners as close to each other as in other 12-strings.

Btw: compensation at the bridge might be a real issue. Maybe You should consider nut compensation as well, mainly because compensation at the nut will reduce the amount of compensation at the bridge. And You need to thoroughly plan the bridge angle and do a rough compensation already that way.

I will be using planet waves tuners on all strings... they work fine for all the strings.

Damon, on your sketch it looks like your scale length is 29.75 inches. May I ask how you intend to string and tune this thing? Most baritone guitars are around 27 inches and tuned A to A or B to B, including Leadbelly's iconic Stella which was strung with 0.016 to 0.060. I've built 26.5 inch 12 strings which I string with 0.013 to 0.056 (heavy for a 12 string) and tune to C#.

One very real problem with long scale instruments if simply finding strings that are long enough - this is even worse with a tailpiece or vibrato.

It also looks like you are going to make a quasi-Rick headstock with half of the tuners mounted slothead style. That should work fine if you make everything the correct thickness - should be interesting and I'll look forward to seeing it.

Interesting question...
Ive always used TNT GHS Boomers for guitar and the Fender Bass VI strings on it prior.
I am doing the headstock Rickenbacker style so they wont get stupid long, but I see your point...

Just got a response from GHS:
"Our plain steel guitar strings are 42" long, and our wound guitar strings are 38" winding length with a 40" overall length. That's standard for all of our guitar strings, not just the GBTNT set. "
Im sure that will be fine...

Good to know. From my experience standard guitar strings (Elixers in my case) are just long enough to reach the last tuner on my 26.5 twelve string with a tail piece. I don't have to cut anything off - just start winding. And I attended a lecture by D'Addario's engineer Fan Tao who stated that luthiers were pushing the string manufactures to provide what they needed - especially a problem with long scale, bass guitars, special tunings, etc. Sounds like you know what you want and have done the research.

Looking forward to seeing this when its done

What did you mean by "the right thickness"?

Damon Palyka wrote:What did you mean by "the right thickness"?

Paddle head (solid head) guitars are usually somewhere around 9/16" thick. Slotheads are closer to 3/4. It looks like your tuners are designed for a paddle head, therefore the forks of your headstock will be roughly 9/16 x 9/16. Your holes will (probably) be in the middle of them. I like to offset paddle head tuners about 0.475 from the edge to give sufficient space for the back part of the tuner to be mounted.

In addition, there are basicallyt two kinds of tuners - press in bushings and screw in bushings. You should confirm that yours will work with your design.

You can get all the specifications for tuners from the manufactures or vendors sites (or you can buy them and measure). I would recommend doing that.

Another consideration with a twelve string is the path of the strings from the nut slot to the tuners - there isn't a lot of space there and it is easy for strings to foul on a tuner post. Sometimes it is difficult to change a string because of interference by others. Here are two 12 string headstocks that might give you an idea of what I'm talking about. Both these work, barely

Thanks...
I went and used D'Adarrio's tension tool and it looks pretty ok...

Another thing...
I was planning on doing the headstock Fender style and not at an angle... I felt this would prevent the issues mentioned above.

Oooops, this is correct...

Damon Palyka wrote:Another thing...
I was planning on doing the headstock Fender style and not at an angle... I felt this would prevent the issues mentioned above.

And in introduces a whole 'nother set of issues.

Barry Daniels wrote:

Damon Palyka wrote:Another thing...
I was planning on doing the headstock Fender style and not at an angle... I felt this would prevent the issues mentioned above.

And in introduces a whole 'nother set of issues.

String tees on 9/16 x 9/16 forks?

Damon, I hate to keep picking away at your design so I'm going to shut up and watch while you build it. I think you've chosen an appropriate name