Hesh,
I believe Taylor bolts the neck on, and also bolts the fingerboard down - no glue. In the players hands, it is not really "adjustable." Later, if the neck angle goes wonky, the Taylar neck can be unbolted (from the heel and top), and tapered shims that Taylor CNCs can be inserted behind the heel and beneath the fingerboard, as necessary, to get the nack angle back to playable. I would be amazed if Bob Taylor sticks with that system, and would expect him to go to a truely adjustable neck sometime in the future.
Craig,
In a heel-less neck, you'd lose that lower contact point to define the adjustable neck pitch. So, I would think you'd need to run a setscrew up toward the neck (near the neck/body joint) to change the pitch. Then you'd either have a hole in the guitar's back (a la Babicz) to get the tool in there, or you'd have to have either just a small neck block glued to the top or a neckblock that looks like a classical Spanish neckblock, empty in the center. Somehow, you'd need to get access to a setscrew head pointing up. (Yes, I can think of a way to screw in and have a mated piece go up, but that would be a machinist's project in itself.) Good or bad, I suspect the heel-less neck would make the neck into a whammy bar to some degree.
Babicz's
patented design holds the neck two ways: horizontally, and vertically. It is held horizontally by a trapped slider (see page 5 of the PDF file), and vertically by a bolt. The bolt it trapped, so it just spins in place, and a threaded insert in the neck thus advanced up and down. To me, it is a complicated system, difficult to produce without CNC, and even if it was not patented, I would not attempt it. I also don't like the exposed hardware port.
The one thing I don't like about the butt joint neck (whether adjustable or not), is using inserts. I guess they work OK if you drill up through the neck heel and insert a wood dowel, so that the inserts have something other than end grain to bite into. But, to my eyes (thinking like a furnituremaker), the mortise and tenon with the cross dowel seems stronger and nearly foolproof, so why screw with inserts. (pun intended)
That leaves Mike
Doolin and Grant Goltz. I have to say, I had never seen Mike's joint when I used Grant's. They both work, but I do like the added adjustability afforded by the setscrews. In fact, I now know for sure that I can easily hear a difference in intonation when I change the neck angle on my guitar using the Goltz method. So, at a minimum, I'll add upper setscrews to allow me (after a neck angle change) to tweak the string length back to exactly the same as when the saddle was intonated. Then, there is also the added benefit of being able to adjust the yaw (side-to-side) angle of the neck by manipulating a pair of setscrews. That could be a lifesaver especially if the neck block/body joint is off even by a degree compared to the centerline of the body. Finally, there's that bottom setscrew. The Goltz method does not use one, and it still works. However, it might just be the very easiest way to accurately change the pitch of the neck.
In conclusion... (I know, I'm long winded) by the time I add the 3 setscrews to Grant's design, I'm really close to Doolins, maybe even
there, in terms of the core engineering. I do like the more graceful heel design (like a woman's high heel shoe), rather than the constant width heel I have seen on Mike's guitars. And, I disagree with Mike's decision to access the lower setscrew from the exterior of the guitar.
That's my $.02
Dennis