The Hub

This is a 1983 Martin Shenandoah D-2832. From what I've found, this joint continues to be used on similar models until at least 1987, after which I don't know.

It has a single bolt accessed inside the body behind a wood cover. The face of the heel is inset a mm or two and is glued fully at the face of the body joint. Drill holes under the 14th fret right at the joint to loosen the glue.The neck is removed laterally rather than vertically.

They also used some unknown glue which is really tough to loosen so go slow with the fretboard extension removal. And be careful not to release the extension where the dovetail is, which holds the truss rod.

There appears to be a little bit of glue in that dovetail, so I used a pin vise to drill holes through the upper cross brace to the joint, and inserted heat sticks to help with the removal. I don't know if this was necessary, as there wasn't much glue and it didn't cause much trouble, but if you're having trouble maybe try that. They definitely helped with the fretboard extension removal as the heat lamp I was using wasn't enough to loosen whatever glue they used.

This was a complicated removal but wasn't overly difficult once I knew what I was dealing with.

Hope it helps!