Here’s another golden oldie on the workbench, a Gibson Hummingbird made in 1977.
Introduced in 1960, the Hummingbird was Gibson’s second-most expensive acoustic guitar.
This guitar is interesting from a luthiery point of view as it has a Double X Brace system which was introduced on this model in 1971. In this system, two overlapping X shapes form a diamond which surrounds the bridge plate. Some manufacturers prefer this system where additional strength is required.
Here’s a mirror image of the Double X Brace system inside this Hummingbird
For reference purposes here’s a photo of a double X brace system that I built a few years ago.
This vintage beauty is in the workshop for a set up. It becomes clear during a workbench examination that this ol’ Hummer has some problems that will need to be addressed before it will set up to its optimum playability.
It has a very high action with a very low saddle height, no room for adjustment there.
Its bridge is beginning to lift
On investigating the guitar’s action it becomes clear that the string height cannot be lowered at the bridge saddle and the only repair solution will be a neck reset. The bridge will need to be removed and re-fitted.
The Neck Removal and Reset
The 15th fret is removed
The fingerboard extension is heated and loosened
A hole is drilled through the vacant fret slot into the dove-tail cavity
The lacquer is scored around the heel
The neck is fitted into a Neck Removal Jig. Steam is pumped into the join to soften the glue
The neck becomes loose and is separated from the body
This date stamp authenticates the guitar’s age
The neck angle is adjusted using the neck reset formula and re-fitted
The Bridge Re-fit
The bridge is heated and removed
Herein lies a problem; this bridge (for some unknown reason) has been inlayed into the soundboard. This could be a reason as to why the bridge has begun to lift and will need to be remedied before the bridge can be refitted.
Take a closer look at the internal image; the bridge-pin holes (through the soundboard and into the bridge-plate) have become distorted. This could cause a problem when trying to re-stringing the guitar as the bridge-pins will not seat correctly.
The solution is to inlay a soundboard patch to restore the soundboard height and to repair the distorted pin holes
The Soundboard Repair
The area under the bridge is levelled and cleaned up
The pin holes are drilled out and fitted with new Spruce
The scratchplate is removed for ease of working
A soundboard patch is made up from Sitka Spruce, glued into place and trimmed to thickness
The underneath of the bridge and soundboard patch are gently heated to extend the open time of the Hide Glue
The Hide glue is applied and the join is clamped and left overnight
The hole in the fret slot is plugged and re-sawn
The scratchplate is replaced
The 15th fret is replaced
A new bone nut is made and the guitar is re-strung and tested for correct intonation
Back to full health again
More enlarged photos here…
More info here…
More history here…
A major worry as this meant that this guitar was destined for the scrap-heap if this couldn’t be resolved. It appeared that the 
Using a heavy-duty straight-edge, blocks of wood placed at either end of the neck and a clamp at the centre of the straight-edge, the neck was gently forced back into a back bow. This took the strain off of the truss rod and held the neck in a back bow. With the truss rod under no pressure from the neck I was able to tighten the adjuster further to hold the neck in a back bow with the truss-rod. The splits seemed no worse for this action.
