Double Bass - Repair

The half-sized student bass arrived suffering from an earlier repair.  The neck had been repaired - with screws -  and reset, but the angle had been too flat for the bridge.  Worse, with the fingerboard in place the action of the strings was too high for the bass to be playable. The bridge had been lowered by taking wood off the feet, to the point where new wafers had been glued on to reinstate the feet profile. 

Still too flat, the neck had been pulled forward.  The concave bow had popped the fingerboard off.

Note the curtains, visible through the gap.

The repair involved three main elements - the neck, the nut and the bridge.

The neck was planed flat, removing the bow.  This had the effect of removing four mm from the height of the heel.  The two small screws were removed before planing, and their countersinks redrilled before their reinstatement.

A piece of recycled Rimu (tongue-groove flooring!) was cut and shaped to form a wedge, which was then glued onto the neck, taking care to cut a rebate to keep the screw heads exposed.

  

I then glued a strip of maple to the base of the nut, raising it to counter the slight elevation of the fingerboard.  The fingerboard end was then shaved to counter the new angle, and the fingerboard reinstated.

The edge of the fingerboard, wedge and neck was then dressed and refinished with linseed oil, shellac and rosin finish.  The fingerboard, simply painted spruce, also had a couple of cracks glued, and refinished with black wax polish.
The bridge was the final part.

Each of the feet had ben shaved so high that the feet were grafted slivers of maple.  Owing to the new angle of the fingerboard, the bridge was now 15 mm too low.

I cut two blocks of maple, and shaped the top and bottom surfaces of each to match the concave contact surfaces of each foot.  The blocks were then glued to each foot.  Not visible are the two spruce dowels (aka violin sound posts) that were drilled-glued into each foot, providing structural support to the joins.  The blocks were then sawn to shape the legs and feet of the bridge.
With final finishing and feet shaping, the bridge was fitted and the bass restrung.