The owner had cut out the rusted section of the sunroof frame (apparently a quite common problem on older cars) and provided a replacement roof section cut from a wrecked car. This new section was in reasonable condition but required some rust to be cut out and replaced before it could be used.
The sunroof has a support frame separate from the standard roof frame structure, and this is glued in place with industrial adhesive during manufacture. This adhesive joint prevents flexing of the roof surface.
The support frame has to be repaired as well. In the above photo, the edge of the roof frame had rusted out, and a new section was cut from the donor car roof. This section was initially fitted using the three M6 bolts visible, to align the frame section, but also to allow welding access. See the last image in this series.
The replacement section has been shaped, and the roof is cut to suit.
A 3cm wide section of the donor roof is used as a joining strip and clamped to the existing roof. A series of 6mm holes are drilled in the roof, and then filled with weld i.e. equivalent to a spot weld. The joining strip provides contour alignment and additional strength to the weld joint.
The new roof section, also with 6mm "spot" holes is aligned to the roof join strip.
The sunroof glass is fitted, the new roof section tightly aligned to it. It's tacked into place, "spot" welded along the joining strip, then carefully seamed along the join.
The welding as expected caused some deformation of the roof contour. Here's the completed roof, with initial filler to start the final contouring.
The final issue is fitting the replacement roof support section that was rusted out. A large bead of urethane construction adhesive was applied to the new section and pushed into place on to the inner roof surface, and located with the M6 bolts previously mentioned. Once the adhesive was dry (about 2 minutes), the new section was welded into place.
Total repair time for the job as shown here was about 16 hours. The owner was to complete the roof contour filling and painting.
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