|I had noticed a small crack running
down vertically for about an inch from the rear of the
tread plate and I knew this was the tell tale sign that
the bonded in metal reinforcing plate had expanded so
much with rust that it had split the fibreglass. I got a
bit of a shock when I removed the tread plate, as you can
see in the picture. The fibreglass had split nearly the
complete length of the tread plate on the outside and
about half way on the inside so it must have been pretty
weak. The metal plate rusts because the ends of the sill
are open and therefore allow all the muck & spray
from the wheels to inside the sill and onto the metal.
I know the proper way to repair this is to remove the remains of the metal by lifting up the body from the chassis and cutting out the fibreglass from underneath, putting in a new metal plate and then re-glassing from underneath, but I didn't want to remove the body again. I reasoned that the car must have been very weak in this area for quite a while and was already split the length of the sill so therefore I would have a go at repairing it from the top.
Badly cracked fibreglass only apparent after tread plate removed
I cut out the top part of the sill, down to where the metal would have been, and removed the remaining rusted metal and cleaned up the the lower layer of fibreglass. Now what I did next will probably be seen as a bodge by a lot of people but I reckoned that the metal plate hadn't been doing much for quite a few years so I decided to replace it with more layers of fibreglass as this would allow me to overlap the matting underneath for the required 6 inch overlap you should have for a strong bond. It was a bit of a messy job but the end result looks good and seems very strong, certainly stronger than it was before I started.
Cleaning out the remains of the metal plate
Ready for spraying