Here is a description of how I replaced the offside sills on Spooky
Preparation is very important when you do anything like this, here is a list of all the things I did in preparation:
A cross-section of the original construction
Removing the belly pan was relatively straight forward as it was all going to be replaced I just cut a huge hole in it so that I could get behind the sills and jacking points.
The outer sill and some of the centre panel skin was corroded so I decided to remove the whole lot. This meant cutting back the centre panel up as far as the cabin floor level. The centre panel skin is spot welded to the floor at the flange on its outer edge so I chiselled off the small spot welds (carefully so as not to distort the centre panel) so that the centre panel skin was no longer attached to the floor.
A cross-section of the area after I had cut everything away and cut the centre panel skin along the floor flange.
To remove the outer sill I cut as much of it away as I could so that I could see what was going on, I then drilled out the spot welds through the floor from inside the bus and hacked around until it all came off.
I then repeated this process until the inner sill was off remembering that it is also spot welded to the end flanges of the floor beams and top-hat sections so I ground through these spot welds being carefull not to damage the end flanges of the floor beams and top-hat sections.
At the same time I was progressively removing the jacking points and outriggers.
I then cut back the top-hat sections where they were badly corroded and fitted new sections
With everything removed and the whole area cleaned up we're ready to start putting the new bits on. First its the inner sill and this is plug welded to the ends of the top-hat sections and plug welded through the floor.
I offered the new sill up with the new outriggers and jacking points clamped in place so that I could make sure that it was in the right position, once happy I drilled a couple of holes through the floor and bolted the sill in place, this was to make sure that it was nice and tight against the floor. I then marked the sill where the top-hat sections and floor beam flanges contact it so that I could drill some holes through the sill to plug weld.
I removed the inner sill to the bench and drilled the marked areas for the plug welds. I then cleaned up the holes in the floor and the ends of the top-hat sections and floor beams ready for welding.
Right, I just offered it up, put the locating bolts back in, tightened up and clamped it all so it was a nice tight fit and started welding.
The inner sill welded into place, there are no jacking points or outriggers fitted and you can see where the sill is plug welded to the front top-hat section and just behind it the frontmost floor beam. At this point I hadn't started doing the B pillar repairs or the front wheel arch.
A cross-section showing where the welds are
I now fitted the outriggers and jacking points and started welding in the nut-plates for the belly pan
The inner sill fitted and painted, the front jacking point and outrigger fitted and the B pillar repair section in place.
Fitting the middle sill is a very similar process to fitting the inner sill first making sure that the outer surface of the inner sill and inner surface of the middle sill are painted. The middle sill fits very nicely against the inner sill but a I did put a couple of bolts through the floor so that I could get a nice tight fit between the middle sill and the floor. Once the floor area holes had all been cleaned up I started welding. Plug welds through the floor and plug welds along the bottom flange are all that is needed as well as the small vertical flange at the front of the sill.
The middle sill after welding (and grinding off by the look of it).
A cross-section of the inner and middle sill welds
The last part of the repair is not conventional in the fact that I did not use the standard outer sill, this was because I'd had to cut the centre panel up to the floor level due to the excessive corrosion in that area.
I got hold of a full length Veng repair section that was desighed to fit from the B pillar right back to the rear wheel arch. It was also tall enough to go from the sill bottom flange to well above the floor level, so all I had to do was cut this to fit nicely between the B and C pillars, I had at this point made up the repair section for the C pillar and fitted the reinforcments.
I cut the repair section to the correct height, cut it slightly longer than required and formed a flange at it's rear edge so that it would sit snuggly between the B and C pillars and fitted nicely along it's top edge join with the centre panel.
The new repair section plug welded along its bottom flange and plug and seam welded along the join with the centre panel.
And heres a cross section
The last bit of knifing stopper going onto the repair.
And finally the sprayed finish, if you look closely you can see the front closing panels fitted and the holes in them so that I have access to the void between the outer sill and middle sill and the void between the middle sill and inner sill so that a WaxOyl spray tube can be shoved through.