Sill question

My roadster had some sill work done by a PO. The rust was cut out, where needed, but instead of welding in steel patches, the holes were patched with fiberglas. Looks great but the passenger side is a bit more "springy" than I think it should be. I'm concerned about structural weakness from the repair. Would it be possible to fabricate a structural "rail" that could be welded into the bottom of the chassis to strengthen things up? I'm looking for alternatives to cutting out what is otherwise rust-free and cosmetically good. Plus, the car doesn't appear to be sagging, at this point, and I'd like to get things shored up before they do. Creative ideas would be appreciated.

Its hard for me to picture in my mind your issues. But the springy is telling you the fix wasn't correct. Sooner or later the rags and glue are going to fail. I think it needs to be removed and done correctly FWIW...

If the fiberglass work was to the outer sill, and the inner box section is still solid, I don't think it's a big deal. The vast majority of the bending strength of the shell is in those rectangular sections (made up of inner sill, castle rail and membrane). The outer sill doesn't add much strength, relative to that box section.

That said, if the outer sill was rusted out bad enough to need repair, there's likely rust issues with the fwd and rear (at least) sections of the box. I'd inspect the whole structure very carefully.

You can test it, too. Measure the door gap 'unloaded', then load up the structure (e.g., get a couple of your 200 lb good buddies and have them stand on top of the sill with the door open - and measure the gap). Maybe one at a time if you're really concerned about it....

If it's not sagging (determined by checking the top door gaps, frt and rear) then I'd leave it alone until you get to the point where it bugs you enough to fix it right.

since the work was done by the PO, I doubt he would take on a full sill job.

I bet dollars to donuts that they just did a cosmetic repair. I am willing to bet the inside is worse and will need more work than just the outers. Usualy the outers dont start going til the inside is pretty bad first.

That said..chances are that the car can be driven a while before it is a problem. I have seen many cars that should have been scrapped years ago still runnign around even with the sills folding and barely able to close the door. I dont thing this car is that bad, but am willing to bet there is more rust than JUST the ext sills