idocdan wrote:I'm still wavering between using pop rivets with bent steel to bridge from the sill to the floor, cutting out the rust and treating per POR15 instructions, then fiberglassing over, or welding instead of rivets. maybe a combination? I'm have arc welded once upon a time, but would not attempt this myself in this application, so I would need someone with experience. I have someone taking a look at it tomorrow. Will be interesting to hear what he has to say.
for a larger hole in the sheet metal, you'd be better with some real support put down first, like some sheet metal and pop rivets. you can also apply a high quality epoxy putty (like slow cure JB weld )in between the metal patch and floor as a "epoxy and rivet sandwich" that is a very strong and fairly permanent alternative to welding. I drill the holes in the over sized patch and the floor for the rivets, then run a nice bead of epoxy along the entire outer edge where the holes are, and then put in the pop rivets, squeezing the metal pieces together with the epozy in between before it has hardened.
Por 15 can take the place of fiberglass resin and be used with the fiberglass matte or cloth, but I would only recommend doing that for very small repairs--like on floor boards that have heavy surface rust but only a few small perforations. Not recommended for bridging large holes. Its just not strong enough for that.
Again, I don't like to use regular fiberglass polyester resins for any kind of rust or metal repair. they just don't bond well enough to be anything but a very short term band aid. Take the time to acquire a real epoxy resin like I linked earlier in the thread if you don't want to have to repair this again in a couple of years.