It was time to get rid of the rust
The Airstream Bathroom was in very bad shape, when you walked around you could feel the floor squishing beneath your feet. We did not know where the rot was comming from or where it ended but we knew it was extensive.
Once we got the closet out and got down to the water heater we found the source. one of the fittings going into the water heater had a constant drip that had soaked the floor plywood and rotted out the frame. the full back plywood panel and large sections of the second panel all had to be replaced. the main frame rail was completely rotted out and had to have significant welding reinforcement.
With substantial welding to the primary C-Chanel and newly fabricated outrunners we were ready to start welding the floor back together. Fortunately that was the extent of the frame repairs necessary in the back half of the trailer, all things considered, given the amount of water in the plywood the frame could have been a lot worse.