I am right in the middle of it myself, just finished taking the rotted floor out the back and front. I will replace the back 4 feet of floor. I have taken the blacktank out as well [59 Tradewind] and now cleaning the frame for the welder.
The thing I have found is once you start the process, you have to make up your mind when and where to stop. I am new to this myself, but have learned to do as much as possible to get the floor sound as it is part of the main structure and thus the back part of the trailer is important to have sound.
I used a grinder to take off the elevator bolts, and luckily my C-channel is in good nick. You will need to take off the inside lower skin. My trailer is gutted completely, and I am not using it as a camper, but rather a studio so I have the luxury of no tanks to replace etc.
I would make sure the frame is ok, and again you have to weigh how much work you want to take on. I guess how much you will be towing this etc is something to consider, tough call as my emotions have been up and down throughout this process. Right now I feel positive, but only because I have come to a compromise in what needs to be done, rather than what could be done, compared to the many people here doing right. In other words, some folks will spend years and thousands doing the work, but that is a passion to restore these beasts to perfection. I am getting it done so it is safe and hopefully free off any leaks.
There are products that can restore rotted wood, some threads explain this.
Good luck and keep us posted.
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