Thanks guys. Guess I'll be pulling the back apart whether I want to or not. I want this trailer to be in good shape so we can sell it in a year or two & get something newer that's not set out and had wood rot away unseen. This is the 2nd Sunline I've had that needs major structural repair, and I have too many other things to do than just fix trailers. Our next one will be a late model fiberglass one I think.
This wonderful tear happened when I was taking the window out the 2nd time after just re-installing it. My problem was that I should have replaced all the interior wood structure, not just the rotted out stuff. I actually cut back way into the "good" wood, but what happened was the screw holes in the "good" wood was rotted such that I couldn't get the screws to tighten the window up on the top left and left side. So off came the window again to rebuild the holes & that's when the siding tore on the bottom. The bottom was all new wood, so the butyl tape was well adhered. Darn.
I rebuilt the screw holes with wooden match sticks (and toothpicks when necessary), all coated with wood glue. It worked fine, and the window is now well sealed. Of course it will have to come off again to replace the siding. When that happens, the whole back will come off and the wood structure be completely rebuilt.
Now I need to install the water heater anode, flush the fresh water system, re-panel the interior back where I replaced the wood for the window, rebuild a drawer that is falling apart, and get ready for the Maine trip Memorial Day weekend.
2009 GMC Canyon with factory tow package & new fangled brake controller
2008 Subaru Outback
1983 Sunline T-1550
Image to come as soon as I figure out how to flatten a pic!