Other folks must have encountered this problem, but I have not found any discussions of it. My tanks (fresh/black/gray) all hang down about six inches below the bottom of the steel beams that make up the frame of my trailer's chassis.
I had intended to use coroplast to enclose the underbelly and the insulation that I will be adding. But although coroplast is semi-flexible, it is not infinitely flexible -- I doubt it would clamp to the exterior beam flanges and still bend down around the tanks without breaking.
I see two possibilities: use a heavy plastic fabric instead of coroplast. That would be pretty simple -- it would just bend around the bottoms of the tanks. But I would not be able to glue the insulating foam panels to the top side of the fabric because the fabric would not be flat.
Or a more expensive and tricky solution: bolt some sort of downward extension to the beams -- maybe aluminum I beams -- so that the bottom of the "add-on" beams would be below the level of the tanks, so that the coroplast would not have to bend. I would also add thin aluminum cross-bars under the coroplast to support it. (And I would probably glue the waterproof styrofoam insulating panels to the top side of the coroplast.)
Fortunately, I have a lot of extra ground clearance, so I have plenty of room to add additional "sidewalls" underneath the trailer.
Your thoughts and advice, as always, will be greatly appreciated!
2012 Fun Finder X-139 "Boondock Style" (axle-flipped and extra insulation)
2013 Toyota Tacoma Off-Road (semi-beefy tires and components)
Our trips -- pix and textAbout our trailer"A journey of a thousand miles begins with a single list."
