Hey there, master builders of wonderful trailers!
Continued to fairing of the interior ceiling using tools and materials that will be used on the roof and trailer exterior for smoother finish. Wanted to try and get some experience on the ceiling first.
But first I decided as a good measure to scuff and wash the panel epoxy coating just in case (although unlikely) there was any potential amine blush on it. It is pretty simple procedure, just sprayed some soapy water and scubbed it with pads and then cleaned and dried out with microfiber towels (other people use paper towels).


Then I went onto sanding with 5" orbital sander of all the ceiling surface to remove high spots on the epoxy coating only, making sure that the fiberglass cloth never touched with the sander.

Then I went to local autobody supplies shop and got the 3M Platimun Filler 01171, long board with 80 and 180 grit sand paper, black flat paint for guide coat.
You can also see in the photo how the sanded epoxy FG surface looks like after 80 grit sanding; it only has some low spots that need filling.

I did many mixing batches and put a thin coat of the filler over the whole roof to fill low spots and then hooked my sander to my mighty/trusty dust collector and started sandind it down... and then

... I think I did some mistakes with the 3M Filler mix... and although I can somewhat sand it, the paper clogs almost right away, so it is going slow and I did not finish it today as I hoped, will continue tomorrow. Hopefully the filler will harden some more and will not clog sand paper that much.

I did try to sand with long board and it was fine, but slow and cloged sandpaper slowed down things a bit, but then I decided to leave the long board excersize for exterior, the orbital sander does a good job of sanding the ceiling surface to a good even finish and it will be painted with white-off eggshell acrylic, so no worries there. I think it also helps that the panels where planed to the same thickness and only minor fairing is needed where the panel seams are not exactly matched or there is a fiberglass cloth overlap. In fact I might use the orbital sander on exterior as well since the cured epoxy serves as a good barrier helping with the surface fairing.
Cheers and thanks for reading
