Today was all about prepping the trailer to install the skin on the passenger side. I’ve finished the wiring that side. I’ve installed the insulation. The two things I need to finish before I can glue down the 1/4″ plywood is to mark out the wiring chases and insulation spaces so I can avoid them while nailing/screwing this down.

To mark out the wiring and insulation locations I clamped the plywood to the wall, and started measuring and marking. Eventually I traced the top and rear edge of the sheet onto the trailer so I could move it to a table and transfer the elements hidden behind it.

Once complete I have a sheet of plywood mostly ready to be glued on. My plan is to use polyurethane construction adhesive and brad nails to hold it while it sets. Once it is set, I’ll use a router with the straight bit and bearing to trim the front edge exactly to match the inner wall. I’ll also cut out the door opening the same way.

Placement

You might be wondering why I positioned the plywood where I did. Well, the trailer side are larger than a sheet of plywood in both directions. The positioning allows the lower edge to line up with the bottom of the trailer frame, hiding it. The rear edge lines up with an unbroken (other than one wiring chase) section of inner wall. The top edge bridges some insulation and the door opening. It can’t be helped. No matter where you put it, something crosses something. I could rotate it the other direction (vertical) as I did with the interior plywood, but that is less efficient and puts the seams exactly over those in the inner wall. This way seams don’t line up hopefully adding strength.

Keeping the Water Out

The lower edge of this skin will not be glued to the inner wall since it hangs down below it. It will but up against the trailer frame and will be exposed to the weather. To protect it, I’m coating it with a roof sealer. This is the same thing I did with the underside of the floor. I’m only protecting the lower 3 inches since everything above that will be glued to the interior wall. I don’t want the coating to interfere with the glue.

The plan is to run calk along the upper portion of this black stripe. It sits against the soft flashing that wraps the edge of the floor. Hopefully this will keep water and other stuff out of the non-weatherproof parts of the walls.

Lower Nose

With the skin section prepped, I turned my attention to a long outstanding bit of fabrication… The existing walls end at the top of the floor, but the side wall should continue down to the lower edge of the frame.There is a strange stair step that needs to be accounted for to make the lower edge look right. 

I also need a way to seal the front lower edge with the outer roof skin.The weather sealing part is more critical and I wasn’t sure how I would handle it until now. What I’ve come up with that will hopefully work pretty well is a cut out piece bridged across the front. The entire assembly is built from 3/8″ marine grade plywood.

Making 3/4″ Plywood

The outer edge needed to be thicker than 3/8 inch so the first thing I did after making the template above was to glue up some blanks to be 3/4 inch thick. I used Tightbond III which is rated for exterior use for this.

↑ Making 3/4″ plywood…

Once those set, I used the template I created and the band saw to cut them out staying proud of the lines. It took a little shaping using the sander to get the fit just right. I added a rabbit to the top edge for the cross piece.

It took a few test fits to get the width exactly right. I snuck up on it since I didn’t want to make it to short by accident.  Once I had the length right, I glued and brad nailed the cross member in place.

The cross piece spans almost 6 feet so it sags. To ensure it stays in place, and to provide a better seal to the front edge of the floor I added an upper lip that sits on top of the floor.The space this sits into is tight so I ended up using a block plane to bevel both the upper and lower edges.

Once everything fit nice, it was time to coat the outside of the lip in sealer just like the other exposed parts. Once everything dries, it is finally time to glue the side wall on.