Thursday, January 22, 2015

Filling out the walls

OK, it's high time to make these special laminated walls.  Why laminated walls?  Well, my hope is that they'll be stiffer and have more insulating value than straight plywood.  The insulation is key, not so much to keep us all warm (a sleeping bag can do that), but to move the dew point into the wall and out of the interior, reducing the amount of condensation inside.  Hopefully.

The stiffness is important too, with such large, luxurious doors.  Thicker foam-core walls will "rattle" less than thinner solid panels because of the "distance between rigid members" I-beam-type principle.

Whew, enough science.  Jeez.  It's like nat geo all up in here.

So, everyone remember that bottom plate we've been juggling back and forth?  Well, this is the last time it's getting moved.  I know that because I glued it in there with Titebond:

Those nuts were epoxied in place while the bottom plate was bolted to the floor, so I know they're in the right spot.  This is all kind of important because I won't be able to touch them once the interior skin is glued on.  I later put some making tape over the top to avoid the hilarious problems associated with accidentally filling the threads with construction adhesive:

The screws are really just for clamping, but they'll stay there to emotionally support the glue through various bumps and bruises on all the trailer's travels.  Don't ask me why I filled the holes with glue.

Now, this is a really fiddly part, and not really my favorite.  Since I can't have foam just hanging out exposed to the elements, I needed to line the door frame and the hatch profile with wood.  This isn't really structural, but it provides a firm surface that can be finished.  I also put some blocks where I plan to attach door hinges and latches.  Other than these wood "plugs" the whole wall will be full of laminated foam.

As it turned out, it was tough to get these vertical during glue-up.  I probably should have done 1 piece instead of using 1/2" plywood stacks, and they could have been a little wider.  This creates a little more sanding and filling later, but such is the life of a home craftsman:

Onto the foam!  I like cutting foam.  It's easy, satisfying, and inexact without it really mattering.  One just needs to trace shapes and cut them out with a jigsaw.  I've been doing that since kindergarten, though I don't recall everyone having jigsaws:

I cut out the pieces and glued them in place with a polyurethane construction adhesive.  I started out clamping, but pressing into place seemed to produce the same results.  Trace, cut, glue, until the whole wall is stuffed full, like so:

I was surprised by how much of this adhesive I went through, but it's a fairly large area.  With glue, 1/2 + 1/8 ply, foam, and adhesive, I do recon that this 1-5/8 wall will be slightly heavier than a solid 3/4 ply wall.  And far, far more complex to put together!  Hopefully, the stiffness and insulation value will be worth it.

Here's one done, and another ready to go.  That's the annoying thing about having 2 walls: you have to do everything twice.  But the alternative is a little too minimalist, breezy and buggy for my liking:

Here's the whole glue-up!

This part was a little stressful.  I dropped the inner skin while positioning it, so I had to scramble to get it in place and clean the buildup off the face.  Worse, the "weight-clamping" technique I had planned on didn't do enough to squeeze the sides down ...

... so I needed to raise it up 2 inches, fit the template over top (god bless that template) and position clamps as needed.

Of course, I didn't own enough clamps, so THAT was a very rushed trip to the hardware store.  I wonder how often people sprint to the clamp aisle, grab handfuls of cheap clamps, and barge to the front of the line cursing and muttering about "re-position time".  It's good to live in a small town:

All's well that ends well!  Well, mostly well.  The wall picked up a bit of a bend near the door because of the panicked clamping.  It's not visible to the eye, but it could be a challenge to fit a flat door in there without it looking strange.

There's also a lot of trimming and filling for the wood sections, but sanding is all part of what I signed up for.

Still, it's a handsome looking devil, like the builder:

This is all going to be hidden under roof skin, so no wood trim required.  Thank goodness:

The other wall is full of foam and ready to glue.  That'll happen in the next few days, and, after trimming and fussing, I'll be ready to assemble the whole mess into something that looks a little like a camping trailer!  Stay tuned!

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