Thursday, January 29, 2015

Barn raising!

So we finally have a 3D object instead of a stack of odd-shaped sheet goods!  Here's the fine-looking beast now.  In all honestly, the photos make it look oddly wide, and it looks a little silly without the fenders.  Nonetheless:


This pretty well blew Fin's mind.  I don't think he's totally sure how the design he and I have worked on on my computer is somehow coming to life.  It could almost seem like magic, but magic would probably happen a lot faster.

The bolts went into the built-in epoxied nuts in the baseplate just fine, which is a relief.  I guess JB-Weld is a good as it claims!  That step was a bit of a question mark.

Interestingly, the trailer frame had a slight downward bow on both sides.  I had a shimming schedule planned if the wood couldn't bend to accommodate the frame, but I was quite surprised to see the 2" tubular metal frame easily bend to accommodate the wood!  Perhaps I overbuilt the walls a little.

Stained carpet scraps not included.  Some assembly required:


The next stage (already in progress) is to fit a couple of squared sheets tightly inside the walls to keep things square while I install the support spars in the obvious slots.  After that will come the headliner (the inside roof skin).  I'm still deciding how to finish that bit, but I'm leaning towards laminating upholstery fabric onto the ply prior to installation.  I think that would help absorb a little inside noise and make the inside seem not quite so "woody".

I flopped a sheet of 1/8" Baltic birch over the tighter roof curve, and it bends beautifully.  My tightest inside radius 45cm, but I don't doubt that it could be used to fit a radius of 20cm or smaller.

Here's the butt end, where the galley and hatch will eventually be:


There's a lot left to do, but progress is being made!  Here's a short list:
  • Inside roof skin
  • Galley
  • Electrical
  • Roof foam core / outer roof skin
  • Doors
  • Galley
  • Exterior finishing
Sounds pretty easy, right?

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!

Wednesday, January 7, 2015

Gleaming polyurethane

Well now.  Here's a nice looking plywood floor, if I've ever seen one:


I hadn't used a polyurethane finish before, so I decided to try it on the floor first.  It'll be covered by the mattress most of the time, but it still needs to be durable and waterproof.  Any screw-ups (as it turns out, it's pretty easy to apply) will be hidden, and it's great practice for the interior and the galley.

Here are the steps I've recently learnt to apply a nice, simple poly finish, at least to softer stuff like this Birch.  It seems like a lot of steps, but it's really just 3 coats of decent oil poly, sanding and clearing off dust between coats:
  1. Don't buy rub-on poly.  I used that for the cabinet knobs.  It makes a nice finish in the end, but it's thinned 50% to make it "rub-able" so you need about 6 coats, which is a huge hassle.
  2. Sand, first with 80, then 220
  3. Quick knap with 220
  4. Brush off and let the dust settle, literally, overnight
  5. Rub with a cloth or suchlike to clear dust, then again moistened with mineral spirits or thinner (NOT water, water will raise the grain again and won't play well with the poly)
  6. Apply coat 1, let dry 24 hours
  7. Light sanding with 220 to get rid of raised grain and dust nibs
  8. Cloth rub, again with the paint thinner
  9. Apply coat 2, admiring how it's starting to coat the wood instead of soak in, dry 24 hours again
  10. More sanding with 220 ... starting to feel tedious now
  11. Cloth rub, thinner, wishing it were done already
  12. Apply coat 3!  If it's done right, this will be the last one, wait for 24 hours to be sure ... make sure to move slow and go lightly over the last brush strokes to pop the tiny bubbles that form in the poly (If bubbles were an issue in the first 2 coats, thin 10-15%)
  13. Pat self on back for doing such a nice looking finish
  14. Sand very lightly with 2000 polishing grade, just enough to get rid of the few remaining dust nibs ... too much will take away the satin sheen and make it glossy

Clearing dust is the hard part.  There are always a few little nibs.  I think I did as well as I could have without making a dedicated finishing area, and that would be GETTING CARRIED AWAY, which I promised myself I would not do, in my very first post.

This is the Minwax floor-grade satin poly, which I'll use throughout the interior and galley.  It sure soaked into the soft birch on the first coat, and even a little of the second.  But by the third, it came out nicely levelled and pretty well free of bubbles.  I went with oil instead of water based because it's supposed to be a little more durable.  Who really knows.

The T-nuts stay exposed, but they're evenly spaced and more or less flush, so that's fine.

Back to the walls!  This needs to cure for awhile, which will result in some awkward sawhorse setups, but after that I'll cover it with cardboard and work right on the trailer.  I've decided to build them lying down, finish the interior, then stand them up.  I think the only reason I wanted to assemble them standing was to make progress right away, but ...

... patience, young man.  Patience.

Sunday, January 4, 2015

Installing the floor so we don't fall through

Well, this marvellous Egg will need a place to sit, so I thought I'd better bolt some kind of flat, smooth surface to the top.  Just for kicks, I decided to use the carefully joined sheet of Baltic birch I made specially a month ago.

I started by marking the positions of the bolts, avoiding the welds and awkward places.  There are lots of attach points in the middle of the floor so the plywood doesn't flex and rattle when it's weighted:


Meanwhile (well, it was at a different time because there is only one of me) I cut the floor to size, being careful to angle the edges to fit the final trailer profile.  Then I turned the thing bottom up and put a couple of coats of a fibre-reinforced roofing tar on.  This stuff is sticky and thick, but it'll make a nice self-healing waterproof membrane between the road and the camper body.  If you were to spill a can accidentally, you'd probably wind up needing to move:


Flipping the whole mess over onto the trailer frame was no small task!  The sticky stuff, even when dry, tacked to the trailer and made it impossible to place precisely.  I wound up wrapping the bottom in cling wrap, placing it on the frame, drilling the holes, bolting it, then sliding the wrap out one side at a time.

I dry-fitted the bottom plates as well, mainly to get the positions for the major anchor bolts.  These photos were taken before the rest of the holes were drilled, but the floor will wind up being peppered with T-nuts as well.  I'm not going to get carried away with hiding them or doing a really show-quality finish on this floor, because, like a dirty magazine, it will spend most of its life under a mattress:


These bottom plates will come off the floor to become an integral part of the wall assemblies.  They'll be pinched in between the interior and exterior skins, and surrounded with building foam.  That means I won't have access to these nuts when it finally comes time to install the walls.  The wood is too thin to use T-nuts like on the plywood, so, after tightening, I epoxied the nut and washer to the bottom plate.  It dis-assembled just fine, and my hope is that it'll bolt together again just as smoothly:


To date, I've got the thing sanded and ready for finish.  I'll let the dust settle overnight, and tomorrow I'll start putting on some polyurethane floor finish.  In between coats, I'll try to get going on the wall assemblies!

Off to work again on Monday after a nice 2-week break.  We had a great Christmas and New Years celebration, and events will be settled down to a dull roar quite soon.  I won't continue quite the pace I have recently, but I hope to continue with regular, small forays into Thunder-Egg land!

Happy New Year!