OK, so I have more ceiling progress to report, though I’m not yet finished. For those of you actually reading this with the hope of restoring your own Spartan (or really any vintage aluminum trailer), here is some more useful information, much of it gleaned from trial and error.
So as you know, I chose to use 1/8″ birch plywood for the ceiling due to weight and relative ease of installment (I should mention right now, do not try to install these overhead panels alone. It requires a minimum of two able bodies). The primary concerns with ply this thin are it’s brittle nature when handling/sawing and its tendency to ripple as it is layed down. Using a Dewalt 18v cordless jig saw, I cut portions off one end and side of each piece. These 4 X 8′ panels do not fit in my IM. I reduced their length to 90.5″ and their width of varying size depending on the distance between redwood lath. Obviously, one must position these panels right down the middle of the lath so that there is room to affix the next adjacent panel.
With these painstakingly finished panels, it is doubly important to adhere to the carpenter’s old axiom “measure twice, cut once…” ’cause you don’t want to screw this up. You don’t have to be perfect along the edges because they will be covered with trim but still, be careful.
The installation is tricky because you’ve got a large, floppy piece of brittle plywood that has a small margin along each side. It might chip or even break if manhandled. Holding the piece up in position (tight along all edges) with an assistant at one end and an extendable shower-curtain rod bracing it up at the other (my idea, I am proud to say), drill small pilot holes in one corner followed by a #8 3/4″ wood screw (remember, along the perimeter you are screwing into steel, not aluminum). Without pilot holes, the metal screws will not sink. Once one corner it affixed, double check the placement and resist tickling your assistant in the armpit. You need her cooperation. Then move along the edge placing screws every 8 – 10″. Two points to remember here: 1) The screws placed into the cross-beams should be close enough to the edge that it and the adjacent screw on the next panel can be covered with 1″ wide trim and, 2) Don’t place screws in all four corners first in the hopes of relieving your assitant’s, by now, burning arms. Think of each panel like a stiff rug which has to be laid in an orderly, progressive manner to avoid ripples.
To adhere the panel in its interior between the edges, I used 1″, #6 brass screws (at $.33/ea., ouch) because they will not be covered with trim and need to look good. You also should drill pilot holes for these even though they only have to pierce aluminum ribs. Place these consistently (I used 3 screws across on two ribs. 6 total at roughly 22.5″ apart to ensure uniform spacing. You don’t want visible brass screw heads weaving down your ceiling all higgly-piggly. You can ensure finding these cross beams under the partially installed panel by using a stud finder and/or a laser line. I used both and still managed to miss once or twice. Darn.
There are two additional tips here for those of you wanting to do a first-class job. 1) Before placing the panels in place I cut 1/8″ thick self-adhesive weather stripping into 1″ pieces and adhered them to the intended screw locations on the lath. This marvelous idea (credit to my brother, Bill) helps ensure a ripple-free appearance of the panels by providing a little wiggle room for each screw. If a dimple appears on the panel where it is screwed in, back it off a turn. This process also helps to minimize a wavy ceiling resulting from uneven lath. 2) After the pilot hole it drilled, replace the bit with one as fat as the screw heads and drill a sink hole so they sit flush. I did not do this with my first panel and noticed many bumpy, protruding heads, which will make it tough to lay down trim evenly.