Not really a "design" question, but using 1/2" rigid foamboard over 3/8" plywood with seams staggered so they are not in line with the plywood seams. Can/should the seams between the foamboards be covered over like drywall seams? If not, isn't movement a issue and the resulting cracks?
I guess you could cover them with something other than plaster cloth, but does one really need to take that extra step? You were going to cover the foam with plaster cloth after carving and shaping were you not? Jim:tb-biggrin:
Bruce - using plaster cloth will avoid the tiny cracks that tend to appear as the underlying wood support shrinks and expands (I failed to do this on my first module, but never again). If you stack foam on foam, then no need to worry - simply fill with putty and sand as needed.
I guess that the answer will depend on what type of scenery is going to go above the foam. Unless the butt-joints between the foam are absolutely perfect, I suggest you use acrylic/latex caulk. Color will not matter, although I would not use clear caulk because I would still see the seams/gaps, but white, brown, black, etc. would work. Start by filling gaps and work in small layers, trying to "feather" the caulk to cover any inconsistencies in thickness. If there is a major thickness inconsistency (more noticeable in smaller scales), go over the previously caulked joints with some lightweight Spackle and feather it out as needed. I see no reason to go to the time and effort of treating it like you would treat a drywall seam. You will most likely just place scenery over it, so flawless joints don't seem necessary.
Use it as a channel (if running in direction desired) for hiding your wiring OR nothing at all OR if scenery needs to go over the cracks, plaster cloth, sheets of styrene, or much cheaper plastic signs that say "For Rent" or "for Sale, painted of course, or whatever with fill the gap.
As Fotheringill mentioned use it to run wires but also I'm not sure of the issue here. I just paint over them after gluing the foam down. It might take a few layers depending on the crack, paint, application and variables.
foam putty would work well here, or even cheap-o caulk - again under the premise that scenery will go over it - don't spend too much time worrying - just lay some track!
"Light-weight Spackle" works great!! Easy to apply, sands, and unless you put in on 1/2" thick, it won't crack. What is the need for plaster cloth???, extra expense, and serves NO need. Contour your foam, Spackle cracks,let spacle dry & sand if needed, give 'er a good coat of cheap earth-tone latex paint, add ground cover, let dry, vacuum, on to detail scenicing.
