Mayne wrote:How thick an insulation would be used? I knw that 3/4" ply is shy of that spec, so.... would 1/2" foam insulation be used?
I haven't had any problems getting 1/2" foam into 1/2" plywood walls (I also use it for 5/8" walls) or 3/4" foam into 3/4" walls. I typically use the Tyvek-backed white sheets from Home Depot or Lowe's
afreegreek wrote:you can get the same benefit, lower weight and room for insulation and wiring by just cutting strips of plywood or solid wood and glueing it around the perimeter, door and window openings, and attachment points.. using a full sheet and making a bunch of cutouts is a bit of a waste of wood and time.. some will argue that it is stronger but when the panel is already 10x stronger that is needed it's a bit of a stretch to split hairs that fine..
personally I'd go for thicker walls.. I have 1-1/2 inches of EPS insulation in my 18 foot trailer ...
Different strokes for different folks, for sure ...

... but the original question was
what is the benefit if doing it that way? What is the thickness of the material ...?
As far as going with thicker walls, again, different strokes ...! Space is much more of a premium in a teardrop over a typical travel trailer, so even an inch-or-so of additional room in a given footprint can be a big deal (to some), and because there is so little room in a TD to begin with, it doesn't take much insulation to make a big difference (and certainly, even a little insulation is better than no insulation ...

...!).
And, as far as weight savings go, on a typical 4'x8' teardrop, I save about 100# over solid plywood construction (but, I also do my cabinetry the same way), and on a 4'x10' it's almost 150#
Don't get me wrong, I'm not saying that this method is the best one (there is NO one best way to build a teardrop!), just that it's the way I've been building 'em for 25 years, and I've found that it saves me considerable time & effort (not to mention the benefit of insulation) ... it also supplied me with some extra wood for the fireplace ...

...!
And, don't forget the standard disclaimer ... others' experiences may vary!
However you choose to build your teardrop (or tiny travel trailer), Good Luck, and as always ...
CHEERS!
Grant