Teardrops n Tiny Travel Trailers

My XPS foam to foam surfaces are not completely (smooth/or perfectly flat).(from 0"-to less than 3/16" gaps). How much of a problem will this create, when gluing them together with gorilla glue ? How important is it to dampen the surface when using gorilla glue? Also my current working temperature is 50-60 degrees, is this OK ?

None, it foams and expands into gaps, in fact many people slash and roughen up for a stronger bond. Use clamps or at least weights to keep them from moving.

Very, get a spray bottle.

Probably, but warmer is better, read their specs. Little space heater for an hour if indoors?

Moisture depends on your climate and season. Too much water makes big bubbles which are weak and when trimmed or sanded result in voids that are difficult to fill (not so difficult to fill, but hard to sand flat again w/o gouging or over sanding adjacent foam). I started out using a spray bottle (from the garden section of the big box) but it never made a nice fine mist, it always seemed to sputter some large drops, too, so I resorted to just wiping one surface with a dampened cloth... not soaking, just slightly damp.

You want nice tight little bubbles, not big blistering eruptions.

It really isn't that hard to make better fitting joints in foam. Perfect on table saw; not bad using a straight edge and stiff bladed steak knife held plumb/vertical and dragged length wise in several shallow strokes; sand edge with long board if required. Little practice and technique is all that is required.

Just did not know if uneven surfaces were a big problem. Right now the weather has cooled down. So looks like , I will be waiting a few more days, to glue my foam walls together.