Step 20: Insulate the walls - Discuss the LIP

Time for more of the pink foam.  I cut to fit solid pink foam, 3/4inch.  Used Titebond II glue to attach to walls. 

One of the features of this build is that you add the headliner from the outside, instead of trying to hold it above your head from the inside.  The approach calls for a pronounced lip all the way around the cabin.  It's essentially the tops of all the spars and insulation cut a pre-determined distance from teh edge of the ply.

What is this distance?  Will it is the thickness of the headliner, plus the spars.  Such that, when the headline r and spars are added, it will create a flat surface for the exterior skin. 

I created a little jig from a razor blade, a piece of headliner (5MM plywood) and a piece of spar.  I deliberately went too high with the spars and pink insulation.  Then I went back and  I used this jig  to score a line where I needed to trim back.  See the pics. 

THERE IS ALSO a lip along the bottom of the side wall.  The spars and insulation also stop a certain depth from the bottom of the wall.  That depth is the depth of the 2x2 subfloor plus the 3/4 inch floor ply.    This lip allows the wall to rest on both the trailer frame (where the outer ply touches) and on the floor (where the spars touch).  
Tangski1 year ago
LOVED that tiny jig!!! A wonderful solution to keep things even...:) I will be adding however, some small l brackets onto the spars, as they need more support (for me) rather than just a scew or two and glue. Just my pref. I saw one that has 3 sides which I will use on mine. I guess a bit of internal over kill, but I have seen those get loose for some reason or other.
I was told to use 3/4 for outside walls, since the wood for outside (inside wood has inside glue and can come delaminated..not fun after all that work. So the 1/2 fir that has the outside glue, also has a better 'filler' but also not constructed as well as the 3/4. At least not the outside stuff I found at good prices. Baltic Birch was 100 per sheet, and much nicer to look at, but as you say, if skinning, best to use basic stuff with the proper glue etc. I may just use the 1/8 laminate for inside walls, but not sure. I do like the stability of the 1/4 inch. After all it will not weigh much more after all is said and done...I hope!LOL
I am also thinking of using spars that are pressure treated and weather treated too, since those tend to be much straighter and tougher for longevity. Any thoughts?
Hi - very clear instructions to this point, but a basic question: you here specify 3/4" ply for floor but earlier you stated 1/2". Which is intended please?