hossesdad wrote:Yes, I am planning to do the walls in ¼” treated ply inside, 2” foamular 250 and 0.036 inch aluminum outside (edited to add a zero!), the whole lot held together by epoxy thickened with West microfibers adhesive blend made up to a putty consistency, spread with a slotted trowel and then a spreader and pressed together by a vacuum bag at about 2psi of vacuum (That is 288 lbs per square foot, of course). Did a test (without vacuum, using weights because my plumbing isn’t ready) held well although needed more weight round the edges...it is for that uniformity that I am using the vacuum. One has to pull off the face of the foam to release the ply or aluminium.
I think you said you plan on using treated wood for the floor and inside--please look into that and be sure. I've heard that can be dangerous to the occupants.
I'm using frame/stringers because I don't entirely trust the foam, plus I like having plenty of attachment points. A note on bonding, I'm pretty fond of using both the carpet seam roller and wallpaper perforator to texture the foam. The foam *will* pull apart first regardless, but the texturing makes it stronger by bonding deeper into the foam. I also like making the filling paste with micro-balloons. They save some weight and cost, and are plenty strong for this application.
hossesdad wrote:rruff, looking forward to your first photos.
hossesdad wrote:I fear the foam will let me down. Logic says it won't.
hossesdad wrote:I am going to rout and epoxy 4” strips of ply flat to the outside walls where the foam pieces join (the foam pieces are 600mm wide). That strengthens the joins and gives me a furring strip to screw or rivet the aly to in the future if it delaminates anywhere.
Inside, I mean to have ply furring strips routed and epoxied into the foam beneath the wall ply, one at bed height, one at shoulder height. I will probably put framing at the door and windows and access hatches when I make the wall panels but I am toying with adding it after, although that is not so easy to do because of the aluminium. I am also considering other material i can use, eg, plastic...don't like wood near the windows and doors.
The shape of the caravan will be determined by building the walls oversize and cutting them to a profile I like, then putting them up. The roof will be wooden stringers, foam and thin ply covered in fibreglass. I may make the roof in place, I may make it elsewhere, in two pieces and epoxy it on and together.
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