Thrifty Alternatives ..Building Foam Campers

[Wobbly Wheels]

Another issue might be in bonding the PVC to the foam. A latex-based contact won't eat the foam...but won't stick to the plastic. In metal boats, I've used PVC pipe as electrical conduit and then it gets foamed in place when the hull is sprayed with polyurethane foam. The foam doesn't stick to the PVC either, it just encapsulates it and locks it in place.

I like the idea for smooth corners...I just don't know what you'd glue it with that wouldn't trash the foam.
Maybe screwed along the edges into a light wood backing ?

PVC pipe also has a thermal 'sweet spot' where you can bend it without melting it.

[Bogo]

With PVC is is possible to bend nearly any shape you want from a sheet of the stuff. A pipe could also slit down the side, and the two sides bent out to make flanges the foam could be glued to. PVC will thermal set. You warm it up to a few hundred F and then it becomes pliable and you can bend it into the shape you want. Let it cool in that shape and it will hold it.

The main reason I haven't used it is the glass transition temperature is close to the rough maximum temperature (225F) that a car surface will reach in the hot sun in the SW USA. I require a little bit more thermal stability than that would provide. Having said that, many bumpers shrouds are plastic...

If you go for sheet PVC, I'd also look at some of the other thermal set plastics too. While PVC foam core may be one of the lightest, some of the other plastics have higher glass transition temperatures so would be better for vehicle use. Do note that many will need UV inhibitors, or need to be painted with a UV blocking paint. It is possible to buy sheets of many plastics with the UV inhibitors already in their structure.

As for glues, I hadn't explored them at all. I wouldn’t be surprised if there isn't at least a few out there that would work. They might not be retail store sold, but often you can buy a case at a time and not be out to many clams. The surface of PVC can be roughed up with sand paper, and a glue that mechanically keys into the surface used.

PVC is solvent welded. You could use a PVC foam, and solvent weld the PVC skin to the foam for a SIP that would be literally 1 piece after. Done right, they will join into one piece with NO ability to separate them.

[Jack B.]

Now if you fellas were mind readers you would know I forgot to mention that the PVC would be put on over the fabric covered foam. And I also see a full length strip along each inner joint that you bolt through all the layers every 12"-18" perhaps. The adhesive would be more for sealing than actually being relied on to hold as strongly as it would with plywood or such

I checked out some industrial adhesives with Google after watching the British caravan construction video above and found some that say they bond to and between anything, listing foam, glass wood, stone - lots of stuff. That was where the adhesive idea came from. Of course the foam is the weak link in any sticking together situation.

Jack

[GPW]

Well now ... that all sounds interesting , but a bit complicated and expensive ... Are you going for a “look” ? Or is this “structural “ ? For structure , why not use PVC pipe as a frame and fit (cove) the foam to fit exact (hot wire) ...

[Jack B.]

I just imagine that the outside corners of things going down the road at 55+mph, especially when those things are made of foam and fabric could use a little exterior protection. The curve of a 6" diameter or so PVC pipe application would offer that and a bit of smoothing of the air flow. The plastic Airstream look would just be a bonus. This just seems like an idea that would stay true(ish) to the simple techniques concept, be not too much extra expense money or weight wise and add some strength. Wood builders use their metal strips and angle strips at corners and long edge runs all the time for protection and appearances all the time. Turn about, fair play and all that rot, say what.

Not having done the hot wire thing I'm not sure how I would be at it. Straight cuts seem to be an easy enough concept but I know, just as in stained glass, once I got going I would want to go all french curve and intricate shapey-wapey.

Jack

[redveloce]

Jack - I use a lot of ABS plastic in my fabrications. Sheets of ABS are very inexpensive, and it cuts, drills, and forms really easily. You can just fasten one side of a strip to on surface on a corner and heat it with a heat gun to form it by hand. PVC is supposed to emit some really nasty chemicals when heated. My plastic supplier recommended ABS over PVC for that reason, and I've enjoyed working with it so much that I've never looked back! It does need to be painted for UV protection, but it holds paint well.

ABS is commonly used for car bumpers, cladding, interior, motorcycle fairings, etc.

[GPW]

QUOTE: “ I just imagine that the outside corners of things going down the road at 55+mph, especially when those things are made of foam and fabric” ...

Seems we’ve heard this before .... Ooh!!! ... scary !!! What about Bears and frozen turkeys ???

Just a word from the plane guys , They’re mixing the Gripper with microballoons as a gap filler , and reportedly works very well ... small gaps we assume ... They’ve taken the Gripper seriously and are doing all kinds of testing , and now on other primers too, which none as yet seem to be as good as the Gripper ...
Foam dust from sanding might make an acceptable filler mixed with the Gripper , might as well use Everything ... Thrifty eh ...

[bonnie]

QUOTE: Just a word from the plane guys , They’re mixing the Gripper with microballoons as a gap filler , and reportedly works very well ... small gaps we assume ... They’ve taken the Gripper seriously

Really? Now that is interesting. BUB may end up smooth after all.

[GPW]

Bonnie , a really smooth finish is just some filling and a LOT of sanding , and repeating that process till you get it as smooth as you want ... and consequently much more difficult to repair , should you need it.. Sometimes “plain” is Good , more time to make the inside more comfortable ... where it counts..

[Jack B.]

I've always been a fan of the light texture of a weave like burlap under a coat or two of paint. Used to share a house with a guy who would buy houses, redo the interiors and then resell them. His favorites were rough cut wood and different colors of burlap under varnish for wall coverings. Rustic, cheap and he was gone before the buyers found out how hard it was to come up with a decorating scheme that wasn't going to be Grant Woods in nature.

Small things - paint 'em. Big things - use vinyl siding. Both are easy to DIY. Just don't know how the siding thing would work on a mobile camper trailer at highway speeds. But then there are those who still think concrete won't float.

Jack

[bonnie]

Bonnie , a really smooth finish is just some filling and a LOT of sanding , and repeating that process till you get it as smooth as you want ... and consequently much more difficult to repair , should you need it.. Sometimes “plain” is Good , more time to make the inside more comfortable ... where it counts..

I am suffering through the funny little thing called; make it nice outside. Just trying to resolve the obvious weave of the fiberglassed part and the coming top, which might end up being canvas. Still trying to decide.

[Bogo]

What about Bears and frozen turkeys ???

I'd be more worried about self mobile cat toys...

[GPW]

Yeah , probably more of them around eh ???

[Wobbly Wheels]

Just a thought Bonnie, but something that came up in another regarding filling the weave of glass cloth. I called the local Glidden guy a couple weeks ago to ask about getting Gripper in Canada and, when I mentioned using it to fill the weave of an epoxy layup, he suggested 'block filler' instead. Apparently I wasn't the first one to have asked him about this.

IIRC, GPW had some first hand experience with the stuff, no ?

[atahoekid]

Bonnie , a really smooth finish is just some filling and a LOT of sanding , and repeating that process till you get it as smooth as you want ... and consequently much more difficult to repair , should you need it.. Sometimes “plain” is Good , more time to make the inside more comfortable ... where it counts..

I am suffering through the funny little thing called; make it nice outside. Just trying to resolve the obvious weave of the fiberglassed part and the coming top, which might end up being canvas. Still trying to decide.

Bonnie, I too suffered from the same affliction. As I realized how tedious weave filling can be, and how expensive epoxy resin is, I let good enough be. It's partly a matter of whether you take the 12" view or the 3 foot view. It looks great at 3 feet, looks OK at 12". Not too many people get to within 12". I'm now OK, without going totally smooth