Metal Conduit frame for Foamie Construction

[Nodrog]

Sorry, I have myself run into inconvenient facts many times over the years! I submit that it is difficult to beat certain minimums in the light trailer endeavor. Really, a wood frame and cover can be pretty darn light, see the Wanderer in the Design Library. Fast to build, also, comparatively.
There are some concerns with a folding design that need attention- the separate parts need to be rigid, resisting racking forces. A young fellow built a trailer with raising roof of foam and had trouble with joints after pulling it many miles over rough roads. Maybe a few 1x2 lap joints with epoxy fillets at the laps would provide lots of rigidity, and be pretty low tech, too.
For rot resistance, a little bit of cedar would maybe be a good choice? Just use in such a way that swelling and shrinking doesn't affect the look and function of exterior covering...on my trailer plywood used in window openings and glued in with some latex goo showed pretty sharp little bumps when humidity increased during rainy season. I have glued on aluminum strips (with polyurethane caulk) to cover those edges. Then put in the windows. I thought the surface looked like it might work enough to crack paint thus compromising waterproofing...My trailer is pretty light, minimum wood...
The upshot is, there are different ways to get there, the main thing is, don't overbuild. Nodrog

[Postal_Dave]

John wrote:

Thing is I'm questioning the need in the first place?

Why don't you think pure PMF alone won't be structural enough?

As you can see in the roof design of my first camper, the roof is in two parts. The main part is 10 + feet long. The second part of the roof lays over the front of the camper body when the camper is folded down. So there is a hinge between the two parts, also there is a hinge at the back of the main roof that connects it to the lower part of the camper.
When I raise the roof, I grab the folded down, front part of the roof and raise it above my head. This puts all the weight of the roof on the front hinge.

On the original camper, the wood that the front hinge was mounted to, has since weakened. I don't dare lift the roof up any more because the screws that hold the hinge in place would probably tare out.

In the new design, if I incorporate a little EMT into the foam, I can attach better, stronger hinges and support the roof better during the lifting of the roof. And I'd never have to worry about rot. Running the EMT down the entire length of the roof should only add about 15 pounds to the overall weight of the roof.
**New Question. Putting the metal EMT 8 - 10 feet up in the air like that. If a thunder storm came up, would that attract lightning?

[John61CT]

Racking forces are low on the road.

Any wood required - for door jambs, other hardware mounting points get fully encapsulated in the PMF slab,

We are talking about a foamie right? The use of wood for structural strength was just a reference to the previous design right?

[GTS225]

**New Question. Putting the metal EMT 8 - 10 feet up in the air like that. If a thunder storm came up, would that attract lightning?

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It might. Lightning is searching for the easiest path to ground. If there's something close by that offers less resistance, then it'll probably it that, but if your camper is the easiest path, even if the metallic structure isn't grounded, it could hit that and burn out some of your electronics in the process. Lightning has enough voltage behind it to arc through just about anything.

Roger

[M C Toyer]

I built my last camper with a wood frame. It turned out much heavier than I would have liked it. Some times the wood would warp and crack. The knot holes in the wood caused problems. I was looking for a substitute to use instead of wood for the frame of my next camper's roof that would be straight, lightweight, strong, and cheap. At first I tried PVC pipe but that was way too flexible. Metal Conduit seemed like a good answer. A 10ft long, small diameter pipe costs less than a 2X4 and is lighter. Connectors are available for joining ends. I was thinking of cutting groves in the foam and then using Great Stuff the glue the foam to the pipe.

Has anybody tried this already? What would be the downside of using it? Is there a better alternative? What are your thoughts on this?

Thanks for your input guys.
Dave

I've used 1" diameter EMT on two trailers. The first was a teardrop shaped cap for a 4x8 trailer with 16" high sides. The cap was hinged at the front to allow lifting to load a dual sport motorcycle through the rear. The roof line radius was hand bent on a jig laid in a sheet of plywood. The roof spars were straight. All joints were made using welded connectors which were then pop riveted. The original covering was a custom sewn canvas but later I replaced with FRP (Fiberglass Reinforced Plastic) pop riveted to the EMT. There was not any rigid foam insulation but could have been easily added between the EMT members.

The second use was for the roof spars on a Benroy design. The spars were set into the plywood sidewalls, a layer of indoor/outdoor carpet placed on top for the interior finish, followed by a sheet of 1/8" Masonite to maintain the radius and then the FRP. All was stapled and glued along the edges then the edges capped with angle.

The primary considerations were for weight saving and strength over comparable wood members, and expedience of construction.

Both trailers traveled several thousand miles, mostly off road or secondary gravel roads, without any problems with the EMT or joints.

Teardrop hinged cap:




Benroy roof spars:

[Postal_Dave]

M C,
Your images didn't show up your post so I looked at them in your gallery. I really liked what you did there.
The teardrop cover for your trailer makes me wonder if you could make an entire teardrop frame out of EMT.

[GPW]

“ makes me wonder if you could make an entire teardrop frame out of EMT.” Why not ??? ( Think light aircraft )
Stay upwind of the white smoke … ( we’ve used EMT to make Chopper bicycles before … )

[John61CT]

Wow! Must be thicker-walled than usual?

[PCO6]

I haven't followed this thread closely so my apologies if this has been discussed, dismissed or is generally off base. I just built a roof/kayak for my trailer and I used residential chain link fence 1.25" OD top rail for most of it. I even used a fence gate for the 90* corners. It was very easy to cut, fish mouth, splice, weld, paint, etc. The wall thickness is 3/64" so it's pretty light and it's strong. Like most things though, strength comes through design. I didn't have to make any bends but putting a slight arch in it would be easy (depending on the span). I wouldn't hesitate to make "larger" items with this provided the design was right.

I just thought you might find this to be a source of relatively inexpensive material for projects like this or other ones.