Aluminum skinned semi-streamliner

[Runout]

Okiedoke...pretty new here, but I've been lurking awhile trying to scavenge ideas. This is probably going to be a slow build, so don't expect a lot of action in here. I was a carpenter for 25 years before health issues shut me down, so I figure I should be plenty handy to tackle this. The theme for this build is CHEAP. I'm going to try to focus on reusing and repurposing as much junk as I can, without looking like that's what I'm doing. This is where I'm at:







The broad strokes:
I'm looking to build a small, lightweight trailer to tow behind my Subaru Crosstrek. It's rated for 1500 lbs tow capacity here in Canada, but the same car is rated for 3000 in Australia, so unless their upside-down gravity does something to the towing capacity of vehicles there, I'm not too scared to go a tad over 1500. Car is 5'9 wide, so that's what I designed the width of the trailer to be, so as not to interfere with the mirrors. Headroom is 6'7" as designed from floor to the bottom of the arch framing, but that's subject to change. I'm 6' tall so I don't think I want to drop too much below that. I have the length set at 12' for now, but that may change as well, depending on minimum space requirements.

Major design elements:
-Floor: Torsion box! The plan is to build the floor similar to the construction of a lightweight hollow core door. The bottom skin will be 1/4 inch plywood, the top will be 1/2 inch ply, and the vertical elements will be made from 3 1/2" wide plywood (some 3/4" and some 1/4") standing on edge, laminated to the top and bottom skins. I expect this to be very strong and light, and intend to build it to piano precision as it will be the foundation of the build. Pretty critical to get this part right. I think I've just about talked myself into fiberglassing the bottom, but we'll see.

-Framing: The majority of the framing will be 3 1/2" wide 3/4" plywood, with some 2x4 construction to make the door area a bit tougher. It's drawn at 3", but I think I'll make it that half inch bigger for some extra rigidity. The shelf at the front of the trailer just above the windows is a fairly important structural member, and should stiffen the framing tremendously. I have some experience building cathedral domes, so the curves aren't too intimidating.

-Aluminum sheeting: I plan on using this stuff, https://www.homedepot.ca/en/home/p.flashing-coil-12-in-x-50-ft----mill-aluminum.1000112299.html, or similar if I can find 16 or 18 inch widths somewhere. I can get the white painted aluminum in 24" x 50' rolls, but I think I want it unfinished so I can polish it a bit. All of the framing is designed so that flat sheets of aluminum can be used everywhere, so I won't need to make any compound curves. That's why the front is 6 sided instead of a curve to match the roof. I had considered canvas or fiberglass, but the canvas seemed to lack lifespan, and FG seems like too much work (and sanding dust). Also, I'm part magpie, I like shiny things.

-Sleeping area: I need me a big bed. I've got an old Ikea futon taking up valuable real-estate in my crawlspace, so utilizing that was a primary concern for this build. Living and cooking spaces are secondary concerns.

-Windows, Doors, Appliances: This is where the scavenging comes in. A buddy of mine is a realtor, and one of his clients has a camper trailer in usable condition that they want rid of and were just going to take to the dump. He remembered that I was looking for a small trailer, and got them to agree to give it to me for free. I haven't seen it, but my plan is to dismantle it and scavenge as much as I can as it's Much bigger than I need. Looks to be about 20 feet, and dual axle from the picture I saw. I intend to make the front windows from lexan, not sure if they'll be openable or fixed. We'll figure that out when I get there.

-Trailer Frame: Again with the donor unit. I'll either be modifying the frame from this trailer to suit my needs, or using an old tent trailer that I turned into a utility trailer. Not too sure about how I'm going to tackle this part yet, but I should have lots of options.

...and that's about as far as I've gotten. I'd appreciate you guys pointing out the gaping holes in my plan before I start. I've given it quite a bit of thought, but it's entirely possible that I've made some sort of huge miscalculation, so don't be shy to speak up. Links to relevant threads here would be appreciated also, for any homework you think I need to do.

Thanks,
Mick

[greygoos]

The design looks very similar to GPW's Foamstream. Maybe take a look at that.

[Runout]

Actually, GPW's foamstream http://tnttt.com/viewtopic.php?f=55&t=45027 was one of the first threads I read here, and my primary inspiration.

[KCStudly]

That half inch of rib "extra" is a slippery slope to over building. 3 inch ribs seem plenty stout to me.

Also, consider using 1/2 ply only where you walk. When fully bonded in a built up floor 5mm is plenty strong enough for distributed and static loads, like under bed storage.

[noseoil]

I agree with KC about the scantlings. If you're using the construction techniques you've mentioned, I would do a "mock-up" of a wall section & play around with it a bit, to see if you can reduce weight & material costs while keeping the strength you need. A sandwich wall/floor system is pretty stout. Weight savings = gas savings as well.

[OP827]

In adition to already mentioned, here is another point, a torsion box floor and its almost 4" total height. It will add to your trailer height and it is perhaps the biggest factor for safer towing and fuel economy. I personaly used 5/8" plywood over a donor tent trailer frame with some stiffeners in trafic area and the floor feels strong.

[Runout]

That half inch of rib "extra" is a slippery slope to over building. 3 inch ribs seem plenty stout to me.

Also, consider using 1/2 ply only where you walk. When fully bonded in a built up floor 5mm is plenty strong enough for distributed and static loads, like under bed storage.

Good points. Maybe I'll use 1/4" skin for the whole box, and just laminate another layer of 1/4" to the traffic areas.

In adition to already mentioned, here is another point, a torsion box floor and its almost 4" total height. It will add to your trailer height and it is perhaps the biggest factor for safer towing and fuel economy. I personaly used 5/8" plywood over a donor tent trailer frame with some stiffeners in trafic area and the floor feels strong.

I think that I'm kinda married to the torsion box idea. Building domes is much easier with a super accurate base, any variations from perfect and the fudge factor starts to get pretty big. If I can get the base and framing perfect, the aluminum skins should be tons easier to work with. I see where you're coming from though. Also, with a torsion box, I figured I could really minimize the steel in the trailer frame, given that the floor will be so strong.

Has anyone used some sort of drop-axle setup to get a lower profile?

[stcyrwm]

Did this ever get off the ground? I love the design including the idea of the aluminum siding.

Thanks, Bill

[Runout]

No, I found a Boler for dirt cheap and rebuilt that instead.

[stcyrwm]

No, I found a Boler for dirt cheap and rebuilt that instead.

That sounds cool too.

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