Large shoebox foamie build log/questions

[rgambord]

Here's my design so far. I've got the trailer frame (Harbor freight 1720 lb) put together, but haven't added any wood yet. I'd like to finalize the design before beginning.

This is my second trailer build, but my first enclosed trailer working with foam. This trailer will be used for a cross-country move, towed behind a CUV (1500 lb capacity), and temporary/semi-permanent housing at my destination. Thus, I have designed it with at least 6' of ceiling height, but 4' compacted height, to save gas on the 2000 mile journey. The design is 7' wide with 2" thick walls, allowing a queen size bed to lay across the width of the trailer, and another 7 feet of space by its side. The dog adds a bit to the size requirements. The floor is 3 sheets of 3/4 T&G osb on <24" centers. I cannot purchase thinner T&G, and I think the weight savings from thinner (7/16) osb or ply would be offset by the necessary blocking in the frame. The walls and ceiling are 1" pink foam with 1x plywood frame embedded and glued.

I have some nagging questions:

• Is 1" foam going to be sturdy enough when said and done? I could move up to 2" foam, and widen the trailer to 7'4". Cost is a huge concern, though.
• The roof will be three piece of foam, joined lengthwise, and the 12' sides will also need at least one butt joint. If I'm planning on a 1x frame, is this a concern, strength-wise?
• I'm worried that canvassing the inside wall might add too much thickness. Thoughts? Are there alternatives to canvas that are cheap/lightweight?
• I heard the floatstream used EPS instead of XPS, but couldn't find that in the build log last night. Is it just as strong and water-proof?
• I'm a little concerned about someone trying to break into my trailer. How burglar proof is foam?
• Can anyone think of a better design? I toyed with hinged roofs/etc, but I thought it would be too difficult to waterproof, and I'm moving to the Pacific Northwest. A hinged roof would only need 6' of clearance from the front to the middle, due to the mattress taking up the rear.

http://imgur.com/a/nsQ1A/all album with more pictures

[KCStudly]

I'm a little confused. You state 2 inch thk walls then mention 1 inch.

Also, 7 ft wide on a 4 ft trailer seems pretty wide to me and might be unstable in side winds depending on height. Despite already buying the HF, you might think twice about using an old PU trailer to start. They are typically wider.

12 ft is a pretty long trailer on an 8 ft chassis, IMO, especially if you are sleeping across-wise.

Sketches would be helpful.

[rowerwet]

unless you aare over 6' tall you don't need 7' wide for the bed. towing something that wide will be no fun, requiring towing mirrors and having the aero drag of a parachute.
you don't need standing height over the bed, 4" feet would give you more than enough, I would slope the front down over the bed for some help with the airflow.
Rather than making a box with a flat roof, how about a pitched roof like a house, tall enough to stand in the middle, but lower on the sides to reduce drag. Make the peak come down at the front like the bow of an upside down boat.
remember a harbor frieght trailer isn't rated for much more than 1250 lbs depending on the model. Once you build a large trailer on it, even with foam, and make a deck strong enough to stand on , you won't have much payload left for hauling stuff while moving.
A queen mattress is almost square, I would put it in the trailer lengthwise with narrow isles along both sides and go with 6' wide, about the widest an average car or truck can tow easily.

[rgambord]

This is kind of the feedback I was expecting. Thanks.

@KCStudly, the walls would be 1" foam, but would be 2" thick when nested (roof lowered). I currently pull a 20 foot trailer for my canoe, with no issues.

@rowerwet, I am 6' tall, and I've got the problem of having a queen size bed that I need to move. Besides being the most comfortable bed I've ever slept on, it's very expensive, so I can't leave it behind. I had considered running the bed lengthwise in the trailer, but it wouldn't leave much room for the dog and the rest of my belongings. I've never towed such a wide trailer, and I am very concerned about handling and stability. Maybe I should re-think the design a bit. Perhaps I can add storage under the bed or something to reduce size. I'm planning on putting the bed in the back of the trailer to add a little tongue weight. The trailer is rated for ~1700 lb, and the car is rated for 1500 lbs, but that's a very conservative rating.

Edit: I just crawled around in my 4' high closet. Definitely need 6' ceilings.

[KCStudly]

I get it now, a nested box pop up.

I would be concerned about the long unsupported edge of the walls. At first I started thinking about interlocking flanges out of 1x2, lower flange extending out, upper flange extending in so that a gasket seal could be formed between them, but then you would probably be better off doing a lifting roof like Sharon or Mike Young did with a partial lifting roof over a raised cofferdam.

Their designs solve many of the issues, like doors and windows, easier sealing, easier articulation, and probably more. I think you would be able to build this way faster and using less material (less weight and cost), and still achieve your goals of standing space with compact towing. The style could easily be converted to foamie/foamie hybrid construction.

Here's Sharon's My Away build.

And Mike Young's Where or When Jr.

Just another option to consider.

[rgambord]

@KCStudly, I actually initially planned on a pivoting roof, like that. It would be well-suited, but I couldn't figure out how to properly keep rain out. Where I am moving, it rains constantly.



I'll be looking at their build logs. I'm also thinking about using torsion boxes instead of foam, as they do seem a little faster/easier to build, and less expensive, because I can use EPS instead of XPS, and don't need to use canvas.

[kudzu]

Speaking as someone who has lived in some tiny spaces & currently has a small folding camper, I would do all I could to maximize underbed storage. This is especially true when overhead cabinets are not practical. If I needed a bed the size of your then I too would want it lengthwise so I could have a narrower trailer. My little Aliner is 78" wide. While that is a manageable width for me, when towing I really wish it was only 72" wide.

Am certainly no expert but I'd suggest you give KC's idea of swapping the HF trailer out for an old pop-up trailer base. It would also give you more payload than the HF trailer. It's a bit of a hassle but if you've already assembled the HF trailer you could likely sell it for what you paid for it, only being out your labor. I believe wider trailers really need a correspondingly wide wheelbase to remain stable & have good towing manners.

While the lower profile of your design will definitely help when towing, I think you could increase fuel economy by building an aerodynamic tongue box. It could also increase storage space. Here's an example just to give you an idea of what I mean. http://tnttt.com/viewtopic.php?p=894520#p894520

These are just some thoughts of mine, for what they are worth... which may not be much.

[Pmullen503]

I'll second the idea of using a pop up trailer. You'll need to build a lift mechanism to get that upper box up and down without jamming (like on a pop up.) You can find pop ups with bad canvas for not too much. It will be wider, heavier and full of parts you can reuse.

I recommend you make a test panel of canvas covered foam and do some destructive testing. I think you'll be surprised how tough it is.

[wagondude]

To help you understand how the lifting roof keeps water out, look at the plans that Mike and Sharon based their campers from: http://www.angib.pwp.blueyonder.co.uk/t ... tear48.htm

Scroll down to the drawings at the bottom for links to the plan PDF drawing links. Once you take a look at it, how water is kept out will be easy to see. There was another attempt at a telescoping box trailer that ended up not being completed. The box is simple enough, it is the lifting that gets complicated. Where there is a will there is a way, but if the way is too difficult, you may not get to enjoy the fruit of your labor.

[GPW]

‘bord... 2” thick foam would be better really !!!

[rgambord]

I am taking all of your feedback into consideration. Thank you very much.

I looked into raising the bed ~3 feet to clear the dog kennel, and make room for storage, etc..., but I think the weight of the bed (100 lb) + occupants (250 lb) + dynamic load would require way too much framing. It would also necessitate having a roof that rises straight up and down, rather than tilting, and it seems there is an opinion here that straight up and down is difficult.

I think I'm going to go back to the drawing board for a bit, and see if I can't come up with a better design.

[KCStudly]

Now is the best time to make changes!

On the other hand eventually you have to (stop) the engineers and go into production.

[GPW]

“dynamic load “ ....on the bed ....