Removable roof?

[scrap_maker]

Hello,

I've been lurking and learning from the people in this forum. I think I am ready to take on designing my first TTT.

First, some requirements for my TTT:
- I have no metal skills/experience, so I prefer a simple unmodified HF trailer (4x8).
- Solo camping most of the time, perhaps room for two in the future.
- No galley needed, I don't cook.
- I want to have a configurable internal space so I can rearrange (eg. all sleeping area, 1/2 sleeping with small desk, etc).
- Prefer insulated walls and roof to keep sound down.
- TTT needs to be garageable.

So I've decided on a simple design.
- Stick built 4'x8'x4' box.
- 1x2 poplar for walls.
- 3/4" insulation in walls.
- FRP exterior skin (may paint with UV exterior paint).
- 1/8" ply interior skin.
- 2x2 poplar around the base of the wall where it meets the floor.
- 1/2" plywood floor.
- Removable roof built from 3/4" EPS foam board, completely covered in canvas and TBII (inside and outside).
- Roof secured to top of 4'x8'x4' box using screws and tee nuts. Small 1/4" plywood pieces will be glued into the foam for tee nuts to secure to.

The roof can be removed when the trailer is moved in/out of the garage. It can even be stored on the side of the trailer, if there's not enough height in the garage. The roof is secured to the top of the 4'x8'x4' box while in motion and camping. I hope this makes sense.

Questions:
- How heavy is the foam roof going to be? Can one person lift it slightly and slide it to the side (as shown below)?
- Is the 4x8x4 box going to be stable enough without roof spars?
- In general, is this design doable? Anything glaringly wrong? Please critique.

Removable Top - Side.jpg (163.18 KiB) Viewed 1703 times

Removable Top - Back.jpg (167.37 KiB) Viewed 1703 times

Removable Top - Inside 2.jpg (251.7 KiB) Viewed 1699 times

[scrap_maker]

Removable Top - Slide 1.jpg (99.28 KiB) Viewed 1701 times

Removable Top - Slide 2.jpg (103.09 KiB) Viewed 1701 times

Removable Top - Slide 3.jpg (117.38 KiB) Viewed 1701 times

[scrap_maker]

Removable Top - Slide 4.jpg (130.99 KiB) Viewed 1700 times

Removable Top - Slide 5.jpg (108.33 KiB) Viewed 1700 times

[S. Heisley]

It looks like it would work. While your removable rooftop would be fairly lightweight, the size of it might be cumbersome; and, if it is a gusty/windy day, the wind could get up under it while you're removing it and cause you to lose control. Consider adding some removable straps to one side of the inside, to use as a wind anchor of sorts and maybe some handles or hand straps to give you some good gripping points. ...Just a thought.

[scrap_maker]

Good point, I didn't think about that and it can get pretty windy. I'll add straps and handles to the TTT to make it easier to handle the removable roof.

[RandyG]

Remember, a lot of the strength of a camper comes from the roof or roof spars. Not having any will make the walls much weaker. Do you plan on putting any cabinets inside? Maybe in the front?

[bobhenry]

There have been a few similar builds on this forum and a couple utilized a fiberglass or aluminum truck topper as the roof element.

http://www.tnttt.com/viewtopic.php?f=50&t=57069&p=1037330&hilit=truck+topper#p1037330

[scrap_maker]

@bobhenry: I took a look at the fibgerglass toppers but they are too heavy for me to lift. It certainly would take a lot less time if I can just drop a pre-made cap on top of the box.

@RandyG: I've added cabinets to the front and I'm hoping it makes the 4x8x4 box sturdier. It certainly makes it look better and more storage to boot. It also serves as a small table to throw my knick-knacks on. Woot!

Removable Top - Inside 3.jpg (158.65 KiB) Viewed 1534 times

[rowerwet]

foam is super light weight! before I dive into a foamie tear build, I learned how to work with foam by building a foam kayak. I've built many plywood ones to the same design so I know they come in around 35 lbs, the foamie mouse weighed in at 13 lbs before paint. It is built of 1 and half sheets of 1" EPS foam board glued together with Gorilla glue and Great stuff.
the kayak thread viewtopic.php?f=55&t=58623

[WizardOfOdds]



"Roof secured to top of 4'x8'x4' box using screws and tee nuts. Small 1/4" plywood pieces will be glued into the foam for tee nuts to secure to.”

I’m no expert in these matters, but if I were building this, reliable roof connection would be a major concern. I would not rely on adhesives directly between ‘small plywood pieces’ and the foam to keep the roof anchored. You might consider running a wood (or perhaps metal or vinyl) member over the full perimeter of the bottom edge of the top with the “fabric sock” over it glued to both the outside and inside surfaces. It seems to me that has a much better chance of holding things together and would also help protect the bottom edge during installation and removal. Frankly, I would probably consider using some kind of hold-down straps like that used in Teal modular design http://www.tnttt.com/viewtopic.php?f=5&t=35892&hilit=teal+modular (modified for the roof). Yea, it might not be pretty, but neither is an airborne top! Put safety first. You might want to post the issue in the “Foamies” Forum.

Have you considered a ‘lifting roof’ http://www.tnttt.com/viewtopic.php?f=5&t=50969&p=1051298&hilit=lifting+roofs#p1051298 ? Simple designs my not give you as much elevation, but that may not be as important over the bed as you might think. If elevation of the roof does not involve increasing the entry height, then construction is greatly simplified. Since your base is 4 ft high and you seem to be happy with a door that is limited to the base height, that may provide you with what you need. Either way, good luck and happy camping!!

[rowerwet]

exterior straps are redundantly redundant, the fabric does the strapping action. If it were me, I would make the cap mating ring overlap the outside of the lower box all the way around. This would make it much easier to keep water out (gravity and surface tension working with a gasket on the mating face) and allow you to have bolts going through both walls horizontally which is much stronger and allows you to have a better reinforcement in the foam lid. A ring of 1/4" plywood 1" wide and all the way around, notched into the foam to lie flush and then with the whole roof wrapped in fabric, would be super tough.

[scrap_maker]

@WizardOfOdds: I have considered the lift top/pop top idea but with the need for hard-insulated sides, I don't think I have sufficient skills to seal the various joints properly to keep the weather out. I think rowerwet's weathersealing approach is more inline with my abilities (ie. non-existent).

@WizardOfOdds, @rowerwet: Thanks for the feedbacks. I've updated the design to include a 1/4" plywood wrap along the base of the roof. The foam will be notched 1/4" so the plywood can lay flush. The tee nut is attached to the plywood before skinning. The entire roof will be TBII and canvased inside and out. I just included one bolt/tee nut in the drawing for brevity. I think this is what you guys were getting at, let me know if I misunderstood.

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Roof Attach - Outside.jpg (74.92 KiB) Viewed 1362 times

[rowerwet]

looks good! you may want a dowel bedded into the foam, with the through-bolt hole drilled through the dowel stub to keep from over tightening/crushing the foam.

[S. Heisley]

Okay, a couple more tips might be in order.

- You could use 1x2" boards instead of 2x2" boards. 1x2 is plenty strong enough.
- I would use latches instead of removable bolts. Even though you plan to imbed the bolts and glue/canvas over them, they could work loose and then you'd have no way to fix them except to cut into your hard work and that could leave a place for water to get in, etc. I would imbed/screw blocks of wood into the foam on the inside and bring it through to the outside wood railing that you have added and screw it into that. Make the blocks big enough so that the block comes flush with the inside docking lip and so that the block rests on the docking lip and so you can also screw your latch portions onto each block and the docking lip board. That way, your top would be easy to remove wherever you are without a wrench or any tools yet secure, with the latches on the inside. (You could use a restroom style toggle bolt system on the inside, if you don't like the latch method; but, I personally like latches better.)
- Instead of a plywood strip on the outside, you could use real wood (not that painted pressed wood stuff) door stop wood or even baseboard, purchased from the orange or blue box stores. It is already formed to give you a nice finished look and will be less likely to delaminate, while still weighing less than a 1x2" board.
- Don't forget to imbed some wood for those handles that you've added. You'll need something to screw the handles onto.

Since you plan to make the stationary portion of your cabin out of wood and plywood, etc, I wouldn't worry about the trailer being too lightweight to handle the extra height. I'd be more worried about your removable roof becoming a kite of sorts. You'll want to have a nice secure and tight fit on that removable roof, not only so that water won't work its way in but also so that air can't get under the edges to make the roof airborne.

You're into me for 4 cents worth of thoughts, now.

[scrap_maker]

@S. Heisley: Thanks for the additional 2 cents Maybe one day, I can pay that forward. I was thinking about using the inside docking lip as a guide for sliding the roof on/off (ie. prevents me from pulling the roof off track) and use bolts with plastic knob handles to make it easier to install/remove. Now that you've mentioned the tee nuts working itself loose, let me stew on the latch idea for a bit. Can you give me a link to an example latch that you have in mind? Something like this? http://www.lowes.com/pd_424846-45395-ST ... facetInfo=