TERRA6, Van cab and chassis 7*14, 4" Polystyrene

[GPW]

And here's a Smaller picture to better see it all at once … and more small screen friendly too … You can still have your simulated rounded roof strength … Arches were probably the most significant architectural development of the ages … they transfer the loads over a large area , adding great strength and structural rigidity … Look Cool too !!! And a good use for foam scraps … We’d expect any flex to be a Torsional flex and arches/gussets can help there .. It can twist , but won't break or collapse.
And you’re really not adding much weight for the amount of strength it will give ...

[GPW]

if you ever watch the videos of RV structural failure , they always seem to flatten out on themselves, the walls don't break , they collapse at the joins …nothing to counteract those diagonal stress forces …

[Projector]

Agreed on the curved roof gussets GPW.
Have considered them for all the reasons that you mentioned.
Any links to trailer failure videos? Would like to see that to study but I can imagine that the wall to roof joint is under reinforced and with today's RVs getting longer and heavier, that span needs way more reinforcement than they come with. It's own weight, length alone requires support.
But then, how much is enough and to what resistance is sufficient? All open to interpretation.

So I was very much concerned from the beginning about this. Extra strength and gussets or arches were considered. At this point I have added walls and boxed cabinets. The major factor is unsupported or nonreinforced wall spans. More than 4 ft to me would be a limit defining bracing requirement need as a general guideline. I look at my build as three 4'*7'*6.5'zones requiring bracing and boxing/support within or at the limit of each.
I have done some testing of this for which I will post a few pics.
One of the important questions that I had for George was if he had, or knew any foamie, that was strong enough that one could walk on the roof. To me this was a benchmark of strength and suitability for the application. If you couldn't walk on the roof, how could anyone say that it was strong enough to withstand all the rigors, forces and stresses subject to the trailer during travel on and off road?
To me, this was the ultimate, quick fast test of any build.
If you couldn't stand on it, how could you say it was strong and resistant?

[Projector]

So I continued with the build.
Delighted to be at this stage, enclosing the box with the final panels. Had to adapt and adjust at the end with an extra 12". But with styrofoam, that was quick, fast and painless and why I had bought extra. I haven't scrapped one piece at this stage but had offcuts which I made do with.
Was contemplating building a GhCoe box trailer as I had enough left for that. Wasn't in the cards with my time constraints and schedule overruns but not ruled out for the future to attempt for sale.
The last panels being mounted and supported with what I could find, a garage wall. One must be resourceful in life with MacGyver skills.

[Projector]

One of the design objectives was to minimize leakage and water infiltration points. Gravity and water have a way of dampening any flaw in workmanship, minute gap and expansion of any seal gap due to time or drying out.
Never a good thing so how to minimize this at the design stage?
No holes in the roof which meant no vents and or minimal intrusions. So I planned a flat solid roof so that in theory, it would never leak. If I moved any cutouts to the side walls, would significantly reduce leak potential. Then it would be sufficient to seal and channel water away. Easier and more effective to seal on the vertical as opposed to the horizontal. But even there, the top lip was critical because it does have a horizontal aspect.
What if I put no windows or ANY cuts to the roof or wall?
That would eliminate any and all sealing issues.
Two aspects would have to be addressed in a novel fashion as a result. Light and ventilation.

Let's start with ventilation. Vents are always placed upon the roof to exhaust hot air as this is where it accumulates. With my 4" of insulation, this aspect shouldn't be as critical. Ideally, hopefully, maybe. Right?
But air circulation is a good thing regardless but does it have to be a roof vent or a window? Could some outside the box thinking come up with other solutions which might be better?
A vent in theory could be placed anywhere couldn't it?
So looking at my build, what was ideally the best place to minimize a sticking out vent with leak potential?
There are six sides to an RV and numerous possible locations.
Here's what I decided...

[Projector]

4" styrofoam would give great insulation but would eventually not change the fact that eventually inside temperature will equalize to outside temperature. The foam would only slow down the transfer rate by hours. And fresh air is always a good thing.
Normally we use vents and opening windows for air circulation and for cooling, closed for cold air.
I was contemplating no windows at this stage for stealth and making do with very bright LED light strips in the interior. When I wanted daylight, I went outside.
But cool fresh air would still be needed. Had found an under spot that would be ideal for an air intake, out of rain infiltration. Perfect location in a dead space, ideal.
From there I could create a duct into the interior from the overcab storage space if need be. Or just have a door and leave it open. Or I could....
Use the 5 12v computer fans that I had bought at Goodwill for this purpose. They could be switched and controlled as required. Should be low cost and effective.
Ideally, hopefully, maybe. TBD, to be determined. It's winter and the nights are cold, and days mild to cool. Not an issue at the moment.
Now for through flow of air, I originally planned air outlets out the back. But I figured I could easily cut and install further ducts and outlets in the back wall or through the floor. Will work with this at a later date as it is low on the priority list at the moment. It's winter and cold air flow isn't desirable!
Phew, that's a breathe of fresh air!

[Projector]

Ventilation also serves the very important function of humidity control. I had a couple things working in my favor minimizing this issue.
The SW and it's constant low humidity weather.
My cooking style is quick fast and easy so wouldn't be boiling liquids for long periods of time, creating a lot of vapor.
Wasnt planning on having long hot showers either. No hot water source, cost or space requirements.

Living a minimal lifestyle, conserving important resources reduces ones needs, waste and resulting issues. Conserving water usage in all aspects gave so many benefits and eliminates many others. Living by minimizing ones needs reduces many problems and issues, humidity and water consumption being some of them.
If you reduce your needs, the less costly, farther and longer one can travel and explore, reducing your requirements and life costs. And one could live on allot less, freeing up your life, reducing stress. A consumerist lifestyle is costly and reduces your one valuable, most precious thing that you have. Your lifetime.
In the words of Steve Miller, " time keeps on slipping, into the future". And you know what's at the end....
Less is more my friends. Spend less, throw off those golden chains of comfort and convenience, love of material things, get out and explore the world I say.
You can live a beer commercial fantasy, without the beer calories and costs. Think about it, beyond conventional marketed hype and lifestyles.

[Projector]

The roof, the roof.
One of the most important elements of any build or shelter.
The size was a concern due to its span and material. 7'*14' and made of supported styrofoam.
The stresses were a concern.
The strength and durability were a concern.
The design was a concern, being flat, made of styrofoam and only covered with PMF, a thin cloth and an even thinner coat of acrylic paint. Not the most weather resistant nor UV resistant. The SW sun is merciless as are summer temperatures. And I was going to be exposed to it 24/7, 365 days a year.

I believe that I have the strength and support issues taken care of, or at least sufficiently so for the moment. Could always add more later if need be.

Water drainage was an important issue for which many slant or curve their roof. My rig already had this built in. GM determined that raking the entire vehicle and making the back higher than the front was advantageous. Unfortunately it's was towards the front but we could live with that. Had to. They do sell leveling kit for the vehicle for this purpose, which I may assess in the future. But for the time being, no problemo.

I had contemplated other roofing options. Covering the roof in fiberglass, plywood, metal, rubber membrane, etc...
I assessed and analyzed the pros and cons as well as the cost of each. I wasn't sold on just foam and PMF as a durable and damage protective roofing sheath. For the sides, sufficient, but not the roof. I remembered Skylab.

I was going to add something to the roof and figured that for the cost, metal was probably the best overall. Got a quote from a custom metal shop to fabricate a three piece pan for $350. Worthwhile and cost effective I thought for 100ft2. $200 if I wanted to just purchase the metal and bend it myself to fit. Now it was seeing if I could do better or the same at a cheaper cost. You may be surprised at my solution which came in at the same ballpark cost...

[Projector]

Ok, my next series of pics might surprise you.
Or blow up the internet.
Or not.

You might be very impressed.
Ideally, hopefully, maybe.
Or not.

Now if I can just upload them...

[Projector]

Any guesses as to what they might be?

[Projector]

This will be fun to watch.
Keep at it and keep posting lots of

Thx W for the interest and encouragement.
My whole purpose with this thread is to share my knowledge and experience gained with others yet keep it interesting and humorous beyond just foamie tech talk.
And to pay it forward.

[GPW]

No worries , we all have these misconceptions when we start ….We all have a tendency to OVERBUILD …

1. You don’t walk on your tent roof eh … and that’s not a priority around here except from the novices ..
2. Your car doesn’t have a vent in the roof , just windows … Around here in our wet clime … putting a vent in the roof is an invitation to a leak … The old timers would put a small vent high on the wall . ( old timers were Smart , not trendy ) The addition of a small floor vent creates a natural flow through ventilation . No fans required … Screened windows (that open ) are always nice to let the air in and out …
3. Metal roof ? Maybe Overkill eh ? Unless you’re parking under trees in a storm … WE used 18oz. canvas on our roof and all, doubled in many places … STRONG !!! … never regretted having a reallty thick roof covering after a tiny limb went right through my Jayco POS roof …… in ten places …
4. JMHO , all cooking should be done Outside the trailer ( why TDs are ideal ) … Otherwise you will need fans … and will be washing the walls often to remove the cooking spatter and remove the smell. FS only has a microwave , toaster oven ,and a coffee maker … If I want to fry fish , I’ll do that over a small campfire outside … just like people do when CAMPING ..

We build to suit ourselves… What you want is what you’ll be happy with !!! … Build what you want , the way you want !!! And don’t worry , anything obvious will likely be noticed and commented on … ( we got your back )
And from our history around here … pictures are much better than lengthy epistles …. Nobody here likes to read much ( especially the BIG threads) , and have told us as so …

[Projector]

You never really know if you overbuild, but you do if you underbuild. We all know what happens to cheapened out items that we purchase, especially plastic. They fail and break when stressed due to insufficient reinforcement in critical areas.

Reduced mass during the molding process means less material used, lower costs and more profit.

And there is allot of stress during transit, wind force, semi wind buffeting creating side forces and impact. Bounce
and impacts over dirt roads with washboard, strewn with rocks and potholes.
Determining strength and reinforcement is definitely a debatable topic. How much is enough, too much or too little? The only one that is certain, is too little. And the one mistake you definitely don't want to make.

[Projector]

One aspect that I haven't covered so far is the deck which is kind of important. On my previous Armorhaul build where I extended a harbor freight trailer from 4*8 to 6*10, I had welded 2*2 angle to do so. It wasn't strong enough and flexed alot. How did I know? First trip that I made, I was flagged down by a motorist, the back door was flapping open going down the highway at 65mph. Lol.
Had to strap it shut and would later screw it shut.
Important lesson learned, the foundation is critical to the strength of the rest of the build. It had better be strong to eliminate any further flex from chassis and ability to absorb impact.

So I started with this

[Projector]

After which I ran around parking lots looking at how cube Van boxes were attached to the chassis.
Surprisingly, many had wood 4*6 simply u- bolted to the frame and small steel cross ribs that the flooring was attached to. That's it.

Unfortunately, the GM chassis isn't flat and couldn't bolt directly to it like the Ford and Dodge were. Plus the axle bump meant that I had to raise the deck above those, adding weight and unneeded layers but had no choice.

So I divised my own deck similarly. Attached treated 4*4 that I triple coated with Rust-Oleum rust paint. My own version of the mix which I think is just as water resistant and durable. I glued and screwed two layers of 3/4" plywood, cross directionally layered, to the cross beams, and quadruple coated them on both sides with Rust-Oleum. Not necessary being in the SW, but would this always be the case?
It's also my plan to lay styrofoam underneath for insulation and keep any splashing water from constant and direct contact with the decking.

Was going to make sure that I had a strong foundation this time with which to build upon. 7 beams total for an approximate 24" on center spacing.