Designing a hard-shell rooftop tent

[vskid3]

While the structure may only weigh 300lbs, will it remain an empty tube for you to stand in while camping? It'll get a lot heavier pretty quick when you add you and whatever camping supplies.

[seifrob]

Hi, i dont want to be a spoilfun, but my back-of-the-envelope calculation indicates that this structure has potential to flip over the car in relative wind speeds of around 100 km/h. So i would not recommend it.

[jakobnev]

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[seifrob]

For others: it's Toppola what jakobnev posted. It offers standing place with small footprint. Visit http://www.toppola.com for more info.

To jakobnev: is it yours? How does it handle in crosswinds? Was your post meant as suggestion what to do instead rooftop whale, or as contradiction to my claim?

[jakobnev]

I don't have one myself, I was just trying to suggest a design that was a bit more sane.

[BigChief]

Originally Posted by seifrob

Hi, i dont want to be a spoilfun, but my back-of-the-envelope calculation indicates that this structure has potential to flip over the car in relative wind speeds of around 100 km/h. So i would not recommend it.

I don't necessarily doubt you, but could you give me some insight into how you arrived at that? Keep in mind the Tesla Model S 90D is 4842 pounds curb weight and it is very bottom-heavy.

[seifrob]

Aha, them i rise whole hand for toppola style. I only fear that one has to have some balls to remove hatch in - how much is for Tesla car??

If I remember right, some lady even made trip around the world in Saab and Toppola, so it definitely is viable proposal.

[BigChief]

Originally Posted by vskid3

While the structure may only weigh 300lbs, will it remain an empty tube for you to stand in while camping? It'll get a lot heavier pretty quick when you add you and whatever camping supplies.

I'm making the seats/tables from the same carbon fiber sandwich panel I'll be using for the structure, so that weight would be negligible. Luckily a lot of camping supplies are designed for the new "ultralight backpacking" fad so there's many things like sleeping bags/pillows that would hardly add any weight at all. I'd be piping the heat/AC in from the Tesla via some flexible ducting when needed, and any occasional-use appliances would probably be stored in the Tesla's frunk.

One of the main reasons I don't want a collapsible tent is that they all suck for insulation. I actually have a stash of vacuum insulated panels which are an inch thick and R-40 but they can only be mounted on a rigid structure.

[aerohead]

Originally Posted by BigChief

Hey All, I'm attempting to design a rigid rooftop camper tent that will be permanently mounted to the roof of a Tesla Model S. This is going to be an around 7-foot diameter tube (I want it to be standing height inside) and 20 feet long so there's no overhang on the sides and about a foot and a half of overhang at the front and rear of the vehicle.

Here's a concept picture here, I used a plane fuselage model since that gets the idea across: imgur.com/BhKIclp

I'm making it out of carbon fiber and nomex honeycomb, I did the math and it'll come in around 300 pounds which is very light for such a huge structure. The Tesla has about the lowest center of gravity of any production car and I don't drive over 45mph so I'm not worried about crosswinds.

The two big aerodynamic concerns I have are:

1) how best to shape it (if it were 40-feet long, it would be easy to shape it like a killer whale with standing room in the middle and a narrower sleeping area in back, but 20 feet with a standing-height requirement makes it really hard to keep the drag coefficient down and still be practical

2) how much of a gap I should have between the floor of the camper and the roof of the car. If there's little gap, I'm worried the frontal area will act like a scoop and totally mess up the aerodynamics of both. The Tesla is 4.7 feet high and I would need to keep everything under 13.5 feet to be street legal.

I tried modeling everything in "Autodesk Flow Design" which is a 3D wind tunnel simulator but I'm not convinced it is giving me Cd values that are anywhere near accurate.

I don't think you'll have proper forwards/upper vision to see traffic lights while stopped at intersections.The sight line will be occulted by the overhang.

[Frank Lee]

That's what autonomous mode is for.