Exactly how does a RTT work?

[STAGE 2]

By this I don't mean how it sets up or functions, but how it works in conjunction with existing roof rack attachments and load capacity. For example, some of the eezi-awns I've looked at have a 1000lb load capacity, yet most roof racks top out at 300 lbs. How does this work.

I ask because I'm considering upgrading my campershell to one with an integrated thule/yakima setup and if I could work this with a RTT I'd be sold. I just don't know if the shell/rack is up to the task as far as handling the load.

Any thoughts?

 

[Corey]

Here is what I was told a few years back when I looked into them.
Most factory roof racks can hold around 160 lb when moving down the road.
A roof top tent weighs much less than that.

When parked and setup, it is a different story, as most rack can support around 600 lbs.
For instance for me:
128 lb Maggiolina AirLander medium
5 lb sheets down comforter
217 lb me
20 duffel bag
25 Campinglab awning
____
395 lb

My rack does not groan one bit with the weight up there.

 

[hurricane harry]

You could use something like these on your existing shell.

I have them on a fiberglass shell now, and use yakima round bars. I haul bikes, sailboards, storage box, surfboards all the time in high winds and never had a problem. I will be getting a RTT in the near future, and not hesitate to put it on the shell.

 

[STAGE 2]

You could use something like these on your existing shell.

I considered that, but my shell isn't cab height and has several aero molds in it so a roof rack in general is out of the question if and until I get the new one.

When parked and setup, it is a different story, as most rack can support around 600 lbs.
For instance for me:
128 lb Maggiolina AirLander medium
5 lb sheets down comforter
217 lb me
20 duffel bag
25 Campinglab awning

This is what concerns me. I'm a featherlike 240 lbs and my better half is a buck 25. That plus the weight of the tent (figure 150) plus bags and extra stuff (30-40) and I'm topping out at over 550 lbs. Thats a fair amount of weight on a standard roof rack bolted to a fiberglass top.

I really like a large amount of wiggle room in my tolerances, but then again I don't know if 500-600 is a hard and fast number given that the tents themselves are rated to 1000lbs.

 

[Corey]

Should get Mike from AutoHome and Martyn from Adventure Trailers opinion too, as racks may be able to take more than the 600 lb I stated.

Every week someone somewhere with their significant other are camping in a roof top tent, and never have I read here or elsewhere that they broke their roof.

 

[18seeds]

i believe the weight rating for roof racks is for when the in motion. They can handle much more weight when stationary.

I have a yakima set up that would work with a shell. The rails are 54 inches long and the cross bars are at 60+ long. Have locks and everything. PM me if you are interested

This is the way i have my rtt mounted

I am going to mount the RTT directly to the truck bed rails.

 

[OffaRex]

I was concerned about the same thing, so I bought a KargoMaster Econo truck rack for $280 and modified it to fit my truck and tent. I was worried about long term fatigue in the shell fiberglass. We have had all six of us (~550lb) in our Mombasa tent at one time with no worries, though only my wife, the two littlest (5 and 1.5) and I sleep in the tent.

These pictures don't show much of the rack, but I'm happy to give you more details.

 

[Lemsteraak]

This is the question I heard most about rooftents, "won't the weight up there crush the roof?"

The short answer is that the weight isn't really on your "roof" but on the support structure. Ideally, it is on the vehicle's rollcage, so the roof isn't the concern.

The real concern should be about the vehicle's stability down the road. Here in the US the maximum is 165 pound above the roof, but internationally the standard is 225 pounds. US has more liability concern. The reality is that even though your vehicle can handle it, best to keep the weight down. For example, I talked with a Land Rover engineer about their standards. His reply is that even though you can and people do load a huge amounts on the roof, he recommends a maximum of 145, because above that weight you will "feel" it. Under that and you don't notice it. That is the key, you want the rooftent to just add to your enjoyment, not detract in any way.

I got a chance to see how intensive vehicle engineering is when I was working with Hummer to get AutoHome's tents certified with them as an approved accessory. They tested everything from the tent's flamibility to how it handles collisions. They performed two "sled" tests with the largest Maggiolinas to simulate 45 mile an hour collisions. They of course passed but shows how cautious the manufacturers are when they give any ratings. So, if we take the Hummer H1 for example, the dynamic rating for roof loading (while you are driving) is 2000 pounds for military applications, 300 pounds for civilian application but still your roofbars are rated at 165 pounds maximum. Even if you add two additional bars to spread the load, in theory it doubles the capacity, no, the 165 pound rating still applies and this is with the big Hummer.

So, the quick answer, load heavy things down low, light things up high, never load more than 165 pounds on your roof when driving. Your vehicle will handle better with less weight up there too.

When parked, the roofbars are normally sitting on your vehicles rollcage structure so no worries there.

Each vehicle is different so it is best to chat with their experts as well as the roofbar manufacturers. I have found with both Thule and Yakima, it is easy to get ahold of their engineers to get your questions answered.

Hope this helps, it is a thorny question.

Rich

 

[STAGE 2]

When parked, the roofbars are normally sitting on your vehicles rollcage structure so no worries there.

The problem is that this will be potentially sitting on a fiberglass truck cap, not an auto roof. If it was I wouldn't have any concern. However a fiberglass cap with no structural reinforcements is far different from a steel roof with reinforcements.

 

[Lemsteraak]

The concept is the same. Most all the major shell manufacturers have a 300 pound dynamic rating. The roofbars are still rated at 165 pounds, so this is still the limit unless you go for a lumber rack or something similar.

There are two approaches if you want to use Yakima or Thule bars, to "track" the roof or to put on artificial raingutters. Putting on tracks, like what most SUVs have will spread the load and is a good solution. I prefer the artificial raingutter approach. My reasoning is that they are bolted to the side which transfers the weight to the sides of the shell which is stronger than the roof. Fiberglass has the most strength if formed into curves, straight sections like roofs do best with reinforcement.

My favorite solution is also the cheapest. There is an old time rack company called Quik n Easy that make die cast alloy towers. They also have stainless artificial raingutters, their crossbars aren't too strong so you bolt on a couple square alloy tubes, like about 3/4 by 1 1/2 section and it makes a very cheap strong and light rack. Last I saw the towers are about $75 for a set of four and the square tubes are like $10 each at the local metal yard. You can get Quik n Easy at NRS, the river rafting folks.

Oh, and the quick answer is I've never seen a problem with a well made fiberglass shell supporting a rooftent using tracks, artificial raingutters or a ladder rack. Plastic on the other hand ...... needs a ladder rack.

Rich