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Discussion Starter · #3 ·
thank you :)
but jeep says, total load capacity 68kg for both roof racks
this is confusing :)


NOTE: Crossbars can be purchased at a authorized
dealer through Mopar® parts. External racks do not
increase the total load carrying capacity of the vehicle. Be
sure that the total occupant and luggage load inside the
vehicle, plus the load on the Roof Luggage Rack, do not
exceed the maximum vehicle load capacity.
The load carried on the roof, when equipped with a
luggage rack, must not exceed 150 lbs (68 kg), and it
should be uniformly distributed over the cargo area.
 

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That sort of a load doesn't seem to be in line with the capacities listed by Jeep. That sort of mount to the roof rack would give you a tensile force and shear force combo that Jeep doesn't reference limits.

There are a few engineers on here that might be able to better explain the theoretical limits of the roof rails, but I wouldn't do that... especially with two people. That's at least 300 lbs of downward and lateral force, even if part of it is being shared by the tree.
 

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I don't think the roof rack is designed for lateral stress. I wouldn't count on that. Those two in the hammock that long with that much sag are exerting a lateral tension exceeding 400 lbf if my math is correct.
 

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I don't think the roof rack is designed for lateral stress. I wouldn't count on that. Those two in the hammock that long with that much sag are exerting a lateral tension exceeding 400 lbf if my math is correct.
I'm not saying your math is wrong, but I want to point out one thing that the picture... hides.

The force is not perpendicular to the center of the roof rail (farthest from the connections to the roof). If you'll notice, it is pulling toward the back of the rail where it is fastened to the roof.

Again, I'm not an engineer, and I'm not saying this makes everything okay, just pointing out that you have to consider the perspective of this photo, where the force is applied in relation to connections, and for how long...

If I WERE (not saying I am) going to do this, I'd tie a rope between the roof racks, at the back where they connect to the roof. Then I would tie the hammock to the center of the rope crossbar I just made, so that the load was distributed between the racks, at the fasteners to the roof. I suspect I'd sleep well enough by myself in this configuration. The person I'd share with only weighs 120...in a soaking wet fur coat... so I doubt the forces would be an issue. But that's just my opinion, YMMV.
 

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I'm not saying your math is wrong, but I want to point out one thing that the picture... hides.

The force is not perpendicular to the center of the roof rail (farthest from the connections to the roof). If you'll notice, it is pulling toward the back of the rail where it is fastened to the roof.

Again, I'm not an engineer, and I'm not saying this makes everything okay, just pointing out that you have to consider the perspective of this photo, where the force is applied in relation to connections, and for how long...

If I WERE (not saying I am) going to do this, I'd tie a rope between the roof racks, at the back where they connect to the roof. Then I would tie the hammock to the center of the rope crossbar I just made, so that the load was distributed between the racks, at the fasteners to the roof. I suspect I'd sleep well enough by myself in this configuration. The person I'd share with only weighs 120...in a soaking wet fur coat... so I doubt the forces would be an issue. But that's just my opinion, YMMV.
I wouldn't do that as from your description, you would be pulling down on the spoiler, which I suspect would result in much badness.
 

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That is just a marketing shot, no engineers were consulted or harmed during this photo shoot.

If you tie it on, and gently sit down, even with two people, you will not create a sudden shock load to the mount points and it will hold. The mounts have a safety factor built in that exceeds the published load rating.

Try this more than a few times and you will get lateral shear forces that will permenatly detach your roof rails from your sheet metal.
 

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