Rising to the Challenge - Mattress on top of Roof

Question

I'm going to be moving across the US in a few days and am looking to transport my queen mattress (no boxspring) about 600 miles. Nearly every single person I've spoken with has strongly advised against putting it on my roof and recommended simply renting a trailer instead (stories of mattresses transforming into sails, hurling through the air, plummeting gas mileage, incessant overhead noise, being ticketed by the police, and physical damage to the roof abound).

However, assuming I would still like to attempt transporting the mattress on my roof, what would be the best (safest) way to proceed? Should I strap it directly to my roof? Leave a gap between for airflow? What is the most secure technique to fasten it down? What speed could I expect to drive at?

I'll be driving a Jeep Grand Cherokee with a roof rails / crossbars.

Answer 1

The flexibility of the piece is the difficulty to overcome. The air blast will make keeping the shape of the mattress difficult so it will let airflow distort it. It will be tough to fasten it securely enough no matter how many straps you use. Wrap your mattress in plastic to protect it from dirt, debris, and insects.

Best way would be to box the mattress so that it will not distort before you place it on a roof rack for secure tie-down as with any stiff package.

Second, minimalist method will be to sandwich the mattress between two boards (2x4s) one-third of the way in from each side for the full length of the mattress to prevent it from flexing. Secure the boards front and back to each other. Cover the assembly with plastic sheet (It might rain.) Tape the loose ends of the plastic sheet. Fasten it securely to the roof rack transport.

Answer 2

Having done exactly this (moved a mattress on a car roof, though not for anything like the distance you intend), I can tell you you'd be ahead to discard the mattress and buy a new one when you arrive.

You have a better setup than I did, however, so there's a chance you can pull it off. You'll want/need to wrap the mattress in plastic to keep off weather, dirt, and highway grime (a special class of dirt that includes oil, and is essentially permanent). You'll need to ensure that it's tied down securely, especially at the front and sides, but at the back as well (to be sure the wind doesn't just slide it off the roof rack) Since the mattress will be longer than your roof, you'll have to let it hang off the back (can't hang off the front, else it'll either block your windshield view, both illegal and unsafe, or have even more tendency to fly), which adds to the challenge of keeping it on the rack.

With the mattress up there, you won't be able to carry anything else on the roof; that puts a limit on how much you'll be able to pack: whatever will fit inside the Jeep.

If the mattress is tied down well enough for this to work at all, it should be safe at highway speed (in fact, I'd call that the criterion for securing it -- if it'll blow off at 75 mph, it's not attached well enough).

Answer 3

Every mattress you've ever seen on the side of the road came from someone like you. Hitting a mattress is like hitting a deer, it will likely total the car, and can ignite chain reactions that can kill.

This is serious business, and it needs to be immediately clear to every cop who stops you that you have done a really good job tying this down. And in a 600 mile journey you will be stopped several times, not least: you are now in the bailiwick of a second tier of cops: commercial enforcement. They don't need reasonable suspicion, and as a matter of routine (for them) they will go over every mechanical feature of your vehicle with a fine tooth comb. Because that's what they do all day every day: random-stop trucks and look for defects in securement or mechanical.

If a police encounter is something that could go badly for you, doing something this attention-getting is out of the question. The laissez-faire attitude toward immigration law held in some sanctuary cities is most definitely not shared with rural police.

Mattress shibari

A mattress has no tiedown anchors. Handles won't cut it, don't even think about using handles as tiedowns! However the idea of carrying something you can't tie down is absurd.

To create tiedowns, wrap the mattress itself in rope, and this should be done in your bedroom so you have convenient handles to haul the mattress around. A mattress is both compressible and flexible, and it will really, really want to escape. The ropes will have many hundreds of pounds of force, from dynamic loading and your preloading the ropes in tension. (floppy-doppy ropes do nothing). So when you try to strap down, it will trapezoid. The only option, then, is to design the trapzoiding right into it and cinch it down hard so the whole structure is already in tension. It tends to not have a single square angle on it, and you're roping the mattress itself - that's why I call it "shibari".

If you want to plastic-bag the mattress under the shibari, that will make it even more slippery, which - well, that's probably a good thing because it will test the mettle of your ropework. If it's slipping all over the place while you're trying to haul it out to the car, you got an early warning so stop and fix it.

Your rope work needs to be tip-top. No granny knots, you need to use at least a proper bowline at every single intersection, preferably with something else as a slip-stop. Hope is not an operating doctrine.

Attach it to the vehicle

With the shibari providing a wealth of tiedown points, strapping it to the car should be a straightforward affair. Always bring the lines down at opposing angles, and in harmony with the shibari, so the ropes are in tension and everything else is in compression. Don't tie it square, or it will flop forward and back, and soon tear something apart. And expect everything which can move back and forth to do so.

Put as much static tension on it as is reasonable. The idea is that road loads are simply more of the tension you have already installed, not new tension in a new direction.

I would also consider a loop around the mattress and through the passenger door openings (with the doors open, that is... unless there'll be no one riding in that row of seats, then through the window is fine), "just in case" the luggage rack lets go. They're not really made for upforce.

I like Stan's idea of the 2x4's, but I would still have the shibari so you can bind the mattress proper, and strap down the 2x4's separately and also. If you wanted to stack other luggage above the mattress, I would put a sheet of plywood or OSB below the 2x4s, strapping all 3 things, the mattress proper, the ply/2x4, and the overtop items. Do not ask the top items to hold down the mattress, it won't work, the forces are much too extreme.

The road

On the road, the mattress will tend to want to "nose up", the slipstream coming off your hood and windshield will try to lift the front and fling it off the car. I've moved mattresses this way many times, but usually below 35 mph and never over 50 mph, and monitoring the rope tension, it was well over 100 pounds of force even at that speed, and it scared me. Aerodynamic forces increase as at least the square of speed, so 75 mph is at least 225% of the forces I observed.

Unfortunately the typical goofus in this situation just throws on a few ropes and goes "la la la, drive like I normally do". Don't do that. Be super mindful and don't get complacent. On the other hand... if you take this thing down the state roads, you will get stopped by every small town local cop. So at least don't speed!

Also check your load after the first 5 and 30 miles, at every stop, and at the first sign of trouble. A stitch in time...