I was wondering if I could make a simple car-top carrier from one standard sheet of Coroplast and a few zip ties. Once the details were figured out on paper and a model was made, I headed to my shop.
It’s actually very similar to Sparky and the coro box boat hull design. No pieces were joined. This is basically one full sheet cut, creased and folded to this shape. There was very little waste.
It holds 5 cubic feet of cargo. Not much, but adequate if extra space is needed for hauling.
Seeing my Honda Accord has no roof railings, I made several slits on the bottom of the box, then ran two 10 foot long cargo straps through the holes. The box was centered, the car doors were opened and the strap ends brought together at the center inside of the car, then ratcheted down.
The front of the box is angled to deflect the wind. The wind also holds the hatch down when under way. I blew some water on the box at a car wash to see if it repelled water. I did get some moisture inside, but I was also blowing water at high pressure in every direction. To make it real water tight I need to add a dab of sealer on the front zip tie entry holes.
I’ve had my car up to 75 mph with no movement of the box or noise coming from the straps. I’ve made several abrupt stops and swerves with no box movement. After several days of driving around with a small load, no scratches of paint were detected after removing the box. Thank God. Mary would have been so pissed!