Yes for weeks at a time. The tubes I use for bunks are the light weight PVC, I like the way they fit to the form of the hull to give what I feel is a bigger foot print on the hull and a little cushion.
For those of us who sail (and cartop) solo, I'd be tempted to add a block (at the "x") and configure a small winch to an existing tow hitch. A light line (parachute cord) could be strung under the Sunfish, secured to the gudgeons (using a long 3/8" bolt and nut). Once it's winched more than halfway up, a nudge would get the Sunfish loaded on the PVC bunks. Watch for gusts of wind!
Like the concept,but the idea of 4 zip ties holding the boat on the roof concerns me.
A heavy gust or an emergency braking situation could prove disastrous. I wonder what the load rating is on the small zip ties holding the wood in place?
The zip ties simply hold the 2 x 2's and tubes in place while the boat is not loaded. Once the boat is loaded I use ratchet straps to hold the boat to the 2 x 2's that are wedged into the roof rack. I will post more photos of the operation once I put the boat back on the van.
Don't remove those end caps...Belay that last idea.
Using PVC or metal U-clamps the end caps can be attached to crank the Sunfish up. Run a metal pipe through the U-clamps, weld a crank-handle to one end—wrap a line around it—leading to the Sunfish's bow handle. (The U-clamps don't appear in the sketch, but holes to fit the pipe could drilled through both end caps instead).
Removal of the cranking apparatus can be accomplished by tapping the end caps off.
I like this idea, I have had the notion to have a line on the bow handle possibly to have assistants in pushing the boat forward and control of boat but with the bunks in place it seems to not be an issue like when I was doing it with only the luggage racks. My van is almost six foot tall and when I lift the front of the boat into the yoke, the boat is setting at a forty five degree angle. Witch is too much for the handle on the boat or the said pulley arrangement. I think if I then lifted the back of the boat over my head, then the Wife could use the pulley to move the boat forward or the line on the bow handle.
I can do it myself. It is easer with the Wife's help! Since I waxed the hull it slides much easer than before. In fact I have to be careful not to push it too far forward, as it slides on the PVC very easily. The yoke attachment allows me to work on simply lifting the stern and the PVC keeps it centered so not to worry about sliding right or left.
As a follow up with "Wavedancer". If you can lift the front of the boat up to the height of the yoke, I would suggest the stern would not be an issue. My Wife helps me usually, as she worries about me doing such things.