As you have seen earlier I have Thule roof racks (four of them and the fifth is an odd german one I came upon) mounted on the roof. While they work well for short trips it would be more convenient for longer trips to have a “cage” on the roof that would make windsurfing kit and other things be more securely strapped down. The concept I have sketched is built on bolting L-shaped brackets on to the ends of the roof rack bars and then have pipes running through the holes located up and down on the brackets.
On the sketch there are pipes just on one side. It will of course be on both sides and the upper and lower pipes will be joined together by u-shaped pipe sections in the front and back.
Here is a closer look at the bracket with pipes running through them. M6 bolts will be mounted through the small holes in the bracket. They serve as barriers for angular movement of the brackets. The brackets have holes in their horizontal lowest surface so bolts can go vertically through them and the square bars (which will need to be drilled.)
And here is one of eight freshly made brackets! (there are benefits to beeing an engineer working at a manufacturing company) The next step is painting them black. Stay tuned!