Whispbar / Yamika / Prorack roof rack - contoured underside spacer for U-bolt mounting of basket / platform

I wanted to mount a platform or basket on my Whispbar roof racks using U-bolts. Unfortunately, the aerodynamic shape of the Whispbar roof racks meant that the metal plate of the U-bolt had very little contact area with the roof rack.

In Australia, Prorack is the distributor for Whispbar. They sell a fitting kit for putting a basket on the Whispbar, but the bolts point upwards. For most platforms/baskets, the protruding bolts will catch on everything and be a pain in the butt. The fitting kit is here: https://www.prorack.com.au/u-bolt-roof-box-fitting-kit

After several unsuccessful attempts to model the Whispbar cross section using measurements and images, I found a diagram of the Whispbar cross section (1000008427 (1).jpg, attached) . I used this to model a cross section, printed out a slice, and it turned out to be a perfect fit.

This is designed to work with a short leg u-bolt kit. Finding such a kit was somewhat difficult - if the legs were too long it would hit the roof of my Mitsubishi Mirage, but most short leg kits did not accommodate the Whispbar's width.

I eventually found "Roof Rack Basket U-Bolt Kit (55mm) with nyloc nuts (x4)" and that worked for me. See https://roofrack.com.au/product/roof-rack-basket-tray-u-bolt-kit-with-nyloc-nuts-x4/. The width of the metal bracket is 20mm. Spacing between bolts is 100mm. If your bolts vary you will have to alter the model.

It's all installed now, and appears to be rock solid.

Hopefully it helps someone at some point, even if it's just to pull the 2D cross section for the Whispbar out of the FreeCAD file.

Anna