I designed and cut a set of prototype elliptical twin keels for Craig in Tasmania for his new wooden fish. Four inches deep with a NACA 0012 foil. Squashed Spitfire profile with a longer chord length which is great for colder denser water. The fins were designed in FreeCAD and cut on my CNC machine out of AA grade marine ply.
Some feedback from the man himself.
"I finally gave the fins a try yesterday. The fins really loosened up the board compared to the quad set-up but held turns fine. The board seemed quicker than previously, but that may be due to the twin rather than quad set-up. Had heaps of fun on the board. Will send some more feedback after my next few surfs."