This one's a round tailed version of the Hotkurl 10-5. So far the deck and bottom panels have been made and the two fins: Shown here is the initial foiling on the central planar cutaway fin which we call the 'Patu' fin because of its resemblance to a Maori war club. The thickness to chord length ratios are 13% through the base, and 8% through the tip area. http://www.roystuart.biz/2013/06/rampant-surfboard-3-initial-fin-foiling.html Here is the Vort-X tunnel fin with scalloped trailing edge. Half pipe tunnel fins produce a beneficial flow rotation inside the the tunnel when experiencing lateral angles of attack ( which is the case most of the time). The purpose of the scalloped trailing edge is to induce counter rotating vortices in the flow outside the tunnel, so that when it meets the flow from inside it does so more smoothly and with less drag. Slight channels are a consequence of the sine curve shape of the trailing edge, these channels are used only on the outside of the fin to prevent non beneficial vortices occurring on the inside flow. Viewed from the tail this results in an undulating trailing edge line. approximately 16 hours of hand foiling has been applied to get the fin to this stage. The thickness to chord length ratio of the tunnel is approximately 8%.
