The fastest FD in the world? Ferns designed it (and built PlanaTech)


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fdAt the recent Flying Dutchmann World Championships, Hungarians Szabolcs Majthenyi and Andras Domokos in Scotland literally routed the competition, winning five out of seven trials. Bravo to them, but the medium also matters: and, as it happens, there is an Italian hand in it. It is an FD designed by the Felci studio.. The deck layout (rigging and aesthetics), production engineering (pattern and mold design), and identification of construction technologies were developed entirely within PlanaTech. The Formello (Rome) shipyard deserves credit for being able to develop complex designs in-house, produce the artifact 100 percent, and crown it all by bringing “the result home.”

The Flying Dutchman World Championships - Largs 2014FERNS’ COMMENT
The FD class allows rather “generous” hull tolerances, so it is possible for designers to intervene in such a way as to optimize the boat’s performance. And judging by the results, Felci Yachts has succeeded big time. Let’s read Felci’s commentary on the project directly: “The design of the new FD commissioned by Plana Tech led us to carefully analyze both the tonnage regulations of this historic one design and the evolution that FD hulls have undergone over the years, up to the latest state-of-the-art products. Our hull is developed by taking advantage of the tolerances allowed by the current class regulations, which originated many years ago and provide for tolerances that can now be described as generous. In fact, it was originally intended to include vessels that for construction reasons deviated slightly from the original design, while remaining fundamentally in accordance with the plans. For some years now, the best yards producing FD have been trying to take advantage of these possible variations to improve the performance of their boats, but nowadays, thanks to the increased skills of engineers, through three-dimensional design and the construction of models and molds using CAD-CAM processes, it is really possible to optimize a new hull within the spaces these tolerances leave.

The possibility of changing the course of the keel line, on the basis of maximum and minimum variations, with respect to a reference profile, allows decidedly important diversifications both at the level of curvature of the profile itself and at the level of longitudinal arrangement of the volumes associated with it. This variation is critical for hull development because many factors are related to it that have an important influence on hull strength at various relative speeds. Associated with this keel line, by tonnage, are then 6 sections, one of which represents the transom, which can have a variation in their geometry between zero and 12.5 mm. The combination of the tolerances allowed at the level of the keel line, which can vary + or – 12.5 mm from a theoretical “zero” keel (except for the transition for the two points of start at the transom and end at Station 9), and the tolerances allowed at the level of the sections, can lead to important variations in the final shape of the hull. If you try to imagine the hull dissected by a horizontal plane passing through the zero point of the transom and the zero point of ST9 and measure the “live” volume of two hulls both meeting the tolerances but designed on opposite limits, you can get differences at the volume level equal to 100% of the volume itself, with significant differences at the level of coefficients and strength at different relative speeds.

FD construction 2THE INTERVENTION.
Logically, we had the opportunity not to start from a blank sheet of paper. In recent years, the hull shape of the best FDs has evolved within these tolerances, following a certain trend, and this has emerged from the analysis of some certificates that precisely show the profile trend. Certainly, having clear in mind what the target could be, having excellent tools for comparative three-dimensional geometric analysis and theoretical hull strength analysis, we were able to operate analytically, making a comparative strength analysis of a good number of test hulls, obtained by modeling different canoe bodies and trying step by step to approach the allowed limits. In particular, we worked hard to try to make the FD’s hull less “machined,” especially in the bow. First and foremost, we tried to make the keel line as taut as possible, shifting the volumes somewhat toward the ends of the canoe body, so as to “lay ” the hull on the water, stretching the length both statically and, more importantly, dynamically. We also tried with these variations to increase the Prismatic Coefficient, an important dimensional factor that tends to make the resistance at high relative velocities proportionally lower. Quite laborious at the modeling level was the attempt to make the longitudinal flexion that currently characterizes the original FD design less pronounced, thus trying to increase the volumes in the extreme bow area, to decrease them as much as possible by moving back toward the central part.

At the level of appendages we can point out that the tolerances allowed are proportionally less than those allowed for the hull. Our attempt was to achieve the best ratio of strength to performance. To do this, we have been able to draw on the results resulting from multiple CFD analyses that we have carried out over the past few years and that have contributed so much to the prestigious results of many of our vessels.

As I said at the beginning, the fact that this very accurate design, made with the highest possible precision granted by three-dimensional software, was then made a reality through the use of machinery “driven” directly from our virtually modeled surfaces, allowed us to “pull” more than the limits granted by having the certainty that the machining precision was far superior to a traditional craft method. Additional advantage related to these technologies, which has already been verified in two of our designs made for the Star class (with one of which Torben Grael won the bronze medal in Sidney …) is that related to the possibility of obtaining a perfectly symmetrical and booted hull and that both the fin and rudder would benefit from near-perfect alignments, characterized by tolerances of less than one mm precision.”



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