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Trans RINA, Vol 155, Part C1, Intl J Marine Design, Jan -Jun 2013


A market matrix (Figure 1) was formed as part of the research process of the Logos project, combined with benchmarking data (Figure 2) which indicated a market shift towards luxury and performance. The burgeoning sizes of multihulls offers a clear opportunity for design innovation to meet the ecological and economic demands of tomorrow. Overall the research informed a design which was governed by the principles of Passive Design, which provides commercial advantages, through reduced operating costs, greater resale value and preparedness for ecological legislation in the year 2020.


2. ENERGY AUDIT


As part of the design research an energy audit was conducted to determine the amount of energy consumed relative to other systems. The blue circles are the largest, in relation to their consumption. Figure.3 shows the initial layout of apparatus in relation to their emitted heat. Where high heat emitting applications were placed in immediate proximity to ventilation shafts.


3. DESIGN ANALYSIS


Figure.4 demonstrates the level of analysis employed to determine the weaknesses in current designs and discover design opportunity.


4. DESIGN PROPOSAL


The front 3/4 view of the vessel and rigid wing is shown in Figure 5, shows the control surfaces of the self trimming rigid wings with tubercle Tubercle


leading edge. technology was incorporated within this


concept built upon the research of Dr. Frank Fish, Professor of Biology at West Chester University, USA, who identified that tubercles themselves found on the leading edge of the dorsal fin of humpback whales, improved the hydrodynamic performance of the fin in terms of generating lift and fin efficiency, and suggested the potential application to sailing masts.


This biomimetic approach seeks advancement


technological through a transfer of technology from


natural technologies to engineered systems. These sinusoid-like rounded bumps are arranged periodically along the leading edge. The presence of the tubercles modifies the water flow over the wing-like surface, creating


regions of vortex generation


aperture which facilitated the stack effect of the natural ventilation system. The choice of a rigid wing was not purely a technical one but also that of usability and speed. Whilst a rigid wing is easier to operate and self- trimming it


also removes much of the shrouds and


supports that a conventional sail may require. De- cluttering the deck and reducing the number of crew necessary to operate the vessel leads to lighter load but also decreasing the size of the crew quarters leading to more space for passengers and more autonomy for the aging user.


The technical challenge of rigid wing implementation is that large compressional


technology stresses


concentrated near the base of the mast. Although it has self-trimming ability, such a large rigid wing may be subject to damaging forces in extreme tropical weather typical to that of the Caribbean climate. However, new designs are now emerging such as the Wally Wow sail, which is composed of a semi rigid wing structure which can be reefed depending on wind conditions, thus operating like a


normal soft sail, but with the


performance benefits of a rigid wing. Supported by 19, 80watt solar cells to support auxiliary systems, “Logos” has complete autonomy and the silent luxury of rigid wing technology.


The vessel's side profile (Figure 6) has a sleek dynamic geometric form, conveying a sense of motion direction and speed even when the vessel is stationary.


The coach roof extends over the stern deck section to provide natural shade for the alfresco dining area, as shown in Figure 7.


5. NATURAL VENTILATION between the


tubercles. These vortices interact with the flow over the tubercle and accelerate that flow, helping to maintain a partially attached boundary layer. This hydrodynamic effect can delay stall to higher angles of attack, increases lift, and reduces drag compared to the post-stall condition of conventional wings. The use of tubercles on the leading edge of the yacht's mast was supported by scale model wind tunnel


testing as an integral part of the


design research. This biomimetic allowed the mast to be of a greater diameter, without increasing the aerodynamic drag and thus leading to a greater exhaust


Inspired by investigations into termite mounds, it became clear that heat and ventilation shafts were integral to the biomimetic based mechanics of sustaining a stable thermal environment. Other animals such as Zebras demonstrate Passive Design through the use of white and black stripes to create minor convection currents on the surface of the skin to cool itself. There are many examples of thermal control in nature, all of which operate in a passive manor. Unlike nature, humans derived a system which relies on refrigeration technology to actively regulate the thermal composition of air using high grade energy driven by fossil fuel technology.


In the “LOGOS” project ETFE cushions are used to capture solar energy and heat the air trapped in an air gap in the roof


section sandwiched between a highly


insulated roof and a suspended polymer roof (Figure 8). The Cushions themselves have been designed to have a certain refractive index to ensure solar absorption at even very low sun angles but fundamentally the air gap is designed to create the greenhouse effect. The heated air rises along to the apex of the roof and up through the mast which behaves like a chimney.


C-46


©2013: The Royal Institution of Naval Architects


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