28TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES ADVANCE SEAPLANE CONCEPTUAL DESIGN ADAPTING TRIMARAN BOAT HULL CONCEPT A Canamar, L Smrcek University of Glasgow [email protected];[email protected] Keywords: Seaplane Design, Trimaran, Retractable Floats, Abstract a French engineer Henry Fabre [1], and since then, much research on seaplane aviation was Early seaplane designs adapted the concept of widely conducted. adding a boat hull or either twin floats into an Many experiments on seaplanes were aircraft to convert it into a seaplane. The conducted in order to design an efficient purpose of this paper is to adapt the best of seaplane. However, in the mid-1950’s, with the using both ideas, a flying boat hull adapted with introduction to improve aircraft designs and the floats, i.e. a trimaran technology concept. The construction of suitable landplane infrastructure, conceptual idea of the trimaran gives the the use of seaplane traffic and operations seaplane an advantage over other type of design drastically drop [2]. No new experimental or concepts. The hydrostatic stability, dynamic theoretical approach has been done ever since. stability, wave handling and water performance Most studies conducted today are by adapting are some of the advantages that trimaran existing aircraft with a floating device (floats) to resulted. One concern of the trimaran idea is convert a landplane to seaplane. Some of the the extra aerodynamic drag generated by the advantages that seaplanes can afford today are floats. The solution is to place the floats inside the use air-sea rescue missions, fire bombers, the boat hull, the same way landing gear is tourism and can afford point to point mounted undercarriage. The preliminary results connections to places inaccessible to other types showed that the trimaran concept gave an of transportation [3]. Seaplanes can. Based on a excellent hydrostatic stability, a greater water research made by Cronin Millar Consulting speed, and retracting the floats decreases the Engineers to Harbour Air Ireland [4] and the US aerodynamic drag, hence better flight Army Corps of Engineers [5] seaplanes have a performance. very low environmental impact. The main problem with seaplanes today is compared to the case of the duck. I duck can fly, 1 Introduction swim and move through land, but it cannot fly eaplanes are a type of fix wing aircraft as fast as an eagle, swim like a penguin, or run S adapted with a floating device (floats or boat like an ostrich. It is well known that air hull) that is capable to land, takeoff and operate performance is compromised due to the increase on water. With the creation of the world’s first of the water components added to the aircraft. successful airplane done by the Wright Brothers But the main problem that seaplanes face today in 1903, the idea for improving and exploring is the water performance due to the lack of the world of aeronautics have been expanding efficient and economical floating ideas for a rapidly throughout the 20th century. With the modern seaplane design [6]. lack of suitable landplane infrastructure and the In this paper, a new approach for an advance availability of vast motor boats, the idea of seaplane design will be analyzed. Manipulation creating a seaplane could not be held. The first of old empirical formulas with modern ideas motor seaplane flight was conducted in 1910 by will be adapted. 1 ADVANCE SEAPLANE CONCEPTUAL DESIGN ADAPTING TRIMARAN BOAT HULL CONCEPT 2 Conceptual Design Proposal With the decrease in seaplane traffic and operations, modern seaplane designs stagnated. Most conceptual design ideas and theoretical approaches made for seaplanes are mainly used with early 1900’s empirical equations and experimental testing. For this seaplane design, a new, modern and advance design would be approach in order to satisfy the needs of this futuristic idea. Fig. 1: Trimaran Example 2.1 Proposal Ideas Based on the market research and the 2.2 Advance Design Ideas technological review, the creation of a new The trimaran possesses some advantages seaplane design will require time and costs in over other types of boat hull designs [7]. manufacturing, regulation, certification, and Low wave resistance at high speed due to its social acceptance. The most convenient solution slender ship hulls for the near future will be to create an Superior stability attributable to suitable innovative seaplane design based on existing layout of the side floats. A trimaran can keep certified aircraft, i.e. converting an existing a high speed under high sea conditions. landplane into a seaplane by adding a floating The wave interference between the main hull device. The seaplane conversion will be cheap and the outriggers can produce a beneficial to repair due that it will share all the parts of its wave interference optimizing the speed and landplanes counterparts, except for the floating engine power required correlation devices that will be used. In case of an emergency the all float structure Many proposed ideas were analyzed for remains floating even when the hull or the possible technical solutions that will aim to outriggers are severely damaged. reduce costs on research, manufacturing and Trimarans are superior in terms of stability operation of an advance seaplane design. Some because the arrangement of the hulls is such that of the proposed ideas that were considered are individual centers of buoyancies have a righting the use of retractable floats, inflatable floats, moment about the centre of gravity that helps in advance navigation aids, hydrofoils, water stabilizing the vessel as shown in Fig. 2. This thrusters, folded wings, advance composite gives the boat or in this case the seaplane, more materials, advance power plants, reversed roll stability, better water maneuverability, and thrusters, among many more ideas. After better water performance at docking and even at analyzing all of the proposed ideas, the high waves. complexity and high costs of some of these narrow the search for technical solutions that will meet the requirements of this seaplane. First, it was decided to use trimaran boat hull technology that will increase hydrodynamic performance of the seaplane as shown in Fig. 1. One concern of using trimaran will be the exposed floats at flight. One solution is to retract the floats or either mount them inside the undercarriage, which in theory will reduce Fig. 2: Trimaran Stability-Beam Model aerodynamic drag. Another important aspect to analyze is wave performance. Seaplanes must have the ability to 2 ADVANCE SEAPLANE CONCEPTUAL DESIGN ADAPTING TRIMARAN BOAT HULL CONCEPT perform in any weather and water conditions. factor added by the floats and boat hull [10], When a wave passes through a conventional hence decreasing the aerodynamic drag. float, it reaches the bow producing a lift force which pushes the stern down; as the wave passes through the body of the float, the center of buoyancy changes along with the wave. When the wave reaches the stern, the lift force Fig. 4: Retracting Float Concept [9] pushes the bow; at high speeds, during rough water conditions, a dangerous pitch effect could However, retracting the floats into this cause the bow to be submerged and capsize position will not reduce entirely the violently. For the outriggers, when the peak of aerodynamic drag caused by the floats. A final the wave moves towards stern, the lack of solution is to place the floats inside the boat buoyancy on this section to the shape, negates hull, as shown in Fig. 5. the lift force which produces the pitching effect, therefore the outriggers are capable to operate in a wider range of rough water conditions than the conventional floats. Past studies conducted on trimaran shows that wave resistance of trimarans is significantly lower compared to an equivalent catamaran as shown in Fig. 3 [8]. For this instance, in theory, trimaran has superior Fig. 5: Example CAD Model with undercarriage Floats seagoing performance. The floats will be retracted inside the boat hull, the same way the landing gear is retracted undercarriage. The only drawback will be the added structural support required, compromising an increase in weight of the strutting. 3 Conceptual Design and Theory 3.1 Conceptual Design As stated, an existing landplane aircraft will be converted into a seaplane configuration. In that case, the proposed design equations will Fig. 3: Resistance comparison curves [8] have to be manipulated in order to design the Since the trimaran concept will exposed seaplane in this manner. the floats in the air when the seaplane is flying, Many old seaplane design books approaches this will generate extra aerodynamic drag that the seaplane design by first designing the will compromise the air performance of the floating device (i.e. the design of the boat hull seaplane. or floats) and then designing the aircraft Tigerfish Aviation developed the use of components (wings, fuselage, empennage, etc.) retractable pontoons called Retractable around the floating device [6],[11],[12]. Amphibious Pontoon Technology (RAPT) [9]. However, since these design idea is to convert a Adapting the same concept idea, the floats will landplane into a seaplane, a new theoretical form a single component embodied to the hull approach will be conducted. The conventional and fuselage when retracted, as shown in Fig. 4. equations shall be manipulated to arrange the This will reduce the drag form interference design idea. Since the proposed idea of the seaplane is to adapt an advance trimaran 3 ADVANCE SEAPLANE CONCEPTUAL DESIGN ADAPTING TRIMARAN BOAT HULL CONCEPT concept, trimaran design theory and characteristics. The sizing code will follow a conventional flying boat theory will be blended series of calculations in order to meet the together to obtain the most optimum trimaran specify goals before it continues the loop design for this seaplane.