Abstract:
A floating vessel comprising, in the orientation of use, a central longitudinal member ( 2 ) having a vertical height, and to each side of the longitudinal member an upper substantially laminar panel ( 3 ) connected to the longitudinal member and extending outwardly therefrom and a lower substantially laminar panel ( 4 ) connected to the longitudinal member at a distance below the upper panel and extending outwardly from the longitudinal member, wherein the outermost edges of the upper and lower panels are connected and the lower panel is larger in the outward direction than the upper panel such that the panels form a stable structure.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a floating vessel. 
       BACKGROUND TO THE INVENTION 
       [0002]    Water sports are popular outdoor activities. In recent years new sports such as windsurfing and kite boarding are growing in popularity, compared to traditional sailing. They offer more fun and are more accessible in terms of money and space. 
         [0003]    Mapping the practice of sailing around the targeted use of the boat, we observe that new alternative water sports such as windsurfing and kite surfing are getting more popular and are relatively less expensive than traditional sailing. 
         [0004]    On the other hand these alternative sports have higher access barriers, consisting of training time to learn how to windsurf and kite board. This is the major unique selling point of leisure boats such as rotomoulded catamarans (e.g. the Funboat manufactured by Performance Sailcraft Europe Limited of Northamptonshire, UK, or the Bravo® manufactured by Hobie® of California, USA) which ensure higher stability and have easy boomless rigs. 
         [0005]    Existing boats need to be transported on a trailer or the on top of a car. In this case it is difficult for one person to lift the boat over the top (weight over 50 kg). On the other hand windsurf equipment can be transported on top of or in a car and one person can load and unload it. Furthermore windsurf equipment can be carried on the plane, while that is impossible for boats. 
         [0006]    Based on personal experience and informal exploration with sailors I have focused my attention on small recreational sailboats for one person. This segment represents an important slice of the boating market and ranges from easy leisure boats to racing sail crafts. The common needs expressed by users during the early informal exploration are portability and easy of use. Hence the initial brief:
       Sailing fun in a bag: “Create a new sailing experience that enhances the fun of sailing given by the interactions with the elements wind and water and that reduces the hassle associated with assembling, transporting and storing the equipment.”       
 
         [0008]    The open brief allowed me to investigate in the early stages new forms of sailing and generate hybrid concepts. The choice has been then for a craft that sails like a conventional dinghy but offers more portability and accessibility for new sailors. The project has focused on the boat hull which is the real bulky part of the boat. Moreover, compatibility with existing collapsible sailing rigs, like the windsurf ones, lowers the cost barrier for new users. 
         [0009]    Nowadays the use of a foldable sailing boat responds to very specialized needs. Most foldable boats are designed for fishing, kayak travelling or as emergency dinghies. Some of them have an optional sailing rig offered by third parties. A new product needs to be placed in a wider scenario of water and recreational outdoor sports. 
         [0010]    Direct competitors are the very few collapsible sailing boats and foldable kayaks with custom sailing rigs. Major examples of collapsible sailing crafts are: the Aquaglide®, an inflatable multi-sport craft deriving from windsurfing manufactured by Aquaglide® of Washington, USA (retail price £350); the Stowaway® plywood sailing dinghy manufactured by Stowaway® Boats Ltd of Northamptonshire, UK (£1,000-£2,000); and the Tinker® inflatable with sailing kit manufactured by Henshaw Inflatables Ltd of Somerset, UK (£2,500-3,000). Foldable kayaks are quite popular and their price range is £1,000-£2,500. Small companies offer custom sailing kit for the most popular kayaks (£500-£1,000). The kit comprises boat appendices because of the kayak&#39;s poor sailing performance. The most common folding rowboats, mainly used for fishing or as emergency dinghies are probably the polypropylene Portabote® manufactured by Portabote®, California, US (from £1,300) and the aluminium Instaboat® manufactured by Instaboat®, Montmagny, Quebec, Canada (£800). For the first one there is now available an optional sail rig for £600. Finally an entry level sport sailing dinghy has retail prices starting from £1,675 (the Topaz Taz®, manufactured by Topper® of Slough, UK), while the best-selling (the Laser® manufactured by Performance Sailcraft Europe Limited of Northamptonshire, UK, with over 190,000 units worldwide) is £3,500. 
         [0011]    The markets where collapsible sailing boat could compete are:
       1. traditional sailing dinghies, by generating an affordable entry level solution, which adds ease of transport and storage.   2. windsurfing, by sharing the same sails and making the switch from one sport to another less expensive.   3. inflatables, by means of providing an easier and quicker assembling system.   4. outdoor “week-end” sports and leisure activities such as skiing, snowboarding, mountain biking, kayaking, thus winning more enthusiasts to the boating sports.       
 
       SUMMARY OF THE INVENTION 
       [0016]    This invention provides a floating vessel comprising, in the orientation of use, a central longitudinal member having a vertical height, and to each side of the longitudinal member, an upper substantially laminar panel connected to the longitudinal member and extending outwardly therefrom and a lower substantially laminar panel connected to the longitudinal member at a distance below the upper panel and extending outwardly from the longitudinal member, wherein the outermost edges of the upper and lower panels are connected and the lower panel is larger in the outward direction than the upper panel such that the panels form a stable structure. 
         [0017]    It may be that the outermost edges of the panels are releasably connected. If they are then the panels are releasably connected to the longitudinal member. It may also be that the panels are releasably connected with hook and loop fasteners. 
         [0018]    It may be that the panels are formed of cellular or corrugated plastics material. If this is the case, then the corrugations or cells of the upper panel may run transversely to the corrugations or cells of the lower panels. 
         [0019]    It may be that the longitudinal member comprises an aluminium beam. 
         [0020]    It may be that the vessel is a boat. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    An embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which: 
           [0022]      FIG. 1  is a graph showing the righting behaviour of one embodiment of the invention at various angles of heel; 
           [0023]      FIGS. 2 to 7  are pictures showing the process of packing one embodiment of the invention flat; 
           [0024]      FIG. 8  is an illustration of polypropylene after profile rolling according to an embodiment of the invention; 
           [0025]      FIG. 9  is a picture showing the fixing and sealing solution for the external edges of an embodiment of the invention; 
           [0026]      FIGS. 10 to 15  are illustrations of the hull in use with various sails; 
           [0027]      FIG. 16  is an exploded diagram of a hull according to one embodiment of the invention; 
           [0028]      FIGS. 17 to 21  show a hull according to one embodiment of the invention from various angles; 
           [0029]      FIG. 22  shows a hull according to another embodiment of the invention; and 
           [0030]      FIGS. 23 to 25  show three possible hull configurations according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0031]    The proposed product is a small boat, designed for leisure sailing and compatible with conventional sailing rigs (windsurf). The main features are the portability and the accessibility that aim to attract new enthusiasts to the boating sports. When needed, it folds to a flat pack with the dimension of windsurfing equipment. 
         [0032]    From the industrial design point of view the key factor of this project is the application of corrugated extruded polypropylene sheet to boat building, using its properties to perform more functions. The folded sheets are at once the boat skin and the structure; they form the living hinges and generate embedded reserve safety buoyancy. 
         [0033]    This product can be a first boat for young people, a leisure boat for families, new sail enthusiasts. It can have a price range much lower than traditional boats and therefore comparable with other popular recreational sport equipment such as high end mountain bike and or a skiing set. To enter the target markets the strategy could be to offer a boat compatible with existing sailing rigs, thus lowering the price barrier to access for existing sailors and newcomers. This would also lower the barrier regarding acceptability and feasibility, with the possibility of partnering with existing known sail brands for delivering complete boats over their distribution channels. 
       Product Specifications: 
       [0000]    
       
         
           
             Crew: 1 adult person, average weight 75 kg 
             Sailing performance comparable to beginner sailing dinghies such as Topper® Topaz Taz® or Laser® Pico® 
             Compact dimensions when folded for car transportation, comparable with windsurfing equipment (Weight 25 Kg, Length 3 m, “flat pack”) 
             Compatible with existing sailing rigs (e.g. windsurfing sails) 
           
         
       
     
         [0038]    The boat is made out of a folded lightweight plastic sheet; e.g. sealed corrugated extruded sheets, since they provide rigidity and high buoyancy. 
         [0039]    In the fold up configuration (sailing) it forms a hollow body, rigid enough to hold one passenger. In the closed position (transport) it is a ‘flat pack’ of folded panels, which store inside the other parts (rudder, centreboard and sail rig). 
         [0040]    The development of the concept has been carried out by dividing the design work in packages and reiterating the following design steps:
       Hull design (shape the boat in the water)   Folding patterns (geometry studies to convert 2D in 3D)   Deck design (design the space for the crew)   Material and process   Detail design (fixing, sealing solutions)   Rig definition   Prototyping       
 
       Hull Design 
       [0048]    The idea of folding flat panels to obtain the three-dimensional hull shape suggests that the boat is going to have a polygonal surface, a “mesh” of flat or curved faces. Several methods for generating hull shapes have been considered: 
         [0000]    Wrapping: using a flexible sheet and bending or wrap it in order to find a stable configuration (fixed in the minimum number of points). This method generates curved surfaces, but is quite hard to model on software, because of the important role played by the material elasticity. Thermoforming sheets has been used to sketch models.
 
Meshing: starting with a traditional curved hull surface, is it possible to mesh it on software packages to polygonal surfaces with small number of faces. The difficult of controlling the mesh generator on the tested software makes it difficult to obtain desired foldability and rigidity.
 
Geometrical assembly: as the opposite of meshing, it is possible to build polygonal surface from scratch by adding polygons to simple shapes. In this way it is possible to control the geometry and keeping the foldability of the hull. 3D software packages allow to generate quickly many shapes, which have been easily visualised with paper models.
 
         [0049]    With the last method a classification of possible polygonal surfaces, according to simple parameters as number of sides on the plan and on the main section. By increasing the number of sides the hull comes closer to the traditional curved hull, thus improving the performance but making the folding and structural issues more complex. 
         [0050]    The hull shapes have to satisfy basic parameters to be considered for a boat. With the help of naval architecture texts and experts, I compiled a list of the primary criteria to analyze a sailing vessel: 
         [0000]    Structural rigidity: especially longitudinal rigidity. The boat must not bend due to the effect of compression between water and crew weight.
 
Buoyancy: besides keeping afloat the crew without drafting too much, the boat needs to have reserve buoyancy for safety reasons. Positive flotation is the property of floating when filled with water (e.g. after capsize), and is normally achieved with extra floating bodies (e.g. foam) attached to the boat.
 
Stability: especially transversal stability is important for sail boats. The boat needs to generate a righting moment when heeled on the side. For small dinghies without a keel, this is anyway not enough to withstand the force of the wind on the sail and the position of the crew is crucial to keep the boat upright. Nevertheless stability is also comfort: not heeling hull design excessively when the crew moves from centre to side, is also much appreciated.
 
Drag: the resistance to the motion in the water is mainly given by the friction of the water on the boat, and it is proportional to the wetted surface. The second main component is generated by the motion of the waves.
 
Plane: the capacity of the boat to generate a vertical lift by the flow of the water under the hull depends on the hull geometry. If so the boat rises from water at speed (plane) and reduces the resistance to motion. This hydrodynamic effect is quite complicated to calculate also with software and is generally tested in water with models. Generally the flatter the hull, the more the lift it generates.
 
“Sailability”: or behaviour of the vessel in the sea in different conditions; e.g. sea-worthiness and sea-kindness.
 
         [0051]    The first four criteria can be predicted with calculations based on the hull geometry and have been analyzed for the generated hull shapes. A professional software (Rhinomarine, a 3D CAD/CAM program for modelling boats, their hydrostatics, stability and performance, produced by Proteus Engineering) has been used for the calculations. They do not exclude any of the shapes nor do they give us a clear winner. They confirm the intuition that increasing the number of sides, the performances increase as we have more parameters to adjust. The choice of the shape is then a trade-off between hull design and the other design areas, where these naval architecture criteria have also been considered. 
         [0052]    The hydrostatic parameters for the proposed design have been also calculated and following these results, we can make following considerations. 
         [0053]    Structural rigidity: The boat is designed for a displacement of 125 kg, i.e. the weight of a person (75 kg) plus the boat and eventual equipment. The pressure on the hull is therefore 125 kg over the wetted surface (about 2 m 2 ), which in different sailing conditions may reduce up to 50% (boat on a wave or on the plane): therefore 125 Kg/m 2 . 
         [0054]    Buoyancy: The twin-walled plastic sheet is extremely buoyant and gives the boat an embedded safety reserve buoyancy, able to hold a person afloat in the case the boat should open up in water. The boat is made of about 10 m 2  of empty sheet: with an average thickness of 6 mm weight of 1 kg/m 2 , the material accounts for a positive flotation of 50 kg, enough to hold the equipment (mast) and support the person afloat. When folded up, the boat generates an enclosed volume of about 300 litres, which gives an displacement for 300 kg, useful for safe navigation on waves, when water may fill up the deck. 
         [0055]    Stability: As can be seen in  FIG. 1 , the boat has a positive righting moment (i.e. tends to return upright) up to a heel angle of around 80 degrees. The curve is calculated for an initial draft of 10 cm and a weight of 100 kg (in the middle of the boat). 
       Folding Patterns 
       [0056]    Since the first paper models it has been clear that the folding plays an important role for the structural strength. A constant rule for the generation of folds, has been the utilization of triangular faces, in order to create only volumes composed by a number of tetrahedrons, to maximize the structural stability of the shape and to not rely only on the rigidity of the material. This approach guides the choice of the hull shape towards those with the least number of sides. The chosen shape is composed of two symmetrical tetrahedrons joint in the middle. More complicated shapes require dividing up the volume into more tetrahedrons and requiring more material, which then has to fold to a flat pack of minimal dimension. 
         [0057]    In order to maximize the longitudinal rigidity no bends have been made on the longitudinal dimension. The boats folds up as a book with the spine on the length. 
         [0058]    Important structural element of the boat is the transom. Different are the possibilities offered by the fold: 
         [0000]    Double bottom: elegant and efficient solution that resist the folding in order to achieve necessary rigidity and sealing.
 
Solid transom (inserted panel): easy and structurally sound solution, adds an extra part to be carried and stored in the boat.
 
Solid transom (folded up): the sheet folds on the back as they fold on the front. This is the solution chosen for the proposed design.
 
       Deck Design 
       [0059]    After the water test of the test rig the deck has been redesigned. The crew on a sailing boat has to change position quite often and be able, especially on small dinghies, to sit anywhere in order to balance the boat. While a flat and slightly concave deck is actually quite appropriate for the latter purpose, it is quite uncomfortable for the legs, forcing the person to kneel rather than sit. 
         [0060]    A raised border on the sides has been added to the final design in order to allow the passenger to sit on it. The border is an additional small tetrahedron with many functions. Besides forming a seat for the crew and something to hold on, it adds rigidity to the side. Most important function it joins the two sheets and forms the sealing. 
         [0061]    Compared to the test rig configuration, the final design has two sheets of corrugated plastic, fixed in the middle to the central frame. 
         [0062]    This configuration besides allowing the raised side border, allows also to use material of different thicknesses and to orient the corrugations of the two sheets in different directions, to increase the stability. 
         [0063]      FIGS. 2 to 7  show the chosen folding pattern.  FIG. 2  shows the boat ready for use. To pack the boat away the user must open the sides ( FIG. 3 ), open the back ( FIG. 4 ), insert the spars and close the internal sheet ( FIG. 5 ), close the external sheet ( FIG. 6 ) and pack the boat flat ( FIG. 6 ). 
       Material and Process 
       [0064]    Materials suitable for this application are:
       Multi-walled extruded polypropylene sheets, such as those used for signs, packaging or construction. For example, Correx® is a product produced by Kaysersberg® Plastics of Kaysersberg, France. Similarly Corriboard® is a product produced by Northern Ireland Plastics Ltd, Country Down, Northern Ireland. Corrugated polycarbonate sheets, which are available in a wider range of thicknesses and rigidity and often used for clear roofing.   Plain polypropylene sheets   Woven polypropylene sheets such as CURV®, which is produced by Propex Fabrics® GmbH Gronau, Germany   Aluminium sheets joined with rubber or neoprene hinges       
 
         [0069]    The choice of Correx® has been guided by the idea of realizing many functions in one part. The sheets act as the skin of the boat, have structural properties given by the rigidity of the corrugation, work as living hinges and when sealed on the edges they assure an extra buoyancy, very useful for a boat. With any other solution an additional material should have been introduced to realize those functions: i.e. a foam insert on the plain sheets to increase buoyancy. 
         [0070]    Correx® is commercially available with a thickness range from 2 mm to 10 mm, with different grades. The test rig has been made out of 10 mm twin-walled polycarbonate sheet, proving to be rigid enough. The two sheets included in the proposed design can have different thicknesses, the internal one being lighter. Rigidity depends mostly on the thickness of the single layers or walls of the sheet profile. The right choice has to be made after building full scale prototypes with sheets in the 6 mm to 10 mm range. 
         [0071]    The availability and the price on the market of this material is one of its advantages. 
         [0072]    If the boat would be produced on a large scale, it might be possible to develop a custom extrusion. In that case the external layer should be thicker to increase the resistance to abrasion, the cells should have a triangular profile, which increases stability and makes scoring the folding lines easier. 
         [0073]    Different solutions have been investigated to create the folding lines. The choice has fallen to profile rolling because it does not require bonding of material to polypropylene, which is possible only through welding (no adhesive are available for polypropylene) and therefore difficult for large surfaces.  FIG. 8  illustrates the appearance of polypropylene after profile rolling. 
         [0074]    To score the folding lines on the corrugated sheets, different tools and combinations of process parameters have been tested (i.e. temperature of material and tool, pressure and speed). The most successful process has been realized with a custom made tool that resembles an industrial pizza-cutter and prototypes a manual profile rolling. The material has been heated close to melting temperature and a cold tool has achieved better surface finishes. 
         [0075]    Profile rolling allows furthermore to create curved hinges. These are quite important aesthetic features for the final design, as well as they allow the creation of curved surfaces. 
       Detail Design 
       [0076]    The central frame has been introduced to add longitudinal rigidity to the boat and provide a structural element where all the equipment can be fixed: mast, centreboard, rudder, mainsheet and foot straps for the crew. 
         [0077]    Materials that have been considered are: injection mould, pultrusion, aluminium extrusion, PVC extrusion, composite and fibreglass (GRP). 
         [0078]    While the injection mould tends to be too expensive and technically difficult for this length, the pultrusion does not work well in torsion. The PVC extrusion has been used for the test rig and had to be reinforced to achieve sufficient rigidity. Aluminium extrusions can be realised in custom profiles, which would allow a better fixing of the Correx® sheets. It would be realised as the aluminium spars, which are the most common material for actual sailing masts. 
         [0079]    The edges of the external Correx® sheet are welded at the bow and stern, in order to realize a closed surface in contact with the water. External and internal sheet are fixed to the central frame. The external edges of the two sheets fold on themselves realizing the seal to water, when rubber sealing strips are provided on the contact surfaces. 
         [0080]    Several possibilities have been considered for the fixing of the fold: buttons, straps, bolts and Velcro® (hook and loop fastener). The last possibility has many benefits: lightweight, easy to open and close, invisible. Industrial types of Velcro® are available with high strength. Especially the moulded tapes, with symmetrical “mushrooms” sides. These plastic tapes can be glued or better welded to the polypropylene sheets. The symmetric tapes can used both for fixing the boat in the fold up configuration as well as flat pack. 
         [0081]    An alternative to seal solution is an inflatable chamber inside the enclosed volume between the sheets. Such a chamber, realized in thin elastic material which folds on one of the sheets when closed, would solve completely the sealing problem, occupying the volume with air and giving extra rigidity to the structure. This solution has not been integrated so far to simplify the assembly process for the user and avoid pumping. 
         [0082]      FIG. 9  shows the fixing and sealing solution for the external edges. 
       Rig Design 
       [0083]    The design of a foldable sailing rig was included in the initial concept and different configurations have been considered. On the other side, masts in sections are quite collapsible and I decided to focus on the hull, which is the real volume to collapse, as the result of this project. 
         [0084]    On the other hand, the idea of fitting commercially available rigs from other boats and especially from windsurfs has many benefits: 
         [0000]    Wider range: windsurf sails are available in wide range of sizes to match the wind conditions. Similar concept could fit this lightweight boat.
 
Weight: windsurf rigs are lighter, because using fibre masts and that is essential for this lightweight boat.
 
Business model: attractive commercial strategy to enter the market with lower barrier: entry level customers do not need to buy a sail, but can reuse old ones. Windsurfers can have a low cost switch to sailing for a day or for the family. Custom sail could always be offered as optional.
 
         [0085]      FIGS. 10 to 15  show the hull in use with various sails:  FIG. 10  is a windsurf like rig (boomless), for example a ‘batwing’ sail for a kayak;  FIG. 11  is a rigid wing (more efficient, smaller size);  FIG. 12  is a traditional mast/boom rig, for example a Topper;  FIG. 13  is a Lateen sail (boomless) with front mast supports;  FIG. 14  is a Lateen sail (boomless) with back mast supports; and  FIG. 15  is a foldable rigid sail (in sections), same material as the hull. 
       Prototyping 
       [0086]    During the whole process models and prototypes have been used: 
         [0000]    Paper models
 
Polypropylene and Correx® scale models: to test the folds with thicker and harder material and to test in water.
 
RC model: the first sailing of the proposed hull shape has been realized with a radio controlled model with a polypropylene hull in scale 1:5.
 
Full-size cardboard model: The model has been used as test rig for the folding/unfolding process. The model showed how easy the folding could be and give an idea of the handling of boat in real size. Focusing on the fixing, this prototype inspired the idea of welding together the sheet edges at bow and stern; so that they are automatically in place during the opening/closing process. The idea of embedded handles for easy transportation came also from this test rig.
 
Full-size sailing test rig: It is made out of separate corrugated polycarbonate roofing sheets. The frame is obtained welding PVC square tubes and the hinges are realised with PVC tubes fixed to the sheets with fibreglass reinforced tape and hinged on an aluminium rod. The sailing rig and equipment is borrowed from a Topper dinghy and the weight of the mast has forced us to use a metal reinforcement on the PVC frame. The sealing has been obtained by taping the hinges, thus partially restricting the unfolding process. The total weight of the boat is 27 kg.
 
         [0087]    Features introduced during prototyping are: Improved deck design with raised borders; Velcro® fasteners; curved hinges; two corrugated sheets with corrugation in different direction for added rigidity. 
       Proposed Design 
       [0088]    Dimensions:
       fold up: 2.8 m×1.55 m×0.35 m   flat pack: 2.98 m×0.90 m×0.10 m   weight: 25 kg       
 
         [0092]    Twin-wall extruded polypropylene sheet is used, cut and scored (profile rolling) to form the folding lines. Edge sealing and welding the material weights 15 kg and the required quantity (10 m 2 ) costs on the market about £60. 
         [0093]    The frame is aluminium extrusion Machined to realise the fitting to the other parts. The supports (mast, centreboard, rudder) are injection moulded parts. The fasteners are industrial moulded “Velcro®” tape (welded on the polypropylene sheets) supports internal sheet frame sealing and fasteners external sheet 
         [0094]      FIG. 16  shows the design, which is composed of an external sheet of multiwall extruded polypropylene  1 , an aluminium frame  2 , an internal sheet of multiwall extruded polypropylene  3 , a nylon injection moulded mast support  4 , nylon injection moulded centreboard supports  5 ,  6 , a nylon injection moulded rudder support  7  and rubber and Velcro® sealing stripes  8 , 9 . 
         [0095]      FIGS. 17 to 21  show a completed hull from various angles.  FIG. 22  is another illustration of a completed hull.  FIGS. 23 to 25  are three possible two-sheet configurations of the hull.