WO2000075007A2

WO2000075007A2 - Stable tunnel hull

Info

Publication number: WO2000075007A2
Application number: PCT/GB2000/002231
Authority: WO
Inventors: William Francis Pentecost
Original assignee: William Francis Pentecost
Priority date: 1999-06-08
Filing date: 2000-06-08
Publication date: 2000-12-14
Also published as: GB2350820B; GB2350820A; AU5237300A; WO2000075007A3; GB0013840D0

Abstract

A monohull (1) has a tunnel (2) which runs in a generally forward to aft orientation. More than one tunnel (2) can be incorporated into the monohull (1). The one or more tunnels (2) define a dry region which is above the water and separates wetted areas (9) which sit substantially below the water. The bow of the monohull (1) is adapted to restrict water flow into the one or more tunnels (2) and to reduce wave slap on the forward roof of the tunnels (2). The entrance of the one or more tunnels (2) at the bow is smaller and nearer water level than the size and height of the tunnel (2) further aft. The tunnel (2) may also have a surface which is shaped to deflect water. The present invention allows the stability of a displacement, semi-displacement or planing craft to be increased without significantly increasing drag, that is the amount of effort needed to push the boat through the water.

Description

STABLE TUNNEL HULL

The present invention relates to an improved monohull for use on water craft. The monohull is especially, but not exclusively, suitable for use on displacement and semi- displacement sea craft such as canoes, kayaks, dinghies, punts and also rowing boats, motor boats, speedboats, sailboats, keel boats and the like. The monohull is also suitable for use on planing craft, and in particular load carrying planing craft.

Tunnel hulled speed and sail boats are well known small, light craft, so called because they have narrow sections which can ride on water, separated by a wide tunnel which allows air to be funnelled under the craft. The resultant craft is a type of catamaran, having a monohull with narrow pontoons which sit in the water whilst most of the hull is suspended over the water.

Present tunnel craft are suited to low load bearing and fast speed non-displacement or planing craft, as the tunnel is used to give "lift" to the craft by virtue of the passage of air through the tunnel. The craft must travel at an appropriate speed to allow enough air to travel through the tunnel at once, in order to lift the craft so that it is substantially suspended over, and travels "on" the water. Conventionally tunnel craft are not load carrying, displacement, semi- displacement or planing craft. Displacement and semi- displacement craft travel through, and displace water from, their pathway and do not travel at sufficient speeds to come onto the plane. Furthermore these types of craft are usually too heavy in relation to their speed to be suspended over the water by air flow through the tunnel.

It is important that any sea craft, but in particular small water craft such as canoes, kayaks, punts, and also speedboats, motorboats and the like are relatively stable. Small craft are generally considered to be those up to 6 or 7 metres in length and tend to be from about 1.5 to 2 metres wide. Usually the hull of these crafts narrow towards the bow, but widens at the transom. The bow tends to have a sharp "V" profile and flattens towards the aft of the boat such that the width of the boat diminishes from the gunnels to the waterlines. As the stability of the boat depends primarily on its width at the waterline, this limits the stability of the craft. It will be appreciated by anyone who has used a canoe or kayak that it is relatively easy to capsize such a vessel by sudden weight shift, i.e. if weight is moved from side to side. It is also particularly difficult to re-embark a canoe or the like after capsizing, due to their instability.

Present attempts to make boat monohulls more stable include making the beam wider, building weight in as low to the hull as possible and incorporating a keel. However, extending the beam often results in unacceptable drag, that is a considerably increased amount of power is required to push the hull through or over the water due to the extra wetted surface. As a consequence speed is lost and an increased effort is required to move the boat through the water. This is particularly problematic if the boat is a paddle boat. Therefore a compromise is usually chosen to produce a craft which may be less than ideally stable, but which does not require prohibitive amounts of energy to achieve a planning movement or reach reasonable speed.

It will be appreciated that the inclusion of one or more tunnels on a displacement, semi-displacement or planing boat would unduly increase drag, as waves, water and air would enter and the resultant increase in wetted surface would provide a pressure build up. It is therefore an object of the present invention to provide a boat monohull which has superior stability over conventional monohulls, which can be used on displacement, semi- displacement or planing water craft, but which does not significantly increase drag, or restrict the speed of the water craft.

According to the present invention there is provided a monohull boat having a monohull with one or more tunnels, the one or more tunnels having a generally forward to aft orientation, wherein the one or more tunnels define a dry region located above the surface of the water, and wherein the monohull has means for reducing drag.

Preferably the drag reducing means restricts water flow into the one or more tunnels. Optionally the drag reducing means is a constricted bow.

Typically, where the drag reducing means is a constricted bow, the entrance of the one or more tunnels have a reduced height and width relative to the height and width of the tunnel further aft.

The drag reducing means may be provided by the one or more tunnels having a width, which is less than 55% of the average width of the monohull.

The drag reducing means may be provided by virtue of the one or more tunnels having a surface which is adapted to deflect water.

Optionally the surface of the one or more tunnels is contoured.

Alternatively the surface of the one or more tunnels comprises steps.

The one or more tunnels may provide part of the seating in the monohull boat.

Optionally the one or more tunnels form a housing for an extending bowsprit .

Optionally the boat may have one or more keels. The keels can extend from the tunnels and may be fixed or retractable.

The tunnel may form part of the deck or flooring support. Optionally one or more hydrofoils may be located within the one or more tunnels.

Optionally the one or more tunnels are adapted to house a spinnaker or gennaker.

Optionally the contours in the one or more tunnels form casing and support for centre plates, dagger boards, drop plates or drop keels.

Optionally the one or more tunnels may house propellers.

The monohull boat may be a rowing boat such as a canoe, punt, dinghy, kayak or the like. Alternatively the boat may be motor powered such as a speed boat, inward or outward powered motor boat, motor yacht, jet boat, lifeboat, cabin cruiser or the like. The boat may be a tender or a keel boat and may also be an inflatable boat, rib or rigid inflatable boat.

The boat may be powered by kite, water jet, sail or more than one means of propulsion.

Optionally the one or more tunnels comprise ropes which act as safety lines in the event of the boat overturning.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which :-

Figure 1 is a cross section of a monohull with tunnel, Figure 2 is a view of the under side of the monohull of Figure 1 with tunnel, Figure 3 shows a cross section of a monohull with a contoured tunnel, Figure 4 is a view of the underside of a monohull with contours running parallel to the length of the tunnel, Figure 5 shows the underside of a monohull with steps along the tunnel, Figure 6 and 7 show respectively the underside and a bow to stern hull view along the centre of a monohull craft with cross section stations SI to S6 marked along it, Figure 8 to 13 show transverse stations SI to Sβ as marked on Figures 6 and 7, Figure 14 is a cross section of a hull with a double tunnel, Figure 15 shows the under side of the twin tunnel hull of Figure 14, Figure 16 shows a transverse section of a twin tunnel hull with contoured tunnels, Figure 17 shows the under side of a double twin tunnel hull with contoured tunnel, Figure 18 shows an underside of a twin tunnel planing hull with transverse cross sections XSl to XS6, Figure 19 shows a cut along the central keel line of the twin tunnel hull of Figure 18 from bow to stern with XSl to XS6 marked, Figure 20 to Figure 25 are views of cross sections XSl to XS6 from Figures 18 and 19, Figure 26 shows a transverse section of a twin tunnel hull with twin keels and a single motor between the tunnels driving a propeller in the tunnels on each side, Figure 27 shows a twin tunnel hull with motors positioned on the outside of each tunnel, Figure 28 shows a transverse section of a twin tunnel hull with motors in each part of the hull, Figure 29 shows the underside of a twin tunnel displacement hull or motor sailor hull type with transverse sections MSI to MS6 marked, Figure 30 shows a cut from stem to stern of the twin tunnel hull of Figure 29 with transverse sections MSI to MS6, Figures 31 to Figure 36 show cross sectional views of MSI to MS6 relating to Figures 29 and 30, Figures 36 and 37 show a keel fitted to twin tunnel hull, Figure 37 shows a twin tunnel hull with motor between the tunnels and central keel, Figure 38 is a central cross section of a tunnel hull from bow to stern with an extending bow sprit housing located in the tunnel contours, Figure 39 shows a section of hull wall with a step protruding into it, Figure 40 shows a tunnel hull cross section with a hydrofoil extending across the tunnel, Figure 41 shows a tunnel hull cross section with a hydrofoil extending below the hull line, Figure 42 shows the underside of a tunnel hull with two hydrofoils across the tunnel, Figure 43 shows the underside of a canoe with a tunnel running from bow to stern, Figure 44 shows a cross section of a tunnel hull craft where the tunnel also is a support for a seat, Figure 45 shows a cross section of a tunnel hull kayak, Figure 46 shows a bow or stern view of a tunnel hull canoe, Figure 47 shows a bow or stern view of a tunnel hull kayak, Figure 48 shows a cross section of a tunnel hull where the mast foot is located in the tunnel contour; and, Figure 49 shows a tunnel hull where the centre plate/dagger board housing is located in the tunnel contour.

Referring firstly to Figure 1, a boat monohull is generally shown in cross-section at 1. The hull (1) has a tunnel (2) which runs in a generally forward to aft orientation, parallel to the keel (6) of the monohull (1). In the depicted embodiment, the hull (1) has one tunnel (2) positioned in an essentially central location relative to gunnels (3) . The tunnel (2) may be of any shape, but typically resembles a half tube or half box section or an upturned half tube. It can be seen that the roof (4) of the tunnel (2) is raised high above the waterline (5) to create a dry region of the monohull which is above the water. The tunnel (2) is also substantially narrower than conventional tunnels. The shaded areas (9) are located substantially below the surface of the water and displace water as the boat moves. The shaded areas (9) are described herein as the "wetted areas". The boat may be a keel boat with one or more keels (6) which can be angled forward or aft. The keels (6) can also be extended downward and outward to provide extra lift. The keels (6) are an extension from the sides of the tunnel (2) and may be fixed or retractable. A double keel (6) may be provided on the two wetted areas (9) of the hull (1) or as extensions of the sides of the tunnel (2) .

Figure 2 illustrates the same monohull boat as shown in Figure 1, viewed from the underside, i.e., from under the surface of the water. Figure 2 shows more clearly that the tunnel (2) runs along the length of the hull (1) from fore to aft, that is from bow (7) to stern (8) and separates wetted areas (9) which sit substantially below the surface of the water. The tunnel (2) defines area (a) which is above the water line and is high enough to clear wavelets, and which minimises wave slap and reduces the wetted surface of the monohull (1), particularly under calm conditions. It can also be seen from Figure 2 that the shape of the outer wetted areas (9) of the hull (1) are asymmetric.

Turning now to Figure 3, a monohull (1) has a tunnel (2) similar to the hull depicted in Figure 1. However, the surface of the tunnel (2) has a plurality of contours (10) , which give lift to the hull (1) at speed and also help break up wave slap and minimise water drag. The contours (10) run essentially parallel to the length of the tunnel (2) as can be seen from Figure 4. The tunnel (2) may also have transverse steps (11), as can be seen in Figure 5, which further help to control water flow through the hull by deflecting water running along the tunnel (2) .

To illustrate the design of a monohull tunnel, Figure 6 shows the underside of the hull with tunnel (2) with cross-sections SI to S6. Figure 7 shows a hull view along the centre of a single tunnel craft from bow (7) to stern (8) sectioned by SI to S6. It can be seen from Figure 7 that the bow (7) is shaped to reduce the volume of air and water which enters the tunnels. The bow (7) has a droop nose (13) which sits forward of the tunnel (2) and allows for as much water as possible to be deflected from entering the monohull (1) tunnel (2) . It can be seen from Figure 9, which is a cross section through S2, that the tunnel (2) is constricted (14) at the bow end. The droop nose bow (13) is in fact a normal bow where the tunnel (2) entrance or entrances on the forward end of the bow (13) are smaller and nearer the water level than the size and height of the tunnel (2) further after, and this reduces the amount of wetted surface and therefore drag within the tunnel. Cross sectional views through SI to S6 are shown in Figures 8 to 13.

Inclusion of the tunnel (2) in the monohull (1) creates a wider boat which consequently has an improved stability. The advantage of the present invention lies in the fact that an increased stability can be achieved without significantly increasing the amount of effort needed to push the craft through the water. The monohull (1) provides increased stability without creating addition drag as is the case with previous methods which have been used to stabilise boats which generally consist of increasing the wetted area of the hull (1) . The tunnel (2) roof is raised above the water so as to minimize wave slap and reduce wetted surface under calm conditions and with smaller waves. The inclusion of contours in the tunnel (2) help give lift to the monohull (1) at speed and help break up wave slap whilst the inclusion of steps (11) in the tunnel (2) help control water flow and reduce wetted surface.

Figure 14 is a cross-section of a monohull (13) which has a double tunnel, namely tunnels (15) and (16) . The underside of the twin tunneled hull (13) can be seen from Figure 15. The tunnels (15) and (16) are arranged in such a manner to create 3 wetted areas, namely (a) , (b) and (c) . The tunnels (15) and (16) may have contours (10) similar to the embodiment shown in Figure 3, the contours (10) helping to give lift to the hull (13), minimise water drag and break up wave slap. Figures 18 and 19 show the double tunnel hull of Figures 14 and 15 sectioned into cross sections XSl at through to XS6 in the direction bow (7) to aft (8).

Figures 20 to 25 show the cross sectional view XSl to XS6 in more detail. It can be seen from Figures 20 and 21 that from the front that is the bow (7) of the sea craft the tunnels (15) and (16) are partially or near completely covered by virtue of the tunnel (2) entrances being smaller and nearer the water surface than the size and height of the tunnel (2) further aft. This limits the amount of air and water which can enter the tunnels (15) and (16) as seen in Figures 22 to 25, and reduces drag, as the amount of waves and water entering the tunnels (15) and (16) is minimised.

Where the monohull boat is a motorboat, a motor (17) can be located in the middle section or wetted area (b) of the hull. This can be seen in Figure 26. The tunnels (15) and (16) may also house associated propellers (18) . Where more than one motor (17) is used, the motors (17) may be positioned in the outer wetted areas (a) and (c) of the hull as shown in Figure 27 or in all three wetted areas (a), (b) and (c) of the hull as shown in Figure 28. The sea craft of Figure 28 also has hydrofoils (19) located in the tunnels (2) which may act as water scoops and/or exit ports for jet water propulsion.

Figures 29 to 35 illustrate a twin tunnel displacement hull in more detail. Figure 29 shows the underside of a twin tunnel displacement hull or motor sailor with transverse cross sections MSI to MS6, which can also be seen from an alternative angle in Figure 30. The views seen from cross sections MSI to mS6 are shown in Figures 31 to 36 travelling from bow (7) to stern (8) . Where the twin tunnel hull is a keel boat one or more keels (20) may be included in the monohull as extensions of the tunnels (15) and (16) as seen in Figures 34 and 35 or alternatively, may be centrally fitted (21) such as in Figure 36, wherein the keel (22) may be connected to a motor (17) as shown in Figure 37.

Figure 38 shows a tunnel hull (1) in a cross-section from bow (7) to stern (8) which has an extending bowsprit housing (22) located within the tunnel (2). Specifically the bow sprit housing is located within the contours of the tunnel (2) . Figure 39 shows a section of a hull (1) wall with a step (23) protruding into it.

As shown in Figure 28, one more tunnels (2) may be used to house a hydrofoil (19) . A hydrofoil (19) may extend across the tunnel (2) as shown in Figure 40 or may extend below the hull line as shown in Figure 41. More than one hydrofoil (19) can be incorporated into the underside of the tunnel hull (1) , as shown in Figure 42 where two hydrofoils (19) are included across the tunnel (2) .

In an embodiment shown in Figure 44 the tunnel (2) of the hull (1) can be adapted to be a support for a seat (23) . The tunnel (2) and contours (10) may also form part of the deck or flooring support.

A tunnelled hull as described in the present invention is particularly suitable for use as small displacement sea craft such as canoes or kayaks. One common type of canoe is the Canadian Canoe, formerly known as an Indian canoe, which is largely open and without significant deck area whilst the commonly known "Eskimo" kayak has a complete deck wherein paddlers sit in "cockpits" cut into the deck.

These craft are relatively narrow of beam and therefore tend to be unstable. Wider beamed boats give more stability but require more energy to push them through the water. Figure 43 shows the underside of the canoe (2) with a tunnel running from bow (7) to stern (8). The tunnel (2) raises the bottom of the canoe along the length of the tunnel (2) above the water line and also widens the canoe by its own width without significantly increasing drag through the water. In addition to widening the boat the tunnel (2) gives the canoe more grip in the water. A bow (7) or stern (8) view of the tunnel hull canoe can be seen from Figure 46. Figure 45 shows a cross-section of a tunnel hull kayak, whilst Figure 47 shows a bow or stern view of the tunnel hull kayak. The tunnel (2) shown in Figures 44 to 47 can be moulded to become part of the seating arrangements of the canoe or kayak. It can be seen from Figures 45 and 47 that the tunnel (2) may also be sloped upward at the bow (7) to provide extra lift when meeting oncoming waves.

In yet another embodiment, the contours (10) of the tunnel (2) can be used to locate a mast (24) and mast foot (25) as shown in Figure 48, or housing (26) for a centre plate/dagger board (27) as shown in Figure 49. The tunnel (2) can also be used as a location for a "Z" drive or drop plate (not shown) .

The advantage of the present invention is that the inclusion of one or more tunnels in the monohull of a displacement, semi-displacement or planing boat increases the stability of the boat but does not unduly increase the drag, that is the power required to move the boat through the water. Without the water and air restricting features, such as the constricted bow, and the steps and contours on the surface of the tunnel, the tunnel would create additional drag. As a consequence the boat is infinitely safer, and is less likely to capsize under sudden weight shift. Furthermore, an individual who has fallen into the water will be able to pull themselve back onto the tunnel hull boat without capsizing the boat. The one or more tunnels (2) of the monohulls described in the present invention typically have ropes strung along the tunnel (2) which act as safety lines should the craft overturn. The user will be able to use the ropes to pull his or herself back onto the craft. It will be appreciated that the tunnel (2) forms a type of walkway along the bottom of the craft, which the user can pull his/herself into and shelter out of the water, should the craft overturn. As a result of the increase in stability and safety, canoes or kayaks in the spirit of the present invention are better suited to train learner canoeists than conventional canoes or kayaks, and can also be used in novelty games such as obstacle courses and jousting.

Further modifications and improvements may be incorporated without departing from the scope of the invention herein intended.

Claims

1. A monohull boat having a monohull with one or more tunnels, the one or more tunnels having a generally forward to aft orientation, wherein the one or more tunnels define a dry region located above the surface of the water, and wherein the monohull has means for reducing drag.

2. A monohull boat is claimed in Claim 1, wherein the drag reducing means restricts water flow into the one or more tunnels.

3. A monohull boat as claimed in any one of the preceding Claims, wherein the drag reducing means is a constricted bow.

4. A monohull boat as claimed in Claim 3 wherein the entrance of the one or more tunnels has a reduced height and width relative to the height and width of the tunnel further aft.

5. A monohull boat as claimed in any of the preceding Claims wherein the drag reducing means is provided by virtue of the one or more tunnels having a width which is less than 55% of the average width of the monohull.

6. A monohull boat as claimed in any one of the preceding Claims, wherein the drag reducing means is provided by virtue of the one or more tunnels having a surface which is adapted to deflect water.

7. A monohull boat as claimed in Claim 6 wherein the surface of the one or more tunnels is contoured.

8. A monohull boat as claimed in Claim 6 wherein the surface of the one or more tunnels comprises steps.

9. A monohull boat as claimed in any one of the preceding Claims wherein the monohull has a droop nose bow.

10. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels form seating in the monohull boat.

11. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels form a housing for an extending bowsprit.

12. A monohull boat as claimed in any one of the preceding Claims wherein the tunnel forms part of the deck or flooring support.

13. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat has one or more keels.

14. A monohull boat as claimed in Claim 13 wherein the keels are an extension from the sides of the tunnel.

15. A monohull boat as claimed in any one of the preceding Claims, wherein the contours in the one or more tunnels form casing and support for centre plates, drop plates, drop keels or dagger boards.

16. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels house a hydrofoil.

17. A monohull boat as claimed in Claim 16 wherein the hydrofoil acts as a water scoop and exit port for water jet propulsion.

18. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels house a spinnaker or gennaker.

19. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels house propellers.

20. A monohull boat as claimed in any one of the precerding Claims wherein the one or more tunnels have ropes which act as safety lines in the event of the monohull boat overturning.

21. A monohull boat as claimed in any one of the preceding Claims wherein the contours in one or more tunnels form casing and support for a mast foot and mast.

22. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels provides a location for a "Z" drive.

23. A monohull boat as claimed in any one of the preceding Claims wherein the one or more tunnels house an outboard engine.

24. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a canoe.

25. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is an inflatable boat.

26. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a tender.

27. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a sailing dinghy.

28. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a rowing boat.

29. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is an inboard or outboard motor powered boat.

30. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a planing hull.

31. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a kayak.

32. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a punt .

33. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat is a speedboat.

34. A monohull boat as claimed in any one of the preceding Claims, wherein the monohull boat is a yacht.

35. A monohull boat as claimed in any one of the preceding Claims, wherein the monohull boat is a rigid inflatable boat.

36. A monohull boat as claimed in any one of the preceding Claims, wherein the monohull boat is a yacht .

37. A monohull boat as claimed in any one of the preceding Claims, wherein the monohull boat is powered by kite.

38. A monohull boat as claimed in any one of the preceding Claims, wherein the monohull boat is powered by a water jet.

39. A monohull boat as claimed in any one of the preceding Claims, wherein the monohull boat is powered by sail.

40. A monohull boat as claimed in any one of the preceding Claims wherein the monohull boat has a combination of or more than one means of propulsion.

41. A monohull boat as described herein with reference to Figures 1 to 49 of the accompanying drawings.