CA1256324A - Boat equipped with three semi-submersible floats - Google Patents
Boat equipped with three semi-submersible floatsInfo
- Publication number
- CA1256324A CA1256324A CA000478085A CA478085A CA1256324A CA 1256324 A CA1256324 A CA 1256324A CA 000478085 A CA000478085 A CA 000478085A CA 478085 A CA478085 A CA 478085A CA 1256324 A CA1256324 A CA 1256324A
- Authority
- CA
- Canada
- Prior art keywords
- boat
- float
- semi
- hand
- submersible
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
- B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
- B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
- B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
- B63B1/12—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly
- B63B2001/128—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly comprising underwater connectors between the hulls
Landscapes
- Ocean & Marine Engineering (AREA)
- Fluid Mechanics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
- Toys (AREA)
- Aerodynamic Tests, Hydrodynamic Tests, Wind Tunnels, And Water Tanks (AREA)
- Vehicle Step Arrangements And Article Storage (AREA)
- Artificial Fish Reefs (AREA)
- Motorcycle And Bicycle Frame (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to a boat equipped with three semi-submersible floats connected to a deck via strut members, one central float being provided at the fore part of the boat and two side floats being positioned symmetrically with respect to the longitudinal plane of said central float.
According to the invention, the ratio of the ordinate of the area curve of the complete boat at the crossing point of the area curves of the side floats, on the one hand, and of the central float, on the other hand, to the maximum ordinate of said area curve of the complete boat is at least equal to 0.45; and, the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.
The invention finds an application in the construction of boats inexpensive to run.
The invention relates to a boat equipped with three semi-submersible floats connected to a deck via strut members, one central float being provided at the fore part of the boat and two side floats being positioned symmetrically with respect to the longitudinal plane of said central float.
According to the invention, the ratio of the ordinate of the area curve of the complete boat at the crossing point of the area curves of the side floats, on the one hand, and of the central float, on the other hand, to the maximum ordinate of said area curve of the complete boat is at least equal to 0.45; and, the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.
The invention finds an application in the construction of boats inexpensive to run.
Description
~25~3:2~
Naval architects of today have at their disposal a number of fundamental dispositions for designing surface ships, of which the buoyancy is obtained by adopting more than one hull.
For example, boats are known to be supported by three hulls.
The best known of these boats are equipped with hulls which, understandably, are partly submerged, but also partly emerged : this is the case illustrated for example in French Patent 1 414 492. Other types of boats, less known of the public, but of an already older design, are equipped with fully submerged support hulls, such as described for example in U.S.
Patent 1 825 286.
Other designs are also known and even more pro;ects of surface crafts of this last type, the buoyancy of which is achieved by a plurality - two, three or four - of torpedo-like hulls connected with the rest of the boat by partly submerged high and narrow strut members playing a part in the buoyancy.
The effective part of such a boat is situated above the water surface and the assembly constituted by the hull proper and by the submerged part of the strut member is conventionally called a "semi-submersible float".
Designs of "semi-submersible crafts" have, these last few years, been concerned with saving and viability, and no longer with the sole fact of finding new lines. But the number of crafts built is few and the acquired experience remains limited.
This novel design, however, is promising as far as the construction of boats with good seaworthiness and comfort is concerned. Yet there remains to determine the particular dispositions which will lead to a minimum drag, hence to the construction of crafts inexpsnsive to run.
Not one of the known boats that are e~uipped with "semi-submersible floats" has -the nautical
Naval architects of today have at their disposal a number of fundamental dispositions for designing surface ships, of which the buoyancy is obtained by adopting more than one hull.
For example, boats are known to be supported by three hulls.
The best known of these boats are equipped with hulls which, understandably, are partly submerged, but also partly emerged : this is the case illustrated for example in French Patent 1 414 492. Other types of boats, less known of the public, but of an already older design, are equipped with fully submerged support hulls, such as described for example in U.S.
Patent 1 825 286.
Other designs are also known and even more pro;ects of surface crafts of this last type, the buoyancy of which is achieved by a plurality - two, three or four - of torpedo-like hulls connected with the rest of the boat by partly submerged high and narrow strut members playing a part in the buoyancy.
The effective part of such a boat is situated above the water surface and the assembly constituted by the hull proper and by the submerged part of the strut member is conventionally called a "semi-submersible float".
Designs of "semi-submersible crafts" have, these last few years, been concerned with saving and viability, and no longer with the sole fact of finding new lines. But the number of crafts built is few and the acquired experience remains limited.
This novel design, however, is promising as far as the construction of boats with good seaworthiness and comfort is concerned. Yet there remains to determine the particular dispositions which will lead to a minimum drag, hence to the construction of crafts inexpsnsive to run.
Not one of the known boats that are e~uipped with "semi-submersible floats" has -the nautical
2~
properties, such as the drag, whlch will make it an attractive propositlon to run, thLs probably being why all the pending projects generally appear so lnactive and non-productive.
So lt is one of the objects of the present invention to optimize the shapes and relative positions of semi-submersible floats when working out those special novel dispositions.
To this effect, the invention relates to a boat with three semi-submersible floats connected to a deck via strut members, a central float being provided at the fore part, and two side floats being symmetrically positioned with respect to the longitudinal plane of said central float, according to the prlnciple disclosed 15 in U.S. Patent No. 1 815 286 for example The main preoccupation of any naval architect when designing a craft of this type is therefore to solve the problem of reducing the drag, and more particularly reducing the effect of wave action~ problem which past projects have come up against, without really solving it.
It is true that a number of solutions have been proposed for boats with non semi-submersible sur-face hulls, and French Patent 1 414 492~ for example, defines the principles of dispositions which, for that type of boats, permit to reduce the effects of waves.
~Z56~
The inventive act has been perormed in the present invention when the Applicant has provided that, in the boat in question:
a) the ratio of the ordinate of the area curve of the complete boat at the crossing point of the area curves of the side floats, on the one hand, and of the cen-tral float, on the other hand, to the maximum ordinate of said area curve of -the complete boat is at least equal to 0.45; and, b) the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.
The following advantageous dispositions are also preferably adopted:
- for each float, the ratio of the depth ~5~2~
of immersion of the maximum part of the area curve of the horizontal sections (namely TcL), to the equivalent diameter of said float is between 0.6 and 1.4;
- the coefficient of asymmetry of the boat is less than 0.3;
- the aspect ratio of each float is between 5 and 10;
- at least one substantially horizontal fin connects each side float with the central float;
- the two side floats are, on the one hand, identical to, and on the other hand, separate form the central float.
The invention will be more readily understood on reading the following description with reference to the accompanying drawings in which:
- Figure 1 is a view, following arrow F of Figure 2, of a boat according to the invention;
- Figure 2 is a view, following arrow G of Figure 1, of the same boat;
- Figure 3 is a cross-section along line III-III of Figure 1;
- Figures 4, 5, 6, 7 and 8 are area curves of ths boat according to the invention, shown as several separate embodiments.
~ eference is made hereafter to a number of notions, whose unusual nature invites a definition, this being given in the accompanying schedule, presented as forming part of the present patent application.
The boat illustrated by way of example is a surface-type boat with three floats, called "trimaran". It is constituted by:
- an entirely emerged platform 1 comprising a deck 2 and containing the effective volume of the boat (transporting holds, cabins, etc...) - a front cen-tral hull 3, which is oblong and has a vertical longitudinal plane of symmetry S, and which is ~251~i32~
entirely immersed below the water surface ~;
- two side hulls 5, which are disposed symmetrically with respect to the plane of symmetry S, at the back of the central hull 3, are identical and entirely immersed;
- a strut member 6 which extends vertically and substantially parallel to the plane of symmetry S ancl connects -the central hull 3 with the lower face 7 of the platform 1;
- two strut members ~, extending vertically, substantially parallel to the plane of symmetry S, each one connecting a side hull 5 with the lower face 7 of the platform 1;
- two substantially horizontal fins 9, which connect both side hulls 5 to the central hull 3.
The special features have been observed:
- the assembly of a hull and the corresponding strut member (central hull 3 and a strut member 6, each side hull 5 and its strut member 8) constitutes a semi-submersible float;
- each semi-submersible float has a positive buoyancy, the assembly of three semi-submersible floats conferring its buoyancy to the boat;
- the hulls 3,5 and their strut members 6,8 can be constituted of tanks or water-ballasts, but they can also be constituted of compartments containing the installations o~ th~
boat; for example, three "Diesal" type engines, a main one, and two lower-powered ones, may be installed in the central hull 3 and in the side hulls 5, to drive the propellers; likewise, the hollow strut members 6,8 are designed to enable the passage of numerous connections (electric cables, piping, access), between the hulls 3,5 an~ the deck 2;
- the transverse vertical planes passing through the ends of the area curves of the vertical transverse sections of the semi-submersible floats 3-6 and 5-8 are marked:
V 3 AR : plane passing through the aft end of the area curve of the semi-submersible float 3-6;
V 3 AV : plane passing through the forward end of the area curve of the semi-submersible floa-ts 3-6, V 5 AR : plane passing through the aft ends of the area curve of the semi-submersible floats 5-8, V 5 AV : plane passing through the forward ends of the area curve of the semi-submersible floats 5-8, and it is noted that there is an overlapping in the longitudinal direction, parallel to plane S, of the relative posi-tions of the semi-submersible central float 3-6 and of the semi-submersible side floats 5-8, (see figure 2) plane V 5 AV being situated ahead of plane V 3 AR.
Figures 4 to 8 show the curves of the surfaces according to several different embodiments and corresponding, for each one:
- curve A 3 to the semi-submersible float 3, - curve A 5, to the whole assembly of the two semi-submersible floats 5-~, - curve A 1, to tall three semi-submersible floats, namel~ to the boat itself.
Due to the aforesaid overlapping, curves A 3 and A 5 have an intersecting point I contained inside a transverse vertical plane VI, situated between planes V 3 AR and V 5 AV.
Also represented are:
- the value ~I of the surface of the cross-section of the boat (curve A 1) situated inside the plane VI, - the maximum value AM1 of curve A 1.
~2~ i3;~4 In the embodiment which corresponds to - Figure 4, AI is substantially equal to AM3 and AM5.
A*ll is therefore equal, substantially to any one of said three values. Curve Al is flat between planes V3~ and V5~ . This is very helpful to reduce the efEect of wave action for speeds corresponding to a number of Froude of between 0.4 and 0.6 approximately (curve Al "balanced" between the front and the rear of the boat and free of trough or accentuated crest, particularly in thearea of plane VI). Moreover, the volume of the two semi-submersible side floats5-8, on thè one hand, and the volume of the semi-submersible central float
properties, such as the drag, whlch will make it an attractive propositlon to run, thLs probably being why all the pending projects generally appear so lnactive and non-productive.
So lt is one of the objects of the present invention to optimize the shapes and relative positions of semi-submersible floats when working out those special novel dispositions.
To this effect, the invention relates to a boat with three semi-submersible floats connected to a deck via strut members, a central float being provided at the fore part, and two side floats being symmetrically positioned with respect to the longitudinal plane of said central float, according to the prlnciple disclosed 15 in U.S. Patent No. 1 815 286 for example The main preoccupation of any naval architect when designing a craft of this type is therefore to solve the problem of reducing the drag, and more particularly reducing the effect of wave action~ problem which past projects have come up against, without really solving it.
It is true that a number of solutions have been proposed for boats with non semi-submersible sur-face hulls, and French Patent 1 414 492~ for example, defines the principles of dispositions which, for that type of boats, permit to reduce the effects of waves.
~Z56~
The inventive act has been perormed in the present invention when the Applicant has provided that, in the boat in question:
a) the ratio of the ordinate of the area curve of the complete boat at the crossing point of the area curves of the side floats, on the one hand, and of the cen-tral float, on the other hand, to the maximum ordinate of said area curve of -the complete boat is at least equal to 0.45; and, b) the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.
The following advantageous dispositions are also preferably adopted:
- for each float, the ratio of the depth ~5~2~
of immersion of the maximum part of the area curve of the horizontal sections (namely TcL), to the equivalent diameter of said float is between 0.6 and 1.4;
- the coefficient of asymmetry of the boat is less than 0.3;
- the aspect ratio of each float is between 5 and 10;
- at least one substantially horizontal fin connects each side float with the central float;
- the two side floats are, on the one hand, identical to, and on the other hand, separate form the central float.
The invention will be more readily understood on reading the following description with reference to the accompanying drawings in which:
- Figure 1 is a view, following arrow F of Figure 2, of a boat according to the invention;
- Figure 2 is a view, following arrow G of Figure 1, of the same boat;
- Figure 3 is a cross-section along line III-III of Figure 1;
- Figures 4, 5, 6, 7 and 8 are area curves of ths boat according to the invention, shown as several separate embodiments.
~ eference is made hereafter to a number of notions, whose unusual nature invites a definition, this being given in the accompanying schedule, presented as forming part of the present patent application.
The boat illustrated by way of example is a surface-type boat with three floats, called "trimaran". It is constituted by:
- an entirely emerged platform 1 comprising a deck 2 and containing the effective volume of the boat (transporting holds, cabins, etc...) - a front cen-tral hull 3, which is oblong and has a vertical longitudinal plane of symmetry S, and which is ~251~i32~
entirely immersed below the water surface ~;
- two side hulls 5, which are disposed symmetrically with respect to the plane of symmetry S, at the back of the central hull 3, are identical and entirely immersed;
- a strut member 6 which extends vertically and substantially parallel to the plane of symmetry S ancl connects -the central hull 3 with the lower face 7 of the platform 1;
- two strut members ~, extending vertically, substantially parallel to the plane of symmetry S, each one connecting a side hull 5 with the lower face 7 of the platform 1;
- two substantially horizontal fins 9, which connect both side hulls 5 to the central hull 3.
The special features have been observed:
- the assembly of a hull and the corresponding strut member (central hull 3 and a strut member 6, each side hull 5 and its strut member 8) constitutes a semi-submersible float;
- each semi-submersible float has a positive buoyancy, the assembly of three semi-submersible floats conferring its buoyancy to the boat;
- the hulls 3,5 and their strut members 6,8 can be constituted of tanks or water-ballasts, but they can also be constituted of compartments containing the installations o~ th~
boat; for example, three "Diesal" type engines, a main one, and two lower-powered ones, may be installed in the central hull 3 and in the side hulls 5, to drive the propellers; likewise, the hollow strut members 6,8 are designed to enable the passage of numerous connections (electric cables, piping, access), between the hulls 3,5 an~ the deck 2;
- the transverse vertical planes passing through the ends of the area curves of the vertical transverse sections of the semi-submersible floats 3-6 and 5-8 are marked:
V 3 AR : plane passing through the aft end of the area curve of the semi-submersible float 3-6;
V 3 AV : plane passing through the forward end of the area curve of the semi-submersible floa-ts 3-6, V 5 AR : plane passing through the aft ends of the area curve of the semi-submersible floats 5-8, V 5 AV : plane passing through the forward ends of the area curve of the semi-submersible floats 5-8, and it is noted that there is an overlapping in the longitudinal direction, parallel to plane S, of the relative posi-tions of the semi-submersible central float 3-6 and of the semi-submersible side floats 5-8, (see figure 2) plane V 5 AV being situated ahead of plane V 3 AR.
Figures 4 to 8 show the curves of the surfaces according to several different embodiments and corresponding, for each one:
- curve A 3 to the semi-submersible float 3, - curve A 5, to the whole assembly of the two semi-submersible floats 5-~, - curve A 1, to tall three semi-submersible floats, namel~ to the boat itself.
Due to the aforesaid overlapping, curves A 3 and A 5 have an intersecting point I contained inside a transverse vertical plane VI, situated between planes V 3 AR and V 5 AV.
Also represented are:
- the value ~I of the surface of the cross-section of the boat (curve A 1) situated inside the plane VI, - the maximum value AM1 of curve A 1.
~2~ i3;~4 In the embodiment which corresponds to - Figure 4, AI is substantially equal to AM3 and AM5.
A*ll is therefore equal, substantially to any one of said three values. Curve Al is flat between planes V3~ and V5~ . This is very helpful to reduce the efEect of wave action for speeds corresponding to a number of Froude of between 0.4 and 0.6 approximately (curve Al "balanced" between the front and the rear of the boat and free of trough or accentuated crest, particularly in thearea of plane VI). Moreover, the volume of the two semi-submersible side floats5-8, on thè one hand, and the volume of the semi-submersible central float
3-6, on the other hand, are substantially equal ~areas of the curves of parts A3 and A5 substantially equal) this permitting, in the adopted design of trimaran, to reduce even further the effect of wave action.
If the solution illustrated in Figure 4 may appear as an ideal solution from the aforesaid points of view, it nevertheless remains obvious that other solutions, although they may not be as good, may still be satisfactory.
For example, in the embodiment illustrated in Figure 5, AMl = AM5; AM3 is slightly less than AM5 and AI/AMl = O.45. The volumes of the semi-submersible side floats 5-8 and central float 3~6 are substantially equal. This is a limit case, adapted for high speeds (Fn 0.6), AI/AMl should in principle be selected to be higher than 0.45 in order -to allow a maximum reduction of -the effect of wave action.
The embodiment illustrated in Figure 5 is characterized by a strong unbalance between the volumes o-E the semi-submersibIe side floats 5-8 on the one hand, and of the semi-submersible central float 3-6 on the other hand : the ratio of these volumes is equal to 0.3. Thereagain, the limit is a minimum limit which should not be exceeded. In addition, AI/AMl is substantially equal -to 1, which is satisfactory.
32~
Figure 7 shows an embodiment in which the volume of the semi-submersible side (and rear) floats 5-8 is equal to 1,7 times that of the semi-submersible central (and front) float 3-6. This embodiment constitutes the upper limit not to be exce0ded.
Moreover, AI is substantially equal to AM1. The curve A1 is relatively flat between the crests of curves A3 and A5, hence the fact that a relatively poor effect of wave action is obtained for speeds corresponding to Fn=0.4 to 0.6.
Figure 8 illustrates an embodiment in which the curves of the surfaces Al of the boat is strongly asymmetrical. The coefficient of asymmetry DIS of the boat is equal to 0.3, this constituting the maximum limit below which it is recommended to stay. Semi-submersible side (and rear) floats 5-8 are bulgy with respect to semi-submersible central (and front) float 3-6.
For the boat illustrated in Figures 1 to 3 (semi-submersible floats 3-6 and 5-8 shown in block lines in Figure 1) the aspect ratio of the floats is about equal to 7. To obtain a compromise between the effect of wave action and the resistance to friction reducing the overall drag, the shapes should be so selected that the aspect ra-tio lies between 5 and 10.
Finally, to derive the maximum advantages from said technique of semi-submersible floats, it is important, first to immerse the floats 3-6;5-8 to depths that are sufficient to reduce the movements of the boa-t and to reduce the effsct of wave ac-tion, and second, to limit the immersion of said floats to depths which will eliminate any great structural problems from the construction of the boat, and which will keep the wet surface to a reasonable value. This is -the reason why the ratio TcL/Deq of the immersion depth of the maximum of the curve of the surfaces of horizontal section to the equivalent diameter, is, ~or every semi-submersible float, between 0.6 and 1.4, this corresponding -to the drawings in broken lines shown in Figure 1 : the drawing of -the floats closest to the water surface corresponds to TcL/Deq = 0.6 and that farthest from the water surface corresponds to Tcl/deq = 1.4.
The boat definition given hereinabove obviously confers on that boat all the ~ualities specific to all semi-submersible bloats, but, in addition, it gives it a new optimization of its drag. For the first time, a semi-submersible boat has a yield substantially equivalent to that of a conventional surface boat of identical capacity, which makes the technique a viable one.
Compared with semi-submersible boats of the catamaran type, the effect of wave action is considerably more advantageous than that between the two semi-submersible floats of the catamaran, because there is a deliberate longitudinal overlapping of the curves of areas A3 and A5 to prevent damaging interferences be-tween the flow along the semi-submersible central float 3-6 and the semi-submersible side floats 5-8, and thereagain, to reduce the effect of wave action. The very choice of the curve of areas A1, preferably the flattest between the two crests of the curves of parts A3 and A5, and close to point I, is, on this point, a sign of an important reduction of the drag.
It should also be noted that the recommended structure is especially strong. It is a known fact that, catamarans for example, have particularly delicate structures, considering the very great strains normally developing thereon. The new "trimaran" type struc-ture which is proposed, has none of the fragility of the prior ~Z~;iE;3~
designs, since, on the one hand, the boat is supported overall on three points instead of 4 for the catamarans, and on the other hand , the ailerons 6 close up the structure constituted by the struts 6 and 8 and by the hulls 3 and 5. Thus, any stresses in the area where the struts 6 join up to the body 1 are less than those existing in the equivalent joining up areas in a semi-submersible catamaran in the central point thereof.
The invention is in no way limited to the description given hereinabove and on the contrary covers any modifications that can be brought thereto without departing from its scope or its spirit.
.
2 ~
SCHEDULE
The object of the present schedule is to facilitata an understanding of some of the terms used herein and the following definitions are not to be taken as limiting the scope of the invention as defined herein.
Area curve of a boat The immersed part of the hull of a boat is usually defined by the values of its successive vertical cross-sections between the verticals passing through the outermost submerged points of the hull, and called forward perpendicular and aft perpendicular in the lengthwise direc-tion of the boat. The plotting in y-axis of the areas of the cross-sections, and in x-axis of the distances between said cross-sections and a reference point of origin, enables to draw -the curve of the areas.
Volume of a semi-submersible float -This volume is equal to the surface defined under the graph of the curve of the areas of vertical cross-sections, by said curve of the areas and the x-axis.
Semi-submersible float An immersed body can be defined, at least partly, by horizontal sections.
By semi-submersible float is meant a float showing a posi-tive buoyancy, of which the curve of the areas of its horizontal sections (or water lines) has a maximum under the water surface at a depth TCL.
In such a float, the value of said maximum is preferably greater than twice the value of the area of the horizontal section of the waterline.
Said maximum may be realized for various depths of waterlines. In this case, TCL designates the arithmetical mean of said depths.
~ 5~;~
In conventional manner, a semi-submersible float is constituted by the assembly of an entirely submerged hull and a strut joining it at least to the water surface, and then to an above surface platform.
Equivalent diameter It is often difficult to distinguish the strut from the totally submerged hull to which it is joined. Then it is advantageous to refer to the diameter De~ of a circle of which the area is equal to that of the maximum cross-sectional area of the semi-submersible float (assembly of strut -~ totally submerged hull).
Aspect ratio of a semi-submersible float The aspect ratio is the ratio of the length of the area curve (ie. length between perpendiculars) of the vertical cross-sections to the equivalent diameter of said semi-submersible float.
Coefficient of asymmetry The curve of the areas of the ver-tical cross-sections of a float extends along the total len~th of said float, namely:
x, the abscissa, marking the position of a vertical cross-section, measured from a point of origin O
situated at the median abscissa of the curve of the areas. The median abscissa of the curve of the areas is the abscissa of the vertical cross-section which separates the boat in two e~ual volumes A(x), the value of the area of the vertical cross-sec-tion corresponding to abscissa x V , the total volume of the submerged part of the float Xav , abscissa of the front end of the curve of the areas Xar , abscissa of the back end of the curve of the areas Xmax , the higher of the two values Xav and Xar.
~L2~
The lon~itudinal asymmetry of the float corresponds to the differences of values of the areas of vertical cross-sections corresponding to abscissae x and t-x), symmetrical with respect to the origin of the abs-cissae~
The quantity ~_ x max IA(X) ~(-X) ¦dx is a representation of said asymmetry. It has the di-mensions of a volume and it is possible, and obviously preferable, to convert it in order to obtain a coefficient without dimension. It suffices, to do so, to divide it by the volume V of the float.
With ~ xav 1 A(x) dx , V J xar the coefficient of asymmetry DIS of a float is defined by : r xmax ~ ~ xav DIS ~ 1 ¦ A(x)-A(-x~ldx J / ~Jxar A(x) dxJ
If the solution illustrated in Figure 4 may appear as an ideal solution from the aforesaid points of view, it nevertheless remains obvious that other solutions, although they may not be as good, may still be satisfactory.
For example, in the embodiment illustrated in Figure 5, AMl = AM5; AM3 is slightly less than AM5 and AI/AMl = O.45. The volumes of the semi-submersible side floats 5-8 and central float 3~6 are substantially equal. This is a limit case, adapted for high speeds (Fn 0.6), AI/AMl should in principle be selected to be higher than 0.45 in order -to allow a maximum reduction of -the effect of wave action.
The embodiment illustrated in Figure 5 is characterized by a strong unbalance between the volumes o-E the semi-submersibIe side floats 5-8 on the one hand, and of the semi-submersible central float 3-6 on the other hand : the ratio of these volumes is equal to 0.3. Thereagain, the limit is a minimum limit which should not be exceeded. In addition, AI/AMl is substantially equal -to 1, which is satisfactory.
32~
Figure 7 shows an embodiment in which the volume of the semi-submersible side (and rear) floats 5-8 is equal to 1,7 times that of the semi-submersible central (and front) float 3-6. This embodiment constitutes the upper limit not to be exce0ded.
Moreover, AI is substantially equal to AM1. The curve A1 is relatively flat between the crests of curves A3 and A5, hence the fact that a relatively poor effect of wave action is obtained for speeds corresponding to Fn=0.4 to 0.6.
Figure 8 illustrates an embodiment in which the curves of the surfaces Al of the boat is strongly asymmetrical. The coefficient of asymmetry DIS of the boat is equal to 0.3, this constituting the maximum limit below which it is recommended to stay. Semi-submersible side (and rear) floats 5-8 are bulgy with respect to semi-submersible central (and front) float 3-6.
For the boat illustrated in Figures 1 to 3 (semi-submersible floats 3-6 and 5-8 shown in block lines in Figure 1) the aspect ratio of the floats is about equal to 7. To obtain a compromise between the effect of wave action and the resistance to friction reducing the overall drag, the shapes should be so selected that the aspect ra-tio lies between 5 and 10.
Finally, to derive the maximum advantages from said technique of semi-submersible floats, it is important, first to immerse the floats 3-6;5-8 to depths that are sufficient to reduce the movements of the boa-t and to reduce the effsct of wave ac-tion, and second, to limit the immersion of said floats to depths which will eliminate any great structural problems from the construction of the boat, and which will keep the wet surface to a reasonable value. This is -the reason why the ratio TcL/Deq of the immersion depth of the maximum of the curve of the surfaces of horizontal section to the equivalent diameter, is, ~or every semi-submersible float, between 0.6 and 1.4, this corresponding -to the drawings in broken lines shown in Figure 1 : the drawing of -the floats closest to the water surface corresponds to TcL/Deq = 0.6 and that farthest from the water surface corresponds to Tcl/deq = 1.4.
The boat definition given hereinabove obviously confers on that boat all the ~ualities specific to all semi-submersible bloats, but, in addition, it gives it a new optimization of its drag. For the first time, a semi-submersible boat has a yield substantially equivalent to that of a conventional surface boat of identical capacity, which makes the technique a viable one.
Compared with semi-submersible boats of the catamaran type, the effect of wave action is considerably more advantageous than that between the two semi-submersible floats of the catamaran, because there is a deliberate longitudinal overlapping of the curves of areas A3 and A5 to prevent damaging interferences be-tween the flow along the semi-submersible central float 3-6 and the semi-submersible side floats 5-8, and thereagain, to reduce the effect of wave action. The very choice of the curve of areas A1, preferably the flattest between the two crests of the curves of parts A3 and A5, and close to point I, is, on this point, a sign of an important reduction of the drag.
It should also be noted that the recommended structure is especially strong. It is a known fact that, catamarans for example, have particularly delicate structures, considering the very great strains normally developing thereon. The new "trimaran" type struc-ture which is proposed, has none of the fragility of the prior ~Z~;iE;3~
designs, since, on the one hand, the boat is supported overall on three points instead of 4 for the catamarans, and on the other hand , the ailerons 6 close up the structure constituted by the struts 6 and 8 and by the hulls 3 and 5. Thus, any stresses in the area where the struts 6 join up to the body 1 are less than those existing in the equivalent joining up areas in a semi-submersible catamaran in the central point thereof.
The invention is in no way limited to the description given hereinabove and on the contrary covers any modifications that can be brought thereto without departing from its scope or its spirit.
.
2 ~
SCHEDULE
The object of the present schedule is to facilitata an understanding of some of the terms used herein and the following definitions are not to be taken as limiting the scope of the invention as defined herein.
Area curve of a boat The immersed part of the hull of a boat is usually defined by the values of its successive vertical cross-sections between the verticals passing through the outermost submerged points of the hull, and called forward perpendicular and aft perpendicular in the lengthwise direc-tion of the boat. The plotting in y-axis of the areas of the cross-sections, and in x-axis of the distances between said cross-sections and a reference point of origin, enables to draw -the curve of the areas.
Volume of a semi-submersible float -This volume is equal to the surface defined under the graph of the curve of the areas of vertical cross-sections, by said curve of the areas and the x-axis.
Semi-submersible float An immersed body can be defined, at least partly, by horizontal sections.
By semi-submersible float is meant a float showing a posi-tive buoyancy, of which the curve of the areas of its horizontal sections (or water lines) has a maximum under the water surface at a depth TCL.
In such a float, the value of said maximum is preferably greater than twice the value of the area of the horizontal section of the waterline.
Said maximum may be realized for various depths of waterlines. In this case, TCL designates the arithmetical mean of said depths.
~ 5~;~
In conventional manner, a semi-submersible float is constituted by the assembly of an entirely submerged hull and a strut joining it at least to the water surface, and then to an above surface platform.
Equivalent diameter It is often difficult to distinguish the strut from the totally submerged hull to which it is joined. Then it is advantageous to refer to the diameter De~ of a circle of which the area is equal to that of the maximum cross-sectional area of the semi-submersible float (assembly of strut -~ totally submerged hull).
Aspect ratio of a semi-submersible float The aspect ratio is the ratio of the length of the area curve (ie. length between perpendiculars) of the vertical cross-sections to the equivalent diameter of said semi-submersible float.
Coefficient of asymmetry The curve of the areas of the ver-tical cross-sections of a float extends along the total len~th of said float, namely:
x, the abscissa, marking the position of a vertical cross-section, measured from a point of origin O
situated at the median abscissa of the curve of the areas. The median abscissa of the curve of the areas is the abscissa of the vertical cross-section which separates the boat in two e~ual volumes A(x), the value of the area of the vertical cross-sec-tion corresponding to abscissa x V , the total volume of the submerged part of the float Xav , abscissa of the front end of the curve of the areas Xar , abscissa of the back end of the curve of the areas Xmax , the higher of the two values Xav and Xar.
~L2~
The lon~itudinal asymmetry of the float corresponds to the differences of values of the areas of vertical cross-sections corresponding to abscissae x and t-x), symmetrical with respect to the origin of the abs-cissae~
The quantity ~_ x max IA(X) ~(-X) ¦dx is a representation of said asymmetry. It has the di-mensions of a volume and it is possible, and obviously preferable, to convert it in order to obtain a coefficient without dimension. It suffices, to do so, to divide it by the volume V of the float.
With ~ xav 1 A(x) dx , V J xar the coefficient of asymmetry DIS of a float is defined by : r xmax ~ ~ xav DIS ~ 1 ¦ A(x)-A(-x~ldx J / ~Jxar A(x) dxJ
Claims (6)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Boat equipped with three semi-submersible floats connected to a deck via strut members, one central float being provided at the fore part of the boat and two side floats being positioned symmetrically with respect to the longitudinal plane of said central float, boat wherein:
a) the ratio of the ordinate of the area curve of the complete boat at the crossing point of the area curves of the side floats, on the one hand, and of the central float, on the other hand, to the maximum ordinate of said area curve of the complete boat is at least equal to 0.45; and, b) the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.
a) the ratio of the ordinate of the area curve of the complete boat at the crossing point of the area curves of the side floats, on the one hand, and of the central float, on the other hand, to the maximum ordinate of said area curve of the complete boat is at least equal to 0.45; and, b) the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.
2. Boat as claimed in claim 1, wherein for each float, the ratio of the depth of immersion of the maximum part of the curve of the areas of the horizontal section (namely TcL), to the equivalent diameter of said float is between 0.6 and 1.4.
3. Boat as claimed in claim 1, wherein its coefficient of asymmetry is less than 0.3.
4. Boat as claimed in claim 1, wherein the aspect ratio of each float is between 5 and 10.
5. Boat as claimed in claim 1, wherein at least one substantially horizontal aileron connects each side float to the central float.
6. Boat as claimed in claim 1, wherein the two side floats are, on the one hand, identical to, and, on the other hand, separate from the central float.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR84.05.161 | 1984-04-02 | ||
| FR8405161A FR2562026A1 (en) | 1984-04-02 | 1984-04-02 | SHIP COMPRISING THREE SEMI-SUBMERSIBLE FLOATS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1256324A true CA1256324A (en) | 1989-06-27 |
Family
ID=9302729
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000478085A Expired CA1256324A (en) | 1984-04-02 | 1985-04-01 | Boat equipped with three semi-submersible floats |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0161953B1 (en) |
| JP (1) | JPS60226385A (en) |
| CA (1) | CA1256324A (en) |
| DE (1) | DE3560211D1 (en) |
| ES (1) | ES8801886A1 (en) |
| FI (1) | FI851295L (en) |
| FR (1) | FR2562026A1 (en) |
| NO (1) | NO851246L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104709435A (en) * | 2015-03-01 | 2015-06-17 | 徐见金 | Triple-hulled manual ventilating supercavitation ship type |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO981678L (en) * | 1997-04-21 | 1998-10-22 | Marcelo Luis Dodero | Boat with hull carried by submerged floats |
| ES2159451B1 (en) * | 1998-04-17 | 2002-04-16 | Antoune Ivan Lahuerta | THE HYDROBUS. |
| FR2960206B1 (en) * | 2010-05-19 | 2013-08-09 | Architecture Et Conception De Sytemes Avances | SHIP COMPRISING A SUPERSTRUCTURE WHOSE LOWER PART IS EQUIPPED WITH A HANDLE |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1815286A (en) * | 1930-05-16 | 1931-07-21 | William R Blair | Seagoing craft |
| GB809736A (en) * | 1957-10-08 | 1959-03-04 | Paul Horsdal | Improvements in or relating to boats |
| FR1414492A (en) * | 1963-11-25 | 1965-10-15 | Improvements to boats | |
| US3623444A (en) * | 1970-03-17 | 1971-11-30 | Thomas G Lang | High-speed ship with submerged hulls |
-
1984
- 1984-04-02 FR FR8405161A patent/FR2562026A1/en not_active Withdrawn
-
1985
- 1985-03-28 DE DE8585400603T patent/DE3560211D1/en not_active Expired
- 1985-03-28 NO NO851246A patent/NO851246L/en unknown
- 1985-03-28 EP EP19850400603 patent/EP0161953B1/en not_active Expired
- 1985-03-29 ES ES541779A patent/ES8801886A1/en not_active Expired
- 1985-04-01 FI FI851295A patent/FI851295L/en not_active Application Discontinuation
- 1985-04-01 CA CA000478085A patent/CA1256324A/en not_active Expired
- 1985-04-02 JP JP6861385A patent/JPS60226385A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104709435A (en) * | 2015-03-01 | 2015-06-17 | 徐见金 | Triple-hulled manual ventilating supercavitation ship type |
Also Published As
| Publication number | Publication date |
|---|---|
| ES8801886A1 (en) | 1988-03-01 |
| EP0161953A1 (en) | 1985-11-21 |
| DE3560211D1 (en) | 1987-07-09 |
| ES541779A0 (en) | 1988-03-01 |
| EP0161953B1 (en) | 1987-06-03 |
| FI851295L (en) | 1985-10-03 |
| NO851246L (en) | 1985-10-03 |
| FI851295A0 (en) | 1985-04-01 |
| FR2562026A1 (en) | 1985-10-04 |
| JPS60226385A (en) | 1985-11-11 |
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| MKEX | Expiry |