CA1092446A - Marine craft - Google Patents
Marine craftInfo
- Publication number
- CA1092446A CA1092446A CA296,355A CA296355A CA1092446A CA 1092446 A CA1092446 A CA 1092446A CA 296355 A CA296355 A CA 296355A CA 1092446 A CA1092446 A CA 1092446A
- Authority
- CA
- Canada
- Prior art keywords
- craft
- frames
- hull
- value
- length
- 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
- B63B1/04—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with single hull
Landscapes
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
- Auxiliary Methods And Devices For Loading And Unloading (AREA)
- Hydraulic Turbines (AREA)
Abstract
Abstract of Disclosure A fast marine craft suitable for operation in the range of Froude numbers between 0.5 and 1.0 has a hull which can be considered as being defined by a series of transverse spaced apart frames, the frames nearest the head of the craft being generally triangular in section and having slightly concave sides, and the frame shape flattening gradually to define a flat planning section aft of the midships frame and the base of the hull subsequently developing into a concave tunnel profile.
Description
The invention concerns a fast marine craft for operation in the range of Froude numbers 0.5 - 1.0 with especially favourable characteristics for operation in calm waters and also especially for sea passages. Such characteristics are particularly required for emergency sea rescue craft, pilot boats, motor yachts and faster auxiliary craft operating from near the coast to open waters.
Such marine craft are customarily built with lengths in the range 5m to 50m. The range of Froude numbers 0.5 to lù. 1 refers to the relative speeds at wnich,depending on the construction of the ship in question,it reaches,partially or completel~,a planing condition.
It i6 known that the seaKeeping qualities of a boat in this plani~g condition are not good ~ecause the necessarily 15. flat bottom of the forward portion of the boat must withstand extremely strong impacts arising from the high sKimming speeds duri~g sea passages. These impacts can not only easily damage the structure but can make a stay on ~oard the ship unbearable.
Apart from this it is unavoida~le, at least in the case of craft 2u. that are fully planing at sea, that the propellors rise.if not completely, at - least partially out o~ the water. For this reason the present invention is concerned with craft which utilise the dynamic lift effect at high speeas to avoid diving of the craft and whose propulsion, even in this condition,is 25. made possible in large part by the displacement of water.
A iurther characteristic o$ Auch maril~e craft is that the part of the ship's hull above water can be considered as a series of divergent frames whicn divergence, for many oraft, continues right to tne stern and which for others reduces 5. in the astern direction. With such craft this arrangement has enabled a simple tunnel li~e co-lstruction of the extreme stern end of the ship so that the suctio~ experienced by the stern of the craft on account of the propellor strongly opposes the movement of the stern oY the craft out of the water which lO. in turrl prevents the propellor risi-lg out of the water and in addition pitching movement durl..g the voyage is especially strongly damped. Such craft, a..d especially those i.- which the construction of the tunnel starts at the midship frames are descriDed in Italian Pate~t Specification No. 65992u of 15. y.l1.19610 - ~he present i~ventioll has as its o~ject to considerably improve the charactèristics o~ such craft, (which are already in themselves good), by novel mealls.
The Italian Patellt Specificatiol- el-tirely disregards 20. a series of characteristics that are of greater importance for optimum sea-keeping properties. In particular the sequential arrangement of the frames or cross-sections of the ship ul-der water ~nd change i~l the local coefficie--ts o~ filleness of the frames alo~lg the length of the snip.
By the expression l'local coefficient of fineness of a frame"
one understands the ratio of the submerged frame area to a rec-tangle whose width corresponds to the width of the individual frame at the water line and whose height is determined by the local depth of the frame. An attached keel is not taken into account in performing this calculation.
Nothing can be deduced either from the drawings or from the description of the Italian patent specification in this respect although it is of significance.
Frame plans and resistance results for fast craft are known from the S.N.A.M.E. Data Sheets Nos. 3, 4 and 7 issued by the Bureau of Ships, U.S. Navy Department, Washington, D.C., which appear from their dimensions to be suitable for the above mentioned purposes. In addition, ship plans of English emergency sea res-cue craft are given in the October 1975 edition of the magazine "The Naval Architect" at page 304 whose principal dimensions and range of Froude numbers lie exactly in the previously described range.
According to the invention, there is provided a marine craft adapted for fast operation in the range of Froude numbers between 0.5 and 1.0, the hull shape being considered as a series of trans-verse frames spaced apart along the hull, the frames above the water line being generally divergent and with the base portions of the frames at the head of the craft being generally triangular and progressively changing from the head of the craft towards the stern to a tunnel shape, the minimum values of the inclinations to the horizontal of the individual frames below the water line and in the forward two-thirds of the craft's length reducing sub-stantially linearly towards the stern, the reduction amounting to a value in the range 8 - 13 per frame on division of the . ~s length of the craft into lQ frames, wherein the minimum value of the inclination to the horizontal of the frames below the water-line passes through a null position in the sternmost third of the craft at which the minimum value is zero and becomes negative further towards the stern.
The characteristics of the hull profile taught by the pre-sent invention will now be explained, by way of example only, with reference to the accompanying drawings which also enable comparisons to be made with prior art hull shapes and which show, for hull profiles divided into ten notional frames along the length of the hull:
Figure 1 plots the variation of minimum frame inclination versus frame position for various hulls;
Figure 2 plots the variation in the coefficient of frame fineness versus frame position for various hulls; and, Figure 3 is a series of frame profiles illustrating the change in shape of a hull in accordance with the present teach-ing from one frame to another along the length of the hull.
The invention starts from the knowledge that the most im-portant point along each frame is that point on the underwaterpart of the frame at which the inclination of the frame to the horizontal has a minimum value. This minimum value is positive if the frame, along its entire length, has tangents which are directed outwardly and upwardly. The minimum inclination is O
(null) if a horizontally directed tangent to the frame exists (small external radii which customarily occur at the feet of the frames of the head of the ship are not taken into consideration.) ~, -3a-.._ . , .
lO9Z~46 The minimum value is negative if, i..side a particvlar range, the frame is direoted sideways and downwardly. This definition of the minimum i..cli..ation of t~e frames call also be seen illustrated in Fig 3 in which the mi~imu~ values of various 5~ frames of a craft are give-l. It should be emphaRised here that for the shape of the oot~om of the whole craft only those taken into flat parts are/consideration that have a large expansion and thus form the principal surfaoe~ol tne shape of the craft.
Local cut outs out of an otherwise Rmoothly faired surface 1~. which are occasionally arranged for the artful ducting of particular propellors should not De taken into co~sideration.
Plots of the sequential minimum il-cli-~atio-ls to the underwater frames of the tnree cra~t pu~lished i.. the aforementioned S.N.A.M.E. data sheets are shown i~ dotted lines in Fig 3.
15. The abscissa of this graph represents the dimensionless ships length divided into 10 frames, whilst the ordillate reproduces the minimum i~clillatio~s of the frames. The plots for the three cra~t from tAe data sheets are designated ~y the Roman numerals 1, 11, 111. It is to be noted that at frame 20. 9 thc three curves have mi~imum incli~lation values of ~etween and 4u . ~rom there towards the stern the minimum values decrease but remain however positivc even at the sternmast point, frame ~. ~or the craft designated 111 the i~clination at frame 9 is only approximately 20 and falls gradually by 25. trivial amounts and at frame O still has a value considerably in excess of 10 . That is to say that for all three craft the minimum inclination at frame 9 is less than 50 and remains ~092446 po6itive along the entire length ot the ship.
lihe minimum inclinatio~ curve of tne emergency sea rescue craft disclosed in the .~aval Architect is given in Fig. 1 in this but full lines a..d is designated lV. At frame 5. 9 this curve shows a value of approximately 6~, i.e. the extreme forward frames are co-lsiderably steeper tha~l i5 the case for the previously mentioned America~l craft. The plot however quickly reduces towards the stern and over the entire stern end of the ship remains very flat u~ltil it finishes 1~. at a value of approximately 15 positive at tne stern most position.
All these craft show minimum frame i~lcli~lations along their respective lengths that either over- their entire lengths or at least over a large part oY tne ship run very flat and 15- end at the extreme stern with positive values. Moreover they mainly begin with a relatively low value, with the exception that is of the Englisn craft for which tne relatively high value rapidly decreases a..d collti~lues irl relatively flat fashion.
`~ The invention 6eeks to provide mari~e craft a~ld hulls therefore which not only in smooth ~aters but also ~uring sea passages will give extremely good results. In order to fully satisfy such requirements the frames ;~ the extreme head of the ship must be arranged to ~e very-steep in order 25. to provide a steeply sided keel snaped form, by meas of .
lO9Z~46 which impaots from the sea from i-l fro~t and bolow are oonsiderably alleviated and which both in oalm waters and begi-.s heavier seas/to turn the water at tne head of the ship outwardly towards the sides. It is advantageous if further 5- downstream the frames slowly change illtO the flat pl~nln~
shape from which the tunnel snape is then developed at the extreme stern end of the ship. In tnis ma..ner the water diverted by the sharp head of the snip is progressively changed into a flow alo-lg the uase of tne snip alld still further towards the stern is guided over t~e base of the hull i~to the tunnel. This process is optimally ensured when the transitioll from the steep frames of the head of the ship to the flat position at the extreme rear quarter avoids abrupt transition~.
15. In this connection the il-ventio-l suggests a co.. tour in which the minimum illclillation over the ship's length decreases linearly, or approximately li~learly f~om a relatively high value in the forequarter o~ the ship t~wards the rear and indeed at least over two thirds of the length of the 20. ~hip. In the sternmost third the 0 (null) poi... t, i.e. the lowest horizolltal tangcnt value is acllieved and subsequently the tunnel begills in the negative range of mi.limu~ tangent values.
The negative tangents are then allowed either to have 25. a constant value or after reachi..g an aDsolute millimum value in the negative range can be allowed to turn DaC~ towards lO9Z~46 the 0 (nùll~ value. The most advantageous gradient of this minimu..l inclination plot alo..g tne ship amou"ts to approximately 9 to 10 per ~rame whell the ships le-lgth is divided into 10 frames. Exceptionally pleasi--g results are 5. however obtained whe~l the gradiel,t o~ tne curve is between 8 and 13 per frame.
Particular details of the shapes desired for hulls of fast marille craft will now ~e descrioed i,- compariso~l with the ~IOW~l hull shapes with reference to tne accompanyi..g 10. drawings,figures 1 to 3.
Referring first to Fig 1 plots for values of the minimum frame inclinatio~ ~or craft in accorda~lce with the in~ention are shown in full lines ~y the curves A, B, C.
'rhese curves refer to ships of various le~lgths which are 15. -given in the respective brackets. From tnis figure it can be seen that the plots for relatively lo..ger craft are somewhat higher than, and that the 0 (nUll) transition is somewhat further towards the stern tha~ for s~aller craft.
The position of this 0 (NUll) point wnich lies generally
Such marine craft are customarily built with lengths in the range 5m to 50m. The range of Froude numbers 0.5 to lù. 1 refers to the relative speeds at wnich,depending on the construction of the ship in question,it reaches,partially or completel~,a planing condition.
It i6 known that the seaKeeping qualities of a boat in this plani~g condition are not good ~ecause the necessarily 15. flat bottom of the forward portion of the boat must withstand extremely strong impacts arising from the high sKimming speeds duri~g sea passages. These impacts can not only easily damage the structure but can make a stay on ~oard the ship unbearable.
Apart from this it is unavoida~le, at least in the case of craft 2u. that are fully planing at sea, that the propellors rise.if not completely, at - least partially out o~ the water. For this reason the present invention is concerned with craft which utilise the dynamic lift effect at high speeas to avoid diving of the craft and whose propulsion, even in this condition,is 25. made possible in large part by the displacement of water.
A iurther characteristic o$ Auch maril~e craft is that the part of the ship's hull above water can be considered as a series of divergent frames whicn divergence, for many oraft, continues right to tne stern and which for others reduces 5. in the astern direction. With such craft this arrangement has enabled a simple tunnel li~e co-lstruction of the extreme stern end of the ship so that the suctio~ experienced by the stern of the craft on account of the propellor strongly opposes the movement of the stern oY the craft out of the water which lO. in turrl prevents the propellor risi-lg out of the water and in addition pitching movement durl..g the voyage is especially strongly damped. Such craft, a..d especially those i.- which the construction of the tunnel starts at the midship frames are descriDed in Italian Pate~t Specification No. 65992u of 15. y.l1.19610 - ~he present i~ventioll has as its o~ject to considerably improve the charactèristics o~ such craft, (which are already in themselves good), by novel mealls.
The Italian Patellt Specificatiol- el-tirely disregards 20. a series of characteristics that are of greater importance for optimum sea-keeping properties. In particular the sequential arrangement of the frames or cross-sections of the ship ul-der water ~nd change i~l the local coefficie--ts o~ filleness of the frames alo~lg the length of the snip.
By the expression l'local coefficient of fineness of a frame"
one understands the ratio of the submerged frame area to a rec-tangle whose width corresponds to the width of the individual frame at the water line and whose height is determined by the local depth of the frame. An attached keel is not taken into account in performing this calculation.
Nothing can be deduced either from the drawings or from the description of the Italian patent specification in this respect although it is of significance.
Frame plans and resistance results for fast craft are known from the S.N.A.M.E. Data Sheets Nos. 3, 4 and 7 issued by the Bureau of Ships, U.S. Navy Department, Washington, D.C., which appear from their dimensions to be suitable for the above mentioned purposes. In addition, ship plans of English emergency sea res-cue craft are given in the October 1975 edition of the magazine "The Naval Architect" at page 304 whose principal dimensions and range of Froude numbers lie exactly in the previously described range.
According to the invention, there is provided a marine craft adapted for fast operation in the range of Froude numbers between 0.5 and 1.0, the hull shape being considered as a series of trans-verse frames spaced apart along the hull, the frames above the water line being generally divergent and with the base portions of the frames at the head of the craft being generally triangular and progressively changing from the head of the craft towards the stern to a tunnel shape, the minimum values of the inclinations to the horizontal of the individual frames below the water line and in the forward two-thirds of the craft's length reducing sub-stantially linearly towards the stern, the reduction amounting to a value in the range 8 - 13 per frame on division of the . ~s length of the craft into lQ frames, wherein the minimum value of the inclination to the horizontal of the frames below the water-line passes through a null position in the sternmost third of the craft at which the minimum value is zero and becomes negative further towards the stern.
The characteristics of the hull profile taught by the pre-sent invention will now be explained, by way of example only, with reference to the accompanying drawings which also enable comparisons to be made with prior art hull shapes and which show, for hull profiles divided into ten notional frames along the length of the hull:
Figure 1 plots the variation of minimum frame inclination versus frame position for various hulls;
Figure 2 plots the variation in the coefficient of frame fineness versus frame position for various hulls; and, Figure 3 is a series of frame profiles illustrating the change in shape of a hull in accordance with the present teach-ing from one frame to another along the length of the hull.
The invention starts from the knowledge that the most im-portant point along each frame is that point on the underwaterpart of the frame at which the inclination of the frame to the horizontal has a minimum value. This minimum value is positive if the frame, along its entire length, has tangents which are directed outwardly and upwardly. The minimum inclination is O
(null) if a horizontally directed tangent to the frame exists (small external radii which customarily occur at the feet of the frames of the head of the ship are not taken into consideration.) ~, -3a-.._ . , .
lO9Z~46 The minimum value is negative if, i..side a particvlar range, the frame is direoted sideways and downwardly. This definition of the minimum i..cli..ation of t~e frames call also be seen illustrated in Fig 3 in which the mi~imu~ values of various 5~ frames of a craft are give-l. It should be emphaRised here that for the shape of the oot~om of the whole craft only those taken into flat parts are/consideration that have a large expansion and thus form the principal surfaoe~ol tne shape of the craft.
Local cut outs out of an otherwise Rmoothly faired surface 1~. which are occasionally arranged for the artful ducting of particular propellors should not De taken into co~sideration.
Plots of the sequential minimum il-cli-~atio-ls to the underwater frames of the tnree cra~t pu~lished i.. the aforementioned S.N.A.M.E. data sheets are shown i~ dotted lines in Fig 3.
15. The abscissa of this graph represents the dimensionless ships length divided into 10 frames, whilst the ordillate reproduces the minimum i~clillatio~s of the frames. The plots for the three cra~t from tAe data sheets are designated ~y the Roman numerals 1, 11, 111. It is to be noted that at frame 20. 9 thc three curves have mi~imum incli~lation values of ~etween and 4u . ~rom there towards the stern the minimum values decrease but remain however positivc even at the sternmast point, frame ~. ~or the craft designated 111 the i~clination at frame 9 is only approximately 20 and falls gradually by 25. trivial amounts and at frame O still has a value considerably in excess of 10 . That is to say that for all three craft the minimum inclination at frame 9 is less than 50 and remains ~092446 po6itive along the entire length ot the ship.
lihe minimum inclinatio~ curve of tne emergency sea rescue craft disclosed in the .~aval Architect is given in Fig. 1 in this but full lines a..d is designated lV. At frame 5. 9 this curve shows a value of approximately 6~, i.e. the extreme forward frames are co-lsiderably steeper tha~l i5 the case for the previously mentioned America~l craft. The plot however quickly reduces towards the stern and over the entire stern end of the ship remains very flat u~ltil it finishes 1~. at a value of approximately 15 positive at tne stern most position.
All these craft show minimum frame i~lcli~lations along their respective lengths that either over- their entire lengths or at least over a large part oY tne ship run very flat and 15- end at the extreme stern with positive values. Moreover they mainly begin with a relatively low value, with the exception that is of the Englisn craft for which tne relatively high value rapidly decreases a..d collti~lues irl relatively flat fashion.
`~ The invention 6eeks to provide mari~e craft a~ld hulls therefore which not only in smooth ~aters but also ~uring sea passages will give extremely good results. In order to fully satisfy such requirements the frames ;~ the extreme head of the ship must be arranged to ~e very-steep in order 25. to provide a steeply sided keel snaped form, by meas of .
lO9Z~46 which impaots from the sea from i-l fro~t and bolow are oonsiderably alleviated and which both in oalm waters and begi-.s heavier seas/to turn the water at tne head of the ship outwardly towards the sides. It is advantageous if further 5- downstream the frames slowly change illtO the flat pl~nln~
shape from which the tunnel snape is then developed at the extreme stern end of the ship. In tnis ma..ner the water diverted by the sharp head of the snip is progressively changed into a flow alo-lg the uase of tne snip alld still further towards the stern is guided over t~e base of the hull i~to the tunnel. This process is optimally ensured when the transitioll from the steep frames of the head of the ship to the flat position at the extreme rear quarter avoids abrupt transition~.
15. In this connection the il-ventio-l suggests a co.. tour in which the minimum illclillation over the ship's length decreases linearly, or approximately li~learly f~om a relatively high value in the forequarter o~ the ship t~wards the rear and indeed at least over two thirds of the length of the 20. ~hip. In the sternmost third the 0 (null) poi... t, i.e. the lowest horizolltal tangcnt value is acllieved and subsequently the tunnel begills in the negative range of mi.limu~ tangent values.
The negative tangents are then allowed either to have 25. a constant value or after reachi..g an aDsolute millimum value in the negative range can be allowed to turn DaC~ towards lO9Z~46 the 0 (nùll~ value. The most advantageous gradient of this minimu..l inclination plot alo..g tne ship amou"ts to approximately 9 to 10 per ~rame whell the ships le-lgth is divided into 10 frames. Exceptionally pleasi--g results are 5. however obtained whe~l the gradiel,t o~ tne curve is between 8 and 13 per frame.
Particular details of the shapes desired for hulls of fast marille craft will now ~e descrioed i,- compariso~l with the ~IOW~l hull shapes with reference to tne accompanyi..g 10. drawings,figures 1 to 3.
Referring first to Fig 1 plots for values of the minimum frame inclinatio~ ~or craft in accorda~lce with the in~ention are shown in full lines ~y the curves A, B, C.
'rhese curves refer to ships of various le~lgths which are 15. -given in the respective brackets. From tnis figure it can be seen that the plots for relatively lo..ger craft are somewhat higher than, and that the 0 (nUll) transition is somewhat further towards the stern tha~ for s~aller craft.
The position of this 0 (NUll) point wnich lies generally
2~. in the sternmOst third o~ the cra~t is calculated as a percentage of the ships lengtn from the sternmost point~ the fou..~
most advantageous position is/from tne relatiollship K/ (1 + L/20) and the optimum value of tne constant ~ is ta~en as 40. The 25. results remain however very close to tne optimum when ~ is chosen to lie between 35 and 45. The length L used in this relationship is measured at the waterlille and is given in metres~
~ ig 1 further shows tnat the mean inclination, at least in the forward two thirds of tlle ships length is practically 5, identical for all craft and is there~ore i-.depe~ldent of the ship's length.
Undesired hydrodynamic shocks are avoided if the frame inclination changes linearly from the steep frame inclination at the head of the ship to the ~legative inclination 10. in the stern part of the ship, i.e. in tne smoothest possible manner. A ft of this null position the frame incli~lations curve gently towards either a constant negative value or curve upwardly again to a new null pOSitiO~l at the stern end of the craft.
15. ` For craft which are shaped in accordance with this principle the centre of gravity can lie further forward without disadvantage than is the case with customary craft. This becomes clear if one reca]ls that the head of the ship is constructed as a steep displaceme..t hull and that the transition 2u. to the planing or tu~lnel shape only takes place further towards the stern.
it is however al80 possible to simultaneously arrange that the broadest position of tne craft at the waterli~e is displaced some lû - 20 % behi~d the middle of the ship whereby _~_ the water line profile in the ~`orward part of the ship can be of sharper corlstructiol~ usi--g smoother curves.
Whilst for similar craft the literature recomme-lds that the centre of gravity snould lie from 3.5~ to 6% of the ships 5. length behind the centre of tne ship, for smaller ships in accordance with the inventioll, up to approximately 20 m length, the most advantageous position for tne centre of gravity is at,or in the direct vicinity of,the middle of the ship and only for larger craft in accordance witrl the i..vention i~l the 1~. range 30m to 50m length is tne centre of gravity displaced rearwardly.
Apart from the previously ~entio.~ed characteristics the change of the local coefficient o~ fineness ol tne frames along the ship plays an important role especially in the case 15. of craft under 20m long.
In Fig 2 are illustrated in thin li,.es plots for the variations i~l the coefficients of fi-leness of the frames for -the three known American craft,and for the ~IOWn English craft, along the lengths of those craft. The plots are designated 20. by the Roman numerals 1 to lV as in Fig 1.
In the forward part of tne ship aroul-d frame 9 all these craft have approximately tne same value of 0.5 for the coeffic~snt of fineness of t"e ~rames whicn correspollds to triangular shaped frames. Craft 111 mai~ltai~s this value 25. along its entire length, in co.ltrast the value for craft 1 climbs slowly in the rearward direction whilst for craft 11 and lV the coefficient of fineness of tne frames is constant 1092~46 for the whole of the forward part ol the ship and aft of this ourve upwards and indeed craft lV il. smaller measure than craft 11. Even at the sternmost pOlllt ol tlle ships the highest values remain clearly u,lder tne value 1.
5. In contrast for tne craft i-- accordance with the invention the coefficient of fineness of tne frames at frame 9 begins with a value a little u.lder 0.5 which correspo~lds to a lightly concave frame shape. This value could be 0.4 without significant disadvantage. Between frames 7 and o the frame 10. shape becomes triangular in order to co,-tinue the tendency to slowly become convex towards the stern. The increase of the coefficient of fineness of the frames is smooth over the forward part of the ship but is however very pronou~ced behi-ld the midship frame. At between 15 a~ld 30% of the lel-gth of the 15. ship as measured from the stern the coef~icient of fineness of the frames reaches the value 1 i.e. a box like cross-section prior to climbing further above the value 1 which is only possible through the hull developillg a correspollding tullnel shape.
2 `~ A change in the coefficient of fi--eness o~ the frames as outlined a~ove ensures an especially distinctive hydrodynamic harmony between frame incli~lation and frame shape whlch is of importance,especially for smaller craft.
Fig 3 shows a body plan of the marille craft defined by 25. plot C in ~igs 1 and 2 in which oll the left halld side of the central longitudinal axis M are showll half of each of frames Nos O, 1 and 4 and on the right hand side hal~ of each of the frames Nos 5 and o. Reference K i..dicates the keel beam, the angles ~ are the previously mentiol-ed minimum inclinations and reference L.W.L. is the water lille.
The term marine craft as used throughout this specification is to De considered as emDracillg all ki~lds of boat, ship or ~essel irrespective as to whether it is intended 5- for use in the sea or on inland waterways such as lakes, rivers or canals.
most advantageous position is/from tne relatiollship K/ (1 + L/20) and the optimum value of tne constant ~ is ta~en as 40. The 25. results remain however very close to tne optimum when ~ is chosen to lie between 35 and 45. The length L used in this relationship is measured at the waterlille and is given in metres~
~ ig 1 further shows tnat the mean inclination, at least in the forward two thirds of tlle ships length is practically 5, identical for all craft and is there~ore i-.depe~ldent of the ship's length.
Undesired hydrodynamic shocks are avoided if the frame inclination changes linearly from the steep frame inclination at the head of the ship to the ~legative inclination 10. in the stern part of the ship, i.e. in tne smoothest possible manner. A ft of this null position the frame incli~lations curve gently towards either a constant negative value or curve upwardly again to a new null pOSitiO~l at the stern end of the craft.
15. ` For craft which are shaped in accordance with this principle the centre of gravity can lie further forward without disadvantage than is the case with customary craft. This becomes clear if one reca]ls that the head of the ship is constructed as a steep displaceme..t hull and that the transition 2u. to the planing or tu~lnel shape only takes place further towards the stern.
it is however al80 possible to simultaneously arrange that the broadest position of tne craft at the waterli~e is displaced some lû - 20 % behi~d the middle of the ship whereby _~_ the water line profile in the ~`orward part of the ship can be of sharper corlstructiol~ usi--g smoother curves.
Whilst for similar craft the literature recomme-lds that the centre of gravity snould lie from 3.5~ to 6% of the ships 5. length behind the centre of tne ship, for smaller ships in accordance with the inventioll, up to approximately 20 m length, the most advantageous position for tne centre of gravity is at,or in the direct vicinity of,the middle of the ship and only for larger craft in accordance witrl the i..vention i~l the 1~. range 30m to 50m length is tne centre of gravity displaced rearwardly.
Apart from the previously ~entio.~ed characteristics the change of the local coefficient o~ fineness ol tne frames along the ship plays an important role especially in the case 15. of craft under 20m long.
In Fig 2 are illustrated in thin li,.es plots for the variations i~l the coefficients of fi-leness of the frames for -the three known American craft,and for the ~IOWn English craft, along the lengths of those craft. The plots are designated 20. by the Roman numerals 1 to lV as in Fig 1.
In the forward part of tne ship aroul-d frame 9 all these craft have approximately tne same value of 0.5 for the coeffic~snt of fineness of t"e ~rames whicn correspollds to triangular shaped frames. Craft 111 mai~ltai~s this value 25. along its entire length, in co.ltrast the value for craft 1 climbs slowly in the rearward direction whilst for craft 11 and lV the coefficient of fineness of tne frames is constant 1092~46 for the whole of the forward part ol the ship and aft of this ourve upwards and indeed craft lV il. smaller measure than craft 11. Even at the sternmost pOlllt ol tlle ships the highest values remain clearly u,lder tne value 1.
5. In contrast for tne craft i-- accordance with the invention the coefficient of fineness of tne frames at frame 9 begins with a value a little u.lder 0.5 which correspo~lds to a lightly concave frame shape. This value could be 0.4 without significant disadvantage. Between frames 7 and o the frame 10. shape becomes triangular in order to co,-tinue the tendency to slowly become convex towards the stern. The increase of the coefficient of fineness of the frames is smooth over the forward part of the ship but is however very pronou~ced behi-ld the midship frame. At between 15 a~ld 30% of the lel-gth of the 15. ship as measured from the stern the coef~icient of fineness of the frames reaches the value 1 i.e. a box like cross-section prior to climbing further above the value 1 which is only possible through the hull developillg a correspollding tullnel shape.
2 `~ A change in the coefficient of fi--eness o~ the frames as outlined a~ove ensures an especially distinctive hydrodynamic harmony between frame incli~lation and frame shape whlch is of importance,especially for smaller craft.
Fig 3 shows a body plan of the marille craft defined by 25. plot C in ~igs 1 and 2 in which oll the left halld side of the central longitudinal axis M are showll half of each of frames Nos O, 1 and 4 and on the right hand side hal~ of each of the frames Nos 5 and o. Reference K i..dicates the keel beam, the angles ~ are the previously mentiol-ed minimum inclinations and reference L.W.L. is the water lille.
The term marine craft as used throughout this specification is to De considered as emDracillg all ki~lds of boat, ship or ~essel irrespective as to whether it is intended 5- for use in the sea or on inland waterways such as lakes, rivers or canals.
Claims (7)
1. A marine craft adapted for fast operation in the range of Froude numbers between 0.5 and 1.0, the hull shape being considered as a series of transverse frames spaced apart along the hull, the frames above the water line being generally di-vergent and with the base portions of the frames at the head of the craft being generally triangular and progressively changing from the head of the craft towards the stern to a tunnel shape, the minimum values of the inclinations to the horizontal of the individual frames below the water line and in the forward two-thirds of the craft's length reducing substantially linearly towards the stern, the reduction amounting to a value in the range 8° - 13° per frame on division of the length of the craft into 10 frames, wherein the minimum value of the inclination to the horizontal of the frames below the water line passes through a null position in the sternmost third of the craft at which said minimum value is zero and becomes negative further towards the stern.
2. A marine craft according to claim 1 wherein aft of said null position a plot of the minimum value of the frame inclination against position along the hull curves gently towards a constant negative value from said generally linear reduction upstream of the null position.
3. A marine craft according to claim 2 wherein after reaching said constant negative value the plot curves upwardly to a new null position at the stern end of the craft.
4. A marine craft according to claim 1 wherein the null point is located at a position forward of the stern end of the craft and corresponds with a point in the range determined by the expression K / (1 + L / 20) and expressed as a percentage of the craft's length in which K has a value between 35 and 45 and L
corresponds to the length in meters of the craft measured at the water line.
corresponds to the length in meters of the craft measured at the water line.
5. Marine craft according to any one of claims 1 to 3 wherein the broadest part of the hull measured at the water line lies at a position aft of the centre of the craft within a range equivalent to 10 to 20 per cent of the length of the craft and the centre of buoyancy lies in the immediate vicinity of the centre of the craft for craft up to 20 meters length and for longer craft lies between the centre of the craft and the broadest point of the hull measured at the water line.
6. A marine craft according to any one of claims 1 to 3 wherein the coefficient of fineness of the frames at the head of the craft has a value in the range 0.4 to 0.5, constantly and smoothly increases towards the centre of the craft, sharply increases in the after portion of the craft and exceeds the value 1 at some point within the range of 15 to 30 per cent of the craft's length measured from the stern end of the craft.
7. A hull for any marine craft in accordance with any one of the preceding claims 1 to 3.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT21251A/77 | 1977-03-15 | ||
| IT2125177A IT1113512B (en) | 1977-03-15 | 1977-03-15 | FAST VESSEL FOR OPEN SEA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1092446A true CA1092446A (en) | 1980-12-30 |
Family
ID=11179049
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA296,355A Expired CA1092446A (en) | 1977-03-15 | 1978-02-06 | Marine craft |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1092446A (en) |
| DE (1) | DE2804123A1 (en) |
| ES (1) | ES466890A1 (en) |
| FR (1) | FR2383824A1 (en) |
| IT (1) | IT1113512B (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB191113506A (en) * | 1911-06-06 | 1911-09-07 | Lothar Von Koeppen | Improvements in or relating to Ships' Hulls. |
-
1977
- 1977-03-15 IT IT2125177A patent/IT1113512B/en active
-
1978
- 1978-01-31 DE DE19782804123 patent/DE2804123A1/en not_active Withdrawn
- 1978-02-06 CA CA296,355A patent/CA1092446A/en not_active Expired
- 1978-02-10 ES ES466890A patent/ES466890A1/en not_active Expired
- 1978-02-16 FR FR7804344A patent/FR2383824A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| IT1113512B (en) | 1986-01-20 |
| FR2383824B1 (en) | 1984-11-30 |
| DE2804123A1 (en) | 1978-09-28 |
| FR2383824A1 (en) | 1978-10-13 |
| ES466890A1 (en) | 1978-10-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR100540335B1 (en) | Sleep Float Ship | |
| JP2793364B2 (en) | Ship and ship operation method | |
| US5191848A (en) | Multihull vessels, including catamarans, with wave piercing hull configuration | |
| CN101484351A (en) | Ship | |
| NZ502407A (en) | Hull for high-speed ship with main float and two side floats, with predetermined fineness and length to beam ratios, with all floats remaining under water | |
| PL185609B1 (en) | Skimming boat | |
| US5231946A (en) | Monohull fast sealift or semi-planing monohull ship | |
| KR970010819B1 (en) | Speed-increased small boat | |
| US4224889A (en) | Multihull sailing craft and hull structure therefor | |
| KR100879555B1 (en) | Vessel provided with a foil situated below the waterline | |
| US20080216729A1 (en) | Hull For Sailing Craft Whereof The Bottom Enables Water Gliding Performances To Be Enhanced | |
| EP0719225B1 (en) | A ship's hull | |
| CA1092446A (en) | Marine craft | |
| KR970006351B1 (en) | Mono hull fast ship | |
| AU2002325480B2 (en) | Seagoing Vessels | |
| Hoppe | Recent applications of hydrofoil-supported-catamarans | |
| RU2165865C1 (en) | Planing vessel | |
| RU2502627C1 (en) | Hull of semi-catamaran | |
| US20220250717A1 (en) | Pontoon boat with hull extension | |
| RU208484U1 (en) | Planing vessel | |
| WO2023022624A1 (en) | Planing boat | |
| RU165727U1 (en) | SMALL BOAT HOUSING | |
| WO2000075007A2 (en) | Stable tunnel hull | |
| RU2566804C2 (en) | Hull of displacement ship-half-trimaran | |
| RU107760U1 (en) | FAST BOAT BOAT "STORM 4" |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |