US20100000461A1 - Foil shapes for use in barge skegs and marine propeller shrouds - Google Patents
Foil shapes for use in barge skegs and marine propeller shrouds Download PDFInfo
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- US20100000461A1 US20100000461A1 US12/459,693 US45969309A US2010000461A1 US 20100000461 A1 US20100000461 A1 US 20100000461A1 US 45969309 A US45969309 A US 45969309A US 2010000461 A1 US2010000461 A1 US 2010000461A1
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- 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
- B63B1/16—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces
- B63B1/24—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving additional lift from hydrodynamic forces of hydrofoil type
- B63B1/248—Shape, hydrodynamic features, construction of the foil
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- 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
- B63B1/08—Shape of aft part
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- 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
- B63B1/32—Other means for varying the inherent hydrodynamic characteristics of hulls
- B63B1/40—Other means for varying the inherent hydrodynamic characteristics of hulls by diminishing wave resistance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/28—Barges or lighters
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
- B63B39/06—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by using foils acting on ambient water
- B63B39/062—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by using foils acting on ambient water the foils being mounted on outriggers or the like, e.g. antidrift hydrofoils for sail boats
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T70/00—Maritime or waterways transport
- Y02T70/10—Measures concerning design or construction of watercraft hulls
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- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Transportation (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
An airfoil shape exhibiting low drag and a high lift/drag ratio has a low thickness/chord ratio and a low camber/chord ratio. The airfoil shape provides desirable results when used in barge skeg assemblies and in propeller shrouds for tugs used to tow ocean going barges.
Description
- This application claims the benefit of the filing date of co-pending U.S. Patent Application Ser. No. 61/134,220, filed Jul. 7, 2008.
- The present disclosure relates to airfoil shapes and their utilization in propeller shroud or nozzle structures and in skeg arrangements for barges and other towed vessels having displacement hulls.
- Gruzling U.S. Pat. No. 4,789,302 discloses the use of an airfoil shape in propeller shrouds to improve the efficiency of propeller performance by utilizing a nozzle section design providing for turbulent flow with a higher lift coefficient and lower drag coefficient than nozzles in use previously. Gruzling U.S. Pat. Nos. 4,217,844 and 4,569,302, and Heyrman et al. U.S. Pat. No. 4,782,779, disclose skeg arrangements for barges, in which airfoil shapes are utilized to improve water flow characteristics at the stem of a barge, in order to reduce yawing of a towed barge, thereby reducing the power required to tow the barge. When the barge tracks in line with the towing vessel less energy has to be utilized to turn the barge back into line and to tow the barge at an angle to the desired direction of advance.
- Disclosed herein and defined by the claims appended hereto are airfoil shapes for a skeg system and a propeller nozzle having improved performance characteristics and providing improved economy in use, by virtue of utilizing foil shapes and sizes resulting in less drag, together with greater lift.
- In one embodiment a skeg system for a displacement hull of an ocean-going barge includes novel airfoil shapes with an improved lift/drag ratio in a skeg arrangement including horizontally-aligned and vertically-aligned foils.
- In one embodiment of a skeg system for a barge, vertically-oriented skeg elements each lying in a vertical plane have a chord length that is smaller than the chord length of associated horizontally-oriented skeg elements. The vertically-oriented elements thus have less surface area and less surface drag while still producing sufficient laterally-directed lift forces to effectively reduce yawing of the barge during tow.
- An airfoil shape for use in an embodiment of either the vertically-aligned or the horizontally-aligned elements of a skeg system may have a thickness-to-chord length ratio in the range of 13% to 20%.
- In one embodiment an airfoil shape for use in either a vertically-aligned or a horizontally-aligned element of a skeg system may have a maximum ratio of camber to chord length in the range of 6.5% to 8%.
- In one embodiment of a skeg system each vertically-aligned or horizontally-aligned skeg element may have a size providing a Reynolds number in the range of 1×106 to 18×106 for speeds in salt water in the range of 2-25 knots.
- In one embodiment of a skeg arrangement for a barge, horizontally-aligned skeg foil elements having an airfoil shape of the type disclosed herein may be oriented at angles of attack in the range of −5 degrees to +5 degrees with respect to the slope of the surface of the underwater counter portion of the barge hull in order to provide a forwardly directed component of lift force generated by movement through water.
- The foregoing and other features will be more readily understood upon consideration of the following detailed description of embodiments taken in conjunction with the accompanying drawings.
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FIG. 1 is an isometric view of a barge under tow equipped with a skeg arrangement, taken from abaft the starboard quarter thereof. -
FIG. 2 is a isometric view of a portion of the barge shown inFIG. 1 taken from a point below and off the starboard quarter of the barge shown inFIG. 1 . -
FIG. 3 is a side elevational view of the stem portion of a barge such as the one shown inFIG. 1 , equipped with a skeg system incorporating the airfoil shapes disclosed herein. -
FIG. 4 is a sectional view through the skeg system shown inFIGS. 1-3 taken along the line 4-4 ofFIG. 3 . -
FIG. 5 is a detail view at an enlarged scale of the lower portion of the skeg arrangement shown inFIG. 3 , taken along line 5-5 ofFIG. 4 , showing the shape and orientation of the horizontally-oriented foil. -
FIG. 6 is a sectional view through a propeller shroud, showing an associated propeller and illustrating the foil shape utilized in the shroud. -
FIG. 7 is a sectional view of a foil shape useful in connection with the skeg systems and propeller shroud disclosed herein. - Referring now to the drawings which form a part of the disclosure herein, in
FIG. 1 abarge 10 is shown at sea under tow. Thebarge 10 is being pulled by a tug (not shown) by means of a tow line attached to thebow 12 of the barge by abridle 14. - At the
stern 16 of the barge 10 a pair ofskeg assemblies 18 are mounted beneath thewater line 20 and extend downwardly away from araked counter portion 22 of the hull of thebarge 10, as may also be seen inFIGS. 2 and 3 . There may be aseparate skeg assembly 18 near each side of thestern 16 of thebarge 10, as shown herein, or a unitary skeg assembly (not shown) may extend across the entire breadth of thestern 16. - As shown in
FIGS. 2 and 3 , the rakedcounter portion 22 of anoceangoing barge 10 may be generally flat and inclined upwardly from the extreme depth of the hull of thebarge 10 toward thewater line 20. - Each of the
skeg assemblies 18 as shown herein includes three verticallyoriented foil elements vertical foil element upper end 30 attached to and extending downwardly away from theraked counter portion 22. Abottom end 32 of each of the vertical foil elements is attached to a horizontallyoriented foil element 36 by which each vertical foil element is interconnected with each of the othervertical foil elements skeg assembly 18. Thehorizontal foil element 36 may extend generally horizontally as seen from astern, with thelength 38 of each of thevertical foil elements horizontal foil element 36 to the bottom of thestern counter 22. - Each of the
vertical foil elements raked counter portion 22 and may be oriented perpendicular to plane generally parallel to the bottom of thecounter portion 22, as seen in profile inFIG. 3 . - Each
skeg assembly 18 may, as shown herein, extend over about one third of the breadth of the stem of thebarge 10, or there may be a single skeg assembly (not shown) including a single horizontally oriented foil element extending over the entire breadth of thestern 16 and including additional vertical foil elements. - As may be seen in
FIG. 4 , each of thevertical foil elements edge 40 forward, toward thebow 12 of thebarge 10, and atrailing edge 42 toward thestern 16 of thebarge 10. An airfoil shape in accordance with an embodiment of the present invention as will be disclosed subsequently herein provides a greater amount of such lift force with the same or a lesser amount of drag than has been heretofore known to be possible. As may be seen inFIG. 4 , each of thevertical foil elements chord plane 43 defined between the leadingedge 40 and thetrailing edge 42, and each of thevertical foil elements attack chord plane 43 and aplane 50 parallel with a vertical centerline plane extending fore-and-aft with respect to thebarge 10. Ideally the reference for foil orientation would be the free flow path of water around the hull of the vessel at the location of the foil element, but in practice the foils must be constructed by reference to the hull of thebarge 10. The angles ofattack attack attack - Each of the
vertical foil elements chord length 54, between the respective leadingedge 40 andtrailing edge 42, and each of thevertical foil elements distance 60 which may be at least as great as thechord length 54. Thevertical foil elements barge 10. If thebarge 10 yaws while being towed thevertical foil elements stem 16 has yawed will then be oriented so that the respective angles of attack of thevertical foil elements barge 10, to move thestern 16 of thebarge 10 back toward the desired position and heading of thebarge 10 astern of the towing vessel. - As may be seen in
FIGS. 3 and 4 , thehorizontal foil element 36 is mounted at thebottom ends 32 of thevertical foil elements horizontal foil element 36 has a leadingedge 62, atrailing edge 64, a chord line orneutral plane 66 interconnecting the leadingedge 62 andtrailing edge 64, and achord length 68 between the leadingedge 62 and thetrailing edge 64. Thechord length 68 is at least as great as, and may be greater than thechord length 54 of thevertical foil elements chord length 68 may be as much as twice as great as thechord length 54. Where thechord length 68 is greater than thechord length 54 thevertical foil elements horizontal foil element 36. - The
horizontal foil element 36 may be oriented as seen in side view inFIG. 5 to establish an angle ofattack 72 in the range of −5 degrees to +5 degrees, and optimally between −3 degrees and −4 degrees, relative to a plane H. Because of the direction of flow of water that has been displaced by the hull of thebarge 10, as thebarge 10 moves forward through the water, water flows generally parallel with theplane 74 parallel to the effective shape of the bottom surface of theraked counter 22, and upon encountering thehorizontal foil element 36 creates a lift force L2 generally perpendicular to theneutral plane 66. Because theneutral plane 66 is inclined forward below a horizontal plane H, at anegative angle 72 with respect to the horizontal plane H, the lift force L2 has aforward component 78 tending to urge thebarge 10 forward. So long as the size of thehorizontal foil element 36 is small enough that the surface area doesn't generate too much drag and the Reynolds number is small enough, thisforward component 78 of lift will reduce the amount of energy necessary to move thebarge 10 forward through the water, contributing to fuel economy for towing thebarge 10. - As shown in section view in
FIG. 6 , apropeller shroud 90 surrounds apropeller 92 carried on apropeller shaft 94. Thepropeller 92 as shown has 4blades 96, one of which is shown in section view. Anarrow 98 indicates the direction of movement of that blade when thepropeller 92 is rotating in the usual direction in order to provide forward thrust through theshaft 94. It will be understood that propellers of various blade configurations might be used, and the propeller shown is merely one of several possibilities and not meant to be limiting. - The
propeller 92 has adiameter 100, and theshroud 90 defines an interior diameter that is greater than thediameter 100 of thepropeller 92 by a distance sufficient to assure that theinterior surface 102 of thepropeller shroud 90 will not be struck by thetip 122 of any of theblades 96 as thepropeller 92 rotates. The clearance between the rotatingblade tips 122 and theinterior surface 102 of the propeller shroud is desirably kept as small as practical without unduly risking interference between the two, taking into consideration the expected flexure of the related structures. - In
FIG. 6 , thepropeller shroud 90 is shown in section view. Theshroud 90 has anouter surface 104 which defines, in cooperation with theinterior surface 102, an airfoil shape having aleading edge 106 defining the circular forward end of thepropeller shroud 90 and a trailingedge 108 defining the after end of the propeller shroud. Thepropeller shroud 90 thus acts as a nozzle with aninlet end 112, anoutlet end 114, and alength 115 in the range of 0.3-0.6 times thediameter 100, and usually about equal to 0.5 times thediameter 100 of thepropeller 92. At any point about the circumference of theshroud 90, a chord line orneutral axis 116 extending between theleading edge 106 and the trailingedge 108 of the airfoil sectional shape defines an angle ofattack 118 with respect to a line parallel with thecentral axis 120 of the shroud, which is normally coincident with the axis of rotation of theshaft 94. - The sectional shape of the shroud is that of an airfoil that will be described in greater detail presently, with the
interior surface 102 representing the upper surface of such an airfoil shape and theouter surface 104 being the lower surface of such an airfoil shape. Theshroud 90 may normally be located with respect to thepropeller blades 96 so that thetips 122 of thepropeller blades 96 are aligned with the position C of the point of maximum camber of the airfoil shape. The resulting effect as a nozzle enables thepropeller 92 to provide a greater propulsive force than would be possible without theshroud 90. The negative angle ofattack 118 of the airfoil section shape allows more water to be drawn through theshroud 90 to be driven at a greater velocity by thepropeller 92 than the propeller would be able to move effectively without theshroud 90. - Water drawn into the
shroud 90 passes over theinterior surface 102 of the shroud at an increased speed and reduced pressure, causing a net lift force LT normal to theneutral axis 116. A net thrust component T of the lift force LT urges the shroud forward, while the radially inward component of LT essentially sums to zero. Using an airfoil shape such as is described below an angle ofattack 118 as great as −8 degrees can be used to allow more water to enter the nozzle than is possible with previously known nozzles, in which the maximum angle of attack has been −6 degrees, without decreasing the lift force LT to a useless amount. - An
airfoil shape 130, shown inFIG. 7 , is calculated to provide desirable lift and drag characteristics in the range of Reynolds numbers in which askeg assembly 18 or ashroud 90 is likely to be used. The shape of the airfoil is defined, for one example, by the offsets listed in Table 1. -
TABLE 1 Prototype AirFoil Offsets Section Longitudinal Location Displacement from Neutral Plane 1.00000000 0.00000000 0.99743466 0.00079972 0.98976497 0.00309903 0.97706963 0.00649761 0.95947891 0.01031398 0.93717331 0.01390046 0.91038172 0.01693123 0.87937905 0.01932935 0.84448345 0.02109677 0.80605298 0.02212220 0.76448199 0.02232138 0.72019708 0.02168834 0.67365266 0.02028115 0.62532633 0.01817777 0.57571398 0.01542160 0.52532470 0.01205427 0.47467554 0.00819478 0.42428620 0.00404683 0.37467374 −0.00019721 0.32634726 −0.00434447 0.27980269 −0.00826753 0.23551761 −0.01179841 0.19394647 −0.01480588 0.15551583 −0.01711130 0.12062003 −0.01855941 0.08961713 −0.01902380 0.06282523 −0.01839397 0.04051917 −0.01661490 0.02292769 −0.01373497 0.01023085 −0.00990420 0.00255744 −0.00556657 0.00000000 −0.00000000 0.00256992 0.00815640 0.01023689 0.01888232 0.02293198 0.03122573 0.04052255 0.04419256 0.06282795 0.05735818 0.08961929 0.07031909 0.12062167 0.08273630 0.15551698 0.09430334 0.19394717 0.10472343 0.23551791 0.11376513 0.27980274 0.12116876 0.32634717 0.12674560 0.37467355 0.13027027 0.42428597 0.13166384 0.47467532 0.13088411 0.52532453 0.12794693 0.57571386 0.12294330 0.62532625 0.11602893 0.67365262 0.10745297 0.72019708 0.09750468 0.76448201 0.08651320 0.80605299 0.07482401 0.84448346 0.06284826 0.87937906 0.05105590 0.91038172 0.03987534 0.93717331 0.02950656 0.95947891 0.01994017 0.97706963 0.01146193 0.98976497 0.00496561 0.99743466 0.00120015 - The
airfoil shape 130 includes a convexleading edge 132, asharp trailing edge 134, anupper surface 136, abottom surface 138, and a chord line orneutral axis 140 extending between theleading edge 132 and the trailingedge 134. - A
chord length 142 is defined along theneutral axis 140 between theleading edge 132 and the trailingedge 134, and amaximum thickness 144 is in the range of 0.13 to 0.20 times thechord length 142. Themaximum thickness 144 is located at adistance 146 from the leading edge that is within the range of 0.30 to 0.50 times thechord length 142. - The
airfoil 130 has amaximum camber 150 in the range of 0.065 to 0.080 times thechord length 142, and the location of maximum camber is at adistance 152 from theleading edge 132 in the range of 0.35 to 0.55 times thechord length 142. - An airfoil defined by the offsets listed in Table 1 above is one example of an
airfoil 130 within the parameters mentioned above and has amaximum thickness 144 of 0.131 times the chord length and located at a distance of 0.326 times thechord length 142 from theleading edge 132. It has a maximum camber of 0.065 times the chord length and located at a distance of 0.374 times thechord length 142 from theleading edge 132. - Using the
airfoil shape 130 shown inFIG. 7 for the foil elements of askeg assembly 18, with achord length 142 of 2.5 ft. for each of thevertical foil members chord length 68 of 5 ft. for ahorizontal foil element 36 and with a transverse length of thehorizontal foil element 36 equal to 16 ft., a Reynolds number of about 3.5×106 will result for theskeg assembly 18 at about 5 knots, as set out in Table 2 below. - Use of the
airfoil shape 130 described above and in Table 1 for the vertically orientedskeg elements barge 10 equipped withskeg assemblies 18 than has been possible using the previously known airfoil shapes for the components of such skeg assemblies, with high lift/drag ratios at various speeds, as may be calculated from Table 2 below. -
TABLE 2 Skeg Assembly Using New Airfoil Section with Shorter Chord Length on Vertical Airfoil Sections Vertical Horizontal Section Vertical Section Horizontal Kinematic Chord Section Chord Section Reynolds Viscosity Density Length Length Speed Speed Length Length Number (Ft{circumflex over ( )}2/Sec) (lb-sec{circumflex over ( )}2/ft{circumflex over ( )}4) (Ft) (Ft) (ft/s) (Knots) (Ft) (Ft) 1.00E+06 1.28E−05 1.99 2.50 15.00 2.56 1.52 5.00 16.00 2.00E+06 1.28E−05 1.99 2.50 15.00 5.12 3.03 5.00 16.00 3.00E+06 1.28E−05 1.99 2.50 15.00 7.68 4.55 5.00 16.00 4.00E+06 1.28E−05 1.99 2.50 15.00 10.24 6.06 5.00 16.00 5.00E+06 1.28E−05 1.99 2.50 15.00 12.80 7.58 5.00 16.00 6.00E+06 1.28E−05 1.99 2.50 15.00 15.36 9.09 5.00 16.00 9.00E+06 1.28E−05 1.99 2.50 15.00 23.04 13.64 5.00 16.00 1.20E+06 1.28E−05 1.99 2.50 15.00 30.72 18.19 5.00 16.00 1.50E+06 1.28E−05 1.99 2.50 15.00 38.40 22.74 5.00 16.00 Lateral Total Lateral Vertical Lift Lift per Lift per per Total Total vertical 3 vertical horizontal Speed Total Area Cd Cl Drag Drag airfoil airfoils airfoil (Knots) (Ft{circumflex over ( )}2) (alfa = 0) (alfa = 0) (lbs) (HP) (lbs) (lbs) (lbs) 1.52 385 0.00688 1.0099 17 0.08 246.95 740.86 526.83 3.03 385 0.00585 1.0178 59 0.55 995.54 2986.61 2123.81 4.55 385 0.00544 1.0252 123 1.72 2256.24 6768.72 4813.31 6.06 385 0.00523 1.0293 210 3.91 4027.14 12081.41 8591.22 7.58 385 0.00510 1.0323 320 7.45 6310.74 18932.22 13462.91 9.09 385 0.00501 1.0346 453 12.65 9107.71 27323.13 19429.78 13.64 385 0.00487 1.0385 990 41.49 20569.60 61708.79 43881.81 18.19 385 0.00483 1.0398 1746 97.53 36613.95 109841.85 78109.76 22.74 385 0.00484 1.0404 2734 190.88 57242.31 171726.93 122116.93 Chord length for vertical sections, using the new airfoil section, has been reduced by a factor of ½. Calculated values for the drag show a reduction in drag for each vertical airfoil section while lateral lifting forces still remain higher than the NASA LS(1) airfoil section. This shows that new airfoil section creates equivalent lateral lifting forces with ½ the chord length which results in same directional stability to barge during tow but with reduced drag for skegs. - A
shroud 90 manufactured using theairfoil shape 130 as defined above will also provide significantly improved thrust at a lesser investment of horsepower than required using previously known airfoil shapes for such shrouds. - The
vertical foil elements horizontal foil element 36 may be constructed, for example, in accordance with the methods described in U.S. Pat. No. 7,363,872. - Tank testing of models has shown surprisingly significant superiority in the ability of skeg systems utilizing airfoil shape disclosed herein, by comparison with those disclosed in Gruzling U.S. Pat. No. 4,217,844 and widely used in barges manufactured over the past twenty-plus years, to reduce yawing and lateral excursions of barges under tow in moderately loaded or fully loaded conditions and in sea states two to five.
- While the skeg systems that have been modeled and tested have been designed with surface area equal or similar to that of the skeg systems of the commonly used Gruzling design built by NautiCan, indications based on model testing are that even better overall performance will be seen using skeg systems of similar design. Particularly in such skeg systems having reduced surface area, obtained by using a smaller number of vertical members, oriented to provide greater lateral lift force per vertical member, the desired yaw-opposing steering ability is expected to be obtained with less drag and thus with greater fuel economy while a barge so equipped is towed at higher speeds and in a more fully loaded, deeper draft condition.
- The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.
Claims (14)
1. A skeg system for a barge, comprising:
(a) at least a pair of vertically-oriented foil elements each having an upper end and a lower end; and
(b) a horizontal foil element attached to and extending transversely between the vertical elements, wherein each of the vertical foil elements has a chord length and a thickness and the thickness is related to the chord length by a ratio in the range of 0.13 to 0.20, and wherein each of the vertical elements has a maximum camber, with a ratio of the maximum camber to the chord length in the range of 0.065 to 0.080.
2. A skeg assembly for a barge, including at least a pair of vertical foil elements each disposed in a vertical plane and a horizontal element attached to and extending horizontally and transversely between the vertical foil elements, wherein each vertical foil element has a ratio of thickness to chord length (t/c) in the range of 0.13-0.20, and a ratio of maximum camber to chord length in the range of 0.065 to 0.080 and has a maximum thickness located at a distance from the leading edge in the range of 0.30 to 0.50 of the chord length.
3. The skeg assembly of claim 2 wherein said vertical foil elements are oriented at an angle of attack in the range of −5° to +5° relative to a vertical plane parallel to a longitudinal centerline of the barge.
4. The skeg assembly of claim 2 wherein the horizontal foil element is oriented at an angle of attack in the range of −5° to +5° relative to a plane parallel with a raked counter portion of a hull of the barge.
5. The skeg assembly of claim 2 wherein the horizontal foil element has a chord length greater than the chord length of the vertical foil elements.
6. The skeg assembly of claim 5 wherein the horizontal foil element has a chord length at least 1.25 times as great as the chord length of the vertical foil elements.
7. The skeg assembly of claim 5 wherein the horizontal foil element has a chord length twice as great as the chord length of the vertical foil elements.
8. The skeg assembly of claim 2 wherein the lift/drag ratio of each vertical foil element is at least 170 at a speed in salt water in the range of 5-15 knots.
9. The skeg assembly of claim 2 wherein the horizontal foil element is oriented at an angle of attack, relative to a flow path of water already of the horizontal foil element beneath a raked counter portion of the barge, in the range of −5 to +5°.
10. The skeg assembly of claim 9 wherein the angle of attack relative to the flow path is in the range of 0° to +5°.
11. A propeller shroud for a marine propeller having a central shaft and plurality of radially extending blades, the shroud comprising:
(a) a tubular nozzle structure having an interior surface shape and an exterior surface shape, the exterior and interior surface shapes cooperatively defining a foil section shape as seen in a radial plane extending through the tubular structure, the foil section shape having a thickness to chord length ratio in the range of 0.13 to 0.20, a camber to chord length ratio in the range of 0.65 to 0.080, with maximum camber located between 35% and 55% of the chord length from the leading edge; and wherein
(b) the foil section shape has an angle of attack in the range of 0° to −8°.
12. The propeller shroud of claim 11 wherein the angle of attack is in the range of −4° to −8°.
13. The propeller shroud of claim 11 wherein the foil section shape of the tubular nozzle structure has a lift to drag ratio of at least 100 at an angle of attack within the range of 0° to −8° and operating at a Reynolds number in the range of 1×106 to 18×006.
14. The propeller shroud of claim 11 wherein the drag coefficient (Cd) is in the range of 0.01-0.007 at speeds in salt water in the range of 5 knots-18 knots.
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US12/459,693 US20100000461A1 (en) | 2008-07-07 | 2009-07-06 | Foil shapes for use in barge skegs and marine propeller shrouds |
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US12/459,693 US20100000461A1 (en) | 2008-07-07 | 2009-07-06 | Foil shapes for use in barge skegs and marine propeller shrouds |
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US (1) | US20100000461A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2826703A1 (en) * | 2013-06-14 | 2015-01-21 | Mehmet Nevres Ülgen | A modular underwater foil for a marine vessel |
US9745948B1 (en) * | 2013-08-30 | 2017-08-29 | Brunswick Corporation | Marine propeller and method of design thereof |
US11111849B1 (en) | 2019-12-19 | 2021-09-07 | Brunswick Corporation | Marine propulsion device and lower unit therefor |
US11214344B1 (en) | 2019-12-09 | 2022-01-04 | Brunswick Corporation | Marine propulsion device and lower unit therefor |
US11751551B2 (en) * | 2021-04-15 | 2023-09-12 | Bradley David Cahoon | Hydrofoil fishing lure apparatus |
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US6691632B2 (en) * | 2001-12-05 | 2004-02-17 | Mac Stevens | Sailing craft stable when airborne |
US7617793B2 (en) * | 2002-08-28 | 2009-11-17 | Van Oossanen & Associates | Vessel provided with a foil situated below the waterline |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2826703A1 (en) * | 2013-06-14 | 2015-01-21 | Mehmet Nevres Ülgen | A modular underwater foil for a marine vessel |
US9745948B1 (en) * | 2013-08-30 | 2017-08-29 | Brunswick Corporation | Marine propeller and method of design thereof |
US11214344B1 (en) | 2019-12-09 | 2022-01-04 | Brunswick Corporation | Marine propulsion device and lower unit therefor |
US11111849B1 (en) | 2019-12-19 | 2021-09-07 | Brunswick Corporation | Marine propulsion device and lower unit therefor |
US11751551B2 (en) * | 2021-04-15 | 2023-09-12 | Bradley David Cahoon | Hydrofoil fishing lure apparatus |
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STCB | Information on status: application discontinuation |
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