US2803211A

US2803211A - Tubular rudder

Info

Publication number: US2803211A
Application number: US489586A
Authority: US
Inventors: Robert W Erlbacher
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-02-21
Filing date: 1955-02-21
Publication date: 1957-08-20
Anticipated expiration: 1974-08-20

Description

Aug. 20, 1957 R. w. ERLBACHER 2,303,211

TUBULAR RUDDER Filed Feb. 21. 1955 2 mails-sheet 1 2 0, 1957 R, w ERLBACHER 2,803,211.

TUBULAR RUDDER 'Filed Feb. 21, 1955 2`Sheets8heet 2 /A/l/E /7'OR: ROBERT W. ERL @nef/5e) .5y ,wir

nited States Patent Office TUBULR RUBBER Robert W. Erlbacher, Cape Girardeau, Mo. Applieaann February 21, 195s, serial. No... 489,586.

4 Claims. (Cl. 114-166).

This invention relates. to a tubular rudder'for marine use... and-'in particular is concerned with, a. tubular rudder which is pivotedf aft of the propeller.

In` the past, blade rudders have been conventionally used behind a propeller on marine vessels for steering. These rudders have been objected to inA varying degree because of vibration, excessive power requiredin, steer. ing, poor etliciency in ysteering which is reflectedl inpoor maneuverability andA extremely turbulent wash. The rst three of these features are reliected in disadvantages in ship operation which necessitates rugged construction. and control devices. The last feature, the turbulent wash, is.. dangerous to surrounding small craft which are often capsized when. a vesesl. of substantialy proportions is in the neighborhood.

Attempts have been made in the past to obviate the diilicultiesfound. in the blade rudder, and one such attempt to this problem resulted inthe Kort rudder. The Kort rudder consisted of a tubular shell positioned around a propeller wheel with a very small clearance for the wheel; just suicient for the wheel to fit within the rudder. Although the turbulent wash was reduced by theKort rudder, it has still left certain desirable-.features to/be obtained relative to vibration, easier steering, which is reected in less torque onI the rudder stem, and greater maneuverability.

By means. ofthis. invention there has been provided a tubular rudder which is pivoted aft and spaced from the propeller-wheel. Thisrudder receives the fullforce and extent. of the water propelled through the propeller Wheel inside the. shell of the rudder and passesit. outwardly through a rear opening in such a manner as. to fully enclose andcontrol the propelled race. The rudder is of slightly smaller internal diameter than the propeller. wheel to accommodate the reduced diameter of the jetl stream of water propelled from the propeller which, un. dergoes a slight contraction after leaving the propeller.

Thus, afull control and enclosure of this propelled water is obtained.

Preferably, the. rudder is also of an airfoily designin. its wall sectionwith the internal diameter ilaring some.. what at the front behind the propeller wheel. Also, the leadingfront edges of theA rudder` are` recessed at. the sides between the top and bottom to provide for. greater cross section of entry when the rudder is pivoted away froml the straight` position either to port or starboard whereby greater steeringcontrol is obtainable.

- It has been foundrthatby the use of this invention the vibration. and. steering. power requirements have been. decreased, and maneuverability orl response to rudder; position has been improved. The actual thrust from the propeller obtainedA by the usek of the tubular rudder; of; this invention, also has been increased-over thel pre. viously known bladerudders, and the Kort rudder. Further-maintenance of the propeller shaft is facilitated by. use of the .tubular rudder since the rudder needV not bedisnrantled for, removalofthe shaft. Likewise, the wake` or.,VV wash behind the tubular. rudderr of this invention has Patented Aug. 20, 1957 been reducedA to.` a smooth, even roll so as to facilitate marine tracin; the neighborhood. of the shipV equipped with this invention` whereby marine hazards have been greatly minimized.

Accordingly, it is a principal object of thisA invention to provide a tubular rudder situated. aft of the vessels propeller wheel to obtain increasedV operating benefits.

Another object of this invention is to provide a tubular rudder aft of a propeller wheel: in which therudderhas an airfoil wall design.

A further object of thisinvention istofprovidea tubular rudder which has recessed side portions. on its front end so that it can be pivoted. behind a propeller'and receive a maximum ow of race therefromy for increased maneuverability. and steeringY efficiency;

Still another object' of this invention is: to provide ak tubular rudder` aft of la propeller wheel which is ofi a reduced size with respect to said Wheel for a full con trol of the wheel race for the,A presentation of a restricted opening to. accommodate the propeller race.

Still; a further. object of this invention is to provide a reduced. draft tubulary rudder spaced' aftv ofv a propeller which reduces vibration.

Still anothen object of this. invention is toprovide al tubular rudden spaced. aft of the propellerwhich-increases forward. thrust.y of the vessel andV reduces engineload Still another object of this invention is to provide a: tubular rudder. spaced: aft offa propeller which increases maneuverability of the vessel; and reduces power required for maintaining.v theV rudder in a desired position.

Still another object of' this. invention is to. provide ay tubular rudder spacedfaft'of. a. propeller whichvvdoes notf increase the draft ofthe vessel. andv c an-l be used withi standard steering. and propeller rigs.y

Still azfurtherA object of` this invention is to provide aA tubularV rudder whichy provides a: minimum of flow re-r striction of Water presented to the propeller whenthe.

engines are reversed so that high efficiency can be obtainedfin backing.

It is still a further object off this invention. toprovide a tubular rudder spaced aft of a propeller to produce` asmooth wash, andl therebylessen thehazardl presented to small-boats in the neighborhood. v

vIt is stilly another object of this` invention to providea tubular rudder which is adapted for use with=conve1r tional vessels and canbe easily installedand maintained,v

be had to the accompanying drawings'showing, preferred embodiments of, this invention. It isto be understood,

however, thatthesedrawings are for the purpose ofillus tration only, andthat. the invention is not limited thereto..

In lthe drawings:A

Figure 1 is aviewinside elevation` of a propellerl equippedvessel providedwtihkthe.tubular rudder. of this invention which is partiallybrokenaway toshow theside.

wall construction;`

FigureZis .a somewhat enlargedviewshowing the pro-v peller and rudder combinationwith. thefl'ow streamsof the propellerV raceindicated in dotted` lines;`

Figure isa View similar,- to FigureZ, but showing the l rudder in the hard port position with the changed flow lines of the race;

Figure 4 is a view in front elevation of the propeller looking back through the rudder of Figure 2;

Figure 5 is a force diagram showing the eifect of depth below the water surface on the propeller race;

Figure 6 is a view similar to Figure 4 showing a modied form of rudder;

Figure 7 is a view partially broken away in side elevation of the modified rudder of Figure 6; and

Figure 8 is a view similar to Figure l showing the employment of a backing rudder positioned forwardly of the propeller.

In Figure l, a vessel 10 is shown equipped with a conventional multibladed propeller 11 affixed to a propeller shaft 12 which is journaled within a bearing support 13. The tubular rudder is generally indicated at 14 and is spaced aft of the propeller. A rudder post or stem 15 is fixed to the rudder and extends vertically within the vessel where its pivotal operation is controlled in a known manner.

The propeller 11 is preferably equipped with a fairwater 18 which tends to equalize out the flow lines in the race of wash aft of the propeller in order to reduce turbulence. The force lines of the race are shown at 16 in Figure 2 where it can be seen that the fluid flowing through the propeller wheel and which is Worked upon by the blades of the wheel is propelled aft of the wheel in the form of a generally cylindrical jet of extremely high velocity. Actually the cross-sectional shape is not exactly cylindrical as will be made more apparent hereinbelow. This generally cylindrical wheel race undergoes a partial contraction aft of the wheel or a necking-down to a point just behind fairwater where it evens out to a subsequently constant cross section until quite some distance behind the propeller (not shown) the force is dissipated. The diagrammatic showing of the force lines in the propeller race of Figure 2 represents the standard condition of a heavily loaded propeller wheel race independent of the use of any rudder at all.

. This substantially cylindrical wheel race is enclosed by the tubular rudder 14 to attain full effects in thrust, maneuverability, and steering power requirements, while at the same time vibration is minimized through the rudder post 15 to the vessel. To effectuate the enclosing of the race, the rudder is made of the approximate internal diameter of the neck-down race after the race is contracted at point 17.

To determine this diameter the following procedure is followed. The cross-sectional area of each blade is obtained at its thickest part. This area is multiplied by the number of the blades and then added to the cross-sectional area of the propeller hub at the thickest part of the blades. This sum is then subtracted from the total propeller area. Lastly, for heavily loaded screws an additional 15% is subtracted as the slippage is fairly high while with more lightly loaded screws this percentage can be decreased. This diameter is generally about 80 to 90% of the diameter of the propeller wheel and varies somewhat depending upon the propeller design and the load placed upon it, as is understood in the art.

As is apparent from Figures 2 and 4, the tubular rudder 14 has an open front end 20 and rear end 21. The rudder is supported behind the propeller by the rudder stem 15 which is xed to the rudder 14. The pivot point is spaced behind the propeller a distance approximately equal to the diameter of the propeller at a point approximately where the necking-down of the propeller race is completed. It will be noted that the top portion 23 and bottom portion 24 of the front end 20 extend forwardly of the pivot or rudder post 15, while the port side portion 25 and starboard portion 26 are both recessed with respect to the top and bottom portions. Thus, both side portions 2S and 26, as shown in Figure 2, are cnt back about to the rudder stem. This provides for greater access of entrance when the rudder it turned to the hard port position, as shown in Figure 3 where the force lines of the propeller race are given greater access of entry due to the recessed portion 25. Obviously this also applies to the starboard positioning of the rudder through recessed portion 26.

A modification of this design is shown for the rudder 14 in Figure 8 where the front bottom wall is cut back in relation to the top to provide a lower front end portion 29, which is more or less straight-edged about the lower half of the rudder. This design is suitable in debris infested Waters and obviates the possibility of any debris lodging in the recesses at the side portions. Actually, this lower front end may be vertical or slant toward the rear at the bottom.

The actual wall configuration of the tubular rudder includes, besides the aforementioned straight-sided exterior surface 22, an interior surface which is of a generally airfoil configuration. Thus, the forward or leading side of the interior surface is outwardly flaring and curved at 27, after which toward the rear the curvature straightens out into a straight side 2S, which provides a constant diameter bore to the rear end 21. The extent of the curvature of the surface 27 is fairly substantial along the axis of the rudder so as to provide a goodly amount of surface more nearly perpendicular to the propeller race than wall 2S when the rudder is turned in a hard-over position such as shown in Figure 3.

Although the propeller race has been described as being substantially cylindrical in the description above, in actuality it may be considered to be somewhat flattened out at the bottom. Thus, due to pressure differentials which increase with the distance below the surface, namely, about 0.44 p. s. i. for each foot of depth in fresh water, there is a greater exterior pressure on the propeller race at the bottom which causes a partial attening out, as shown in Figure 5. The force lines which are greater at the bottom, as shown in Figure 5, cause the distortion of the propeller race to be shaped as shown. ln order to enclose and mate as fully as possible with this configuration of the propeller race, a tubular rudder having an internal cross section of the same general configuration as that shown in Figure 5 is shown in Figures 6 and 7. The modified rudder is indicated at 30 and is alike in all respects to the generally cylindrical shaped rudder 14 except for its cross section at the front end, and like numbers have been given for like elements.

In the modified tubular rudder 30, full acceptance and enclosure of the propeller race is eiected with a maximum attainment of operating efficiency. Thus, there is no obstruction and consequently no deleterious turbulence presented in the tubular rubber to the ow of the propeller race passing through it. Although this form of the rudder is somewhat more difficult to construct, its operating ad-y vantages are improved over the rudder 14.

In this rudder the front end 31 is of the partially flattened conguration shown conforming with the wheel race in Figure 5. This configuration is then changed within the rudder to the circular open end 21 as this shape is most eflicient for the race exhaust in the benefits to be derived from this invention.

The dimensioning of the rudder 14 and rudder 30 is substantially the sarne with respect to relative spacing behind the propeller blade. Thus, for rudder 14, as has been previously mentioned, the internal diameter of the circular rudder wall 28 at the rear end is approximately to 90% of the diameter of the propeller 11.` In the rudder 30, the cross-sectional area at the front end is the same as that for the rudder 14. However, since the configuration is changed somewhat, the major axis at the front end is greater than the internal diameter of wall 2S and may be increased up to approximately the diameter of the propeller while the minor axis is less and may be about 75 to 85% of the propeller diameter. The most desirable length of the rudder from the front, i. e., be-

tween top and bottom portions 24 and 213 and the end 2l, is approximately equal to the diameter of the propeller. It will, however, beunderstood that this invention is not limited to these figures since, as has been previously mentioned, propeller design and operational requirements may provide differentdinien'sions, as will be understood in the art.

With respect to the spacing between the propeller and the pivot point of the rudder stem l5, therev should be a distance about equal to the internal diameter of the rudder Wall 28. However, this Yspacing is controlled somewhat by the length of the fairwater, and thev longer the fairwater the greater is the spacing, and vice versa for shorter fairwaters.

The recessed sides 25v and 26 of the front of the tubular rudder are cut. back from the top and

bottom portions

23 and 24, respectively, about one-third of the internal diameter of theA rudder as defined by the wall 28. This amount of recess is variable, as will be understood in the art. However, for the instant rudder which permits of turning about 35 away from the straight-forward position, either port or starboard, this has been found to present a full access of the propeller race to the rudder so that greater maneuverability and steering control are obtained together with increased thrust in a very advantageous manner.

In Figure 8, there is shown still a further modification of this invention where a backing rudder 40 is supported forwardly of thev propeller lll on a vessel 41. This backing rudder is in addition to the previously described stern rudder 14v (which here, is slightly modified by slanting lower front end 29)., or where desired, the modified rudder 30, and can even be used with blade rudders. The rudder 4tlis pivoted from a rudderstem 42 and may be of a design like the rudder 1.4, 1,4' or the rudder 30. The propeller shaft 12 fits entirely through the backing rudder so that the backing rudder may be turned within limits defined by its contact withy the propeller shaft 12. Where desired, stop means may bev provided with the rudder control so as to prevent actual engagement of the rudder with the propeller shaft.

It will be noted that inthe modification of Figure 8 substantially full access andflow of water to the propeller is provided whether the propeller is used in forward or reverse, since water flows through either the rudder 40 in the forward positionor through rudder. 14 in the reverse position. The only change in this rudder. is that the crosssectional area of its opening is slightly increased by the area of the propeller shaft since the wheel race of necessity flows around this and cannot retract. to its full extent.

Operation For a full and complete understanding of this invention a consideration should be given to the nature ofthe propeller race. It has been found, that the propeller race is propelled aft of the propeller in the general form of a cylindrical jet at a very high velocity with respect to the surrounding water. The propulsive force of this jet on the water from the propeller and aft of it furnishes the reaction required to propel the vessel forwardly. The force lines of this jet stream aft of the propeller are generally shown in Figure 2 where the necking-downfeature to the constant diameter at point 17 has been previously discussed. Actually, this is a rotating column of water in a like manner to a screw due to the rotational effect of the propeller 11.

The increase in velocity of the water propelled through this screw as it rapidly rotates causes a decrease in pressure in accordance with the Bernoulli theorem. Simultaneously with this increase in velocity and decrease in pressure, there are serious cavitation effects and internal turbulence within the propeller race. All of these factors contribute to a very turbulent wash or roll at the water surface aft of the vessel. However, with the tubular rudder 14 yor Si) of this invention as utilized, the propeller race is enclosed and the full benefit and effect of the propulsion or thrust of the race is realized without any outside interference or disturbance. Thus, as shown in Figure 2 where the propeller race is enclosed, there is protection against outside interference from the undisturbed water medium surrounding the race which is at a higher pressure than the propeller race within the rudder. By enclosing thepropeller race as s hown,` a full control can be had and the thrust is more efficiently utilized in 'a manner similar to a jet propulsion where there is very little` inefcientdissipation of the high velocity. race.

In Figure 3, there is shown the action of-` the propeller race within. the rudder. 1.4 when it is turned over tothe hard port position. In this. condition, the force lines on the starboard side impinge. against the open flared internal side of the airfoil section 27 of the rudder and through, a substantially normal or Vertical impingement tend tocause therudder. topivoty in the clockwise. position about the rudder stem. Thisv action is counter-balanced by the force linesV ontheport side` which, due to the. airfoill or outwardly flaring front portion, causes a slight vacuum on the inside ofthe straight. wall 28, as is shown in the dotted lines, to create anl area of reduced pressure. This area of.l reduced pressure tends to cause a counterclockwise rotation of the rudder about the rudder stem so that there are equal and opposite forces which tend to maintain. the rudder in the position to which itvr is turned.

The particular :nii/.antagey of this invention can be readily, understood when compared with the operation ofl astandard straight-,bladed rudder. In such a bladed rudder, there are aA series of irregular forces upon the rudder since it isdisposed vertically directly behindL the propeller wheel. There. areliute cycle vibrations as the propeller race is propelled aft of the propeller in the aforementioned. screw-like2 or spiral direction, and since the rudder is righrin thecenter there is a positive force on oneY side andi a negative force or area 0f;.reduced;

pressure on the other sideas each flute passes the rudder. Thus, in the case of the commonblade rudder, there are two flute cycle vibrations, one at the top of the rudder and one at.- the bottom ofthe rudder as each flute passes the leading edge of the rudder. This not only causes torque on the rudder, but imparts a very substantial force. or vibration v to the rudder and through it to the entire ship.

Further, since the blade rudder is placed directly. in.

the path of the wheel race, it causes a break-up or loss of the smooth, even configuration of the propeller race, and a4 great turbulence.

forward position so that this turned position is difficult.- to maintain andrequiresa substantial amount of force,

or. torque.

v In the casev of the Kort` rudder andl other propeller` shrouded rudders, therey aredisadvantages since the vfull effect of the propeller race is lost as this race is not enclosed and controlled as has been done in this invention. Further, in addition to the loss in thrust and greater steering force required, relative to the present invention, the propeller shrouded rudders are disadvantageous because of the small clearance they have around the propeller and their increased draft. These rudders have been found to be susceptible to breakage since foreign objects, which inevitably are drawn into the propeller, tend to jam the clearance space on the outside of the propeller and are caught therein which causes breakage and disrepair of the blades of the propeller and the rudder.

Likewise, due tothe relationship of the bladed rudder directly in the path of theV Because of the comparative considerations discussed above, it has been found that the tubular rudder of this invention has greatly improved maneuverability over the blade rudder, through response to control and force or torque required, in the amount of 70%. Vibration in the employment of the rudder of this invention over the blade rudder has been extremely reduced and the forward thrust has been improved as much as 10%. Also, the wheel wash leaving the tubular rudder is smoother or flatter and causes less turbulence at the surface of the water so as to greatly reduce hazards to small boats in the neighborhood.

Experiments with the tubular rudder have also been made with respect to the Kort rudder where it has been found that steering maneuverability has been increased by about 10% and the vibration has also been very substantially reduced. Further, the thrust from the rudder of this invention has been increased by approximately 10% over the Kort rudder.

The rudder 30 of Figures 6 and 7 operate in the same manner as described above for the

rudder

14 or 14. However, in the case of the rudder 30, the operational advantages will be even greater since the capture of the propeller race is more perfectly effected, which is the prime consideration of this invention. As has been previously discussed, the propeller race actually is attened out somewhat at the bottom due to an increase in pressure which varies directly with the depth below the surface of the water. This consideration is greater in deep draft and large vessels using propellers of substantial dimensions. In such vessels, where maximum thrust steering efciency and maneuverability are very important, the rudder 30 has its greatest application. Such demands on large vessels as large ocean-going ships or river tow-boats of great power which are designed to push a number of barges make practical the manufacture of this specially shaped rudder, although this rudder is somewhat more difficult to fabricate than the cylindrical shaped rudder 14.

The backing rudder of Figure 8 operates in the same manner as above described for either the rudder 14 or the rudder 30 and can be made in a manner similar to either of these rudders. When a backing rudder is utilized, it surrounds the propeller shaft and, as previously mentioned, can be turned within the limits of contact with this shaft to effect steering or maneuvering of the vessel when the propeller is reversed. Since the regular rudder 14 is tubular, it provides substantially full access of llow of water to the propeller 11, which then has its propeller race projected through the tubular rudder 40 which controls in the manner above described.

Maintenance of the propeller and its shaft for vessels equipped with the rudder invention herein disclosed is especially easy and expeditious to effect. To remove the propeller shaft and propeller, the rudder 14 in either Figure 1 or Figure 8 need not be removed since the propeller can be loosened from its shaft, and the shaft, after the removal of the propeller, can then be withdrawn 6() through the bearing 13 out through the rear end 21 of the rudder. The rudder need not be touched at all in the propeller and shaft removal operation, which is of great advantage over the common blade rudder.

It is obvious that various changes and modiiications may be made in this invention as will be apparent to those skilled in the art. Such changes are within the scope of this invention as defined by the claims appended hereto.

What is claimed is:

1. A rudder for marine vessels adapted to be used in spaced relation behind a propeller on the vessel, said rudder comprising a hollow shell completely open and unobstructed at its front and rear ends, said shell having a continuous wall at its top, bottom and sides to define a hollow space enclosed by said shell, said hollow space being slightly smaller than the diameter of the propeller with which the rudder is adapted to be used, said top, bottom and side walls defining a substantially cylindrical shell, and pivot means whereby the rudder can be pivoted, said shell having its side walls at the front end recessed rearwardly of the front top and bottom walls.

2. A rudder for marine vessels adapted to be used in spaced relation behind a propeller on the vessel, said rudder comprising a hollow shell completely open unobstructed at its front and rear ends, said shell having a continuous Wall at its top, bottom and sides to define a hollow space enclosed by said shell, said howwol space being slightly smaller than the diameter of the propeller with which the rudder is adapted to be used, said top, bottom and side walls defined a shell having a front opening of rounded cross section, said cross section being substantially circular at the top and sides and somewhat flattened at the bottom.

3. In combination with a vessel having a bladed propeller, a hollow backing rudder for steering the vessel when the propeller is reversed, said rudder being spaced forward of the propeller and being open at its opposed ends to receive and exhaust the propeller race when the propeller is operated in reverse, and to pass water therethrough with a minimum of flow restriction when the propeller is operated in forward.

4. In combination with a vessel having a bladed propeller, the improvement comprising a hollow rudder, said rudder being spaced aft of the propeller, said rudder having an open front end to receive said propeller race and an open rear end to exhaust the race, a hollow backing rudder for steering the vessel when the propeller is reversed, said rudder being spaced forward of the propeller and being open at its opposed ends to receive and exhaust the propeller race when the propeller is operated in reverse, and to pass water therethrough with a minimum of flow restriction when the propeller is operated in forward.

References Cited in the le of this patent UNITED STATES PATENTS 899,359 Wadagaki Sept. 22, 1908 2,139,594 Kort Dec. 6, 1938 2,601,837 Dean July 1, 1952 FOREIGN PATENTS 677,849 Great Britain Aug. 20, 1952 740,224 Germany Oct. 14, 1943