CA1171739A - Sailboat propeller - Google Patents
Sailboat propellerInfo
- Publication number
- CA1171739A CA1171739A CA000388843A CA388843A CA1171739A CA 1171739 A CA1171739 A CA 1171739A CA 000388843 A CA000388843 A CA 000388843A CA 388843 A CA388843 A CA 388843A CA 1171739 A CA1171739 A CA 1171739A
- Authority
- CA
- Canada
- Prior art keywords
- propeller
- thrust face
- trailing edge
- reverse thrust
- sailboat
- 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
- B63H—MARINE PROPULSION OR STEERING
- B63H1/00—Propulsive elements directly acting on water
- B63H1/02—Propulsive elements directly acting on water of rotary type
- B63H1/12—Propulsive elements directly acting on water of rotary type with rotation axis substantially in propulsive direction
- B63H1/14—Propellers
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
Campbell 1/c SAILBOAT PROPELLER
ABSTRACT OF THE DISCLOSURE
A propeller for use on auxiliary drives for sailboats has at least two blades. Each blade has a forward thrust face, a reverse thrust face, a leading edge and a trailing edge. Lateral dimensions extend between the leading edge and the trailing edge. The reverse thrust face has a portion which is laterally concave. Preferably, the reverse thrust face has a convex portion extending laterally from the leading edge towards the trailing edge. The concave portion extends from the convex portion towards the trailing edge.
ABSTRACT OF THE DISCLOSURE
A propeller for use on auxiliary drives for sailboats has at least two blades. Each blade has a forward thrust face, a reverse thrust face, a leading edge and a trailing edge. Lateral dimensions extend between the leading edge and the trailing edge. The reverse thrust face has a portion which is laterally concave. Preferably, the reverse thrust face has a convex portion extending laterally from the leading edge towards the trailing edge. The concave portion extends from the convex portion towards the trailing edge.
Description
1171~ 9 (1) BACKGROUND OF THE INVENTION
The invention relates to a propeller for use on auxiliary power drives for sailboats.
Many sailboats today employ gasoline or diesel engines as auxiliary power drives. These are used when insufficient wind is encountered or, for example, for maneuvering in marinas. Propellers used on such auxiliary drives clearly provide a source of drag which impedes the movement of the vessel when under sail. In order to mini-mize this drag, the blades of sailboat propellers are relatively narrow.
However, this narrowness of the blades results in poor performance when the boat is moving astern. It therefore would be highly desirable to provide a sailboat propeller which would have relatively narrow blades to 15 reduce drag, but with improved performance when the boat is powered astern.
Various novel shapes of marine propellers have been suggested in the past, for example, as shown in United States Patent #4,073,601 to Kress. Referring to Figure 4 of this patent in particular, the blade has a pressure side or face which includes a convex portion near the leading edge and a concave portion near the trailing edge.
However, the propeller has a convexly curved suction side or back. Since it is the suction side or back which provides the thrust during motion of the boat astern, such a propeller would not improve reverse performance.
Propellers commonly have convex backs and it is this feature that inhibits adequate performance of sailboat propellers when operating in reverse.
British Patent #22,441 shows a blade having a modified convex surface. The trailing portion is straight instead of being convex.
Vnited States Patent #1,û23,584 to Muhlberg discloses a screw propeller having blades with a concave pressure surface.
, 7T~
The invention relates to a propeller for use on auxiliary power drives for sailboats.
Many sailboats today employ gasoline or diesel engines as auxiliary power drives. These are used when insufficient wind is encountered or, for example, for maneuvering in marinas. Propellers used on such auxiliary drives clearly provide a source of drag which impedes the movement of the vessel when under sail. In order to mini-mize this drag, the blades of sailboat propellers are relatively narrow.
However, this narrowness of the blades results in poor performance when the boat is moving astern. It therefore would be highly desirable to provide a sailboat propeller which would have relatively narrow blades to 15 reduce drag, but with improved performance when the boat is powered astern.
Various novel shapes of marine propellers have been suggested in the past, for example, as shown in United States Patent #4,073,601 to Kress. Referring to Figure 4 of this patent in particular, the blade has a pressure side or face which includes a convex portion near the leading edge and a concave portion near the trailing edge.
However, the propeller has a convexly curved suction side or back. Since it is the suction side or back which provides the thrust during motion of the boat astern, such a propeller would not improve reverse performance.
Propellers commonly have convex backs and it is this feature that inhibits adequate performance of sailboat propellers when operating in reverse.
British Patent #22,441 shows a blade having a modified convex surface. The trailing portion is straight instead of being convex.
Vnited States Patent #1,û23,584 to Muhlberg discloses a screw propeller having blades with a concave pressure surface.
, 7T~
(2) British Patent #295,741 shows propellers with forward and rearward rakes.
None of these earlier patents reveals a propeller suit-5 able for use on sailboats which provides improved performance when thevessel is moving astern.
SUMMARY OF THE INVENTION
The invention provides a propeller for use on an auxi-liary power drive for sailboats. The propeller comprises at least two blades, each having a forward thrust face, a reverse thrust face, a lead-ing edge and a trailing edge. Lateral dimensions extend between the 15 leading edge and the trailing edge. The reverse thrust face has a portion which is laterally concave.
Preferably, the reverse thrust face has a convex portion extending laterally from the leading edge towards the trailing edge. The 20 concave portion extends from the convex portion towards the trailing edge.
Advantageously, the trailing edge is nat and bevelled generally 45 inwardly from the reverse thrust face to the forward 25 thrust face.
Where the propeller has a hub and the blades have a tip and a longitudinal direction extending between the hub and the tip, preferably the concave portion of each blade is progressively thicker 30 towards the tip. Thus, the laterally concave portion is also concave in the longitudinal direction of the blade.
The invention overcomes disadvantages of earlier sail-boat propellers when operating in the reverse mode.
,.. ....... ... .. ... . . . . ..
117~739
None of these earlier patents reveals a propeller suit-5 able for use on sailboats which provides improved performance when thevessel is moving astern.
SUMMARY OF THE INVENTION
The invention provides a propeller for use on an auxi-liary power drive for sailboats. The propeller comprises at least two blades, each having a forward thrust face, a reverse thrust face, a lead-ing edge and a trailing edge. Lateral dimensions extend between the 15 leading edge and the trailing edge. The reverse thrust face has a portion which is laterally concave.
Preferably, the reverse thrust face has a convex portion extending laterally from the leading edge towards the trailing edge. The 20 concave portion extends from the convex portion towards the trailing edge.
Advantageously, the trailing edge is nat and bevelled generally 45 inwardly from the reverse thrust face to the forward 25 thrust face.
Where the propeller has a hub and the blades have a tip and a longitudinal direction extending between the hub and the tip, preferably the concave portion of each blade is progressively thicker 30 towards the tip. Thus, the laterally concave portion is also concave in the longitudinal direction of the blade.
The invention overcomes disadvantages of earlier sail-boat propellers when operating in the reverse mode.
,.. ....... ... .. ... . . . . ..
117~739
(3) The thrust action of the reverse thrust face is consider-ably improved by the concave or cup-shaped surface adjacent the trailing edge of the propeller which leads the leading edge during reverse rotation. At the same time, the forward thrust face is unaltered so there 5 is relatively little change to the normal characteristics of the propeller when operating in the forward direction. Bevelling the trailing edge 45 prevents a whistling noise at low R.P.M.'s as occurs with some propellers.
Figure 1 is a front view of a three~laded sailboat propeller according to an embodiment of the invention, with two of the blades broken away and showing sections along the length of the illustrated blade;
Figure 2 is a side elevational view of the propeller of Figure 1 showing one blade only;
Figure 3 is a typical section of the blade of a prior art sailboat propeller; and Figure 4 is a typical section of the sailboat propeller according to Pigures 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures 1 and 2 of the drawings illustrate a sailboat pr~
30 peller 1 according to an embodiment of the invention. The propeller has a hub 2 with a central aperture 4 for fitting the propeller onto the drive shaft of a sailboat. A keyway 6 is keyed into a similar keyway in the drive shaft to prevent relative rotation between the propeller and the drive shaft.
11'71'7~9
Figure 1 is a front view of a three~laded sailboat propeller according to an embodiment of the invention, with two of the blades broken away and showing sections along the length of the illustrated blade;
Figure 2 is a side elevational view of the propeller of Figure 1 showing one blade only;
Figure 3 is a typical section of the blade of a prior art sailboat propeller; and Figure 4 is a typical section of the sailboat propeller according to Pigures 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures 1 and 2 of the drawings illustrate a sailboat pr~
30 peller 1 according to an embodiment of the invention. The propeller has a hub 2 with a central aperture 4 for fitting the propeller onto the drive shaft of a sailboat. A keyway 6 is keyed into a similar keyway in the drive shaft to prevent relative rotation between the propeller and the drive shaft.
11'71'7~9
(4) The propeller accordhlg to the preferred embodiment is provided with three blades 8, 10 and 12, the latter two being broken away for simplicity of illustration. Blades 10 and 12 are identical to blade 8.
Blade 8 has a tip 14, a leading edge 16, and a trailing edge 18. Arrow 20 indicates the direction of rotation of propeller 1 in order to propel the veæel forwardly. During this normal direction of rotation of the propeller, the leading edge 16 leads the trailing edge 18.
A stipled arrow 22 indicates the direction of rotation of the propeller in order to move the vessel astern. In this reverse direction of rotation, the trailing edge leads the leading edge.
The propeller blade 8 has a relatively flat forward thrust face 24 for providing a forward thrust for the sailboat and a reverse thrust face 26 for providing a reverse thrust for the sail boat, the faces being on opposite sides of the blade. These are best seen in Figure 2 and the sectional views of Figures 1 and 4. The reverse thrust face 26 faces the hull of the sailboat when the propeller is mounted on the drive shaft.
In describing the shape and configuration of blade 8 herein, lateral dimensions and directions extend between the leading edge 16 and the trailing edge 18. For example, the lateral dimension 28 is indicated by arrows in Figure L Longitudinal directions and dimensions are generally perpendicular to the lateral ones and extend between the tip 14 of the blade and the hub 2 for example longitudinal dimension 30 shown by the arrows in Figure L
The cross sectional shapes along the blade 8 are illus-trated by the eight cross sections 32 to 46 located at their positions along the blade in Figure 1. The forward thrust face 24 is illustrated in the top of these sections, while the bottom shows the reverse thrust face 26.
A typical cross section from a blade of a prior art sailboat propeller 48 is shown in Figure 3. The blade 48 has a nat for-1171'739
Blade 8 has a tip 14, a leading edge 16, and a trailing edge 18. Arrow 20 indicates the direction of rotation of propeller 1 in order to propel the veæel forwardly. During this normal direction of rotation of the propeller, the leading edge 16 leads the trailing edge 18.
A stipled arrow 22 indicates the direction of rotation of the propeller in order to move the vessel astern. In this reverse direction of rotation, the trailing edge leads the leading edge.
The propeller blade 8 has a relatively flat forward thrust face 24 for providing a forward thrust for the sailboat and a reverse thrust face 26 for providing a reverse thrust for the sail boat, the faces being on opposite sides of the blade. These are best seen in Figure 2 and the sectional views of Figures 1 and 4. The reverse thrust face 26 faces the hull of the sailboat when the propeller is mounted on the drive shaft.
In describing the shape and configuration of blade 8 herein, lateral dimensions and directions extend between the leading edge 16 and the trailing edge 18. For example, the lateral dimension 28 is indicated by arrows in Figure L Longitudinal directions and dimensions are generally perpendicular to the lateral ones and extend between the tip 14 of the blade and the hub 2 for example longitudinal dimension 30 shown by the arrows in Figure L
The cross sectional shapes along the blade 8 are illus-trated by the eight cross sections 32 to 46 located at their positions along the blade in Figure 1. The forward thrust face 24 is illustrated in the top of these sections, while the bottom shows the reverse thrust face 26.
A typical cross section from a blade of a prior art sailboat propeller 48 is shown in Figure 3. The blade 48 has a nat for-1171'739
(5) ward thrust face 50 and a convex reverse thrust face 52. The force of water acting against the forward thrust face 50 during rotation of the propeller for forward movement of the sailboat is indicated by a plurality of arrows 54. Arrows 56 indicate the force of water acting against the 5 reverse thrust face 52 during rotation of the propeller in the opposite direction for reverse movement of the sailboat. The convex shape of tne reverse thrust face combines with the relative narrowness of sailboat propellers to inhibit backup performance. In simple terms, the convex shape provides insufficient "grip" so that the water tends to slide over 10 the convex surface instead of providing sufficient force. The effective area of the reverse thrust face extends only from the center 58 of the blade to the trailing edge 60.
By comparison, a typical cross section through sailboat 15 propeller 1 according to the invention is shown in Figure 4. The forward thrust face 24 is flat and the same as in the prior art propeller blade shown in Figure 3. The force of the water acting against the forward thrust surface is indicated by arrows 62. On the improved propeller, however, reverse thrust face 26 of blade 8 has a laterally concave 20 portion 64. As with the prior art propeller blade, blade 8 has a convex portion which extends laterally from the leading edge 16 towards the trailing edge 18. Accordingly, the action of the reverse thrust face is similar to the prior art during the forward direction of rotation indicated by the arrow 20. The convex portion 66 of the preferred embodiment 25 extends generally one~uarter the distance between the leading edge 16 and the trailing edge 18 to the thickest section 68 of the blade.
The concave portion 64 of the blade extends from convex portion 66 near the thickest section 68 towards the trailing edge 18. Arrows 70 show the force of water against the convex portion 64 during rotation of the blade in the reverse direction indicated by arrow 22. The "grip" between the water and the propeller is appreciably improved by providing the concave surface instead of the equivalent convex surface of the prior art blade 48 of Figure 3.
1 1'71'7~9
By comparison, a typical cross section through sailboat 15 propeller 1 according to the invention is shown in Figure 4. The forward thrust face 24 is flat and the same as in the prior art propeller blade shown in Figure 3. The force of the water acting against the forward thrust surface is indicated by arrows 62. On the improved propeller, however, reverse thrust face 26 of blade 8 has a laterally concave 20 portion 64. As with the prior art propeller blade, blade 8 has a convex portion which extends laterally from the leading edge 16 towards the trailing edge 18. Accordingly, the action of the reverse thrust face is similar to the prior art during the forward direction of rotation indicated by the arrow 20. The convex portion 66 of the preferred embodiment 25 extends generally one~uarter the distance between the leading edge 16 and the trailing edge 18 to the thickest section 68 of the blade.
The concave portion 64 of the blade extends from convex portion 66 near the thickest section 68 towards the trailing edge 18. Arrows 70 show the force of water against the convex portion 64 during rotation of the blade in the reverse direction indicated by arrow 22. The "grip" between the water and the propeller is appreciably improved by providing the concave surface instead of the equivalent convex surface of the prior art blade 48 of Figure 3.
1 1'71'7~9
(6) Referring to the cross sections of 32 to 46 of the blade 8 shown in Figure 1, it may be seen that the reverse thrust face 26 has the concave portion 64 from the tip 14 of the blade to approximately section 42. The laterally concave portion accordingly extends from the 5 tip 14 generally two-thirds of the distance to the hub 2.
Referring to the profile of blade 8 shown in Figure 2, it may be seen that the propeller has a rearward rake of generally 6 as defined by angle 74. It is also clear from Figure 1 and Figure 2 that the 10 laterally concave portion 64 of the reverse thrust face 26 becomes progressively thicker towards the blade tip 14. The thickest gection 76 occurs near the tip 14 as shown in Figure L The laterally concave portion near the tip, therefore, is also concave in the longitudinal direction of the blade. There is therefore a part of the reverse thrust face near the 15 tip 14 which is both longitudinally and laterally concave. This saucer-shaped part effectively locks the water to the blade surface when the propeller is operating in the reverse direction indicated by arrow 22, cutting down on water slippage at the blade tips. Reverse performance is considerably improved as a result.
Referring to Figure 1 and Figure 4, the trailing edge 18 is flat and is bevelled generally 45 inwardly from the reverse thrust face 26 to the forward thrust face 24. This prevents a whistling noise at low R.P.M.'s as occurs with some propellers.
A sailboat propeller according to the invention ac-cordingly provides the narrow blade width re~uired to reduce drag, while giving good performance in the reverse direction of rotation of the propeller and during backing up of the huLl. The improved performance 30 in the reverse mode i8 obtained by such features as the laterally concave portion of the reverse thrust face and the longitudinally concave portion resulting from t~e thicker section near the tip. Shortcomings in the prior art sailbo~t propellers during reverse operation are thereby overcome.
. .
Referring to the profile of blade 8 shown in Figure 2, it may be seen that the propeller has a rearward rake of generally 6 as defined by angle 74. It is also clear from Figure 1 and Figure 2 that the 10 laterally concave portion 64 of the reverse thrust face 26 becomes progressively thicker towards the blade tip 14. The thickest gection 76 occurs near the tip 14 as shown in Figure L The laterally concave portion near the tip, therefore, is also concave in the longitudinal direction of the blade. There is therefore a part of the reverse thrust face near the 15 tip 14 which is both longitudinally and laterally concave. This saucer-shaped part effectively locks the water to the blade surface when the propeller is operating in the reverse direction indicated by arrow 22, cutting down on water slippage at the blade tips. Reverse performance is considerably improved as a result.
Referring to Figure 1 and Figure 4, the trailing edge 18 is flat and is bevelled generally 45 inwardly from the reverse thrust face 26 to the forward thrust face 24. This prevents a whistling noise at low R.P.M.'s as occurs with some propellers.
A sailboat propeller according to the invention ac-cordingly provides the narrow blade width re~uired to reduce drag, while giving good performance in the reverse direction of rotation of the propeller and during backing up of the huLl. The improved performance 30 in the reverse mode i8 obtained by such features as the laterally concave portion of the reverse thrust face and the longitudinally concave portion resulting from t~e thicker section near the tip. Shortcomings in the prior art sailbo~t propellers during reverse operation are thereby overcome.
. .
Claims (8)
1. A propeller for use on auxiliary power drives for sailboats, the propeller comprising at least two blades each having a relatively flat forward thrust face for providing forward thrust for the sailboat, a reverse thrust face for providing reverse thrust for the sailboat, a leading edge and a trailing edge, lateral dimensions extending between the leading edge and the trailing edge, the reverse thrust face having a portion which is laterally concave.
2. A propeller as claimed in Claim 1, wherein the reverse thrust face has a convex portion extending laterally from the leading edge towards the trailing edge, the concave portion extending from the convex portion towards the trailing edge.
3. A propeller as claimed in Claim 2, wherein the convex portion ex-tends generally one-quarter the distance between the leading edge and the trailing edge.
4. A propeller as claimed in Claim 1, wherein the trailing edge is flat and bevelled generally 45° inwardly from the reverse thrust face to the forward thrust face.
5. A propeller as claimed in Claim 1, further comprising a hub and wherein the blades have a tip, longitudinal directions extending between the hub and the tip, the laterally concave portion of each said blade being progressively thicker towards the tip so the later-ally concave portion near the tip is also concave in the longitudinal direction.
(8)
(8)
6. A propeller as claimed in Claim 1, having a generally 6° rearward rake.
7. A propeller as claimed in Claim 5, wherein the laterally concave portion extends from the tip generally two-thirds of the distance to the hub.
8. A propeller as claimed in Claim 1, wherein the reverse thrust face faces the hull of the sailboat when the propeller is mounted for use.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000388843A CA1171739A (en) | 1981-10-27 | 1981-10-27 | Sailboat propeller |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000388843A CA1171739A (en) | 1981-10-27 | 1981-10-27 | Sailboat propeller |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171739A true CA1171739A (en) | 1984-07-31 |
Family
ID=4121274
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000388843A Expired CA1171739A (en) | 1981-10-27 | 1981-10-27 | Sailboat propeller |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1171739A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2600971A1 (en) * | 1986-07-04 | 1988-01-08 | Alsthom | Marine propeller blade |
-
1981
- 1981-10-27 CA CA000388843A patent/CA1171739A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2600971A1 (en) * | 1986-07-04 | 1988-01-08 | Alsthom | Marine propeller blade |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |