Claims
- 1. A device with a cavitational effect for propellers used for propulsion of watercraft with a planing or semiplaning keel, comprising an air flow duct and wall means for generating a depression area, the air flow duct having an outlet adjacent a propeller, the air flow duct withdrawing air from above a hull water line and releasing the air from the outlet directly to a front part of at least the propeller and the wall means generating the depression area in the front part of the propeller, the device further comprises first support means for said propeller and second support means for said air duct, a top of said air flow duct being in communication with the atmosphere above the water line and being provided with a valve for controlling the air flow therethrough, the first support means forming said wall means and being shaped to generate in the front part of said propeller the depression area favorable for cavitation of the propeller, the second support means being constituted by the first support means, the first support means being shaped to support said air duct, the first support means being hollow and enclosing the air duct and the first support means generates in the front part of said propeller the depression area favorable for cavitation of the propeller.
- 2. The device as claimed in claim 1, wherein a ratio of a cross-section of the air flow duct to an area of a disc generated by the propeller is between 1:5 and 1:50.
- 3. The device as claimed in claim 1, wherein a plurality of propellers are provided and wherein the air flow duct and means for generating a depression area are provided in correspondence with each of the propellers.
- 4. A device with a cavitational effect for propellers used for propulsion of watercraft, the device comprising an air flow duct and means for generating a depression area, the air flow duct having an outlet adjacent a propeller, the air flow duct withdrawing air from above a hull water line and releasing the air from the outlet in front of a propeller, the means for generating the depression area comprising a support means which supports at least a portion of the air duct, the support means being readily adjustable relative to the propeller to generate the depression area in front of the propeller and to positionally set the outlet of the air duct along the diameter of the propeller from at least a central portion of the diameter to a position beyond the tips of the blades of the propeller.
- 5. The device as claimed in claim 4, wherein a plurality of propellers are provided on the watercraft and wherein an air flow duct and means for generating a depression area are provided in correspondence with each of the propellers.
- 6. The device as claimed in claim 4, further comprising a pin and a hydraulic cylinder-piston, the air flow duct being formed with a flap operatively connected to the hull of the watercraft by the pin, the hydraulic cylinder-piston being connected to the flap and the flap being pivotable about the pin by movement of the hydraulic cylinder-piston, movement of the flap varying positioning of the outlet of the duct relative to the propeller.
- 7. The device as claimed in claim 4, wherein a ratio of a cross-section of the air flow duct to an area of a disc generated by the propeller is between 1:5 and 1:50.
- 8. A device with a cavitational effect for propellers for propulsion of watercraft with a planing or semiplaning keel, comprising an air flow duct and wall means for generating a depression area, the air flow duct having an outlet adjacent a propeller, the air flow duct withdrawing air from above a hull water line and releasing the air from the outlet directly to a front part of at least the propeller and the wall means generating the depression area in the front part of the propeller, the device further comprises first support means for said propeller and second support means for said duct, a top of said air flow duct being in communication with the atmosphere above the water line, said second support means forming said wall means and being readily adjustable relative to said propeller to generate in the front part of said propeller the depression area favorable for cavitation of the propeller and to positionally set the outlet of said air duct along the diameter of said propeller from at least a central portion of the diameter of the propeller to a position beyond the tips of the blades of the propeller.
- 9. The device as claimed in claim 8, wherein an air flow duct is provided in correspondence with each propeller present in the watercraft in which the device is mounted.
- 10. The device as claimed in claim 8, wherein said support means of said air flow duct is formed by at least a flap operatively connected to the watercraft hull by pin means and hydraulic cylinder-piston means, which enable said flap to be moved relative to said propeller with consequent variation in positioning the outlet of said duct relative to the propeller.
Priority Claims (1)
Number |
Date |
Country |
Kind |
20092 A/88 |
Apr 1988 |
ITX |
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CROSS REFERENCE TO RELATED APPLICATIONS
This is a continuation-in-part of application Ser. No. 07/333,541 filed on Apr. 5, 1989, now U.S. Pat. No. 5,046,975.
US Referenced Citations (5)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
333541 |
Apr 1989 |
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