US3799103A - Stern drive unit trim tab - Google Patents

Stern drive unit trim tab Download PDF

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Publication number
US3799103A
US3799103A US00266234A US26623472A US3799103A US 3799103 A US3799103 A US 3799103A US 00266234 A US00266234 A US 00266234A US 26623472 A US26623472 A US 26623472A US 3799103 A US3799103 A US 3799103A
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US
United States
Prior art keywords
trim tab
stern drive
propeller
rearward
drive unit
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 - Lifetime
Application number
US00266234A
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English (en)
Inventor
L Granholm
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Outboard Marine Corp
Original Assignee
Outboard Marine Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Outboard Marine Corp filed Critical Outboard Marine Corp
Priority to US00266234A priority Critical patent/US3799103A/en
Priority to CA167,443A priority patent/CA974822A/en
Priority to JP48071380A priority patent/JPS5912513B2/ja
Application granted granted Critical
Publication of US3799103A publication Critical patent/US3799103A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63H—MARINE PROPULSION OR STEERING
    • B63H25/00—Steering; Slowing-down otherwise than by use of propulsive elements; Dynamic anchoring, i.e. positioning vessels by means of main or auxiliary propulsive elements
    • B63H25/42—Steering or dynamic anchoring by propulsive elements; Steering or dynamic anchoring by propellers used therefor only; Steering or dynamic anchoring by rudders carrying propellers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63H—MARINE PROPULSION OR STEERING
    • B63H20/00—Outboard propulsion units, e.g. outboard motors or Z-drives; Arrangements thereof on vessels
    • B63H20/32—Housings
    • B63H20/34—Housings comprising stabilising fins, foils, anticavitation plates, splash plates, or rudders

Definitions

  • the invention relates generally to marine propulsion devices. More particularly, the invention relates to stern drive units and to trim tabs or exhaust snouts for such stern drive units.
  • trim tabs In order to overcome such steering torque, trim tabs have been employed for some time on stern drive units. Such trim tabs project into the wake of the propeller and have served as rudders to counteract the steering torque developed by the stern drive unit. However, the amount of such counteraction developed by the trim tabs has varied with the speed of the boat. Thus, if the trim tab more or less perfectly counterbalanced or neutralized steering torque at high speeds, there remained an unbalanced condition at low speeds, and vice versa.
  • the side of the trim tab subject to impact or thrust from the rearwardly revolving stream of water displaced by the propeller is referred to herein as the pressure side.
  • the invention provides a stern drive trim tab adapted to approximately neutralize stern drive steering torque under both high and low speed conditions.
  • the invention provides a stern drive unit trim tab which includes a side having one or more vertically extending steps provided by a rearwardly located pressure side portion which, in relation to the forward portion of the pressure side, is located in laterally offset relation toward the other side of the trim tab.
  • the invention also provides a trim tab wherein both sides thereof are outwardly convexly formed and in which the side opposite the pressure side, i.e., the lift side has a greater convex curvature.
  • trim tab for a stern drive unit, which trim tab operates to more uniformly counterbalance or neutralize stern drive steering torque at both high and low speeds.
  • Another of the principal objects of the invention is to provide a stern drive unit including a trim tab having forwardly and rearwardly stepped pressure side portions.
  • Another of the principal objects of the invention is the provision of a trim tab wherein each of the sides is outwardly convexly formed and wherein the convex curvature of the lift side is greater than the pressure side.
  • FIG. 1 is a fragmentary side elevational view of a stern drive lower unit incorporating various of the features of the invention.
  • FIG. 2 is a fore and aft sectional view of a portion of the stern drive lower unit shown in FIG. 1 and particularly illustrating the trim tab.
  • FIG. 3 is a rear end view of the portion of the stern drive lower unit shown in FIG. 2.
  • FIG. 4 is a bottom view of the portion of the stern drive lower unit shown in FIG. 2.
  • a stern drive lower unit 11 which includes a drive shaft housing 13 rotatably supporting a drive shaft 15.
  • the stem drive unit can be either a generally upright lower unit as shown, for instancev in the Shimanckas U.S. Pat. No. 3,183,880 issued May IS, 1965 or can be a so-called slant" stern drive unit.
  • the drive shaft 15 is connected to a propeller shaft 17 by means which can include a reversing transmission 19 of conventional construction.
  • Carried by the propeller shaft 17 is a propeller 21 which is also of conventional construction.
  • the drive shaft 15 is driven by an engine (not shown) in the counterclockwise direction as viewed from above.
  • the propeller 21 rotates in the clockwise direction when seen from behind and in the counterclockwise direction when seen from in front.
  • trim tab or exhaust snout 23 Carried on the drive shaft housing 13 above and rearwardly of the propeller 21 is a trim tab or exhaust snout 23 which can be conventionally employed to discharge exhaust gases into the propeller wake and to include a water inlet for an engine cooling system.
  • trim tabs have been employed to counterbalance steering torque.
  • previous trim tabs have sometimes been angularly adjustably mounted as shown in the Canadian Kiekhaefer Pat. No. 687,868 so as to permit selective location thereof depending upon the direction of rotation of the propeller and so as to provide optimum results at a particular speed.
  • the trim tab 23 includes a pressure side or face 25 against which the rearwardly moving stream of water is driven and a laterally opposed or lift side or face 27.
  • the trim tab 23 includes means for more or less uniformly neutralizing or approximately counterbalancing steering torque throughout the operating speed range. While other arrangements could be employed, in the illustrated construction, the trim tab 23 is formed so that the pressure side 25 includes a forward portion 29 and a rearward portion 31 which is laterally offset from the forward portion 29 in the direction toward the lift side 27.
  • trim tab 23 could be provided, in accordance with the invention, with a plurality of steps.
  • the illustrated trim tab 23 is provided with a hollow interior which forms a gas passage 33 adapted to communicate with an exhaust gas passage 35 within the drive shaft housing 13.
  • the hollow interior of the trim tab 23 terminates with a lower exhaust gas outlet 37 at the bottom or lower margin of the trim tab 23 and with a rearward exhaust gas outlet 39 at the rear or aft margin of the trim tab 23.
  • only one of the lower and rearward exhaust gas outlets 37 and 39 could be employed.
  • the lower and rearward outlets 37 and 39 could be integrated into a single outlet extending continuously along the bottom and rear of the trim tab. Other outlet arrangements can also be employed.
  • trim tab 23 is not so constructed, a trim tab could be constructed in accordance with the invention with a water inlet for a cooling system.
  • the trim tab 23 is mounted to the drive shaft housing 13 immediately below the cavitation plate 41 and rearwardly and above the propeller 21 to afford angular adjustment in the position of the trim tab 23 to accommodate forward propeller operation in either rotative direction and to permit location in the position of maximum over-all effectiveness.
  • Such mounting can be accessible solely from within the hollow interior of the trim tab 23 or can be accessible, at least in part, from the exterior of the trim tab 23.
  • the rearwardly revolving stream of water flowing from the propeller 21 effectively reacts with both the forward and rearward portions 29 and 31 of the pressure side 25 of the trim tab 23 to produce a maximum counterbalancing effect which approximately neutralizes steering torque.
  • the rapidly rearwardly moving and revolving stream of water flowing past the pressure side 25 of the trim tab 23 is believed to effectively react with only the forward portion 29 of the pressure side 25 because of the presence of the step between the forward and rearward portions 29 and 31 and the rapidity of the rearward water movement.
  • the counterbalancing effect which is produced is less than would have occurred in the absence of the step and approximately neutralizes steering torque at high speed. Consequently, the trim tab 23 acts to approximately neutralize steering torque during both high and low speed operation.
  • the forward portion 29 of the pressure side 25 and the lift side 27 are, referring to a fore and aft plane, nonsymmetrical with respect to each other. More specifically, while both the pressure side 25 and the lift side 27 are outwardly convexly curved, the lift side 27 has a greater amount of curvature, i.e., has a shorter radius than the pressure side 25. However, the curvature provided for each side can be compound, i.e., need not extend at a uniform radius from a single center. Such nonsymmetry serves to assist in the operation of the trim tab.
  • FIG. 5 of the drawings shows, in dotted outline, the provision of a stepped or offset surface 40 on the lift side 27, which surface 40 is located rearwardly on the lift side and is offset in the direction of the pressure side 25.
  • a stern drive lower unit comprising a lower portion which is at least partially submerged during normal operation and which includes a rotatably mounted propeller shaft, a propeller carried on said propeller shaft for rotation therewith, and a trim tab which is located rearwardly and above said propeller shaft and which includes two side surfaces, one of said side surfaces being subject to impact by water propelled by said propeller and including a forward portion, a rearward portion offset from said forward portion in the direction toward the other of said side surfaces, and a step connecting said forward and rearward portions.
  • a stern drive unit in accordance with claim 1 wherein both said side surfaces are convexly outwardly curved and wherein the convex outer curvature of said other of said surfaces is greater than the convex outer curvature of said one of said surfaces.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Structure Of Transmissions (AREA)
US00266234A 1972-06-26 1972-06-26 Stern drive unit trim tab Expired - Lifetime US3799103A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US00266234A US3799103A (en) 1972-06-26 1972-06-26 Stern drive unit trim tab
CA167,443A CA974822A (en) 1972-06-26 1973-03-28 Stern drive unit trim tab
JP48071380A JPS5912513B2 (ja) 1972-06-26 1973-06-26 船尾駆動下部ユニツト

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00266234A US3799103A (en) 1972-06-26 1972-06-26 Stern drive unit trim tab

Publications (1)

Publication Number Publication Date
US3799103A true US3799103A (en) 1974-03-26

Family

ID=23013732

Family Applications (1)

Application Number Title Priority Date Filing Date
US00266234A Expired - Lifetime US3799103A (en) 1972-06-26 1972-06-26 Stern drive unit trim tab

Country Status (3)

Country Link
US (1) US3799103A (ja)
JP (1) JPS5912513B2 (ja)
CA (1) CA974822A (ja)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304557A (en) * 1980-01-04 1981-12-08 Outboard Marine Corporation Hydro torque skeg foil
US4352666A (en) * 1980-08-11 1982-10-05 Outboard Marine Corporation Marine propulsion device with trim sensitive movable trim tab
DE3332868A1 (de) * 1982-09-13 1984-03-15 Aktiebolaget Volvo Penta, 40508 Göteborg Bootsschraubenantriebseinheit
US4694645A (en) * 1984-05-23 1987-09-22 Kamewa Ab Propeller assembly
US4738644A (en) * 1987-02-27 1988-04-19 Thomas Happel Outboard motor attachment and method
US4810218A (en) * 1986-07-10 1989-03-07 Sanshin Kogyo Kabushiki Kaisha Marine propulsion device
US5085603A (en) * 1990-12-19 1992-02-04 Brunswick Corporation Marine drive with steering torque compensation
US6113443A (en) * 1999-05-10 2000-09-05 Brunswick Corporation Trim tab for jet propulsion system
US20190077492A1 (en) * 2017-02-24 2019-03-14 Edken Laboratories, LLC Rudder technologies for outboard motors
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

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1744138A (en) * 1927-12-02 1930-01-21 Oertz Max Arrangement of cutwater rudders for ships
US1837896A (en) * 1928-08-02 1931-12-22 Costanievich Leone Method of promoting propeller efficiency and means thereof
US3537419A (en) * 1969-08-18 1970-11-03 Outboard Marine Corp Marine engine exhaust system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3029769A (en) * 1961-02-13 1962-04-17 Kiekhaefer Corp Adjustable exhaust snout for outboard motors

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1744138A (en) * 1927-12-02 1930-01-21 Oertz Max Arrangement of cutwater rudders for ships
US1837896A (en) * 1928-08-02 1931-12-22 Costanievich Leone Method of promoting propeller efficiency and means thereof
US3537419A (en) * 1969-08-18 1970-11-03 Outboard Marine Corp Marine engine exhaust system

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304557A (en) * 1980-01-04 1981-12-08 Outboard Marine Corporation Hydro torque skeg foil
US4352666A (en) * 1980-08-11 1982-10-05 Outboard Marine Corporation Marine propulsion device with trim sensitive movable trim tab
DE3332868A1 (de) * 1982-09-13 1984-03-15 Aktiebolaget Volvo Penta, 40508 Göteborg Bootsschraubenantriebseinheit
US4694645A (en) * 1984-05-23 1987-09-22 Kamewa Ab Propeller assembly
US4810218A (en) * 1986-07-10 1989-03-07 Sanshin Kogyo Kabushiki Kaisha Marine propulsion device
US4738644A (en) * 1987-02-27 1988-04-19 Thomas Happel Outboard motor attachment and method
US5085603A (en) * 1990-12-19 1992-02-04 Brunswick Corporation Marine drive with steering torque compensation
US6113443A (en) * 1999-05-10 2000-09-05 Brunswick Corporation Trim tab for jet propulsion system
US20190077492A1 (en) * 2017-02-24 2019-03-14 Edken Laboratories, LLC Rudder technologies for outboard motors
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

Also Published As

Publication number Publication date
JPS4950691A (ja) 1974-05-16
JPS5912513B2 (ja) 1984-03-23
CA974822A (en) 1975-09-23

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