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Stepped trim tab

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Stepped trim tab

The invention relates to a trim tab for watercraft, the inclinable tab of which has gradations having breaking edges, and in front of the sections having a breaking edge on the bracket. The active cylinder is assisted by a gas spring which may also be blockable, and which is released by means of the active cylinder. Underwater lamps that are affixed on the outflow side have a spread angle, and the underwater lamps have a metal housing which is connected to the tab for dissipating waste heat.

USPTO Applicaton #: #20140026800 - Class: 114286 (USPTO) -
Ships > Hull Or Hull Adjunct Employing Fluid Dynamic Forces To Derive A Lift Or Alter Trim, (e.g., Planing Hulls, Etc.) >Movably Mounted Hull Portion Or Hull Adjunct >Trim Tab Or Hull Plate >With Fluid Motor

Inventors: Peter A. Mueller

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The Patent Description & Claims data below is from USPTO Patent Application 20140026800, Stepped trim tab.

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The invention is directed to a trim tab, having a graduated base and side walls, for watercraft, according to the preamble of Claim 1.


Trim tabs are used for improving the glide angle of watercraft, and displace the corresponding buoyancy zones by means of flow deflections to allow more favorable weight distributions and/or to facilitate quicker initiation of gliding of the vehicle, as described in U.S. Pat. No. 3,628,487 or also US 2004/0014376 A1.

Recently, other systems on the market, for example lowerable damming wedges, have been described in patents TW 499382 B and U.S. Pat. No. 6,006,689, among others.

It is now becoming increasingly common to mount underwater lamps on trim tabs, since trim tabs do not require large mounting holes in the side of the ship.


For a trim tab for watercraft of the type mentioned at the outset, the object of the invention is to achieve effective trim with maximum buoyancy and minimum resistance values at lower as well as higher speeds, which is accomplished by graduating the base surface of the trim tab and at the same time raising the side walls at the trim tab. The action of the active cylinder for displacing the trim tab is assisted by means of a gas traction spring or gas pressure spring. In addition, the trim tab should generate a specialized light at night which allows consistent safety-relevant visibility when maneuvering in a port where there is minor light pollution, and which at the same time creates a specialized lighting effect at the stern of a watercraft, which may be directed onto the specialized trim tab and which allows effective heat dissipation by means of suitable materials.

Trim tabs are indispensible in watercraft, and as the result of lowering one or both tabs, a change in the vehicle position in the water is produced which in the longitudinal axis should be as horizontal as possible, and in the transverse axis should have a slightly positive setting angle, so that the vehicle is able to glide through the water with the least resistance possible, and the passengers thus automatically have a better feeling of well-being when the base of the vehicle is more or less horizontal and steady in the water. This is made possible by means of one or more gradations having breaking edges on the trim tab base, which allows use of longer trim tabs, and thus, production of the same change in trim angle on the vehicle as with short trim tabs, at a smaller setting angle, and at the same time with lower overall resistance. At higher speeds, at which the resistance is disproportionately noticeable, the wetted surface area is decreased by means of the gradations, so that above a certain speed the friction has little or no action due to the fact that the flow breaks away at the gradations of the trim tab, and therefore the contact surface of the trim tab base with the water is separated, the frictional resistance is thus reduced, and a higher final speed of the vehicle is made possible or less fuel consumption results. The gradations may also be easily produced by cutting plastic plates to various lengths and sharply contouring them on the outflow side and connecting them to the tab, which at the same time results in a desired reinforcement of the trim tab and thus subjects the tab to less torsion.

It is self-evident that, by means of the longer trim tabs on the exterior of a watercraft, rolling while at anchor as well as pitching due to the lever length of the trim tabs is improved, since the trim tabs act as baffle plates or stabilizers.

The primary purpose of raising the side walls at the trim tabs is to ensure that little or no water flows onto the tabs at moderate speeds, so as to consistently guarantee optimal buoyancy, and at the same time to positively influence the flow and produce a type of artificial extension of the hull; otherwise, the flow would combine at the stern too quickly, possibly resulting in corresponding turbulence, even eddying, which is extremely detrimental for the efficiency of a hull.

The active cylinder may also be assisted by a gas spring. In particular for an electric active cylinder having a spindle; this results in a new concept of activation, since the gas spring may provide practically the same extension force as the active cylinder, and therefore the overall power for lowering the trim tab may be almost doubled. For this purpose, the active cylinder must correspondingly deliver more power during raising of the trim tab, since the gas spring always presses against same. In addition, the gas spring may be blocked by means of a check valve, so that the entire load of the trim tab does not rest on the spindle and spindle nut, but instead, the load is also supported by the gas spring.

Furthermore, underwater lamps are mounted on the trim tab with a deflection angle from one underwater lamp to the other, so that good illumination of the body of water downstream from the watercraft is still achieved, using focused light with fewer powerful lamps for this purpose, and thus eliminating the light pollution, which now also surrounds the vicinity of the body of water, without impairing the quality of the visibility conditions.

According to the invention, this is achieved by the features of claim 1, which by means of gradations on the tab base allow the flow to break away cleanly in each case at appropriate speeds by means of breaking edges, and thus allow the resistance to be reduced, resulting in a higher final speed of the vehicle or less fuel consumption at cruising speed, and by means of a gas spring are used as assistance for the active cylinder and the appropriately placed underwater lamps, which require less power and less light and nevertheless allow equivalent safety-relevant visibility downstream from the watercraft compared to conventional, more powerful lamps. The core of the invention is to achieve a completely efficient trim tab which uses less energy and achieves the same or better results with regard to trim of a watercraft by means of gradations and breaking edges, to assist the active cylinder in terms of force by means of a gas spring, and to ensure good visibility at night downstream from a watercraft, using less light energy.

Further advantageous embodiments of the invention result from the subclaims.


Exemplary embodiments of the invention are explained in greater detail below with reference to the drawings. Identical elements are provided with the same reference numerals in the various figures.

The drawings show the following

FIG. 1 shows a schematic side view of a graduated trim tab which is pivotably mounted to the stern of a watercraft by means of a bracket, together with an active cylinder and a gas spring, as well as a blocking cable for the gas spring; and

FIG. 2 shows a schematic three-dimensional view of a graduated trim tab having the gradations, the fastening for the active cylinder by means of an emergency bolt, and the reinforcements on the base plate, the side walls, and the individually angled underwater lamps.

Only the elements which are essential for the direct understanding of the invention are schematically shown.


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