Magnus Effect Devices - Active Trawl System

The Magnus Effect and other Rotor Devices First Observation The effect was first noticed in the 17th century in connection with inaccuracies when firing cannonballs and was

investigated by Heinrich Magnus. He developed a theory to account for this. Although it has been shown that his

theory was not valid, the effect is still known as the "Magnus Effect". Flettner's Rotor Ships In his search for a "simple and more efficient way of using the free wind

power available", Anton Flettner came up with the idea of using the Magnus Effect. In 1926, the three-masted schooner rig on the 52m "Buckau" was

replaced by two rotors. Each rotor was 18m high and 2,7m in diameter. She exceeded all expectations, being faster than before and able to sail much

closer to the wind. Because of this success, the Transportation Department of the German

Navy ordered the construction of another rotor ship, the "Barbara". She

was 92m long and fitted with three rotors. Each rotor was 17m high, 4m in

diameter and driven at 150 rpm by a 27 kW electric motor. The "Barbara"

carried 3000 tons of cargo and a few passengers. She plied between

Hamburg and Italy for six years. Depth Control System for Midwater Trawls In 1965, the Gloucester Exploratory Fishing and Gear Research Base of the

Bureau of Commercial Fisheries, together with Mt. Auburn Research

Associates, Inc., of Cambridge, Mass., started a programme of research on controllable depth trawl doors. This led to the development of a rotor door. In view of the apparent advantages of a rotor device in controlling the

depth, the programme was extended to laboratory studies. Tests at the

Massachusetts Institute of Technology confirmed the predicted lift

coefficients and the stability of the design. Two operational prototypes were built, with rotors 1m in long and 0,15m in diameter, driven at 200 to 1200 rpm. Sea trials aboard the "Rorqual" were

very successful: at 3,3 knots the net could easily be raised to the surface

or lowered to more than half the warp length. R.G.I.T. Underwater Vehicle In 1975, a project was started at the Robert Gordon Institute of Technology, Aberdeen, to develop a high-speed

towed underwater vehicle for use in offshore engineering research activities. The vehicle consisted of a streamlined body with a rotor 1,4m long and 50mm in diameter projecting horizontally

from each side. Sea trials confirmed the predictions of downforce and stability. Thereafter design was started on a larger version capable of being towed at 12 knots at a depth of 300m. DAFS Marine Laboratory's Pelagic Trawl In 1970 the Marine Laboratory, Aberdeen, started the development of a

spinning rotor system for improving aimed pelagic trawling.

In their first system, rotor devices were installed in the lower halves of

Suberkrub otterboards. Sea trials aboard FRV "Explorer" during 1973 and 1974

indicated that the measured changes in heel angle and depth were in

agreement with those predicted by a simulation study. Larger rotors were installed in their second system. Sea trials in July 1974

showed that "operation of the rotors quickly produced significant vertical

movement of the gear". In their third system, the rotor was placed in the centre of the otterboard over the full height. Sea trials aboard the FRV "Scotia" in January 1978 showed that

"rotation of the rotors in the same direction produced sideways movement of

the gear and increased the potential swept area by a minimum of 72% without

altering ship's course; alternatively, spread could be increased by 41% by

rotating the rotors in opposite directions". The Marine Laboratory Remote Controlled Towed Vehicle The need for observations of fishing gear at depths greater than 100m led to

the building, in 1978, of a prototype RCTV using rotor devices. A working

model was built in 1982. It uses two pairs of rotors at right angles to each

other to provide both lateral and vertical movement. Each rotor is 550mm long and 150mm in diameter.

Guard rails and skids prevent damage and snagging on the fishing gear. The

vehicle is joy-stick controlled and is presently being used for the observation of trawl gear and fish reactions. The Voith Schneider Turbo Fin The Voith Turbo Fin is a rotating cylinder at the end of the skeg. It ensures

stable flow and increases lift by virtue of the larger angle of attack. As a

result, significantly higher transverse forces can be achieved - a useful

advantage on escort duties in particular. The steering force of a Voith Water

Tractor Tug with Voith Turbo Fin is up to 25 percent greater than that of a

conventional tractor. This increased steering force enhances the safety of ships carrying hazardous loads, such as oil tankers, when they are escorted by Voith Water Tractors in difficult waters. Retrofitting is relatively simple and inexpensive. Van Der Velden Rotor Bow Rudder The rotor bow rudder was specially developed for vessels with large wind surface areas, such as container vessels and push boats with large barge convoys. The rotor bow rudder is based on the Magnus effect principle. A pressure differential is generated by placing a rotating cylinder in an oncoming

water current which results in a thrust force larger than a conventional

rudder. The rotor bow rudder also takes up very little precious onboard space. The latest installation is on the MV Vector, a vessel 135m long and 11.45m

breadth. Quantum MagLift Stabilizer The Quantum MagLift™ stabilizer is based on the Magnus effect. It

uses hydraulic power to deploy and rotate composite cylinders for

roll reduction at anchor, and at lower speeds. It is retractable for

higher speed passages, and used typically on sport fishing vessels

and large yachts. E-Ship 1 E-Ship 1, launched in 2009 is owned by German wind power

company, Enercon GmbH and is used to deliver wind turbine

components around the world. The 130m long vessel has, in

addition to her conventional diesel propulsion, 4 Flettner rotors

27m tall and 4m in diameter which allow for projected fuel savings

of 30-40% at 16 knots. THiiiNK THiiiNK is a leading developer of fuel and

emissions reduction technologies for the

global shipping industry. Its latest product