Energy-Saving Skegs Proven In Barge Service
A Canadian invention said to reduce the power needed to tow loaded barges by up to 30 percent, introduced in 1976, has seen successful operation for the past four years fitted to a fleet of four 400-foot by 100- foot by 25-foot, 16,500-dwt semisubmerging barges.
Developed by Seaspan Development Company Ltd. in Vancouver, British Columbia, the device was conceived by Yugoslavia-born naval architect Josip Gruzling. It represents a dramatic breakthrough in skeg design, enabling a loaded barge to be towed at a higher speed with the same output of power, or at conventional speeds with a reduction in power of from 20 to 30 percent.
Jacques Heyrman, vice president of Seaspan Development Company, which holds the U.S., Canadian, and foreign patents for the device, said that fuel consumption costs can be reduced by 20 percent or more if towed barges are equipped with the new skegs. Traditionally, skegs have made a major contribution to barge transportation in all the oceans of the world. In the Pacific Northwest and elsewhere the first barges were converted sailing ship hulls towed behind a powered vessel. At the end of the towing line these hulls yawed and spun like a waterlogged kite. There were instances of the towing vessel being yanked out of control by the barge it was towing. Then someone invented the skeg, simply two blades or fins attached vertically to the stern of a barge and angled outward to the main axis of the hull. When the barge is towed, the two skegs exert a drag and automatically counter the barge's tendency to move sideways.
Conventional skegs increase total barge resistance by as much as 50 percent. The Hydralift Skegs not only provided directional stability but eliminated skeg drag almost entirely. It was proven by recent model tests at the tank test of B.C. Research that resistance was reduced to nearly that of the bare hull. Under ideal conditions it is theoretically possible to achieve a total barge resistance to slightly less than that of the bare hull due to the propulsive component of the lift generated by the skegs.
Since then, three sister barges have been similarly equipped. The Hydralift Skeg arrangement is the same for all four barges.
As seen in the accompanying photograph, a set of three foils is joined at the port and starboard corners of the after-rake. Each set of three foils is joined at the bottom by a horizontal member, also of airfoil shape. Mr. Heyrman described the invention of the Hydralift Skegs as an amazingly simple and obvious concept. "It was simply a matter of transferring known principles from an air medium to a water medium," he said. "No moving parts, and yet this skeg system saves fuel and energy. To say the least, it is even a more timely invention today in view of the escalation in fuel prices over the past four years." For further information on the Hydralift Skeg,