92 November 15, 1999

Roll Dampening on the Grand Banks

Longtime Newfoundland fisherman Vernon Petten of Port_De_Grave isn't afraid of trying something new. For his most recent boat, the 65x23_foot "Newfoundland Clipper" he installed his first Cummins in the engine room and up on top of the boat's shelter deck, he installed his first roll dampener. He chose the 600 HP Cummins KTA19_M3 main engine because of the company's good service reputation. He installed the anti_roll tank because, unlike the more common "flopper_stoppers" which can cost the boat one knot of speed, the tank allows the boat to maintain its regular speed.

Designed by Dr. Don Bass, at the Faculty of Engineering and Applied Science, at Memorial University of Newfoundland, the tank on Petten's boat is built into the shelter deck cover a few feet aft of the forward mounted deckhouse. Extending nearly the full width of the boat, it is 20 feet long by about 4.5 feet high. The middle of tank narrows to about three feet and bells to around five feet at the extremities. Near the ends of the tank, baffles are installed to reduce the slapping effect on the tank ends, as well as to approximate the natural frequency of the boat in various load conditions. This is the twelfth tank that Bass has designed for Newfoundland fishboats in the 55 to 65_foot range. Even for the regulated 65_foot length, "Every tank is different," explains designer Bass, "I tune each for mid_load conditions."

Bass adds that the tanks are favoured by fishermen, not only for the speed savings, as they are maintenance free and don't interfere with the gear when the boat is fishing. His research has shown them to reduce roll by 55 percent at all speeds compared with the flopper stoppers which range from a 45 percent reduction at cruising speed to only 25 percent at fishing speeds. Bass is currently designing a tank for a 45_footer.

Vernon Petten and his son Blair took delivery of the "Newfoundland Clipper" from her builders at Universal Marine Ltd. in Triton, Newfoundland, last August and put her right to work trawling shrimp. On November 12 under the command of Blair Petten she was headed out in 45_knot winds to the Grand Banks for crab. In shallower 90 to 150_fathom waters, they fish 400 round stackable traps on five strings of 80 traps. For the 400_fathom depths outside the 200_mile limit, to which an exploratory trip will take them, they will remove every other trap to get down to 30 traps per string and reduce the weight when hauling back the 9/16_inch poly steel ground_line.

The "Clipper" is currently set up as an ice boat. Although her refrigeration can take the hold below freezing, for the live crab they hold it to seven degrees celsius. The crabs are iced in 50 pound pans and stowed. The trip 200 miles out to the Grand Banks will involve around 1.5 days running to the grounds, two days fishing and another 1.5 days travelling back in. The crabs stay in good live shape for up to three days onboard. Recent trips have ranged around only two percent delivered in "weak" graded condition and these still have fetched the optimum live price of $1.92 (Can.).

The "Newfoundland Clipper" design work was done by David Porter or the St. John's naval architect firm CEC Marine Ltd. The Petten's matched their Cummins KTA19 to a Twin Disc MG5170 gear with a 5.95:1 reduction. Vernon likes to take the conservative approach to power so has the engine set up for 600 HP at 1800 RPM rather than the optional 640 HP. "We usually cruise at only 1600 RPM and get 8.5 knots out of the boat, but we can put her up to 1800 RPM and get ten knots," he says. That flexibility is important when fishing or weather conditions hold you up on a live delivery.

Universal Marine Ltd., the builder of the "Newfoundland Clipper" is currently building another 65_foot fibreglass fishing vessel for Mr. Maurice Noonan. A sister ship to Vernon's boat, it will be powered by a Cummins KTA19 M3 rated at 640 HP and linked to a ZF BW191_1 gear with a 6:1 reduction. Universal Marine president, Robert Starks, explains, "We build these boats as one_off using a functional male mold. Much of the wood in the mold becomes incorporated in the hull to give it added strength. Both Maurice and Vernon's boats are ice strengthened with 2.5_inches around the waterline at the bow. At 170 tons actual weight, these boats are the heaviest we have built and the heaviest that I know of."

For more information:

Vernon Petten
P.O. Box 58
Port_De_Grave,Newfoundland
Phone: 709 786_6170

Mr. Robert Starks
President Universal Marine Ltd.
Triton, Newfoundland
Phone: 709 675_2076 or 709 263_2544

Harris Mosdel Cummins Eastern Canada Inc.
122 Clyde Avenus Mount Pearl
NFLD A1N 4S3, Canada
Phone: 709_747_0176 Fax: 709_364_4930

Dr. Don Bass
Faculty of Engineering and Applied Science
Memorial University of Newfoundland St. Johns, NFLD
Phone: 709 737_8950
E-mail: dbass@engr.mun.ca

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