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Northern Transportation Com-pany Ltd. of Hay River, Canada,

recently completed a major refit ofone of their quad screw pusher-

towing tugs, the Edgar Kotokak.Vancouver's Robert Allan Ltd. pro-vided design and engineering ser-vices for the refit which improvedthe operational efficiency of the tug.The refit included new CAT 3512Bengines and replaced the open pro-

pellers and rudders with integratedNautican Nozzles and Triple Rud-ders. The results says MikeWhittaker, Captain of the EdgarKotokak, are "superb."

Although total engine powerncreased from 4,500 to 5,640 hp on

the Edgar Kotokak, and obviously

bollard pull trials showed improve-ment, anecdotal evidence from thefirst month or so of operation seemsto indicate that both the nozzles and

Triple Rudders together with thenew engines have improved theoverall fuel efficiency. As one offour of NTCL's 'tower tugs', this refits also allowing a comparison of

open propellers to both Kort and a

type of high efficiency nozzles.Originally designed by Robert

Alllan Ltd. (RAL) and built in the1973, the 153 foot long Edgar Koto-kak had, as her sistership the Henry

Christoffersen still does, four openpropellers in tunnels for propulsion

with twin, transom hung ruddersbehind each prop for steering. Theother tugs, the Kelly Ovayuak andJock McNiven, use four Kort Noz-zles in tunnels, each with twin rud-

ders aft inside the tunnel. All the tugsoriginally had the same engines.

NTCL is a pan-Arctic marineoperator, providing comprehensivemarine transportation and relatedservices throughout Northern Canadaand the Arctic. The Edgar Kotokakworks on the Mackenzie River be-

tween Hay River and Tuktoyaktukduring June, July, and after October1st. In August and September, iceconditions improve enough that italso works in the Beaufort Sea and

Coronation Gulf.Working in the Mackenzie River

poses many problems. Pat Williams,Manager Marine Engineering, West-ern Arctic, for NTCL, says, "there's alot of shallow water. In dry years itcan be really difficult, not only doesthe depth decrease but the channels

narrow as well. Coast Guard does a

good job with Aids to Navigation,marking the channel, but no one doesany dredging." And the river levelcan vary substantially in a givenyear. "I've seen it fluctuate 8 ft. in aweek," says Williams. Another prob-lem is rocks and ice going throughthe propellers and rudders.

Going up- or down-river eachpresent their own problems. Typi-cally the tugs push, from the middleaft barge, two rows of three barges

abeam. Because the Mackenzie flowsso fast, including parts where thecurrent averages 5 to 6 knots, going

downstream is not taxing on the en-gines, but is a challenge for keepingthe barges in the channel. There arealso about four areas, where the rap-ids are fast enough that the tows haveto be broken up before can proceed

though them. Going upstream can bedifficult because more horsepower isrequired; although going against thecurrent slows things down, allowingthe tows to consist of up to 4 rows of

three barges across.Williams provides an example of

the difficult areas. "There's a rockshelf in the river just before Fort

Good Hope, called the 'Ramparts'. Indry years the boats have to actuallypush the barges uphill. You can seethe angle they make as they go over."This led to one observation on the

differences between open propellersand ones in nozzles. He reports that,"Only the nozzle boats could pushthe bigger barges through."

The second observation was onthe maintenance of the rudders. Be-hind the open propellers, the ruddersare, states Williams, "very highmaintenance because of vibration.The linkages and pins needed replac-

ing every two years. They aresusceptible to being knockedboth from the props spittingthrough and by backing too clothe river banks. We noticed theders on the Kelly O. have needed the pins changed once years."

The refit was undertaken besays Williams, "the hulls are finthe design works well but [enparts are starting to be a bit

issue. We also wanted to upgradcapacity to save time." He addlooks like the [Mackenzie V

pipeline is coming, and we areting ready." So besides all four D399 V16 engines (1,125 hp at rpm) being replaced with 3512B Electronic engines (1,41at 1,600 rpm) and the 56-in.

propellers along with each's rudders replaced by 58-in. integNautican Nozzles and Triple ders, new custom Lufkin transions and a Jastram twin-indepe

steering system were installed.One reason Nautican's no

were used was NTCL was hwith the improved performance

resulted after the retrofit of NauNozzles to their three arctic vessels. Additionally, Williamports that, "the nozzles take a bebecause they bounce off the bo

and rocks get spat through. they've stood up well though Joe Gruzling, President of NauResearch and Development

agrees, "it looks like they stanvery well to the bouncing onbottom." He says this is, "due tosolid construction with no welds."

Marine NewsSeptember 20, 2003

Northern Transportation Company Ltd. Of Hay River, Canada, recently completed a major refit of one of

their quad screw pusher-towing tugs, the Edgar Kotokak

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For shallow water operation theoats have tunnels to be able to usearger diameter propellers. Following

he tunnel contour longitudinally aftlong the hull bottom, the surface ofhe tunnel actually rises to above the

waterline where the propeller located

efore descending again to below thewaterline to prevent the propellersrom sucking in air. Gruzling sug-ests the tunnels produce, "lots oferformance losses, especially inhallow water," because the props areimited where they can pull water inrom.

As well for shallow river opera-

on, the Kelly Ovayuak and JockMcNiven's Kort nozzles are not the

tandard 19A profile, but the type 22rofile. According to Gruzling, theype 22 is similar in profile to the

ype 19, but with a larger length toiameter ratio. The result is, "slightlyetter bollard pull, but much greaterrag and therefore worse perform-nce at higher speeds proportional tohe length." Gruzling had to adapt his

Nautican Nozzles for the shallowwater operation as well. "The bottom

f the nozzle is flattened and a large

egment of the nozzle is buried in theunnel."

This installation is the first shal-

ow draft application of the NauticanTriple Rudders and the first time thatNautican has supplied the nozzlesnd Triple Rudders integrated as onenit. Gruzling explains, "The nozzlesre built with a head-box that housedhe rudders together with the ruddertock, bearings, links and seals. Theudders are mounted on a removableover plate to have access for replac-

ng propeller. The idea is it saves aot of shipyard installation time."

Williams agrees, "It was a very easynstallation and definitely savedime."

Chris Mulder, Senior ProjectEngineer at RAL, supervised thebollard pull trials on the Hay River.

The accompanying figure shows thatnot only do the larger engines pro-duce more thrust as expected, from60,000 lbs to over 100,000 lbs, but

the Nautican Nozzles produce morethrust at the same horsepower, almost60% over the open propeller and10% over the Kort nozzle at 4,400hp. However the data from this test isnot complete.

Mulder explains that as there isno one mooring strong enough andclose enough to deep water to take

the 100,000 lb pull, a large bargewith a strong enough bollard was tied

off to several points on shore to actas the 'immovable object'. The EdgarKotokak was positioned about 300 ft.

away at a 45E angle to shore to bothbe in deep water and line up with thebarge. He reports that it was a bittricky keeping the tug and bargelined up in the current. The nextproblem was the tug's prop washbeing so large as to start backing upthe river, creating all sorts of weird

eddies, one of which set anotherbarge on the opposite bank free, tem-porarily halting the tests. After re-starting, the mooring lines of the

large barge began to break, stoppingthe tests altogether including ones formeasuring the astern bollard pull.Gruzling thinks these latter testswould have shown an even betterperformance comparison for the Nau-tican Nozzles.

Captain Whittaker reports thatyou can see the difference the noz-

zles make. "With the open wheel, theboat had a rooster tail. Now [thenozzles] are putting the power in thewater. We've added two knots to thetop end speed, we get 14 knots now.The Kelly O. and McNiven are lucky

to get 12." He also says that, "evenwith the bigger engines, its more fuel

efficient." He has one example, "Onan 1100 mile trip we saved a day anda half in time and a day and a half offuel which adds up to three days offuel."

Williams is taking a more cau-tious approach in deciding whetherthe tug is more efficient, preferring towait until he has all the numbers atthe end of the year. But he does ad-mit the tug's, "utilization is alreadyhigher." Gruzling estimates that, "theNautiCAN Nozzles should be 10-

15% more efficient at towing speedthan the Kort Nozzles and I think theengines are 5-10% more fuel effi-

cient. But great savings will alsocome from the Triple rudders, fromnot having to reverse the engines on

one side when turning around thebends on the river."

The much improved manoeuver-ability is a surprising bonus forNTCL. Williams explains why its soimportant and what happened."When going down river the tow

needs to get split up at four spots togo through rapids. To split up thetow, they have to stop and tie offsome of the barges and to do that,they have to turn 180E upstream

first. All the other boats, includingthe McNiven and Kelly O., will startsetting up to spin the tow .5 to .25mile before the tie-up depending onthe tow and current conditions at thelocation. With the Triple rudders [thetug and tow] turn right now. The firsttime they were operating the boat,

one crew went to turn a quarter milebefore the tie-up, and they finishedturning a quarter mile before the tie-up."

Whittaker has had similar experi-ences, "She turns on a dime. It canstop 6000 tons of freight, turn in its

own length, all going down st

And this is when there are two of three barges, so its 700-ft. lon165-ft. wide. With the split ruddput one ahead with the ruddersover and the other astern witrudders amidships. Half way ar

at 90 degrees I put the one astern into neutral, otherwise wdragged away backwards fromtarget."

So it appears a high efficnozzle, in this case a Nauticanoffers huge performance imp

ments of up to 60% over openpellers, and a substantial impment of 10% or more over the Kort Nozzles, even in a challe

river application. As Mulder pu"It's a no-brainer from a performpoint of view to put nozzles on

very shallow draft vessels." Thezles and Triple Rudders havegreatly helped the boat in the difriver environments because noWhittaker puts it, "she handles w

For more information contac

NautiCAN R&D Ltd

Telephone 604-921-192

josip@nautican.com

www.nautican.com

Although total engine power increased from 4,500 to 5,640 hp on the Edgar Kotokak, and obviously bollard pull trials showed improvement,

necdotal evidence from the first month or so of operation seems to indicate that both the nozzles and Triple Rudders together with new engines

mproved the overall fuel efficiency.