A Fuelish Game to Play M Flikkema the Crew Report 01052009

8/11/2019 A Fuelish Game to Play M Flikkema the Crew Report 01052009

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ISSUE 31 MAY 2009 the crew REPORTwww.yotcru.com



28 crew essentials > environmental focus

PerformanceAnalysis High bunker prices and worldwideeconomic awareness make the issueof fuel saving important in all eldsof shipping. Environmental care isfurthermore an important driving forcefor reduction of fuel consumption. Lowfuel consumption is essential in Atlanticcrossings due to limited bunker capacityof superyachts. Superyacht captainsand crew are confronted with high fuelprices but have the possibility to reducefuel consumption through operationalmeasures.

Reducing fuel consumption onboardsuperyachts requires a different approachto commercial vessels, however the basicphysics is still the same. The MaritimeResearch Institute Netherlands (MARIN)has over 75 years of experience in modeltesting of ships and yachts. Thesemodel tests are done to nd an optimalcompromise between onboard comfort(ship motion and vibrations) and fueleconomy. In designing and operatingsuperyachts, as with passenger vessels,

the compromise often tilts towardsonboard comfort, surrendering on fueleconomy. Whereas in commercial cargoshipping, crew comfort is often secondary

to fuel economy. The need for operationalmeasures to reduce fuel consumption istherefore high in superyachts.

The approach to reducing fuelconsumption at MARIN is to concentrateon the physics of ship hydromechanics,which is applicable to all vessels.Measures introduced for the commercialeet are therefore also applicable forsuperyachts. The main difference infuel saving between superyachts andcommercial vessels is the unclear balancebetween fuel costs and “cargo income”for superyachts. The benet of increasingspeed to arrive at a specic time – say forcharter – or the loss due to decreasing

speed cannot be weighted against thenancial consequences of the decision.Optimisation of the speed for a certaintrip is therefore difcult. On departure, anavigating ofcer will normally choosea higher speed setting to make up forpotential bad weather or other delays lateron. Along the route, when it becomesclear that the ETA will be met, speedwill be reduced to avoid waiting times atport. Due to the non-linear speed-powerrelationship, the fuel consumption of thisscenario is higher than when a constant,

lower speed setting is used. This can bedone when the performance of the vesselis known in relation to weather conditionsexpected along the route (see information

below on fuel consumption and weather).

Other potential fuel savings onsuperyachts can be found in the

settings of the autopilot and ship trim.The autopilot setting is important insuperyachting as tests have shown thatactive use of the rudder increases the fuelconsumption.

Onboard AnalysisEssential in fuel savings, onboard analysisshould be carried out and displayeddirectly to the crew. Performance analysisconsists of correcting for environmentalconditions (wind, waves, current andwater depth) and loading conditions. Bydoing this, a comparison can be madebetween different trips without theinterference of these different conditionsin the results. By changing the autopilotsettings and where possible the trim, thedifference in performance can be foundin the analysis results. This will resultin extensive knowledge of the yacht’sperformance over time.

In addition, by long-term monitoring thedecrease of the hull performance can

be discovered, which is caused by hulland propeller fouling and roughening ofthe hull due to damages caused by, forexample, anchor chains.

A Fuelish Game to PlayWhether the motivation is environmental or economical, reducing the fuel consumption of a superyacht has its benets.Unless your vessel decides to put down roots in a home port and leave adventure to the rest of the eet, other optionsneed to be considered in order to reduce the guzzle of gas. There are manifold ways of improving fuel efciency, fromchanging hardware to operational practice; TCR asked two knowledgeable establishments for their recommendations.

Feadship’s MY Predator : tests in a seakeeping and manoeuvring basin (left) and on full scale (right).

the crew report



crew essentials > environmental focus 29

Marine WeatherNavigational decisions must be takenwithout undermining safety and comfort ofthe guests, which are primary concerns forboth the captain and the marine weather

forecaster. However, how the vessel iscontrolled in the weather may have moreimpact on the operational costs of a yachtthan would be originally presumed.

Before taking the weather factor into theequation, however, it has to be said thatthe fuel consumption is also dependenton the vessel performance and design.For example, in displacement yachts fuelconsumption levels are good at moderatespeed, but increase disproportionately athigher speeds due to the increased power

required to counteract wave resistance(which is high as its hull is more robustand heavier than a high-speed vessel,

ensuring greater stability). High-speedyachts are more sensitive to wind andsea as they plane on the water; in certainconditions they become difcult tooperate, especially at high speed, andsudden changes in wind speed can

negatively affect their stability.

It is not just the wave impact speedthat has an effect on the yacht, butalso its direction. The worst directionin which to travel is directly into thewaves, as the distance between eachcrest is shortest. The vessel can finditself in a situation where the bow ofthe yacht has not completely recoveredstability after hitting a wave beforethe next hits. This “tormented” tackinevitably has a large impact on fuel

consumption, so it is important toadjust the speed and use flaps, wherefitted, for optimised trim.

One signicant technologicalimprovement has been the introduction ofpod propulsion systems – more efcientthan normal propeller-and-shaft enginesbecause they are able to run constantly atan optimised number of revs per minute.

Considerable reduction of fuel costs arealso attained through proper speed-powersetting, optimum trim and autopilotsettings that have proven to improveefciency by ve to ten per cent.

However, performance analysis on its owndoes not save fuel or reduce emissions.Comparing current performance withthat of previous trips helps, but it isalso important to use weather reportsto optimise speed and trim to improveperformance.

How far a vessel travels is important andcharter companies are becoming »

Performance ResultsPerformance monitoring shows that theeffect of fouling on both the hull and thepropeller is signicant. With superyachtsat high speeds, the frictional resistanceis relatively low compared to the wavemaking resistance (a function of the hull’sshape). Since fouling only affects frictionalresistance, it can be said that the relativeeffect of fouling on the fuel consumption isless for superyachts than for commercialvessels sailing at speeds below 20 knots.

On the other hand, a reduction of ten percent in the frictional resistance due toperiodical cleaning of the hull still has asignicant reduction in fuel consumption.With the operational prole of superyachtswhere a large amount of time is spent inthe harbour and in warm waters, the hulland propeller are liable to fouling. In thiscase the effect of fouling on the frictionalresistance might even be higher than theaforementioned ten per cent, which inturn makes the effect of fouling on the fuelconsumption a serious issue.

Fouling on the propeller forsuperyachts is similar to commercialvessels. Full-scale tests of acommercial vessel have shown anincrease in propeller efficiency ashigh as 14 per cent due to propellercleaning and polishing. Periodicalin-water cleaning of the propeller willsave several percent on the fuel bill.Exact figures can be determined byperformance monitoring.

By Maarten Flikkema, MARIN www.marin.nl

the crew report



30 crew essentials > fuel efciency

increasingly aware of the energy crisis.This means, for example, paying moreattention to destination choice anddetermining the most cost-effective route.

One has to bear in mind that sometimesthe direct route is not always the fastestor most favourable. For example, inthe northern hemisphere when havingto cross a low pressure system that ismoving eastwards, you need to takeinto account various factors in orderto establish the route based on wherethe vessel is positioned and how fast itis moving in relation to the low. Thesefactors include whether the low isweakening or deepening, any variations towind speed and direction determined byorography (the study of mountain ranges)or other factors. For a yacht making a

westerly route into this low, it is morebenecial to pass over its northern sectorto nd more favourable conditions, whilston the southern sector winds and waveswill come against the direction in whichthe yacht is moving, generating a muchhigher fuel consumption (see Figure 1).

Usually, the best way forward is to makean optimisation, nding the balancebetween distance covered and the timetaken for a passage. Another important

factor is the stability of the yacht and inthis context the yachts without stabiliserssuffer more in heavy marine weatherconditions.

It should also be considered that, althoughgood planning for a passage is crucial,conditions can change enroute, sometimeseven signicantly – especially on longpassages. This is why continuous observation

of the actual weather and the frequency ofweather updates become very useful.

Often, saving fuel is easier said than donebecause a captain has to stick to tightschedules or sometimes change plans toaccommodate the guests’ wishes to headto a different location or escape a longspell of wet/windy/cool weather.

In general, however, it is not possible tochoose the exact best route to reduce

fuel consumption. Often, especially withguests onboard, the most important thingis that they enjoy the voyage and to stickthe plan. Cruising speed can be betteroptimised with longer passages, but anunexpected change of marine conditionsor the necessity to reach a destinationin timely fashion make it impossible toreduce the speed of the vessel.

Nowadays, naval engineers and architectsare paying increasing attention tothe problem of fuel consumption; butundoubtedly good weather route planningand the extreme care that captains givechoosing favourable sea conditions issuewill make the difference in the future tosave on operating costs and make a lowerenvironmental impact. ■

By Daniele Vitri, weather forecaster atNavimeteo www.navimeteo.eu

Figure 1

Lower fuel consumption

Higher fuel consumption

Documents

A Fuelish Game to Play M Flikkema the Crew Report 01052009