Speed Through Water: Fuel Optimisation with Wavex

The system uses information obtained from the on board X-band radar to measure the ship’s speed with greater accuracy which is 0.5 m/sec that is 0.97 knots. The site mentions that this is 1 m/sec or 1.94 knots for Doppler logs but this is in reality much better. For instance the accuracy of a Wärtsila speed log over ground is ± (0.04 kn + 0.5 % of resulting speed) and the speed through water ± (0.1 kn + 1 % of resulting speed).

They claim that also ocean currents can be measured. In principle if the speed of the vessel increases that could be due to a stern current and the speed could be decreased and so fuel saved. You could even automate that to maintain a constant speed…

If you are looking for real accuracy you can better install a GS-100 Furuno satellite speed log with an accuracy of about 0.02 knots.

On top of that it also provides other useful information:

:arrow_forward: Offers transverse speed at bow and stern position, as well as longitudinal speed

:arrow_forward: Provides transverse speed at any position of the ship utilizing the built-in satellite compass

:arrow_forward: Delivers roll, pitch and angular information for navigation equipment such as Radar, ECDIS and AIS.

dont you just drive at a set rpm and check the gps sog ?

Yes, better to keep rpm constant and let SOG vary by current, otherwise you’d burn more fuel.

The extra fuel burned to counter a head current is going to be more than the amount saved in a current from astern. If the relationship between fuel consumption and speed was linear it would cancel but that’s not the case.

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Here’s an interesting Q&A with relative newcomer Nautilus Labs which claims to be seeing 5-10% efficiencies in fuel use using real-time data, weather, current to dictate routing, speed, rpm, etc.
May be a few extra things added to the Captains plate, but if it’s an intuitive platform maybe not?
Nautilus Labs Interview

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