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Top ten ways to reduce your fuel usage on a boat

Here's a timely topic given the escalation of fuel prices - mainly due to the hedge funds per news reports - and the attention to the need to improve fuel efficiency to reduce the threat of global warming. The natural inclination for us as sailors predominantly is, of course, to get into a discussion of the pros and cons of a sail versus power boat. Yes, while sailing a sailboat does not burn fuel, in reality it does consume power if it has any electronics or electrical gear that are turned on. This power comes from a battery that needs to be charged up at some point, and this in turn consumes fuel. A larger sailboat usually also has an auxiliary engine and possibly a generator, so in effect it has all the same parameters as a power driven vessel. So let's just stick to the parameters guiding use of fuel while under power and use of fuel to power gear.

1. Cleaned and waxed hull: this is self explanatory. Everything below the waterline affects your boat speed and performance more than anything above. If the hull is not smooth there will be resistance between it and the water resulting in increased fuel consumption to attain a given speed.

2. Clean propeller with correct pitch: as above, but with the addition that fouling will impede the prop’s hydrodynamics. The pitch (angle of the blades) also needs to be set for the strength of the engine and the type of boat to be efficient.

3. Optimized engine rpm: Every engine/boat combination has an optimal engine rpm. Making the engine run n% faster does not necessarily result in an equivalent increase in speed. Creating a fuel consumption chart across the range of rpms your boat runs at will help you identify the most efficient engine speed for your boat. As a rule of thumb, you should never try to go as fast as possible. With a displacement hull, keep your speed well below the maximum hull speed: Maximum Hull Speed = 1.34 * LWL1/2. As you get closer to this figure, significantly more energy is required for every incremental increase in speed. It is a worthwhile exercise to create a fuel consumption chart for your boat.

Note: With a sailboat, the LWL increases as the boat starts to heel, which increases its speed by reducing the drag with the same energy (wind) input.

With a planing hull, bring the vessel to a plane quickly and then reduce speed. Planing reduces your wetted area and thus reduces your drag requiring less energy to propel your boat. As above, increasing speed after your boat is planing, exponentially increases fuel consumption.

4. Charged with solar power: an excellent way to augment your energy needs and reduce engine idling to charge batteries. This can be taken to a higher level in an all-solar-powered electric boat.

5. Tapped into wind power: another viable alternative energy source to keep batteries topped off and refrigerators and AC running.

6. Adjusted boat trim: an improperly trimmed boat has undesirable hydrodynamic resistance. Optimal trim can be achieved by redistributing weight, and by adjusting the angle of the propeller to the boat.

7. Reduced weight: reducing the weight the boat needs to carry reduces the wetted area, thereby reducing the friction between the boat and the water and thus reducing the fuel consumption.

8. Energy efficient lighting: Light emitting diodes (LED) consume much less power than equivalently bright incandescent bulbs. They also give off much less heat, which is wasted energy.

9. Fuel additives & filters: can significantly increase engine efficiency. Dirty fuel and clogged injectors make for an inefficiently running engine. Additives will clean engine parts and break down potentially harmful substances such as water or sediment in the fuel. Similarly proper fuel filters and fuel "polishers" (Algae-X) will also help to remove unwanted particles and or water. Always check with the engine manufacturer about compatible additives.

10. Solar powered instruments: being totally ‘off the grid’ and needing no power from the boat’s batteries are the ultimate in efficiency. TackTick instruments are a prime example of this technology.

Maximum hull speed examples

Water Line Length (LWL)

Maximum Hull Speed

15

5.1 knots

20

5.9 knots

30

7.3 knots

40

8.4 knots

50

9.4 knots

60

10.3 knots

 

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