Fitting out a new cruising boat - Part 3, Water supply and Heating

7:38 AM Sun 5 Apr 2009 GMT

'Multihull Solutions’ Lavezzi' Multihull Solutions

Peter Salisbury continues with his series on fitting out a new cruising boat.

This is Part 3 of a four part series. This week Peter considers the issues of water supplies, heating and cooling.

For Part 1, which covered the issues of navigation requirements, click
HERE.

For Part 2, whih covered the issues of power generation, click
HERE.

Water

What you get:
The new boat will be equipped with large fresh water tanks, a hot water service heated from the engine cooling system and a pressure pump so that both hot and cold water are available by simply turning on the taps.

What you need:
If you are extremely frugal with water you might be able to get usage down to 15 - 20 litres per person per day, but this requires considerable commitment. Being a bit more generous and allowing each person a quick shower each day and a hose down after each swim and some hand washing etc. you might use 50 litres per person per day. However a ten minute shower at home could easily use 100 litres of water, so the sky is the limit.

As with everything else, what you need depends on what you want to do. Most boats carry enough water for a week away or maybe two with care. If you want to cruise for longer periods, water will be a problem since it is generally difficult to get access to mains water unless you stay in a marina.

Watermakers:

Watermaker - large or small they all work the same - .. .

Watermakers produce fresh clean water from sea water by forcing the sea water through extremely fine filters that remove the salt and almost all other impurities. The resulting water is as clean as you get in bottled water.

They operate at extremely high pressure and the filters are very expensive so the units themselves are expensive. They are generally 30, 60 or 120 litres per hour in cruising boats. Think in the order of 10 - $20,000. Much larger sizes are available. A 12V watermaker might use 0.5 amps per hour per litre of water.

World’s cheapest watermaker - .. .

However, there are less expensive solutions, if you are prepared to be involved with the construction, either doing it yourself or overseeing a technician. See larger diagram by clicking on the thumbnail at the end of this article, and for further information, see Sail-World story

Hot Water

What you get:
The boat will probably have a marine hot water service of about 20 - 30 litres, heated by the engine cooling system. Thus hot water will be available while the engine is running and for another 12 hours or so, until it either runs out or cools down. The hot water service will have a 240V element, which is only connected if shore power is installed. It is not recommended to run the hot water service from the batteries because of the large power requirement. There should be some form of disconnect to ensure this does not happen accidentally.

How much is enough:
Many boats in the past have not had any hot water and many long term cruisers in the tropics get by without it because they don't want the expense or energy drain.
The middle of the road option is to only have hot water when the motors are used to go somewhere, or when in a marina.
Continuous hot water can be made available but because of the power required they all involve burning some form of fuel.

Options:
Gas hot water services are sometimes used on boats, particularly the instantaneous type that make the hot water as required. The downsides are:
. A gas HWS must be ventilated to the outside air, so it can be difficult to locate.
. Gas usage is quite high and it is difficult to carry sufficient gas offshore.

If a generator is fitted to the boat it is realistic to simply use the standard electric element. It is necessary to ensure that the HWS is large enough to last for the period when the generator is not running each day.
Diesel fired heaters are available that almost silently produce hot water while consuming very moderate amounts of fuel - around 0.2 - 0.6 litres per hour.

As previously mentioned, a Whispergen produces hot water along with electricity.

The hot water tank has one set of inlet/outlet fittings as standard. These are normally connected to the main engine cooling system. If a separate water heater is installed it can be connected to these fittings, or a specialised tank can be purchased with two sets of fittings to allow both connections to be made independently. A secondary water heater should not be teed into the existing heat exchanger hoses.

Heating / Air Conditioning

Hella fan - efficient yes but, more importantly, quiet - .. .

What you get:

Heating options:
For boats used in cooler climates heating can considerably extend the cruising season or allow them to venture into otherwise untenable environments.
The only really practical form of boat heating is diesel. They can be either stand alone air heaters (0.12 - 0.4 litres per hour) or a central unit (0.2 - 0.9 litres per hour) that heats a fluid that is circulated around the boat providing heat to individual fan units in each cabin. The latter can also be used to heat the HWS. A generator could also be used to operate the heating system

Cooling options:
The simple cooling option is to install fans in each cabin. This is relatively inexpensive and consumes
minimal power. The degree of cooling is limited. In the tropics, a combination of fans and sleeping in the cockpit suffices most cruising boats. (But take the mosquito soils)

The only real option is air conditioning. For a cruising multihull, with large internal volume and large windows, this will result in a large power hungry unit or several smaller units. Probably 4 - 6 KW, depending on the environment it is used in. It will also be expensive, think $20 - $50,000.

In addition a large generator will be required, which will need to be running almost all of the time the air conditioner is running. It is possible to moderate the cost and power requirements by only air conditioning selected areas - but
that sort of defeats the purpose, doesn't it?

Sail-World Cruising would like to thank Multihull-Solutionsfor the use of Peter Salisbury's article. For all your multihull needs, click herefor the best solutions.

by Peter Salisbury/Sail-World Cruising

Click on thumbnails to enlarge and find more photos: