Living Onboard Part6

Just about the most important thing to consider when looking at a boat with the view to living onboard is, not surprisingly, human comfort. This month I thought we'd have a look at some of the things that contribute to our feeling of wellbeing when onboard.

Top of the list would have to be the surrounding temperature. It's difficult to enjoy yourself when shivering with the cold, and life is equally unpleasant when the sweat is literally pouring off you. If your boat is berthed at a marina, keeping warm is not a terribly hard problem to solve - simply buy yourself a small electric heater.

I prefer the fan style, as they are compact and distribute heat through the ship very quickly. I consider them to be safe to operate, but I wouldn't be happy leaving them on all night - although I know a lot of people that do.

My biggest concern is that if the fan were to fail or become blocked, the element would then rapidly heat to combustible temperatures - and because the heater case is almost always made of plastic these days, the thing would either melt or catch fire. There are overload devices inside that have been designed to prevent this - generally a bi-metallic set of contacts set near the heating element, which will open-circuit the heater if the element temperature rises above design limits.

Unfortunately, the average fan heater is also a pretty good suction device, and generally gets clogged up with carpet fluff and suchlike. This can either gunge up the safety contacts or catch fire, due to the arcing of the contacts as they operate.

If the heater is kept clean and receives a regular blowout with high-pressure air, then there's no problem. But let's face it - when was the last time you serviced your heater?

Another common type of heater is the simple radiator. When turned on, it produces a nice, cosy red glow and puts out plenty of warmth. Personally I think they are too dangerous to operate in a boat as the element is always well above the combustion temperature of most things, and as such produces a fire hazard.

The fact that the interiors of most modern powercruisers have been manufactured without much thought given to using fire retardant materials means you have to be pretty fire conscious when living onboard. That lovely fabric on the cushions, for instance, could literally burst into flames if it came into close contact with a radiant heater.

THE GOOD OIL
From a safety point of view, a far better heating device is the oil-filled column type. These are convection heaters, which means the air in contact with the columns heats and, as a consequence, rises. Heated air is replaced with cooler air, and this also heats and rises - thus, a constant current of air is naturally circulating through the columns and heating the boat.

The temperature of the columns is far below the combustion temperature of just about anything - damp towels or clothing placed on them soon dry, and I consider them to be totally safe to operate. I would be quite happy to leave one functioning even if the boat were unattended, but not everyone may agree with me on this.

They do have several disadvantages however - not the least of which is their size and weight. They are bulky and really need to be permanently installed if possible. I would hate to see one get away in a rolling seaway - it would be similar to a loose cannon sliding around the decks of sailing ships of old.

Another thing that works against them is their long warm-up time. Imagine it's the depths of winter: the wind is hitting 30kt and the rain is hissing down. You struggle along the marina - your umbrella has long since turned inside out - you're chilled to the marrow of your bones, and all you want to do is get aboard and get warm.

Well, if that's the scene, be prepared for a good half hour wait before anything like heat starts to emanate from the thing - and I can confirm from experience that swearing at it will not make a blind bit of difference!

PRICE IS WHY
The reason they're not the first choice is that there is an even better system - reverse- cycle air conditioning. The only thing against this method is cost - a $20 fan heater will produce the same amount of warmth as a $5000 reverse-cycle system. But as they say, if you've got the dough, it's the way to go.

The principle of operation is fairly simple - it consists of a pump and two heat exchangers. The pump, or compressor, circulates a liquid between these two. The first heat exchanger is in contact with the seawater. The circulating liquid is much colder than the temperature of the sea and, as a consequence, this liquid picks up energy from the water and boils - or for the techos among us, it changes it's state from a liquid to a gas.

This gas is now pumped to the second heat exchanger, which is mounted somewhere in the cabin space and in contact with the air - which is much cooler than the gas.

The air is forced over the surface of the heat exchanger by a fan and cools the gas inside, thus picking up heat itself. This heat is discharged to the cabin space. The gas becomes so cool that it must revert to becoming a liquid again - that is, it condenses - and is pumped back to the first heat exchanger to begin the cycle all over again.

When the temperature in the cabin reaches the desired level - which you set by means of a thermostat - the whole system cycles off. When the temperature drops, it cycles back on. There are no heating elements involved, thus it is completely safe to leave running even when the boat is unoccupied.

Good quality equipment, such as the American-made Cruiseaire, has many safety monitors built in to shut the system down in the event of malfunction, and leaving it operating is of no more concern than leaving your refrigerator going.

An even better idea is to operate it on a timer basis so it commences, say, half an hour before you expect to be back onboard. Imagine now if we replayed that previous scene - the difference that bedraggled, frozen person would feel as he/she clambers aboard to be greeted by a warm, cosy interior is exquisite to imagine. And there'd be no need for coarse language!

COOLING OFF
Of course, the other delightful thing to consider is that it can keep you cool when the weather turns hot - so maybe the money is being well spent after all. For me, being able to keep cool on the boat is consideration number one.

More years ago than I care to admit, I cruised through the tropics in a steel yacht and I can't remember too many nights where I slept well, due to the humidity and heat. Prickly heat rash, crotch rot, sand flies and mosquitoes can combine to make living onboard a misery in these latitudes, and I would strongly recommend air conditioning the boat if this is part of the "moving onboard" plan.

Lowering the temperature seems to deter the mozzies, and the sand flies can be avoided by keeping the boat closed up at dusk when they are at their most severe. Sand flies, by the way, should not be taken lightly. For those lucky enough never to have experienced these pests, it is difficult to describe the torment this insect can inflict. An insect, I might add, that is too small to observe with the naked eye - and too intelligent to drone like a mozzie.

Some people have such a reaction to their bites that they require hospitalisation. I have a friend who suffers severe swelling for three days after being bitten and never goes about at sunset without covering herself with clothing and insect repellent. Trust me when I say that air conditioning will elevate your comfort when living onboard in tropical and subtropical regions by many notches.

PLAY IT BACKWARDS
When reverse-cycle air conditioning is placed in cooling mode, the pump simply reverses the direction of the liquid flow, thus reversing the cycle of operation - hence the name.

The hot gas from the compressor is now directed to the first heat exchanger in contact with the seawater, and the water is much cooler than the gas. This allows the gas to give up its heat and convert back to a liquid, after which it is pumped to the second heat exchanger in the cabin - which, if you remember, is in contact with the air.

The temperature of the air is sufficient to cause the liquid to boil and this action takes energy from the air - and as a consequence, cools it. The cool air is distributed throughout the vessel by the fan.

Another thing happens at the same time, which more than anything contributes to the comfort of people onboard - the reduction in the humidity level of the air. Humidity is measured by a relativity index, which is simply a comparison of the temperature shown between two identical thermometers - one of which has its sensing bulb surrounded by cotton wool, which is kept wet with water at the same temperature as the air.

If the humidity of the air is low, the water in the cotton wool has little trouble evaporating and the energy required to do this lowers the water temperature, causing the thermometer to read lower than the one reading the air temperature.

This is exactly the principle that sweating in mammals hinges upon, and its efficiency depends upon the humidity of the surrounding air. High humidity makes evaporation difficult, thus the variation in the reading between the two thermometers is almost non existent and the relative humidity is said to be 100 per cent.

If you are in conditions such as this, virtually all the sweat produced by the body does little more than soak your clothes and get into your eyes. Most of us feel extremely uncomfortable and if we continue like this for some time, soon start to produce various skin ailments.

Air conditioning reduces humidity simply because the second heat exchanger is operating way below the condensation temperature on the water in the air. Thus, as the air is forced over the cooling fins of the heat exchanger, the moisture leaves the air and condenses on the fins, where it descends by gravity to the pan base of the exchanger. From there it is generally piped overboard.

The air in the cabin is now not only cool, but has also had the moisture reduced to point at which we are comfortable.

WHAT'S THE CATCH?
Apart from the cost, are there any disadvantages to reverse-cycle air conditioning? Well, to be perfectly honest there are a few, as one might expect. There are basically two styles that the equipment is manufactured in - the self contained and the split. This is pretty much the same as in domestic air conditioning.

The self-contained style is self explanatory - it's a complete unit in itself, but because marine systems are invariably water cooled, it will require a water supply from the sea supplied by a pump along with the electricity to operate it. These are often mounted under a bunk, and the air is ducted from an overhead outlet. In this respect, they are very simple to install.

Unfortunately, the noise of the compressor thumping away under the mattress can make sleep difficult - in this case, the split system would be more suited for the sleeping areas.

As the name suggests, the compressor is split from the cooling unit and generally mounted in the engine room. The evaporator and fan are in the space to be cooled. This brings about a significant reduction in operation noise levels, and is thus the recommended method for air conditioning sleeping quarters.

However, the relatively recent introduction of rotary compressors over the old reciprocating type has resulted in the production of much quieter units. Split systems are much more expensive to purchase and install, but both the split and self-contained units have been developed to a high degree of reliability and seldom cause much trouble.

One final word - air conditioning requires large amounts of electricity, which generally means that if your marina berth has only the standard 16amp outlet, you may hit an energy crisis. If that's the case - and it generally is - then it means you have to be careful about what else is switched on when operating the air. Otherwise you'll be making endless trips to reset the circuit breaker.

Being cool when it's hot and warm when it's not is sure going to make living onboard a heap more enjoyable - and after all, you moved aboard because you wanted to enjoy the lifestyle, didn't you?