How to deal with damp during the winter layup

Ruby Dry DH600 Dehumidifier

Condensation is the enemy

Condensation occurs overnight when our breath hits interior surfaces and travels downwards eventually collecting under cushions where it destroys the fabric. Cooking and gas burners increase moisture in the air and humidity does the rest. If you leave your boat afloat the problem is increased as the temperature is sharply differentiated at water level again increasing the chance of condensation.

Ventilation is your friend

To deal with the problem we need to regulate the temperature increase ventilation and dehumidify the atmosphere. If your yacht is laid up ashore it will be much easier to achieve these improvements. Simply increasing the temperature will certainly help dry the boat. But unfortunately if water is still present in bilges or if still in the water and the stern gland is seeping, then the moisture content will increase as the temperature rises. Without proper ventilation the problem will still occur. Ventilation speeds up evaporation and exchanges moist air for dry which is what we want. Make sure you leave your lockers open and that a flow of air is introduced by for instance removing transducers (if ashore) or opening vents. If you have solar-powered vents, all the better. Make sure that your arrangement has an entry point and an exit.

Dehumidifiers extract water from air

These magic devices work by separating moisture from the air by using a fan to pull moist air over a number of cold coils. The air condenses into water which is then gathered into a disposal system vented so that it can drain away via a sink or suitable skin fitting. The drawback is that dehumidifiers don¡¯t like low temperatures and condensing water can freeze if the ambient temperature is less than 10C. You can either arrange it so that the boat is warm enough or you can use a system called 'hot gas defrost'. Avoid opening and closing companionways and hatches, dehumidifiers don't like changes of air.

Small space solutions

Moisture can be absorbed by using the several types of crystals of which silica gel is the best known. Some can be dried after use and used again and again. They are best used in small spaces, and can¡¯t cope with anything bigger than a small locker. There are also mechanical devices which use Hydrium crystals which are dried out by plugging into a mains supply.

Mailspeed Marine Tubeheat 240v Boat Heater - 1220mm 2005

Insulation is a good investment

Next to good ventilation and consistent warmth, insulation will reduce the effect of cold surfaces creating an unwanted reaction. Foam-backed headliners, will help retain heat. My boat has had foam backed carpet lining the interior surfaces and condensation has never been a problem. Mind you we are keen users of the diesel driven heating system during the sailing season, so the interior is a dry as toast.

Unattended heaters

Oil filled radiators or tube heaters are the best bet on a yacht. Remember that many heaters also produce water vapour, so the warm moist air must be changed to dry air through dehumidification and good ventilation. Even if shore power is available it is not a good idea to use fan heaters if the boat is left unattended. I personally like tube heaters, they are not expensive, have a low energy consumption and don¡¯t fall over.