HEATING AND VENTING

Mr Meme says: You have to warm up your boat and continuously draw the less humid air from outside to remove the dampness from within. It works best if you force-draft and heat the air up on its way in.

Heating and Ventilation:

"Air-changes" which is the number of times all the air in all compartments on the boat is changed for fresh air per hour, is the most important aspect of keeping your boat warm, dry and healthy.

There is a set minimum rate on ships and housing accommodation.

We compared the humidity of the air inside the boat with the air outside and found on all occasions, even when it was raining that inside was far more humid than outside. As an example, outside on the foredeck humidity would be 68% and inside would be 82%.

At a humidity of 100% the temperature that was read at that point would be DEW POINT.

It makes it easier then, to understand that DEW POINT would form on a cold surface in contact with moisture laden air.

To prevent this from happening the inside air must be displaced by warmed up outside air which has less water content than the air inside.

This will allow the moisture to be gathered up by the warm dry air and with hot air rising it will be discharged to outside at a high point at the main hatch or companionway of your boat.

We fitted a Webasto Airtop diesel fired heater in each engine compartments of our catamaran.

Each unit has three air delivery points and are arranged as follows:

One for each after cabin, one on each side of the common Saloon one in the Heads port side and one for the main cabin on the starboard side.

On each heater unit air was drawn from a grid on the stern.

Depending on outside air temperature the whole inside of the yacht may be warmed up to  21 degrees centigrade and the humidity is seen to drop considerably as soon as the heaters are switched on.

Ideally if the heaters could be run continuously day and night, all compartments would remain warm and dry. This however was not possible for us as we are reluctant to leave the boat with any thing switched on at all, even our computers must be unplugged and shore power switched off.

It is important that the hot air ducting be fitted correctly. We wrapped the ducting from the heater outlet to the hot ait delivery control vents with a full layer of Glass Wool bonded with duct tape.

The thermostat sensors that controls the air temperature is placed on either side of the saloon. The saloon temperature governed the temperature of the rest of the boat. Each cabin is adjusted by opening or closing the individual flap on the delivery.

When the desired temperature is reached the heater output is reduced to maintain it by slowing the fan down and reducing the amount of fuel consumed. The burner also cuts out and cold air is delivered to a point where it fires up again.

The heater may be noisy if it is mounted in an open compartment or if there is no sound insulation in the compartment and the ducting is not insulated.

To reduce humidity the air must always be taken from the outside unless it can be split to take 1/3 re-circulated from inside and 2/3 from outside.

To us our heaters are quiet whispering warmth that would keep the boat warm and dry in all compartments including the bilges, if they were allowed to run 24 hours a day and 7 days a week.


Venting the Galley

Galley Extraction Fan

Boiling tea pots and cooking on the stove is a main source of water generation which increases the humidity on board substantially.

The fire detector on our boat was a big nuisance during steak or lamb chop fries until we fitted an extractor fan above the galley range.

Mouth watering aroma emanating from the galley was often interrupted by the smoke alarms screeching but a simple extractor unit was fitted above the stove which draws the air above the stove top directly out of the boat into the cock-pit.

For 75p we bought a small plastic bucket from the DIY paint section of our favorite store TRAGO MILLS and modified it to be a base for the wall extractor fan and fashioned an insert out of plywood which was fitted in way of the partially opened sliding window.

 It works like a charm. Having two speeds we are able to clear the air of moisture and smoke and as a bonus , when the central heating is switched off, fresh air from outside is drawn in through the heating system to all compartments.

.

 

Damp Clothing:

It’s amazing how a locker full of clothes would appear to be totally dry but the clothes feel cold and damp. This is probably because they have soaked up all the water that has condensed on the inside of the hull.

To reduce the conducted loss of heat which allows dew point to be reached in our clothing and file lockers, we used the closed cell foam material that we had for insulation.

It was bonded in place with contact adhesive covering as much of the surface area as possible. Steel fittings like the chain plates and stanchion bases had to be covered as tightly as possible reducing the volume of water laden air passing over it.

This would have worked better for us if we had used a thicker insulation material.

I believe that Glass Wool is a good insulation material but it would have to be clad with a durable material like vinyl and panelled off.

There was a vast improvement in our lockers once we fitted large vents to cabinet doors top and bottom.

The main double bed has an air gap between the bunk board and the hull which we filled with Glass Wool.

Meme did wonders with vacuum bagging our linen and summer clothing. Provided that all air is removed and the bag is completely sealed, moisture would form only on the outside of the plastic bag. If there was a tiny hole in the bag, moisture in the air would equalise with the moisture laden air in the boat and as soon as dew point was reached the bag would form a pool of water which would be added to., as the day heated and cooled and the bag would remain as an ever increasing reservoir of water.
The coach roof and deck on our little boat is balsa core GRP which is quite good insulation, but there are sections like in way of the fairing of the foredeck to the window frames, which are thin epoxy glass and these areas had to be insulated with the closed cell foam. Other small areas more difficult to get to shall just have to bloom and grow to the end of the season.

cold feet

Cold Feet:

With the hull surrounded by icy water and the chilling wind blowing down the middle of the catamaran the saloon deck and cabin soles become a source of lost British Thermal Units.

A trip to our favourite store solved that problem with off cuts of new carpeting cut and fitted in double quick time. We expected to do only two winters in the UK but now as we come to the fourth year, the unbound carpet edges are looking rather tatty but who cares they have served their purpose. The visiting cats revelled in pouncing on the threaded edges and bounding off with a ripping sound reducing the length of the carpet by inches. The carpeting shall be binned prior to us setting off south, heading for the sun and the teak deck look alike flooring shall be buffed up to match the colour of warm sock-less feet that shall change from pale white to sun tanned brown.
Happy feet and twinkled toed.

hatches

Double Glazing hatches: (aluminium type)

The same styrene sheeting was fitted where the framed mosquito netting is clipped in place using door weather sealing rubber.

It was a simple matter to use the mosquito netting frame as a template and mark and cut the styrene sheeting.

We sacrificed the light that the rectangular port lights give by covering them from the outside.

We initially used bubble-wrap stuck on with a blob of silicone but the last two years we have used pieces of 4mm closed cell foam stuck on the aluminium frames using double sided tape. Not good for the anodised frame but if left through the summer the double sided tape glue turns to powder and flakes off.

We bought a roll of closed cell foam from the sail maker who uses it in sail making.

Mr. Meme

 Simple methods of saving your boat interior from the MOLD MONSTER

The goal must be to INSULATE, HEAT and VENTILATE or your boat will become a veritable rain forest with all kinds of species of mould growing in your cabinets, mattresses, and on your clothes. It can destroy linings and materials within days.
Horrible black mold monsters start to appear on the deck head and in cabinets.
Some are known to be deadly however mold in general is thought by some, to have an adverse effect on our health. 

http//moldsymptoms.org/

INSULATE

Double glazing can be temporally done or it can be neatly done depending on your class of boat and available finance.

We had to do at least four winters in “sunny” Cornwall and did a permanent job of double glazing on the main saloon large windows which would help against heat in the tropics as well as some inexpensive and simple methods of covering and insulating the main hatches and port-holes.

Double Glazing saloon windows:

Our windows are about six square mtrs of 8mm Marguard. They are bonded on the outside of balsa GRP composite. So the additional glazing would go onto the inside leaving a1 inch air gap between the glazing.

Our local hardware and general store TRAGO MILLS has got various thicknesses of styrene see through sheeting (Perspex type) with suitable sizes available. We chose 4mm thickness and cut it using a small angle grinder with a thin disc for cutting steel.

We have a flat piece of closed cell foam about ½ inch thick that I lay flat and use as a work surface. Mark the sheet to be cut which is covered with a loose film of plastic using a marker pen and gently move the angle grinder along the mark not allowing the styrene to get too hot. May do slight curves forming an initial groove all around and continue until penetration. Dress the edge with a file and emery paper, avoid scratching the surface. The STYRENE is easy to work with and has shown no sign of yellowing yet after 3.5 years.

The sheet was fixed in place with stainless steel self tapping screws 250mm apart and seating on peel and stick door draft sealing rubber. The screw heads neatly covered with white clip on covers.
A good method for heating the boat once it has been insulated and has good galley ventilation is Meme at the oven with a roast lamb and veg!

Mr. Meme

Mr Meme says:

Spending winter in cold climates like Good Old Blighty?

If your boat was built for sunnier climes you’ve got some work to do before the sun creeps further away.

With sub 10 deg centigrade outside and wind chill causing your damp hull to make like a refrigerator, the high moisture created by water in the bilges, your much needed tea pot, cooking and people on board doing the necessary act of breathing, your boat becomes a productive water-maker.

Condensation will run down the hull onto mattresses and drip from cold hatch frames and fittings and usually hit you on the head at two in the morning reminding you that although you are warm under your duvet it is near freezing outside.

We look forward to continue sharing how we overcame the problem and to discuss ideas and products  

My first post,

Meme says:


I have sailed extensively on the South African coast for the last 37 years as it was my home ground. The stretch of coast from the Mozambique boarder down to Cape Town has a formidable reputation and rightly so, as the weather and sea conditions can be hazardous to the unwary and hasty.

The safest way to navigate down or up the coast is to have time to do it. Hurry and you will find you will be hammered by a gale in the wrong direction. You will also find that sometimes you will have to take a gale with you to reach your objective, especially in the Yo-yo weather months from about August/September through to January/February, when the wind blows for a day or two from one direction then from the other, usually at gale force.

My next Blogs are my experiences and hard earned knowledge of the coast to help those wanting to sail safely down the Coast