Rusty the Junk - Heating & Insulation

Staying warm on a steel hulled yacht requires two things, good insulation and a good heating system.

Heating

Rusty's heating system owes a lot to Jan and Rina. We largely copied their system, even down to purchasing the same type of diesel stove. We tried to steal theirs but they seem rather attached to it.

However it was a few years before we got that installed. Winter 2005/2006 we used electric radiators, but we were only trying to keep the bedroom warm, and it was a mild winter.

Winter 2006/2007 we mostly used a little solid fuel stove that Nick made as his journeyman piece on the welding course. We fitted it in the bedroom, and it pumped out a lot of heat, enough to warm the bedroom, and some over for the wheelhouse. It used about a bag of charcoal a day, with occasional bits of wood. However after the first few times it was very difficult to light, and we filled the boat with smoke several times. We eventually worked out that the chimney was too small (it should be at least 3 inch diameter) and started cleaning it regularly. But it was a slow and mucky job, so we used it less. Then a concerned father provided a carbon-monoxide alarm, which kept going off in the middle of the night, and we used it even less. Fortunately it was another mild winter.

Later in the winter we borrowed Jan + Rina’s small heater, the one they refer to as their summer stove. This stove doesn't have a coil, so doesn't drive radiators. To install it we only had to connect up the diesel from the day tank, and install the chimney. It was quite sufficient to keep the saloon and wheelhouse warm and dry, but it was the tail end of a mild winter.

Winter 2007/2008 we went for broke and installed our own stove, with a minimum set of radiators. The diesel feed was the same as for the little stove and the chimney only needed to be cut down a little.

The stove is tilted back in the pictures because the curve of the hull is forcing the chimney out. We need to put in a couple of 45 bends to move it away from the hull. This hasn’t happened yet because the shop didn’t have them in stock, and because they’re fearsomely expensive.

We are now at the stage of trying to tune the system, and improve it’s efficiency. We have various things we can change, most obviously heater setting and pump speed, but also balancing the radiators This is still a work in progress, so look out for further news.

We have had several exciting moments with the heating, mostly as a result of the pump being inadvertently switched off, but also from getting water in the diesel. Details of these adventures are in Rusty News.

Fuel Consumption

The regulator comes without any markings, so we put our own on. 8 is as high as it will go, 0 is as low as it will go without going out. The early results on fuel consumption, very rough figures, are that with the heater at nearly max (7 to 7.5, turned down to 6.5 at night) we use about 10 litres of diesel a day (24 hrs), but with the heater a notch lower at somewhere between 6 and 6.5, turned down to 5.5 at night, we use about 8 litres a day. We had it up at 7 to 7.5 when the night time temperatures were below freezing, and we weren’t quite warm enough. When it was at 6 to 6.5 the overnight temperature was about 7C, and we were comfortably warm. But we don’t have much insulation in yet, apart from what’s in the paint. The headlining will make a big difference (see Insulation). Jan + Rina, who have the same heater as us, but excellent insulation, only use 6 litres a day, and have to have the doors open to avoid suffocating when the overnight temperature is as high as 7C. We’re trying to warm a larger space though, as they don’t have a wheelhouse.

Other Heat Sources

Two other things have had an effect on the inside temperature. One is the sun – we have so much glass in the wheelhouse that a few hours sun raises the temperature there by several degrees. The windows are double glazed, so we don’t loose heat through them.
The other factor is oil lamps, especially the big one with a 4 inch circular wick. Lighting that adds 3C to the wheelhouse temperature. It uses about 100ml of lamp oil an hour, but lamp oil is the same price as white diesel here.

Insulation

Our insulation is a combination of the hi-tec and the old-fashioned.

The hi-tec part is a paint additive in use on the space station. We felt that it was pretty cold out there, so it ought to be good for us. It is called Thermilate (Insuladd in the US) and is made of microscopic ceramic beads that reflect heat. It looks like dust, and the theory is that one adds this stuff to the paint (any paint) and just apply it as normal.

Needless to say, all our boating friends and acquaintances scorned the idea that something a few microns thick could keep the boat warm.

But when we worked out the cost for the whole boat, it only came to around £500.

So we felt it was a worthwhile experiment, since we could always add another form of insulation afterwards if it didn't work. More about Thermilate.

It has definitely had some effect. There’s a distinct temperature difference between the painted and unpainted parts of the stainless steel support columns. And before Rusty was painted, there was a bump on the back deck in hot weather. It was very noticeable, as it would go pop underfoot, but since the paint and Thermilate went on it hasn’t reappeared.

However in winter there has been condensation on the roof, which is where the old-fashioned part comes in. This is a thin plywood facing all over the roof, just below the frames. That creates a 2inch air gap, which is quite good insulation in it’s own right. Exactly how good is a longer story. But it certainly helps, and it either stops the condensation, or stops it dripping on us!

For longer life, the plywood panels are epoxied round the edge, and painted on the back (side facing the ceiling) with underwater wood primer. The front side is just ordinary paint to match the room.

At the moment we’ve only roofed the wheel house and half the bedroom, so it’s too early to tell how much difference it’s making. Our plan is to roof the whole boat, and some of the sides, then see how good the insulation is. We may need to put extra insulation in the air gap. So, to be technical about it, Thermilate insulates against radiant heat and the air gap insulates against conducted heat, but we may need to also stop heat loss through convection in the air gap.

We don’t intend to panel the window bearing walls in the wheelhouse, the coach roof sides in the saloon, or the interior bulkheads, except where we decide it will look better.

Rusty has been fine in hot weather, but then there are plenty of through drafts when we open windows and hatches. We haven’t gone far enough south yet to deal with serious heat.

For a brief summary of the science of heat and insulation, look here.

For those who are interested, here is why we didn’t use foam or rock wool.