Boat Heating—Part I

 

When it’s cold and wet out there…

Just as at home, the heart of any boat heading for colder climes will be a heater of some sort. There’s nothing quite as satisfying on a cold, wet night as settling down in the warmth of a good boat in some wild, windswept anchorage without fifteen layers of thermal wear to keep you warm!

But there are many different ways to approach the question of how you provide the heat to keep the boat cozy and dry. Having tried most of them along the way, here are some thoughts that might help you choose what’s right for you and your boat.

Properly installed with an adequate air supply and an efficient and leak-proof flue, virtually any form of commonly-available fuel can be used. Combined with a fully-insulated hull and deck, all will provide the kind of dry heat that is so effective at providing warmth and keeping condensation at bay.

But in order to get the best out of them it’s necessary to consider a few common problems in the first place, such as siting the stove on an existing boat, where the joinery may dictate what type of stove you can install. And just to reinforce a common theme throughout this saga: Time, care and thought devoted to achieving a correct installation will be critical to ensure that any heater will operate safely and effectively.

Really substantial amounts of insulation are the icing on the cake

Even the best heater will underperform if an optimal installation cannot be achieved. A classic example of this is where the saloon seating will not allow a bulkhead-mounted stove to be installed down at floor level, in which case your upper body and head will be toasty and your legs and feet freezing—hot air rises, after all.

Assuming you have the space to make a good installation, let’s start by considering the types of fuel available, and how they can be used:

Solid Fuel

It may seem remarkable to younger readers, but solid fuel, in the form of wood and coal, used to be the standard means of heating (and sometimes cooking) on old wooden working boats like pilot cutters. But if the idea of a flaming stove on a boat filled with wood fills you with dread, then by all means skip this section!

Hampshire Heater

I had a good example of a very simple solid fuel heater on a 34-ft cruiser/racer back in the 80’s in the form of a ‘Pansy’ stove that burned charcoal briquettes. Bulkhead mounted and with a kiln lining, it was easy to light (with methylated spirits), burned cleanly with little or no smell, and would keep going all night if topped up at bedtime.

Tiny Tot Stove

Owners of traditional wooden boats tend to like stoves to match, such as the US-made Tiny Tot, part of a range of floor-mounted stoves, made in materials suitable for marine use, that run on coal or charcoal. These can even be had with a cooking hob top, if you want to do things the old-fashioned way!

Another popular option for smaller boats is the Dickinson Newport, which can burn coal, charcoal or presto logs (firelogs). Bulkhead mounted, this is a smart-looking stove that won’t look out of place on a more modern boat.

What’s good about solid fuel stoves:

  • Simple—very little to go wrong.
  • Small and neat.
  • No electricity required.

What’s not:

  • Lighting them can be tricky.
  • Bulky fuel in most cases, so not so suitable for extended voyaging.
  • Slow to warm up and adjust temperature.
  • Coal and charcoal are dirty fuels to store and burn.
  • Coal (especially) can leave messy residues on deck.
  • Cleaning up afterwards can be a filthy business, unless you make some sort of hopper to catch the dust (particularly on bulkhead stoves).
  • Installation of floor-mounted and bulkhead stoves can be time consuming and costly, as they must be adequately insulated from surrounding joinery.
  • Only warms one cabin.
  • I’d guess you could run one at sea in light conditions but…who’d want to?

The verdict:

On a small boat without much battery capacity, solid fuel stoves can make a lot of sense, especially those that burn one of the lighter and less messy fuels. Most of them have a relatively modest maximum output (up to 8000 British Thermal Units/BTUs for the Dickinson) and none of them have any heating coil option to run external radiators, so they are limited to heating one cabin.

But a solid fuel stove could make a good option for a boat up to say 35 ft to warm the saloon, if cruising coastally where supplies of the necessary fuel can easily be replenished.

Diesel and Kerosene

Diesel has the advantage that it will almost certainly already be available onboard in abundant quantities—there’s no need to carry yet another type of fuel. Low-sulphur diesel will produce slightly less heat than kerosene per gallon and kerosene tends to burn more cleanly with less smell. But, on the other hand, kerosene is becoming hard to come by in many parts of the world, which can make it impractical to consider for long-distance cruising.

Most stoves will run happily on either fuel, although sometimes the regulator will need adjustment to enable the stove to run well if you switch fuels.

Two Types

There are basically two types of heater available, which can offer more versatility and can be effectively scaled up for larger boats. These are stove-type heaters and blown-air heaters—both have benefits and drawbacks:

Let’s start with the first type and I will cover the second in Part II.

Options

For vessels from 40 ft upwards, I much prefer some form of floor-mounted stove, especially one that can incorporate an internal heating coil to heat water to run radiators in other cabins. A popular example of this type of stove is the Dickinson Antarctic that has an attractive facility to see the flames in the stove.

Another option that I’ve used on several boats (Boréal offer this stove on all models) is the Danish Refleks 62MS. Originally made for fishing vessels, this is a well-made item that can run radiators in each sleeping cabin and an aerotherm blown-air radiator in each of the heads. For us true-blue Brits, it even has a hob on the top for keeping a kettle warm, so the makings for a cup of tea are only ever an arm’s length away.

Refleks 62MS

Installation of these stoves is more complicated, obviously. I have installed this type of stove and run into lots of small issues that made what appeared to be a simple job at the outset far more tricky than I’d originally imagined.

Good Fuel Feed is Vital

Most of them work best if gravity fed, not via an electric fuel pump straight from a tank, which can make them flare up and down with each impulse from the pump. But gravity feeding creates a problem in that you must then fit a sizeable header tank near the deckhead close to the stove. Which in turn demands that you organize some form of simple pump system to electrically or manually replenish the tank, or drill a hole in the deck to enable you to fill the tank externally.

Neither is a perfect solution, and with both there’s a good chance of spilling fuel all over the place if you’re careless. Just to be clear, the fuel tank should not be mounted too close to the stove or, if that is unavoidable, the tank should never be replenished while the heater is in action or still hot. Otherwise any fuel spill might warm the boat up all too effectively…

Re-filling the fuel tank and circulating hot water to the radiators electrically is clean and easy.

Best practice in my experience is to tap the fuel feed off the ship’s main tank and route it to the heater tank via a small electric fuel pump. Put the switch for the pump beside the tank and watch the level rise as you fill the tank. That way you have a clean fuel delivery system with far less chance of overflowing the tank and gravity feed to the burner.

On the delivery side, from the heater tank to the heater there must be some form of in-line fuel filter in the pipe—the regulators for these heaters are fine-scale instruments and any crud in the fuel will soon block tiny orifices.

Copper pipe needs to be used for exposed fuel feed pipe close to the stove itself, for safety reasons. However, the type of olive joints that are often used at copper pipe joints are notoriously difficult to get to seal well, and small leaks are the bane of these stoves.

Take care when assembling the joints, use some form of pipe dope like Loctite 565 (not Teflon tape) to seal them, and do not overtighten—the joints should be firm but not cranked too tight, which will likely damage the olives.

The Right Flue

A critical factor to make these stoves run at their best is flue installation. All of them seem to run most efficiently with a longer than standard flue, especially above deck, so carrying a spare extra length of flue for windy conditions may be worthwhile.

The type of flue cowl has a significant effect, too, and I much prefer the H-shaped ‘Charlie Noble’ type of flue cowl, which enables the stove to run really well in strong winds, without blowing back.

And, when not in use, with the flue removed, any of these stoves must have some really effective form of watertight cap that can be screwed down tight to block the flue off when at sea in bad weather. Boréal make their own deck flange and screw cap to block off the 114-mm Refleks flue at deck level, the perfect solution.

Make Fire

Lighting these stoves takes practice. Small quantities of dry firelighter-type material works OK and Christopher and Molly Barnes recommend gel-type barbecue lighter fluid—as this recommendation comes South Georgia-tested, I’d listen to it!

Regular cleaning out of the burner pot will help to ensure that they remain easy to light and burn cleanly without smoking.

What’s good about diesel and kerosene drip stoves:

  • Once installed they are simple devices to operate and maintain.
  • They have remarkably low fuel consumption.
  • Can be run off the ship’s fuel supply.
  • Are versatile and attractive.
  • Some models can heat a kettle.
  • Can heat other cabins with the optional coils, radiators, etc.
  • Minimal electrical demand (fuel and hot water circulation pump only).

What’s not:

  • They can be tricky to light and run until you get the hang of them—you need to practice.
  • Adjusting the temperature with them is a slow business.
  • They take quite a while to deliver much heat.
  • And even more so with the radiators.
  • A top-notch installation will not be cheap.
  • Cannot be run safely at sea, except perhaps under power.
  • Care must be taken to adequately insulate the stove and flue from adjacent wooden joinery.

The verdict:

These stoves are more for serious voyaging boats and for people who are not afraid to roll their sleeves up and get used to operating and maintaining them. With all of the extras—insulation, stainless steel backing plates, radiators, hot water circulation pumps, etc.—the final bill for installation will be substantial. But, once you get used to the ritual of running one, you’ll never look back.

There is very little to go wrong with them and they should enjoy a long and trouble-free life. With their miserly fuel consumption they are ideal for expedition work where they will be very regularly in use without running the tanks dry.

They are for use at anchor and alongside and, whilst the heat they produce is not instant, they can be left running fulltime if necessary, keeping the boat dry and cozy—including the sleeping cabins. As long as the stove and the radiators can be mounted low, they can heat the boat from end to end and top to bottom.

Coming Next

  • Part 2: Propane stoves, diesel furnace blown-air and water systems, and engine heat-exchanger systems.

Colin, European Correspondent here at AAC, is a deeply experienced offshore sailor who holds a Yachtmaster licence, and a gifted photographer and talented writer who has added a whole new dimension to Attainable Adventure Cruising. In addition, since Colin and Louise are from England and had their OVNI 435, Pèlerin built in France, they bring a European perspective to our site. You can read more about Colin and Louise and their business at their website.

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