Rants & Musings, Mechanical Systems
Index
Basement (Cellar) Sump Pumps
Diesel Fuel Day Tank
Kerosene (Paraffin) Cooker
Basement (Cellar) Sump Pumps (John, 01/2010)
Many offshore boats are fitted with some kind of high capacity emergency bilge pump, sometimes known as crash pumps. We have long considered one for Morgan’s Cloud but have shied away because we don’t like cluttering up the main engine with belted devices and we have yet to find a pump that is compact enough to fit, will run dry—in a flooding situation we would not have time to monitor the pump and shut it down the minute it sucks dry—and handle the kind of trash that will almost inevitably be floating around in a badly flooding boat.
I think
we have found the answer on Polaris:
She is equipped with two 220 volt (also available in 110 volt) high capacity
household sump pumps that will move a huge amount of water and munch up
just about anything thrown at them. These pumps are readily available,
relatively cheap, can be placed wherever needed (even to help another boat)
and be powered by our generator or inverter. Of course we would have to
be very careful with such voltages around water. Also, if the generator
and inverter get flooded, we would be back to our massive Edson manual
pump, but then the same is true of engine driven pumps.
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Diesel Fuel Day Tank (John, 12/2009)
Polaris, the sailboat we looked after for a month in Greenland, is fitted with a diesel day tank that’s installed so the bottom of the tank is higher than the intake on the main engine and Refleks heater. (The Webasto heaters require a combined metering and lift pump, so their position, relative to the tank, is not an issue.)
There are several advantages to this system:
- Finding an air leak in the fuel intake line to a diesel engine, which will quickly stop the engine, can be one of the most frustrating tasks known to humankind. That whole problem goes away with a day tank like this one since the fuel system is under slight pressure from gravity, making a leak both less likely—pressure tends to seal fittings and gaskets, vacuum has the opposite effect—and obvious if one does occur.
- Fuel plumbing is simplified since a boat like Polaris, with four separate diesel tanks and without a day tank, would need a feed and return (where required) line for each diesel burning device on the boat to each tank—a plumbing nightmare. On Morgan’s Cloud we have two tanks and three user devices, together with a fuel polish system, which results in a fuel valve system that looks as if it should require a nuclear plant operator’s license.
- Changing filters on the engine is easier since they will automatically fill by gravity and priming the engine will be easier too. (On Morgan’s Cloud we have a small electric fuel pump in the system that provides the same benefit without a day tank.)
- The day tank can be more easily cleaned, and water as well as sludge more easily drained from the bottom, than the main tanks.
- Since the fuel is filtered when being pumped from the main tanks to the day tank and then again as it goes out to the user devices, a polish system is not really required, particularly when you take into account point four above.
- It is much easier to measure and monitor the fuel consumption of each device using a day tank. For example, we filled in a log of the fuel used by the heater each day while caretaking Polaris.
Hutting, builder of Polaris, has done an installation job on the day tank that is, like all the systems on the boat, a work of art.
The front of the day tank (just above the twin filters) is what you are looking at in the photo. (The smaller black tank in the left middle ground is the engine cooling header tank and nothing to do with the fuel system.) The blue pump on the upper left fills the tank from whichever main tank is selected on a separate manifold (not shown) when the black button on the control box to the right is pressed. The pump also starts automatically if the day tank reaches half empty. The red button stops the pump, which also stops automatically when the tank is full. There is also a manual pump (green) in case the electric one fails. Under the tank there is a deep drip pan to catch the inevitable spills that will occur when the tank is being cleaned or worked on. There is also a simple sight-glass gauge that Michael (owner of Polaris) has accurately calibrated.
Drawbacks to the system—there are always drawbacks since everything on a boat is a compromise—are the substantial amount of valuable space used by the day tank and related plumbing, and the chance of running the engine dry if the automatic refill system fails or overflowing out the vent if the automatic stop fails.
On balance, we would say that a day tank makes a lot of sense.
Reader Comment:
Denis Bone writes: I have installed a similar day tank system to my Fisher Freeward 30 Freewind, the main difference being that, instead of a high/low switched system I have installed an overflow that returns excess fuel to the main tanks. The day tank is fed from the engine's mechanical pump which draws diesel from the low points of the two tanks through a water separator/fuel filter. This way all the fuel is constantly circulated with the engine being gravity fed from the day tank. Should the fuel pump fail I have about 20 litres of fuel in the day tank and my fuel is constantly 'polished' and de-watered. I have had this system in use for about five years with no problems so far, touch wood!Back to Index
Kerosene (Paraffin) Cooker (John, 12/2009)
Back in the day, many offshore voyaging pioneers like the Pyes, Smeatons, and Hiscocks cooked on Primus stoves: Peculiar machines that relied on hand pumped air pressure to force kerosene (paraffin) into a burner that was preheated with metholated spirit (industrial alcohol). Tales abounded of flare-ups, singed eyebrows and sea-cooks totally traumatized by the unpredictable behaviour of these machines.
Polaris, the sailboat we looked after for a month in Greenland, is fitted with a three burner kerosene stove from Switzerland-based Bertschi. The fundamental technology is the same as the Primus, but the pressure is provided by an electric pump (with manual backup) and the burners preheated by electric elements (you could still use alcohol if these failed). However, even with this automation, cooking on this machine requires strong nerves, chanting incantations in an obscure Swiss mountain dialect, and the sacrifice of small animals.
The stove does include a small oven, but this requires substantial reconfiguration of the stove to use and there is no grill. Other problems are the smell of burning kerosene, which can turn even the strongest stomach, particularly at sea, and the risk of some quite spectacular, but probably not actually dangerous, flare-ups if the burner is not heated enough before turning on the valve.
When you add to all that the difficulty of controlling the temperature of the elements and the truly eye-popping cost of the machine, you could be forgiven for wondering what the point of going this route is? Well, kerosene has three big advantages over propane as a cooking fuel:
- Its vapors will not pool in the bilge waiting to blow you to kingdom come the way propane can.
- Kerosene can be procured almost anywhere, albeit in varying qualities, with none of the problems of different valve standards that can make getting a propane cylinder filled difficult or impossible, even where that fuel is available. You can even, at a pinch, use aviation jet fuel in a kerosene stove.
- A kerosene tank, like the one on Polaris that takes up no more space than two 20-pound propane bottles, can hold enough fuel for at least a year of cooking.
Will we be fitting Morgan’s Cloud with a Swiss kerosene stove? No, but we can see the point, given the mission that Polaris was built for.
By the way, as we discovered when I was cooking Christmas dinner, an incompletely combusting kerosene burner can produce carbon monoxide just the same as a poorly adjusted propane stove. All boats should be fitted with a CO detector like both Polaris and Morgan’s Cloud are.
Reader Comments:
Denis Bone writes: I fail to see why people continue to use cookers using any fuel other than that which is normally on board the boat in large quantities, diesel. My diesel cooker works well, is controllable and gives no smell. The fuel will not explode and there is enough on board to cook the largest turkey. Unfortunately, the oven is not large enough to take an ox otherwise there is enough fuel to cook that! The only downside, apart from the cost that seems to apply to the kerosene cooker described in your article, is that it needs at least 12v to start.
Dick writes: I would like to nominate CNG stoves/ovens as a good alternative to both kero and propane. Having survived a blowup and burnup on a 75' ketch as we were leaving New York Harbor for the Med in the late '60's due to propane lying in the bilge and the genset lighting it off, CNG that is lighter than air seems to work well. Outside the US it is reasonably easy to obtain also.
Our Response:
Diesel cookers sound interesting, although the only ones I have ever seen were huge, smelly, heavy, and temperamental. That may have changed.
CNG seemed like it would become the fuel of choice on boats at one point in the eighties but has faded out since. The big drawback with it is that it packs a lot less energy per pound than propane. Also, the bottles are relatively big and heavy because CNG must be stored at very high pressure to remain a liquid. I’m interested that you would say that it is generally available outside of the USA. My understanding, admittedly based on hearsay, is the exact opposite.
While we see the benefits of other fuels for cooking and, as any regular reader of this site knows, we are very concerned about the explosion danger inherent in propane, we can’t see changing from that fuel on Morgan’s Cloud, if for no other reason than the instant and controllable heat ability of a propane cooker. By contrast, as we understand it, all of the liquid fuels, kerosene (paraffin), diesel and alcohol (don’t go there) require a preheat cycle that unacceptably interrupts, at least to us, the rhythm and timing of cooking. But then we are big time food lovers that like to cook quite complicated multi-item meals, often with sauces as well. Doing a John-make-fire act complete with preheating and flare-ups for the three rings and the oven required in the middle of making my pork chops with sherry apricot sauce recipe, would be a sure route to tears!
One alternative that does look interesting, is that of induction and
convection electric cooking. Steve and Linda Dashew have been experimenting
with this technology and have found that it is so efficient that using
it with battery power, through an inverter, is practical. Of course they
have huge battery banks on their boats. We have not got into the details
of what minimum battery bank and generation capacity is required to make
this practical, but it does bear further study.
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