Can a tiny wood-fired tent stove be fired with oil for an all-night-stove?

My investigations into a potential ‘over-night-stove‘ for a small tent concluded that it would be difficult to make a self-feeding wood stick fire stove to serve this purpose while winter backpack camping.

With that failure, I thought back to my other test burners that used wax or oil to provide lengthy self-feeding combustion.

I have tinkered with candle wax and vegetable oil burners as discrete burners, to test their capacity to create useful heat and a sustainable flame. This has resulted in a lot of fun but not in any great success that I could imagine working as an ultralight tent heater.

I knew that the burning of whale blubber on ‘square rig’ sailing ships was standard practice in the days of whaling from the book, Ahab’s Trade a fascinating tale of whaling based on real history.

“I love stories of this period as they make me appreciate what we have today and how we now have to go out-of-our-way to have an adventure.”

On four year voyages, wood was a scarce commodity so whale blubber, in the form of waste whale ‘skin pieces’, were used for whale oil rendering and cooking on the ship. A tricky technique to use on the deck of a rolling sailing ship with wooden decks that were soaked in whale oil! Even the alkaline ash if the whale was used to scrub and degrease the decks and wash their clothing!

To keep the crew happy, the cook would make them a batch of dough that they would use to make doughnuts in the boiling oil (much of which was used for high-quality church candles) in the rendering tub. They were very fussy. They only did this with a freshly killed whale and resisted doing so with ones that were salvaged, as a shark-bitten carcass that had gone rotten drifting dead around the ocean for some weeks.

Good or bad whales, the crew complained of bad pimples as a result of this indulgence, but they kept doing it. Maybe having the exact same weekly meal menu of stodge for four years made anything taste good.

An ode to oil as fuel and food:

Energy-rich oil on a freezing cold night,
For warmth should I eat it or would burning be right?
Heat by digestion or by combustion?
Both heat and doughnuts when the oil stove I light.

“The menu was published at the time of sign-on and crew and officers all ate the same seven meals that were metered out fairly by cubic measure. No prises for plating-up!”

Even worse, their food ingredients were stored in used, rancid, wooden whale oil barrels for up to four years. (The new barrels we ‘Ikea style flat-packed’ and assembled by the ships cooper as required when he was not repairing whaling boat that had be broken by angry whales).

“To me as a fisherman and gatherer of wild foods, I can’t understand why they did not use the abundant fresh meat and seaweed that the sea had to offer. It would be far better than four-year-old salted pork and mutton from a secondhand oil barrel.”

Back to stoves…..

I also am fascinated with the heroic adventures of Shackelton’s ill-fated Antarctic trip and miraculous rescue of his team. “What a story of survival to be then thrown into the horrors of the First World War.”

They too depended on a blubber stove for ice melting to make water and cook as they dragged their boats across the ice as they waited for it to break up and melt under them.

It seems that penguin blubber was the main fuel and two skins were added to the stoves internal rendering rack at about 5-minute intervals. “This was a tedious ‘all-night stove’ indeed. I suppose the reward of rare warmth for the outdoor attendants was some compensation.”

Their ingenuity enabled them to designed and build their stove during the adventure on the ice. This link has a photo of Hurley and Shackelton beside the stove and a description of the stove.

The narrative description of the stoves in the above links differ a little, but that is just how two different accounts of history end up.

Shackleton and Hurley designed and built the stoves out on the ice under those conditions. So, surely I should be able to make liquid vegetable oil burn within a micro tent stove with all the advantages of high-tech materials and tools that I am blessed with today.

Qulliq- oil lamp/heaters

The Aboriginal Arctic people used qulliq oil lamps that were fuelled with seal oil or whale blubber. They were used for light,warmth, melting snow, cooking, and drying their clothes. These lamps were said to be the single most important article of furniture for the Inuit peoples in their dwellings and date back 3,000 years.

It seems that both seal and whale oil was rather special fuel for these lamps and fat from land-based animals was not a good substitute with regard to having a ‘low-smoke’ flame. It is still difficult for me to think that significant heat could be generated by such lamps. However, they did need to constantly trim the extensive wick that ran along the edge of the stone bowl to prevent smoking. “So even with the best fuel, it is still not an ideal all-night stove if you like to also sleep.”

This seems to be consistent with the whaling story above, where particular premium whale oils were used to make premium smoke free church candles. The funny thing was that there was a much bigger proportion of premium oil sold than could ever have been harvested. It is a bit like the free-range egg scandals of today!

Me

Nevertheless, wax or oil quality is probably at the heart of the candle style tent heater failures that I report below, where I using very cheap tea-candles as fuel. Maybe I should just try an expensive church candle?

Current tiny oil heaters

To provide a full context, I can’t go on to discuss my primitive tinkering without mentioning those amazing small, high-tech and efficient diesel heaters (truck cabin heaters).

I have experienced their wonderful performance in large drying rooms of remote mountain ski chalets. They burn a tiny amount of fuel and waste almost no heat and can pump the warm exhaust gas downwards to be vented safely outside. They are tiny (about the volume of two house bricks), and efficient (0.14-0.25L/h) but still not suitable for backpacking. They are very efficient air heater but they radiate very little heat and require fuel pumps and DC power to operate.

My lessons from failures

My wax burner heater. The flame for my wax burner was from a mega candle (One of my alpine candles with a big ceramic wick.) The flame from the wick interacted with a fine stainless steel mesh tower that glowed red and radiated significant infrared heat (just like old kerosine heaters do).

Unfortunately, the fumes and carbon particle from the combustion ended up in the tent. Also, the mesh slowly became clogged with carbon. It was not a healthy, pleasant, clean or sustainable way of providing heat in a tent.

[Add photo of my mega candle infrared heater mesh ]

Oil burner heater. I also experimented with a primitive micro oil heater with a similar mode of operation to those primitive and ubiquitous waste oil heaters. An example is a Demon Heater (Aus) or a Smudge pot heater (US) that can use sump oil or other waste oil for powerful heating outdoors or in a well-ventilated space.

My tiny burner was more like a tiny version of Gerry’s toffee tin burner. I made mine with a short extension burner tube that was attached to the bottom end of one of my standard roll up flue pipes. The burner tube had numerous slits cut in it to make ‘carrot grater’ type air vents. Underneath the tube, I put a sardine can with oil in it (Probably a little bit of sardine as well.) below the burner tube.

The burner tube height was finely adjusted so that it had a very small clearance from the oil surface. I used a strip of copper sheet to transfer heat down from inside the combustion tube into the oil reservoir.

When started with paper, alcohol and kerosine the oil could burn with an exciting pulsating whitish bright flame and the burner tube glowed red hot. It did emit a little flue pipe smoke, but there was no smell of sardines. It was finickity to start and to adjust the burner tube/oil surface gap to maintain the desired flame characteristics without snuffing it out and needing to start it all over again.

Lastly, it would not be a welcome way of providing warmth in my tiny tent. I had no idea of the rate of consumption of oil, but it would have used an excessive amount of oil to consider it as an ultralight backpacking stove for over-night-use. “Probably a bit too noisy to sleep with. “The above performance of Gerry’s burner probably tells you why it would not be good in a small tent!

Wood/oil hybrid stove? My failures/lessons contrasted with the success of the desperate blubber burners on the Antarctic sea ice. However, my knowledge of the potential heating power of this convenient energy-dense food/fuel kept hovering in the back of my bower-bird brain.

Could oil be a suitable substitute for wood fuel to temporarily convert a tiny wood-fired tent stove into an ‘overnight tent stove’ for winter camping?. “This is considered to be the holy grail of many winter tent stovies.”

When looking down into the inferno at the bottom of the fuel tube of my Simple Dome Stove, I could not resist any more. I dripped oil/water emulsion into the centre of the fuel tube onto the residual wood on a bed of glowing charcoal and watched the mix explode into a fireball.

Oil as a substitute fuel in a tiny wood stove

Oil dripper testing.

If without needing to carry a separate oil stove, could food grade oil just be used a supplementary fuel for a tiny wood stove when the intense wood-burning phase is finished with?

For a start, I tried dripping an oil/water emulsion into the charcoal bed of the Simple Dome Stove that had been running on wood sticks. The maximum drip rate was about 1.5ml per minute when the reservoir was about 800mm above the exit point. The oil was emulsified with about 5% water to make the oil explode on contact with with the hot coals. The explosive effect worked well and made a dispersed flash of flame. However, I think there was too much water and it eventually cooled the charcoal a little too much.

Also, a significant portion of the oil mix fell through below the ash layer where it was not hot enough to combust.

A note to Shackelton & Hurley: No penguins were harmed in the conducting of these experiments, but our society is making a good effort to destroying our wonderful atmosphere and oceans.

Wooden oil wick test

For my next test, I used about 1% water in the oil mix. I increased the surface area for vaporizing or pyrolysing the oil to make a combustible gas. I did this by feeding the oil into a gap between two flat-faced fuel sticks so that the oil flowed, dispersed, wicked, ‘stewed’, bubbled and crept its way down, around and over the surface of both pieces of wood.

It made a steady flame as shown in the videos below without the explosions or the pronounced pulses of the drip-feed method above.

This feeding technique also appeared to prevent the loss of oil into the ash layer. I presume it was entirely burnt as there was usually only a small trace of flue pipe smoke and no visible oil in the residual ashes (as was the case with the dripper).

“I observed by, spit on the finger test, that the 100C point on the flue pipe was much lower down (~500mm up from the stovetop) than when burning wood.”

Here is a little Instagram video of the oil combustion in the Simple Dome Stove. Sorry that the recording was a bit noisy, but I left the original sound so that you could hear that lovely chuffy sound from the burner, the boiling pot and the closing of the lid.

If you look at the video, the two flatish fuel sticks are held together experimentally by a rubber band and fuel tube is lightly pinched between them. The next video showed that the wicking worked without this complexity.

A cotton wick on a candle is protected from burning so long as the liquid wax is drawn up into it to replenish the vaporized oil that then burns. I think the wood sticks are similarly protected from normal quick combustion by the oil coating them. The shroud of oil gases produced from the surface preferentially burn in the available oxygen. (This is similar to wood gas protecting charcoal from being burned rapidly.)

Here is a little Instagram video of day time oil wicking burning. In this video, tiny ‘waves’ of oil can be seen slithering down the fuel channel.

However, as I expected the ‘oil wick sticks’ did very slowly erode away. “Not a good all-night burner strategy if you have to get up to replace the wick every half hour! Just a little bit better than the Inuit seal oil lamp and Shackelton & Hurley penguin skin stove that needed attention every 5 minutes.”

An ode to a valiant wooden oil wick for a wood-burning stove:

To make oil burn well, can I use a big wick?
Could a solution schmick just be a thick stick?
No, hope went astray as flames slowly frittered it away,
But a hairy refractory wick by chance may just do the trick?

While not a sustainable system the wooden wick did show me that a similar large soaking wick of suitable porous refractory material might just work. “And unlike Shackelton and Hurley, I don’t have the problem of my workshop being crushed by Antarctic sea ice.”

Discussion/conclusion

I initially started the above investigations assuming that some water in the oil would make the otherwise stodgy oil combustion a little more exciting. I think it did for a while.

I mixed a little Aldi dishwashing detergent into the vegetable oil and then added the water (bucket chemistry style). With a good shake, the emulsion formed quite easily and has stayed quite stable for many days.

I think the water in the emulsion had an undesirable cooling effect on the burner and would best be discontinued. When I tested the adding of the oil by the hot wooden wick, I reduced the water content to ~1-2 %, but I think pure oil would be as good if not better.

“If the oil was pristine olive oil, not oil from a long-dead rotting whale carcass, it would have the advantage of being a food energy source as well as a fuel. “I am told that all good bushwalking items should have multiple uses, including the backup alcohol for stove fuel.”

The stove was not nearly as hot as when burning wood sticks (But wood sets a glowingly high standard on my test-bench!). However, it was able to boil the water in the pot (see the above video) and provide gentle and persistent heat for a tent. “If nothing else, it could be used to replenish the hot water bottle for your sleeping bag during the night.”

Energy density of fuels

Oils are the most energy-dense substances that you and I have at our disposal with about 44 MJ/kg (compared with dry wood at 16 MJ/kg (combustion heat energy values for oil and wood). Hydrogen and methane are a tad better and enriched uranium is ‘off the scale’ at 3900 GJ/Kg. However, none would be welcome in my backpack.

Innocuous and renewable plant-based oils can be a little messy to handle. However, they can be safely carried around in a backpack in something as simple and cheap PET soft-drink bottle. Additionally, the best oils can be used as the richest source of food energy with cooking or as a simple energy supplement if push-comes-to-shoveif your rations run out.

An ode to vegetable oil as fuel and food:

Energy-rich oil on a freezing cold night,
For warmth should I eat it or would burning be right?
Heat by digestion or by combustion?
Both heat and doughnuts when the oil stove I light.

I calculated that the total energy released by perfect combustion would be 3.9 and 6.4 Mega Joules/hour for the oil and wood. I did this by using the above energy densities and fuel consumptions of 0.09 and 0.4 Kg/h for oil and wood respectively.

This means that the oil-fuelled stove would have about half the power of the wood powered stove. This is a very significant power reduction and is consistent with my casual observations.

However, the oil still provides a very significant heat source for continuously keeping a tiny tent at a nicer temperature throughout a freezing winter night.

In the above situation, hot air will accumulate (uselessly) at the apex of a tent. A small Laptop air pump could be beneficial. It could bring down the hot air from the tent apex for the benefit of the tent occupants. It could be battery-operated or run on thermoelectric power generator (TEG). That’s a project for another day.

At a rate of oil usage of ~1.5g/min (0.09Kg/h), the stove could run for about an 8h period on 720g bottle of oil. “That’s a suitable sleep for a grown man who likes to get up early for the best and fastest skiing.” This would all depend upon having a suitable non-combustible stove wick to make the ‘all-night’ burn possible. This will be the subject of another post.

Conclusion

The heat provided by the oil-fired stove may not make the tent occupants warm enough to sleep in only their undies. However, it might just make it more comfortable on a freezing night and at least keep the condensation off sleeping bags, and keep tent icicles at bay.

These preliminary tests show that the Simple Dome Stove and all my other related dome stoves (with the same burner design) should effectively burn oil to provide steady low-level heat that could be sustained for a long time to become a possible ultralight ‘all night tent stove’.

“It is the only option that I have yet examined that might just make it, and will not involve sitting up for the night feeding pairs of penguin skins every five minutes or trimming moss wicks on a seal oil lamp just as often.”

I suspect that the Aussie Antarctic Photographer Hurley would think we are a bunch of wusses. He may be pleased to see me trying to make an adventurer ultralight oil burner that is inspired by him.

Tim

I have another post about storing the heat from a powerful tent stove in a 33g device to use the heat to keep you warm in your sleeping bag all night. Not quite the Holey Grail but a good substitute.

Alpine hot water soft bottle