Camping hot water heater designs
Designs of compact devices to make bulk camping hot water with fallen sticks while backpacking.
Featured image: This is a photo of a large DIY hot water storage bag that was made of silnylon. The HH pressure caused it to slowly leak and more DIY silicone rubber impregnation/coating was needed to fully seal it.
Introduction to DIY camping hot water heater designs
Previously, I have described a DIY design for a stick-fired blower stove and pot that can quickly provide unlimited loads of boiling water (~1L) for camping. As well as normal cooking and snow melting, it can be used to fill a large-capacity Alpine soft bottle hot water bottle.
Also, the camping hot water can be blended with cold water to provide a brief ultralight backpacking soft-bottle hot shower by using the same soft bottle.
Steam heating of camping hot water. Another of my DIY water heating design is a light supplementary DIY fitting (80g) that can turn a stick burning blower stove and pot into a steam generator with almost unlimited steam heating capacity for extended indulgent bathing. The steam device was fitted with a long silnylon steam tube that could deliver the steam at a safe distance from the hot stove.
This for example could supply steam directly to a tiny sauna tent. Alternatively, the steam could be used to heat water for a bath or shower or melt snow. However, because the burner must sit on the ground or snow surface, it is not particularly suitable for snow camping where such warm bathing might be most appreciated while camping.
While testing this device I found that it could produce about 1.3L/h of distilled water to act as a desalinator which may be great for beach camping at locations that do not have a freshwater supply.
Consequently, I thought that a similar very lightweight hot water/steam device with a larger heating power for a group of campers would be worth exploring. It will be designed so that it can hang from a tree (or other structure) to provide gravity feed for the shower or bath and be above the snow when required.
Larger camping hot water heater. The success of using a rigid cooking pot and modifying it to become a steam generator with the use of sealed and glued silnylon fabric led me to think of a larger stick-fired water heater for winter snow camping or base camps with a group of skiers etc. It could still be very lightweight with a small packed volume and have a very large capacity as a water heater, snow melter and steam generator or water still.
Larger lay flat kettle for camping hot water. I had already designed, made and used lay flat water heating kettles. They can be used on a hot surface or a small controlled gas flame, but not on unruly naked wood flames. They have a base made of a flat copper foil heat exchanger that is attached to a water bag made of silnylon. The silnylon is sealed with supplementary silicone rubber to make it fully waterproof. Then it is glued onto the copper with silicone rubber and the joint is rolled and flattened to leave a strong waterproof joint with soft rounded edges to make them both backpack-friendly and silnylon-friendly.
Height limits of stand-alone lay flat kettles. A design limitation of my kettles means that they can not be tall and must be shaped inefficiently with a pyramid shape to maintain stability (~700ml capacity). On the other hand, if the storage bag of such a kettle was suspended from above, the volume would only be limited by the HH pressure limit of the kettle fabric. I have already shown that the HH of silnylon can be increased to 1000mm of water by the application of DIY silicone rubber impregnation and coatings. Here is a little video of the HH testing of such silnylon with extra coating.
A suspendable hot water and steam kettle design concept
Suspension for high-capacity camping hot water. All the above is a very long introduction, but I hope it provides a context for making my next bulk camping hot water and steam generator kettle. It is designed to be a suspended self-heating kettle with a capacity of about 9L. Its large capacity will mean it can be shared by a group of campers.
Suspension for snow clearance and gravity feeding of hot showers and baths. Being suspended means that the kettle can be kept clear of the snow surface on snow skiing camping trips. Preferably it can be set at a suitable height that will allow the hot water to conveniently run downwards for a shower or run a hot bath or provide steam for a sauna or melt snow or make a hot drink or a combination of all five functions.
“In my experience, hot water is always a welcome commodity when winter camping. So simply having abundant hot water on hand or the capacity to melt snow and ice for water will always be welcome in a winter camp, even if you don’t wish to bathe in warm water after a big day of skiing.”
Lastly, suspension of the stove above the ground or snow no longer allows protruding long fuel sticks to be supported, so an extension from the fuel port will be required as a substitute support. Alternatively, it will be a return to the tedium of cutting short fuel sticks that were required for my early blower stoves.
Tilting to improve stability, stove performance, versatility and flame clearance. Once the water heating device is made to be suspended from a single cord at the top of the water bag, the issue of uncontrolled spinning arises. However, a second sideways anchor from another part of the stove, such as the fuel stick support, can arrest this spinning.
Suitable adjustment of this sideways anchoring device can also tilt the whole assembly and provide multiple improved functionalities such as:
- A better clearance of the exhaust flame from the water bag surface.
- Improve fuel stick feed-in angle.
- A better slope for combustion draft.
- Additional mechanical support for a lightweight fuel stick support device.
Height could improve distillation. Lastly, if using the tall kettle for seawater distillation, the large space above the boiling water surface should make an effective splash head to prevent splash contamination of the distillate.
Consequently, for this project, a large (~9L) suspended water/steam kettle will be designed to hang from a tree. Lastly, it will be heated by a blower stove with the fire bowl suspended below the bottom of the kettle heat exchanger base. It will have an exhaust flame shield as described for the previous steam generator.
An extended pot or a lay flat kettle for bulk camping hot water?
A modified pot. With the above issues in mind, I reached a branch in the design road. Should the device be my favourite stove and an extra pot with a permanently attached tall silnylon extension water bag? “It would be simple, a little bulky but would almost certainly work with my well-tested Fiddle-free blower stove. Unfortunately, it would also mean that the heating power would be limited to 0.98kw as determined in the above steam generator post. A much more powerful heat exchange rate would be welcome for a group of campers.” A substitute copper heat exchanger surface may be possible and should improve the power of heat transfer.
A giant lay flat kettle and customised blower stove. Alternatively, should this camping hot water be made with a giant lay flat kettle with a massive 0.1mm thick stainless steel heat exchanger (~4 times thinner than the pot base) with a new customised blower stove suspended below it?
This would entail risks of unknown mechanical strength and clean stove combustion. However, its larger and thinner heat exchanger surface could double or triple the heat transfer power if it survives the suspension process. “Hopefully it would avoid some of the large and wasteful exhaust flames that I observed with the above steam generator as shown in this little video.”
Conclusion
Rather than equivocating about which design to choose I decided to do both. Both will be hangers and hopefully not swingers. This also means that there will be two projects and two more posts:
1. Hanging pot and stove water heater. This device will be made first because it is a simple modification to an existing successful stove and pot combination. I am unreasonably confident that it will work well.
2. Hanging giant lay flat kettle water heater. This innovation will be a higher risk one with questions about the mechanical stability of the large hanging flat heat exchanger that is as thin as paper. If the large heat exchanger survives and works as expected it may greatly increase the rate of water heating.
However, I also am aware, through other stick stove testing that excessive extraction of heat can also spoil the otherwise clean and hot combustion of the fuels sticks, particularly when they are damp, as they invariably are when winter camping. This all means that the project could be a big flop. On the bright side, if it works well, it will mean that the cooking stove will always be available for cooking (its intended purpose) while at the same time, hot bathing will be possible. “I wonder if the cook will deliver hot drinks to the bath?”
Tim
