Heat Vectoring

by Brian Griffin January 07, 2018

If you are a hunter or fisherman, or you just like the out of doors and plan to venture into a wilderness environment this winter, it could be helpful to have more than just a basic understanding of wet weather fire starting techniques. Not because winters are known for wetness around the globe, but because if you can start a fire quickly in wet conditions, then you can start a fire quickly under less humid conditions as well. If you find yourself alone facing the bitter cold of winter, and dealing with the onset of hypothermia and the loss of motor skills, it will be the quickness with which you can produce warmth that is important to your survival.

This photo illustrates one example for setting up a good fire lay for wet conditions. The kindling should be placed on a base made of small limbs or branches as you gather it. That will keep it up in the air flow and out of the dampness while you go about collecting more. Another base should be made for starting the fire upon. This will keep the tinder material and kindling from absorbing moisture from wet ground before you ignite it. As the fire grows in size and intensity it will burn through the base layer drying out the ground beneath it in the process. I almost always build fires in a linear fashion during wet conditions. It is sort of like a shortened version of a long fire, built between two sections of logs, as big in diameter as I can find and use. I use these to vector the heat where I can make the most use of it to dry the fuel as the bottom layer burns down.

This technique is somewhat like focusing a light from flood to beam. It harnesses a lot more of the heat that would normally radiate horizontally away from the base of the fire, and redirects it upward. Thus the heat rises through the spaces between the wet branches drying them as it goes. In the photo below you can clearly see the amount of moisture being evaporated from the upper layers of the fuel by the intense heat of the thick bed of coals below. Wind direction and speed also play an important role in the function of this fire lay. In most cases I have found that laying the logs diagonally across the path of the prevailing winds provides the best results. It allows for some air flow between the logs, but minimizes the amount of wind blowing on the very base of the fire, so it helps to maximize the amount of heat available for warming by.

Due to the more controlled use of the heat being produced by the burning tinder and kindling, this technique produces an effect similar to a chimney, or sort of like a "rocket stove", but with not as much heat intensity, and a little better economy of fuel. The rapid expansion of the heat, as it exits the top of the fuel pile, creates a drawing effect. So the fire pulls in more more oxygen through the openings at the bottom. This feeds the fire causing it to burn even hotter as it rises even faster. So it dries the next layers of fuel pretty quickly as the lower layers burn.

Because the intensity of the heat being produced is so great, this type of fire will create a larger cone of heat, and it will dry the area at the base of the fire fairly quickly, and reduce mud. However the intensity in the early phases does come at the expense of rapid fuel use. So it is important to have enough fuel on hand to achieve sustained fire before ignition. After that phase, more wood can be gathered while the most recent layer on the fire starts to dry. Each successive layer adds to the depth and heat of the bed of coals. In time the bed of coals will be hot enough, and the base dry enough, to slow the tempo and reduce fuel use.

One benefit of having the ends of the fire lay open, is that it allows for long limbs to be laid across the hot core of the fire, and simply burned into lengths, rather than them having to be chopped or sawed into pieces. For recreational purposes, this is good because it makes the trip less work and more enjoyable. In survival or primitive living type situation this will allow you to conserve energy for other tasks.

Building the fire in linear fashion, between two logs, has other benefits as well. It can also aid in with cooking. When the logs are scotched in place well it can help making the fire more secure while sleeping. So it doesn't just allow for control of the heat, it can allow for more control of the fire in general.

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