Monday, August 8, 2016

Chilcotin Holidays

Bushcraft – 4 ways of heat transfer


On June 1st, we had the chance to participate in a speedy bushcraft course.

Nick, our bushcraft and survival guide, took us to the woods behind the Chilcotin Holidays Ranch. There were approximately twenty of us, all eager to discover the secrets of survival. On the way, Nick showed us the plants we could eat and where to set our camp, how to build a luxurious tent out of tarp and how to start a warm fire in less than five minutes. The question in everyone's mind was 'Were we ready for the night?' Not yet! Staying warm is the key to survival. Without warmth our body cools down below normal human body temperature (37°C), reducing the brain activity and putting the whole body slowly into sleep.

So, here is a little physics lesson to start off with: the four ways of heat transfer.

The first mode of heat transfer is evaporation. Limit it as much as possible! Evaporation of sweat from our body is a major risk, not only because it dehydrates us, but mainly because it makes our clothes wet and cold. The one thing to remember while surviving: stay dry!

The second way of heat transfer is radiation, which we want to maximize if it is an external source, or minimize if we are talking about radiation of body heat. When the ambient temperature is lower than our body temperature, heat radiates from our body into the surrounding air. External sources of radiation are for the most part from the sun during the day and fire at night. The closer we are to the source, the more warmth we will feel. Therefore, we had to make a fire by our tent for the night. The fire should be no closer than one meter away from our tent, in case the wind blows towards the tent. The fire should not be too far away either, to make sure it heats our bodies while sleeping. The hard part of the bushcraft night, keeping the fire alive all night – we have to get up every one or two hours to add more wood. In real survival conditions (with very cold weather, snow conditions, limited access to burning elements like wood…), one must stay awake by the fire at all times.

The third mode of heat transfer is convection. Convection is the movement within a fluid (such as air or water) created by heat coming from the bottom. For example, while heating up water in a pot, the water will naturally move within the pot ensuring that all of it is at equal temperature. In our case, we apply convection to wind. When making a fire we must make sure that the wind blows form our side. If it comes from the front, it blows the smoke in our face. If it from the back, it creates a small depression which can potentially kill the fire. When it comes from the side, the wind provides oxygen to the fire, without risk to us.

Last but not least, conduction. Conduction takes place when heat is transferred by contact. It is the most efficient method of transfer. For instance, touching the fire will burn, whereas sitting near it will bring warmth – conduction is indeed more efficient than radiation, hence the main danger when sleeping outside is the loss of heat by conduction. The ground can be cold and humid and can take up to 80% of our body heat. It is best to sleep above the ground. When this method is not possible, we must ensure that there is a layer between the ground and our body. During our experience, we used a tarp and camping mattresses, but when out in the bush we can use Spruce or other conifer boughs.

There are the four ways of heat transfer! Evaporation, radiation, convection and conduction. Not to be forgotten when going out in the bush!

Chilcotin Holidays

About Chilcotin Holidays

We are a licensed guide outfitter and we conduct guided wilderness adventures throughout our 5,000 square km operating area. This guide area has been operational since 1880, making it the oldest in British Columbia. More about us HERE.

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