Pg 16: Weight vs Warmth
Reducing the weight of your hiking and camping gear is important. But when it comes to the weight of your sleeping bag, we have a problem. This is because companies that produce these items tend to exaggerate their specs in order to sell more products.
This was brought home to us during one of our Journey's Flow classes, when a student - completely new to backpacking and camping - brought an incredibly thin sleeping bag with a label clearly stating its temperature rating of 35° F. Its actual temperature rating was more like 65°, and unfortunately the nights were in the low 40's. So for two sleepless nights this poor student experienced the shivering consequences of the company's deceptive marketing. On the third morning the stoic student informed us of the problem, and very sadly we had to send her home.
This type of deception is so rampant, that I know of only one solution - which I have stated in Trail Life. That is, to measure the thickness of insulation for yourself. Only then can you know the sleeping bag's true temperature rating.
As stated in Trail Life, the temperature rating of a bag or quilt is a function of the thickness of insulation covering you.
Ray's formula for the Effective Temperature Rating
ETR = 100 - ( 40 * T )
In this formula, the letter "T" represents the thickness, in inches, of that part of the quilt or bag covering you. Since warm air rises, the part beneath you contributes very little (almost nothing) to warmth.
So you multiply "T" by 40, then subtract the result from 100. This gives you the quilt or bag's Effective Temperature Rating, (ETR) in degrees Fahrenheit.
Here is an easy and reasonably accurate way of measuring thickness of insulation: Lay the quilt or bag on a flat and hard surface. If measuring a sleeping bag, unzip it, and open it so that it is not doubled. Measure only the part that would cover you. Lay a yardstick gently on the quilt or bag. Stand a ruler on the quilt or bag, alongside the yardstick, and press it down onto the underlying flat surface. Read the thickness measurement on the ruler at the yardstick.
Note: To avoid false readings, do not measure the thickness of the insulation on an edge. Take your measurements away from the edges.
Let's say that on a summer journey taking us to the cool mountain heights, we are carrying a sleeping bag having 2 inches of insulation in the part that covers us. Plugging the 2 inches into the formula: 100 - (40 * 2") gives this bag an ETR of 20°F. In other words, when sleeping in this bag we can expect to remain comfortable down to 20°F.
Again this is only a guideline, because some people sleep colder than others; some much colder. But for most people it is reasonably accurate, and the cold sleepers can simply choose more insulation and/or wear more clothing.
If you measure the thickness of insulation, and calculate the temperature rating for yourself, only then will you be immune to the manufacturers' ploy of making their products lighter by reducing the amount of insulation - then grossly exaggerating the temperature ratings.
Manufacturer's claims: suspect
Reality: thickness equals warmth.
The weight of a sleeping bag or quilt depends on what it is made of, and how much it contains. And to be honest, we have sized our 1-person quilt kits extra wide. This is because most people new to quilts tend to thrash around a bit, and for them the wider quilt will be much warmer. But for someone who lies more still, the excess width of quilt lying on the ground does them no good. Once they figure that out, they can trim the quilt to whatever width they like. And yes, a narrower quilt would be that much lighter.
In a certain since, the quilt is like the food - we do not care about its weight. Far more important is that we are well fed, and warm at night. Lightness is important, but warmth is much more so. So we lighten the quilt only as much as we can without sacrificing warmth. And that warmth depends on ample thickness of insulation, along with ample coverage.
Bottom line: Choose one of our Quilt Kits, follow our assembly instructions to the letter, then rest assured that you have a very light and effective sleeping arrangement. Then head into the wilds and enjoy your hiking and camping!
Next Page: Why We Don't Use Goose Down -->