How Do We Build a Sleeping Bag? | Rab Lab
How do we build a sleeping bag?
Ever wondered why we’ve chosen a certain insulation or baffle shape for your sleeping bag?
There’s more than one way to build a sleeping bag. With multiple constructions and types of insulation to choose from, those used in your sleeping bag will tell you a lot about its potential to keep you warm and the environment it's intended for.
Baffled by baffles?
All down bags need baffles. These fabric chambers hold the down in place and stop it migrating to one end of the bag, just like in a duvet. Baffles can be stitch-through or boxwall. Most of our sleeping bags use boxwall chambers as they are the most effective way to minimise heat loss, but some of our ultralight bags use stitch-through construction to help keep weight down.
In down sleeping bags we talk about ‘baffle height’ and ‘baffle offset’:
Baffle height is the height of the internal mesh separating the inner and outer fabrics of the sleeping bag.
Baffle offset is how much the mesh is offset in a horizontal direction, producing a trapezoidal chamber shape.
Baffle construction explained.
All down bags need baffles. These fabric chambers hold the down in place and stop it migrating to one end of the bag, just like a duvet.
Down to detail.
Filling chambers with down might sound straightforward, but simple doesn’t mean easy. Our designers and UK factory team work meticulously to ensure the down is distributed efficiently, maximising the performance of your sleeping bag.
We calculate the precise volume of down required within each individual baffle and ensure this is accurate to the gram when filling our down bags at our Derbyshire factory.
Adding a higher quantity of down around the torso and foot box, and lower levels elsewhere, is an efficient way to keep you warm and optimises the warmth-to-weight ratio.
When you lie down in your sleeping bag, the base of the bag is more compressed while the upper has better lofting potential. We distribute a different proportion of down in the top and base to make the most of the upper’s ability to loft.
Synthetic specifics.
We use a couple of construction techniques to get the most out of the synthetic insulation we use in our sleeping bags.
| Construction technique | What is this? |
|---|---|
| Concertina construction | Single, dual, or even triple layers of synthetic sheet insulation are arranged in a concertina-shaped structure to maximise air trapping and improve heat retention. |
| Offset localised quilting | This means the stitching that holds the insulation in place (quilting) has been minimised to reduce cold air creeping through the stitch lines. |