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sleeping bags

Ever wondered what's actually inside your sleeping bag?

Check out some of the following technical information for an insight into your sleeping bag. (You can also find out more by watching one of our designers talk about the process on a short film.)

Fill Power Fill Power Fill Power

Fill Power

Fill power ratings are a major key element to superior performance in sleeping bag design.

Fill power is defined by the amount of loft that is gained under loft test conditions. The higher the fill power number the greater the loft and the greater the performance of the down insulation.

Goose down fill power ratings within the outdoor industry usually range between 650 and 850 fill power.

Duck down fill power ratings within the outdoor industry generally range between 500 and 700 fill power.

There are many different standards for testing loft values, however the 2 main standards are the US standard and the EN standard. The US IDFB method preconditions the down using steam. Where as the EN method preconditions the down using the tumble dry method. Rab now tests the sleeping bag down using the US standard as this method is primarily used within the outdoor industry.

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Over time down can loose its Fill Power rating due to many different factors. Down fill power ratings can generally be regained by having your sleeping bag professionally cleaned.

Leaving down crushed in stuff sacks can damage the down plumes. To prevent damage and maintain down longevity and loft it is best to store the sleeping bags in the storage sack provided.

 

White goose down

Species and cluster ratios

The species and cluster ratios are a major key element to superior performance in sleeping bag design.

Species is defined by the type of fowl that the organic down / feather insulation originates from.

Water fowl generally have better quality down with higher R values than land fowl. The outdoor industry tends to generally use Goose and Duck down. Goose down generally has higher fill power lofting performance than duck down (excluding the Eider duck). Goose down generally is available with higher down cluster ratios than duck down which offers greater fill power performance. There is no performance difference between white and grey coloured down of the same specification, it is only a visual difference.

Cluster ratios refer to the percentage of down plume content and percentage of feather content. The greater the down percentage the better the quality and fill power of down.

100% down does not exist as down is always contaminated with a portion of feather content. 95/5 cluster ratios are attainable but are not a reliable consistent source. 90/10 cluster ratios are available on a consistent basis from year to year.

Down is an organic product and will vary from season to season due to factors such as weather, bird condition etc.

Rab sources un-crushed sterile European down for use in sleeping bags. The down sourced is a by product from the meat industry.

European down is generally better quality than Chinese down due to the birds being older and having better developed down plumage when the down is harvested.

Rab does not support live plucking of mature birds to yield loft values of 900 fill power.

Rab supports free range bird growing environments.

Rab sources down with cluster ratios measured in US standards as these standards are true to value. Therefore US rated 90/10 is in fact 90% down and 10% feather. Where as EN 100 is in fact only minimum 90.48 % down and EN 90/10 is in fact only minimum 80.95 % down.

All down is IDFB certified.

 

Fill weight

Fill weight

The fill weight is a major key element to superior performance in sleeping bag design.

Fill weight is defined by the total amount of down insulation in the sleeping bag which is measured in grams.

Why have different fill weights?
Different fill weights are required due to the variety of climate conditions that sleeping bags will be used in. For example an expedition sleeping bag may require to be functionally adequate at -50 degrees Celsius. Where as a sleeping bag being used in warmer temperate climates may only require to be functionally adequate at +15 degrees Celsius. Therefore an Expedition sleeping bag with 1200 grams fill weight will have a greater R value (warmth rating) over a sleeping bag with 100 grams of fill weight.

Even though fill weights maybe the same in different styled sleeping bags, this does not mean that they will have the same performance. This is due to factors such as fill power / cluster ratios and the actual designs being different.

Fill weight is an exact measurement in grams. To find the weight of the sleeping bag shell, the fill weight can be subtracted from the total weight of the sleeping bag.

The total fill weight is distributed throughout the sleeping bag's chamber baffles. The down is strategically placed to maximise functionality and performance.

Please note that total fill weight may vary if filled in humid environments.

 

Chamber fill weight

Chamber Fill Weight

The chamber fill weight is a major key element to superior performance in sleeping bag design.

Chamber fill weight is defined by the amount of down insulation assigned to a specific baffle chamber which is measured in grams.

Why specifically assign chamber fill weights?
Chamber fill weights are specifically assigned as the amount of assigned down is specific to the size, shape, volume and location
of the chamber baffle. Primarily the chamber fill weight is driven by the internal volume that can be achieved by the chamber. The second driving factor is the location, for example the upper chest area will be allocated more down than the lower mid back area, this is to help maximise performance through ergonomics and function.

Each chamber is individually filled accurately during the filling process. Down migration is controlled by the baffle which runs around the perimeter of the chamber.

Chamber fill weight is an exact measurement in grams. Continued quality control can be applied due to knowing these chamber fill weights.

Please note that chamber fill weight may vary if filled in humid environments.

 

Baffle Height

Baffles

Baffle height is a major key element to superior performance in sleeping bag design.

Baffle height is defined by the measured width of the baffle material excluding the seam allowance.

Why have different baffle heights?
Baffle height allows down to loft outwards and inwards without restricting natural loft. The different baffle heights are proportionallyallocated to sleeping bags with different loft volumes. For example, a smaller fill weight sleeping bag of 500 grams will require a smaller baffle height than a sleeping bag with a fill weight of 1000 grams. This is because 500 grams of down will loft less and fill less volume than 1000 grams of down of the same down specification.

Baffle height is proportionally assigned not only to fill weight, but also to fill power and cluster ratios. For example 500 grams fill weight at 600 fill power will have less baffle height than 500 grams at 800 fill power. This is because 500 grams of 800 fill power will fill more volume than 500 grams of 600 fill power. This is also true for cluster ratios, for example 90/10 will have greater loft volume over 80/10 of the same fill power and species.

Baffle height can only be applied to products with baffles. Baffle height can not be applied to sewn through products as the inner liner and outer shell are sewn together.

Baffle height allows the down insulation to loft naturally to its full potential resulting in refined science and greater performance.

 

Differential Cut

Differential Cut

Differential cut is a major key element to superior performance in sleeping bag design.

Differential cut is defined by the measured difference in circumference between the inner liner pattern and the outer shell pattern.

Why use differential cut?
Differential cut is used in the same way clothing is graded to sizes small, medium and large. A small item of clothing will fit over a small framed person and a large item of clothing will fit over a large framed person.

Differential cut is not static over different fill weight bags, instead it is proportionally assigned to suite the fill weight. For example, a smaller fill weight sleeping bag of 500 grams will have a smaller differential cut than a fill weight sleeping bag of 1000 grams. This is because 500 grams of down will loft less and fill less volume than 1000 grams of down of the same down specification.

The proportion of differential cut is not only assigned to the amount of fill, but also to the specification of down quality. For example 500 grams of 600 fill power will have less assigned differential cut to 500 grams of 800 fill power, this is because the 800 fill power will have greater loft volume. This is also true for cluster ratios, for example 90/10 will have greater loft volume over 80/10 of the same fill power and species. Essentially the differential cut allocation is assigned to the resulting volume that is created from the
lofting down insulation.

Differential cut can only applied to products with internal baffle walls , sewn through products are unable to have differential cut as the inner liner and outer shell are sewn together.

Differential cut allows the down insulation to loft naturally to its full potential resulting in refined science and greater performance.

 

Offset

Baffle Offset

Baffle Offset is a major key element to superior performance in sleeping bag design.

Baffle offset is defined by the measured horizontal difference between the inner liner attachment point and the outer shell attachment point.

Why apply baffle offset?
Baffle offset is the key to creating a trapezoidal chamber shape. The angle of the offset is crucial. It is essential not to be too steep or too shallow as the baffle angle plays a vital role in creating baffle wall friction which minimises down migration and cold spots. For example an offset angle that is too steep will result in down slipping on the surface of the baffle mesh. An offset angle that is too shallow will add weight due to increased baffle material, but more importantly it will apply un-relaxed forces to the bag making it rest in a crinkle cut state which will ultimately decrease performance.

Baffle off set is not static over different fill weight bags, instead it is proportionally assigned to suite the baffle height. For example a baffle height of 10cm can easily have a baffle offset of 2cm. Where as it is physically impossible for a baffle height of 1cm to have an offset of 2cm, as the baffle height is only 1cm.

Baffle offset can only be applied to products with internal baffle walls , sewn through products are unable to have differential cut as the inner liner and outer shell are sewn together.

Baffle offset assists in refining sleeping bag science and increasing greater performance.

 

chambers

 

Trapezoidal Chamber / Baffles / Chamber Height

The trapezoidal chamber shape is a resulting product of baffle offset and baffle height.

The resulting shape from baffle offset and baffle height is the trapezoidal chamber shape.

The baffle is an internal wall that is sewn / attached into place to prevent down from simply migrating around between the outer shell fabric and the inner liner fabric. The baffle creates distance between the shell and liner fabrics which in turn allows down insulation to loft naturally.

The baffle is made of a light weight mesh which allows air to circulate. Circulating air allows the bag to breathe which helps prevent condensation build up inside the bag, and can assist with the process of stuffing the bag into the stuff sack. Down plumes can get entangled in the mesh, resulting in increased wall friction to help minimise migration.

Sewn through products do not have baffle walls.

Chamber height is a result from many of the discussed factors. Generally the greater the chamber height, then the greater the warmth (R value).

  Shape and Cut
Mummy Shape

Mummy Shape

The mummy shape is suited to fill weights between 800 and 1200 grams. This shape is designed to be used in environments such as polar, high altitude and cold mountain use.

Longitude torso and foot chambers ensure that the down does not migrate from apex points (off the body) whilst sleeping. The longitude chambers are strategically located to ensure vital organs (torso) and extremities (feet) maintain maximum warmth efficiency.

The outer shell patterns consists of extremely large applied proportional differential cuts to allow for high lofting capabilities to ensure warmth is maintained in extreme cold weather environments. The inner lining fabric contains calculated ‘slack’ in the pattern to allow internal lofting to fill dead air space within the sleeping bag. The Expedition sleeping bags have an internal cut that has been design to fit over and work in harmony with lofting expedition clothing.

Mummy Taper Shape

Mummy Taper Shape

The taper mummy shape is suited to fill weights between 100 and 600 grams. The shape is streamlined for use in lighter, faster mountain use applications.

The narrow more tapered cut increases efficiency to weight rating. A taught internal liner pattern will not fill dead air spaces created by limb regions of the body. Therefore, the inner lining fabric contains calculated ‘slack’ within the pattern to allow internal lofting to fill dead air space within the sleeping bag.

The outer shell patterns contain zero to medium amounts of proportional differential cut. The actual amount of differential that is applied is calculated to work in harmony with the fill weight, chamber loft height and temperate rating that is required for that specific sleeping bag.
Sleeping bags that are too streamlined and tapered generally ‘bottom out’ on the shoulder, hip, knee and foot regions which creates cold spots and lowers thermal performance dramatically.

Semi Rec Shape

Semi Rec Mummy Shape

The semi rec wider mummy shape is suited to fill weights between 500 and 900 grams. The shape has a generous internal cut to allow for more casual relaxed sleeping positions without sacrificing performance in general mountain outdoor use activities.

The inner lining fabric contains calculated ‘slack’ within the pattern to allow internal lofting to fill dead air space within the sleeping bag. The outer shell patterns contain moderate amounts of proportional differential cut to harmonise with fill weights, fill powers and targeted use.

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