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Cumulus Sleeping Bag FEATURES
Polish Goose Down Insulation
Sleeping Bag Construction - the shell
Sleeping Bag Construction - other features
Stuff sack and storage bag
The Cumulus Way !
Polish Goose Down Insulation
Performance characteristics of down insulation (LOFT and FILL POWER)
Loft ability of particular sleeping bags (FILL VOLUME)
WHAT IS DOWN
"DOWN" is a pure, natural, thermal-insulation product. It is grown by birds and in cold climates it enables them to survive severe weather conditions. The best down, therefore, is to be found on birds which spend winters in arctic or sub-arctic conditions.
Down is unlike normal feathers
in that it grows without a hard, central "stalk" or quill. In mature birds
it forms a soft, fluffy underlayer close to the body beneath the bird's
In such applications the "down"
insulation that is used is never 100% pure down but is a "down mixture"
containing a small percentage of fine feathers also. This mixture is represented
numerically as a ratio - for example 85:15, which means 85% pure down
and 15% feathers. The greater the pure down % the better the insulation
value, in theory, as long as you compare like-for-like qualities.
In practice, above a 90:10 ratio it is quality differences which are of
more significance in determining how good the insulation is. Quality is
indicated by "FILL POWER" which is a measure of the down's ability to
LOFT - please see below.
Cumulus sleeping bags contain a 92:8 ratio of pure down to feathers (small, fine feathers only) in our Cumulus Ultralight, Cumulus Lady and Mysterious Traveller models. Our up-market Cumulus Prime, Cumulus Expedition and Cumulus Quantum models are insulated with 96:4 'diamond grade' Polish goose down.
Goose down is better than duck down, and POLISH GOOSE DOWN is recognised world-wide as being of THE highest quality. In particular it is beloved of the Japanese who are well known for demanding top quality and who buy large quantities of Polish down each year. The excellent quality of Polish down is partly due to climatic conditions, but is also the result of extensive academic research into breeding techniques, which are unsurpassed anywhere.
Cumulus sleeping bags contain only Polish goose down, whose source is the non-polluted region of forests, lakes and beautiful, natural landscapes of North-Eastern Poland. This is a particularly cold part of Poland, suffering long winter weeks of arctic air with temperatures reaching as low as -36°C in January 2003. It is to combat such severe conditions that the geese, whose natural habitat has been this region for thousands of years, have evolved their protective down to a quality which is unmatched anywhere, both for heat retention and for durability.
Polish goose down is available
in several qualities, as measured by its ability to LOFT (see below).
Cumulus sleeping bags incorporate the two HIGHEST qualities of
Polish goose down. The higher the quality, the LESS WEIGHT of down is
needed to achieve the required temperature rating for the sleeping bag.
Hence high quality down means a lighter weight sleeping bag.
PERFORMANCE CHARACTERISTICS OF DOWN INSULATION
LOFT is the ability of an insulation material to take in air and expand. It is the trapped air which is the actual insulator. The "insulating material" is merely the means for trapping the air and preventing air movement. The greater the amount of air trapped in the sleeping bag, the warmer is the sleeping bag because it retains more of your body heat.
FILL POWER is a measure of the LOFT or expansion ability of down insulation. It denotes the volume (in cubic inches) to which 30 grams of down will expand when it takes in air. The greater the FILL POWER, the greater the expansion, the warmer the sleeping bag. (All other things being equal)
TYPICAL PERFORMANCE FIGURES (FILL POWER) FOR DOWN USED IN SLEEPING BAGS
Cumulus Polish goose down has been tested and certified by the International Down & Feather Testing Laboratory, Salt Lake City, Utah, USA to a MINIMUM rating of 680 cu in and 800 cu in respectively. Our newest 'diamond grade' white down scored 870 cu in, after steam conditioning.
LOFT ABILITY OF PARTICULAR SLEEPING BAGS
FILL VOLUME is
a measure of how much the TOTAL of all the down in a particular sleeping
bag will expand. The
greater the FILL VOLUME, the warmer the sleeping bag.
The ability to loft of a sleeping bag depends on the weight of down that it contains and on the fill power or quality of the down being used. A comparison between sleeping bags can be done using the equation :
(weight of down in grams) divided by 30, multiplied by the fill power
For example, compare a sleeping bag filled with 900 gms of Chinese down, with one filled with 700 gms of Polish, diamond grade goose down.
Here the lighter sleeping bag is actually warmer than the heavier one since it has a higher overall Fill Volume.
When comparing the temperature or "season" ratings quoted by different manufacturers it is worthwhile doing the above type of calculation and comparing Fill Volumes.
The so-called "minimum comfort temperature" that is quoted by most sleeping bag manufacturers is supposed to be a measure of the suitability of a particular sleeping bag for use in cold conditions. However, it is a very subjective measure (different people can tolerate different levels of cold), and furthermore, there is no "standard" to which every manufacturer adheres. Sometimes these ratings are overstated to make particular sleeping bags appear more attractive, hence such information should be treated only as a rough guide. The above FILL VOLUME equation is a measure of a sleeping bag's ABILITY TO LOFT and is, therefore, a useful tool for cross-checking such information when comparing several different sleeping bags.
However, it should
be borne in mind that good design also has an effect and, for example,
a sleeping bag which utilises a Trapezoidal baffle construction will have
a comfort temperature rating of 2 to 3 °C lower (better) than a
sleeping bag containing exactly the same quality and weight of down, but
constructed using the Boxwall method.
- temperature ratings and overall weight
The comfort temperatures that we quote for Cumulus sleeping bags assume that they are being used in average humidity conditions inside typically-sized 1 to 3 person tents (with a relatively small body of still air surrounding the sleeping bag). Use them in a drafty, unheated mountain hut in damp conditions and you will feel significantly colder.
That said, independent tests, carried out on our models in compliance with British Standard BS4745 and ISO 5087-1, gave temperature performance figures that are as good as or better than we claim.
DOWN versus SYNTHETIC INSULATION
Down is a better insulator than the best synthetic materials, "weight-for-weight". It is lightweight with excellent loft yet is extremely compressible to give a small pack size. Down has excellent "drape" properties, settling around the body and eliminating the drafty gaps sometimes left by stiffer synthetics. However, down is a poor performer when wet, unlike some polyester fibres which resist moisture well. "Synthetics" are generally heavier and bulkier and with a much shorter life-span than down. Down's greatest advantage, however, is its versatility as regards temperature conditions. Down sleeping bags have a wider spread of comfort temperature than synthetics, For example, a down sleeping bag with a comfort temperature rating of -15°C will still be comfortable when used at 0°C, whereas a synthetic sleeping bag rated at only -7°C could be too warm at 0°C. Anyone planning to use a sleeping bag at different times of the year in a variety of temperature conditions should consider using a down sleeping bag first and foremost.
Pertex Performance Fabrics
PERTEX, originally manufactured by Perseverance Mills Limited in Manchester, England is renowned World-wide as being the BEST fabric from which to create a shell for DOWN insulation and has been used extensively by many manufacturers for both down sleeping bags and down clothing.
Perseverance Mills Ltd went into liquidation in the summer of 2005, selling the Pertex manufacturing rights to the World famous Japanese company Mitsui & Co. whose textiles manufacturing subsidiary company, Mitsui Bussan Textile Co. began manufacturing Pertex during 2006. Initially supplies were restricted, but fortunately Cumulus had purchased large stocks of original English Pertex in anticipation of these fabric supply problems, so our production was not affected. All of our Pertex fabric is now made in Japan.
PERTEX is water-resistant, windproof and breathable.
PERTEX is inherently "down-proof" and stain resistant. It is light and soft with excellent "drape" quality, yet very strong.
Cumulus sleeping bags
are made using Pertex MICROLIGHT (with Ripstop), which weighs 52 gms/m2, and Pertex
QUANTUM (with Ripstop), which weighs just 35 gms/m2 and is the
lightest grade of Pertex incorporating rip-stop reinforcement.
It should be noted, that the Cumulus Expedition sleeping bags are NOT fully waterproof. Full waterproofing is not desirable as mentioned above - rather, it is breathability which is essential.
Sleeping Bag Construction - the shell
WHAT ARE BAFFLES
"Baffles" is the name given to the chambers in which the insulating material is contained in a sleeping bag. The better the design the better the performance of the sleeping bag.
The design of baffles is important because it determines how well the insulating material is held in place. There is nothing worse than a sleeping bag whose insulation has shifted creating a thick wad in one place and little or nothing in another part of the sleeping bag.
Stitching can be another problem, particularly in the case of cheap sleeping bags. When baffles are created simply by stitching through to create a "quilt" effect, each such stitch is uninsulated which creates lines through which body heat escapes. This is called "stitched-through" construction. The baffles which are created in this way have no sidewalls.
Stitched Through construction:
One way to avoid this heat loss problem is to use two layers of stitched through insulation with the stitches in the second layer offset relative to those in the first layer. Unfortunately, this doubles the weight of the sleeping bag.
More Advanced Designs
Most sleeping bags are constructed using a single layer of insulation.
The only single-layer constructions which do not create cold spots along seams are the "V", "trapezoid" and "boxwall" designs. The baffles in each of these designs do have sidewalls to keep the insulation in place. There are no "lines of cold" as a uniform thickness of insulation is present throughout the sleeping bag.
The simplest is the boxwall design. The baffle sidewalls are vertical, hence the baffle shape is box-like.
Several types of boxwall designs exist, including rectangular, diamond shape and curved. They all have one thing in common, however, which is vertical baffle sidewalls.
A more complicated single layer baffle system is the V system.
Here, each baffle sidewall is inclined at an angle and joins its neighbour to form a series of "Vs".
For a given size of bag and
for a constant width of baffle, the greatest number of baffles is obtained
using the"V" design. "V" gives twice as many baffles as boxwall construction,
given equal measurements.
Trapezoid is an "in between" construction - giving more baffles than boxwall but fewer than "V".
This is a popular design for the high quality sleeping bags of many manufacturers, as it provides a good compromise between warmth and weight - warmer than boxwall; lighter than "V" construction.
Apart from the Expedition range and our two lightest models, the Ultralight 200 and Quantum 200, all of the other Cumulus sleeping bags utilize trapezoid construction in their top sides. Bases are boxwall (see below : "Boxwall construction is best for the base !").
'Brick', otherwise known as 'offset double boxwall' involves two boxwall layers..
The two boxwall layers, one on top of the other, have their baffle walls offset relative to each other, which creates an appearance similar to that of a brick wall. Brick construction is used in sleeping bags which contain a large amount of insulation material.
Brick construction is utilised for the top side in the Cumulus Expedition sleeping bags to provide the high levels of insulation that are needed in conditions of extreme cold. Bases are boxwall (see below : "Boxwall construction is best for the base !").
Other considerations - sleeping bag base
Boxwall construction is best for the base !
For optimum insulation the down should be of uniform thickness over the whole area of the sleeping bag. On the top side the trapezoid construction gives better performance than boxwall.
In the sleeping bag base, however, the insulation value of the down is much reduced because it is compacted by the weight of your body preventing loft. The effect of this compaction far exceeds any disadvantage from using a boxwall construction rather than trapezoid. Furthermore, your body weight prevents displacement of the down - which is another reason why trapezoidal is unnecessary for the base.
Boxwall is lighter than trapezoid, which makes it a better option for the base.
Cumulus sleeping bags utilize boxwall construction in the base.
Differential Fill means that
the quantity of down in the base is less than the quantity in the top
of the sleeping bag. At Cumulus we employ a ratio of top: base
= 3:2 (discounting the hood, neck and zip baffles). Hence the base has
40% of the total insulation instead of the 50% it would have if there
was no Differential Fill.
Note - The Cumulus Lady sleeping bags are shorter but contain the same amount of down as in the corresponding men's sleeping bags. The down 'saved' from the reduced length has been redistributed to the base and foot area of the ladies' sleeping bags, which has altered the Differential Fill ratio to about 55:45.
This is a manufacturing technique by which the outer surface of the top side of the sleeping bag is wider than lower (inside) surface. This helps the down to expand outwards from the centrally located body position thus facilitating optimum lofting.
Sleeping Bag Construction - other features
2. Neck Baffle
3. One handed closing drawcord / toggles
4. Zip and zip baffles
6. Box foot
7. Hanging loops
8. Inside pocket
2. The down-filled neck
baffle is an insulated collar which is designed to prevent cold draughts.
It is featured on all Cumulus Prime, Cumulus Lady, Cumulus Expedition
and Mysterious Traveller sleeping bags. It is drawn snugly around
you by a one-handed pull on its drawcord. The drawcord is elasticated
to allow for "give" when you are turning over in your sleep.
3. The drawcord toggle systems allow for one-handed closing of the hood cowl and neck baffle. This also applies to the drawcord on the stuff sack. The drawcords on the hood and neck baffle are different to make it easier to identify them by touch when in use on a dark night. The toggles are metal-sprung for durability.
4. Cumulus sleeping
bags use the best, YKK zips.
All Cumulus sleeping bags, INCLUDING our lightweight Ultralight and Quantum models, have full length zips.
5. In addition to the
Velcro for the neck baffle mentioned in point 2. above, all
Cumulus sleeping bags also have a velcro closure/flap for the
sleeping bag itself. This allows you to close the bag without having to
zip it all the way up to the top. This is a really useful facility if
you get too warm and want to provide extra ventilation without opening
up the whole of the sleeping bag at the top.
6. The Box Foot
creates a "mummy" shape, which gives plenty of room for your feet. This
is especially useful when the sleeping bag is used whilst you are in "full
gear" on a freezing night at high altitude.
The Cumulus Lady sleeping bags incorporate a Polar Fleece insert within the Box Foot, for additional warmth and comfort.
Cumulus sleeping bags are longer than some competitors' standard sleeping bags. This means that sleeping on your front with your toes pointing downwards presents no difficulty.
7. Down sleeping bags need to be fully dried out after use for which hanging is the ideal treatment. Strong hanging loops are stitched in at the foot.
8. For extra comfort and convenience each model has an easy-to-use internal pocket.
Stuff sack and storage bag
Cumulus Stuff Sack
1. All models except Cumulus Expedition
Down sleeping bags are notorious for their ability to loft as soon as they are freed. This is great when you want to use them, but awkward when you are trying to return them to their stuff sack in the morning. If a stuff sack is too wide the sleeping bag will try to escape around the sides of your hand as you are trying to force it home. Sometimes it can give the impression of being alive and trying to get out !
The Cumulus stuff sack is specially designed for easy, one handed stuffing. It has just the right diameter to enable the sleeping bag to be inserted one handed without it being able to "escape". Finally, when it is all in and you want to withdraw your hand without letting the sleeping bag spring out, a ONE-HANDED pull on the draw cord is all that is necessary to close the neck and complete the job. That is due to having the drawcord toggle permenantly fixed to the side of the stuff sack.
The Cumulus stuff sack is SMALL. We have five different sizes depending on the sleeping bag model. The smallest is TINY - 11x11x25 cm and weighs just 14 gms. Even the largest is small compared with the competition - 17x17x36 cm with a weight of only 23 gms.
Despite being so light, the Cumulus stuff sack is extremely durable. Made from ripstop Pertex material it has specially reinforced seams and will withstand many years of rough handling. Furthermore, a Pertex flap is incorporated at the neck of the stuff sack to close the stuff sack opening, giving added protection to your sleeping bag.
2. Cumulus Expedition
Whilst many of the features and attributes mentioned above also apply to the Cumulus Expedition stuff sacks, there are significant differences resulting from the size of these sleeping bags and from the need to cater for their use in severe conditions. These stuff sacks are more substantial and more robust than those for the rest of the range, being made from a coated, high-tenacity polyamide fabric instead of Pertex.
Cumulus Storage Bag
When not in use Down sleeping bags must NOT be left in their stuff sacks under compression. That will reduce their lofting ability. For storage, therefore, we supply a Cumulus storage bag, free of charge, with each of our sleeping bags. This is made from a very breathable mesh fabric to keep your sleeping bag fresh and fluffy, thus ensuring many years of satisfactory use.
The Cumulus Way !
The Cumulus philosophy is to provide maximum warmth with minimum weight, at a competitive price.
We had 8 models in our original range and this was increased to 11 in 2006 with the addition of the ultra-lightweight Quantum models. In May 2007 two further models were added (the Expedition range), this time to extend the range 'upwards' as regards warmth and usability in extreme conditions. Then in 2010 we added our ladies' range of three models, and also summer and winter Expander Baffles, whose purpose is to increase the inner space of our sleeping bags, for the comfort of stouter users.
Here are the differences :
FOR INDIVIDUAL MODEL SPECIFICATIONS PLEASE LINK TO Summarised Technical Features