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Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 3:37 pm
by Lamont
Might I respectfully say CCF on top of mat, not below for best effect.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 3:58 pm
by Moondog55
Lamont wrote:Might I respectfully say CCF on top of mat, not below for best effect.


I have to say I have experimented with both approaches, CCF on top is warmer initially but underneath it is as warm in the end so I have always used the CCF underneath to protect the expensive blow-up. In very cold weather I might use a 3mm + RFL above as well as underneath. Things changed for mew when it got to -25C when I used both a cheap 8mm CCF and a RidgeRest but that was under my older 3/4 T'Rest

To the OP
Hikingnewbie Keep your eyes open for people renovating and laying engineered flooring, there are usually off-cuts of the underlay being chucked out. This stuff is very usefull for boosting the rating of a mat, but this thin stuff does work better on top, usually 2mm or 3mm foam of some description plus that reflective foil layer. You only need a section across the roll as wide as your mat but if you find a larger piece it is Also very handy under the floor of your tent in place of a factory footprint and as part of a sitamapon

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 4:44 pm
by Warin
Lamont wrote:Might I respectfully say CCF on top of mat, not below for best effect.


Why?

Some of my foam mats have a reflective layer, I place the foam mat on the ground with the reflective layer upper most, then the tent floor then the inflatable mat. This provides protection to the inflatable mat. It would be better if there were an air gap around the reflective layer, but failing that I think placing it between the insulation is better than on the outer side, my thinking is this keeps it cleaner and reduces any damage to it.

I don't see how which insulating mat on top significantly changes the overall insulation. The maths of R values looks to confirm that conclusion. Am I missing something?

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 5:59 pm
by Lophophaps
Lamont wrote:Might I respectfully say CCF on top of mat, not below for best effect.

That would smooth out the bumps in the air mat, but I can't see the insulation improving. Someone with better physics knowledge than me will have to work this out. The sequence when setting up camp may be useful to consider.

Tent up, take out a few things from the pack, and then unroll the CCF mat. Sit on this while unpacking, and then blow up the air mat, which goes on top of the CCF mat.

I like the CCF underneath as it give a layer of protection against prickles. That said, my Thermarest lasted for about 20 years until it developed a giant bubble; prickles were not a problem. Apart from snow camping I did not use a CCF mat with the Thermarest.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 7:24 pm
by Lamont
My thoughts are the "thin (you referred to) CCF pad", (3-4 mm I supposed a la GG for example) will more effectively block the cold air in your mat from getting nearer to you and cooling you and restricts the warm air from escaping.
Putting it under may stop the ground temp from affecting the mat directly as much but, it will not stop the air temp in your tent which may be about or even below zero, from cooling the air in the mat and allowing it to transfer to you if the R value (insulation) is too low. I believe it raises the insulation nearest to your body thus allows you to hold the warmth (or repel the cold) better.
Essentially you get two layers of insulation against all the cold (ground/snow-plus air in tent) that could affect your body.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 7:46 pm
by Warin
Lamont wrote:My thoughts are the "thin (you referred to) CCF pad", (3-4 mm I supposed a la GG for example) will more effectively block the cold air in your mat from getting nearer to you and cooling you and restricts the warm air from escaping.


That assumes that air circulates inside the inflatable mat. If that were so the inflatable mat would have a very low R value.

Lamont wrote:Putting it under may stop the ground temp from affecting the mat directly as much but, it will not stop the air temp in your tent which may be about or even below zero, from cooling the air in the mat and allowing it to transfer to you if the R value (insulation) is too low. I believe it raises the insulation nearest to your body thus allows you to hold the warmth (or repel the cold) better.


If the air in the inflatable mat circulates then it will also circulate when in the lower position thus it will not be very effective there either. In fact the contact with the ground would lead to more loss as the ground contact will transfer energy at a greater rate than air contact. And the contact area with air inside the tent (when used in the upper position) is much smaller than the contact area with the ground (when used in the lower position). Think you will find it best even with a inflatable mat that has lots of air circulation (e.g. the old lie low) on top of the foam mat.

[edit] - Still thinking on it [/edit]

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 17 Feb, 2018 8:02 pm
by Zapruda
There is plenty of anecdotal evidence around claiming that a mat on top is more effective. I have tried both in the snow and haven’t noticed any difference. I certainly prefer the mat on top for comfort.

Roger C may have some thoughts on the matter.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sun 18 Feb, 2018 9:19 am
by slparker
This was discussed at some length on the American forum 'backpacking light'.
The consensus, anecdotally, was that ccf mat on top was warmer but I find the physics very unconvincing.
Except a good point was made that point compression (I.e. elbow, hip) lowers R value ( resistance to conductivity) considerably and adding a stiffer layer on top reduces this.
https://backpackinglight.com/forums/topic/56634/

They did testing, and field testing, of several mats In their technical mat test ( behind a paywall) and they describe a 'foam overlay' as being an effective booster but do not describe why an overlay is better than an underlay; or, so far as I can discern, did not test the combo or explain the physics.
The test was co-authored by Roger Caffin, a regular contributor to this forum, so he might weigh in.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sun 18 Feb, 2018 11:04 am
by Moondog55
My understanding is that with the CCF layer on top you are not wasting any energy heating up the air in the blow-up mat and the colder it is the bigger that cold air sink is going to be. However I think it differs for each mat and each mat combination.
I do notice a small chill when using my old Thermarest mats and that takes a few minutes to dissipate, in other words it takes a few minutes for the air and foams temperature to come up to my own body temperature, this is much less noticeable with my S2S Comfort Plus
There being such big differences between mats and between mat combinations that each has to be taken as an individual case I think
I have some RFL coated Urethane mat here if somebody wants to come and collect to do their own experimentation with this while season

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sun 18 Feb, 2018 11:31 am
by Lamont
Yes, I believe I may have read about it on BPL.
Until we find out more I propose all interested parties head out to the Ponds Institute- sleep 3 nights mat on top, 3 nights mat on bottom.
Identical internal/external conditions for all participants.
Independently randomised groups.
The hypothesis is: Sleeping with a CCF mat of 3mm on top of a Xlite will be warmer than with the CCF on the bottom.
Methodology: Each participant will be woken every 2 hours to record their comfort level as determined by the (choose name) Comfort Scale.
Fully catered with massages after each days walking and a couple of Daquiries/Whiskey before bed.
I would love to do this! Not sure if the Ponds Institute will allow it though.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 22 Dec, 2018 8:22 am
by CBee
I own a standard thermolite reactor and an extreme one. I also use them as standalone mid season in QLD. Paired with my down bag and insulated mat, in NZ below zero, I never had a problem being cold at night. I haven't tried different brands but I'm quite happy with them. Not sure about the claimed temperature gain: one night I was sleeping in a hut and I was little cold. I decided to use the thermolite and made a significant difference. I think it is important to seal them properly to stop cold air going inside the bag.
I also noticed I posted this on the wrong thread. Sorry.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 22 Dec, 2018 4:58 pm
by wayno
its overkill for the milford, all the huts are at low level... you'll sweat.... somewhere around ten degrees is plenty. take some extra clothes if the forecast is bad

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Sat 22 Dec, 2018 8:05 pm
by ribuck
Warin wrote:I try to keep the grams to $ ratio at at least 1 gram to 1$ ... less than that and I think I'm better off spending it on the holiday.

Yay! On that basis I can justify a DCF tent! And to think I've been putting it off all these years.

Re: Down Sleeping Bag - Is Comfort Rating of 0 deg C enough?

PostPosted: Wed 26 Dec, 2018 10:58 pm
by gbagua
Mont is a premium Australian manufacturer of sleeping bags. I can vouch for their products. A1.

https://www.mont.com.au/sleeping-bags

Sure you can find something there that suits your current needs.