Sleeping bag project – anyone know the actual weight of 40-weight thinsulate?

I know for certain that Thinsulate used to be sold as 40 gm/sq. meter and so on – but if they no longer identify it that way it’s possible that they have changed. Also don’t know if the weight of the scrim is included in that number. I note that Quest outfitters states the following weights for the Thinsulate they sell: 100wt – 3.1 oz; 150 wt – 4.6 oz; 200 wt – 6.2 oz..

However, were I you I might rethink the Thinsulate. The real big benefit of a layer of synthetic in a winter sleeping system is in moving the dewpoint out of your down, so that condensation of the outward moving moisture (which you are producing) occurs in the synthetic. A layer of 40 gm/sq meter anything is not moving that dewpoint much; it just has so little insulating value.  A layer of 2.1 or 2.5 climashield would do this much better. My 2 cents.

Are you sure what you have experienced in winter is “external moisture”.  What I have noticed  while winter camping in California where tempertures fall below 32 degrees is moisture (respiration/perspiration) from me travelling through the bag and condensing or freezing on the out side of the bag.

That being said, something like climashield could extend the range of a 2 or 3 season bag into winter.  MLD recommends such a use case for their Spirit Quilts.

Bruce, I’m pretty sure that it’s external because sleeping under bushes or a tarp will stop it.  But I’m not sure.  Either way I think the synthetic layer would help.

I just got back from a trip where I had some good time in my bag to think about this.  I’m leaning towards a new plan, similar to what Aaron posted on another thread – have a regular down sleeping bag/quilt and then a separate dew cover.  The synthetic cover will go around my sleeping pad rather than the entire quilt/bag in order to save weight.  That will also make it stay in place even if I twist and turn underneath it.

The thing I’m trying to figure out right now is a way to make a quilt/bag that works well with my sleeping habits (curling up most of the time but still needing to stretch out).  The challenge is to avoid drafts in the dead of winter when curled up, but not be too roomy when stretched out.  I like my montbell down hugger but the shell weight of that bag is a full pound!  I will probably borrow their trick of cutting the fabric on the bias with diagonal baffles, but probably not the elasticized thread.

I think my solution is going to be a quilt with loops sewn up each side, alternating.  Then a single strip of elastic will zig-zag between them and get tied off at the end.  This way if my knees push the bag out in one spot it will tighten up in the others.

I’ve been cowboy camping for 50+ nights.  850 down + M50 shell.  Never had any problem it getting wet.  Even when I screw up and water gets onto the bag.

I tried experiment with M50 and some other DWR fabric.  Puddle of water on top.  The other fabric did fine, but after an hour the water all of a sudden found a path and quickly leaked through.  M50 didn’t leak for days.

Do you breath into your sleeping bag?  That could get it wet.

Thinsulate is designed for gloves – maximum warmth for a small thickness.  But as a consequence it’s heavy for the warmth.

Better to use the thinnest Climashield you can find.  Do they make something lighter than 2.5 oz.yd2?

Were you planning on adding a 3rd layer of fabric with the insulation in between?

if not, insulation will not work with down. The down gets completely caught up in the insulation and doesn’t loft. What doesn’t get caught get through to the top as the insulation is heavier.

Interesting about the M50.

Made an overquilt with 2.5 oz climashield, shell and lining .67 argon, to fit over my Marmot Hydrogen. 12.7 oz. Works nice for snow camping. Had one night in a poorly set up shelter and big winds that meant spindrift coming in. Got pretty frosty on the outside but I stayed warm, and the thing dried out really fast the next day.

sometimes you can find 2.1 or 2.2 oz climashield, I think OWF had some.

So I think OWF has 2.2 oz climashield but from my understanding it’s the same as the 2.5oz and just a measurement difference (possibly meters squared versus yards).  Either way, I’m warming up (pun intended) to the idea of having a 2.5oz climashield cover.  It would add some warmth to my sleep system and would give me some nice flexibility.  On warmer nights (like if we have cloud cover) I could skip it.

I don’t breath into my sleeping bag, I just tend to hike in canyon country when it’s cold.  For example camping next to the Colorado River in December, you tend to get frost.  Even on the plateaus where it tends to be warmer, sometimes there’s enough moisture in the air for a strong frost.  One memorable time in a remote part of the Grand Canyon (thankfully away from habituated critters) we fell asleep with our stuff yard-saled all around our sleeping bags.  Woke up with a nice layer of frost on all of our food, our packs, our clothes and shoes.  And of course we had some pretty damp sleeping bags.  Took a while to pack up that morning, but fortunately we had early sun.  I make sure now to put everything inside my pack before I go to bed.

On another night on that same trip, I was eating dinner in my sleeping bag while watching the sunset and noticed frost appearing on the foot of my sleeping bag!  It wasn’t even 6 pm yet, but it had gotten a bit damp during the day from an improperly sealed backpack and that moisture was freezing.

I think I gave up and slept in the tent that night with the doors open, which is the obvious solution to this problem.  But I really love my cowboy camping, and half of my trips I leave the tent at home so that’s not always an option.  I used to cowboy camp more than 200 nights a year when working for a conservation corps, and I would just use a cheap synthetic bag to keep the dew away from my down bag (we were car camping).  Those were the days…

Anyway, back to the quilt ideas.  I’ve never made a down quilt before so this will be fun.  I’ve been researching today and I have an interesting idea I might try.   I would do 5 vertical baffles and then add karo-style separating baffles every 10 inches or so.  So a hybrid of a traditional and karo quilt.  It would have the advantages of only 5 baffles to fill, thus simplifying the filling of down.  But not the tendency for down to filter down to the sides of the bag.  Seems like it would work pretty well to me.  Or I could put a couple small openings in the vertical baffles so that I could move down if I wanted to.  Then I could reap the full benefits of adding all of the down at once to the bag, sealing it up and then redistributing.  It would be a pain to move the down around initially but I think I still might prefer that to weighing the different chambers.

One question I have now is ventum ripstop v. argon 67 v. m50 v. membrane 66.  All have pretty much the same weight.

Like I said, M50 has a really good DWR, but I know nothing about the others

My bag has got frost on the outside before and the down stayed dry inside.  And significant rain splash.  Whenever it has started raining I put up tarp – I suspect the rain drops falling from the sky are faster so put more pressure on the fabric and the M50 won’t be effective.

RBTR says about Robic 7D “Because of reduced air permeability, we do not recommend using ROBIC 7D for both the inner AND outer layers of any fully enclosed application (e.g. quilts)”  That suggests to me it might have a really good DWR too.  Trivially heavier (spec).

I’ve read comments about karo baffles that it’s good to redistribute down that shifts.  But more recently I have heard skepticism.  It seems sort of like a fad.  Not to be disrespectful to people that like it : )

karo makes it easier to shift down back to the front, but that means it shifts to the side easier too.  Better to have regular sideways baffles with a lengthwise baffle to keep the down from shifting from the top to the side.

Or use regular sideways baffles and don’t worry about it.  If it’s going to be cold relative to the rating of your bag, when you set out your bag, vigorously shake the down from the sides to the top.

A time or two I noticed that I was rather cold, then noticed there was very little down on top of me, it had shifted mostly to the sides.  Now I’m mre careful.

As far as minimizing the number of baffles to make putting down into them easier – it’s not that big a deal.  Once I have some containers and scale set up, it’s not that much more difficult to do larger number of baffles.  Especially, compared to how long it takes to order, lay out, cut, sew.

Nick,

You mentioned not having frost issues under bushes or tarp.  Any recollection if those were clear nights?  If so, that sounds like a radiant cooling issue more than a moisture issue.  But I’m guessing you’re probably already familiar w/ that?

My synthetic summer quilt is dimensioned to fit over my down bag for exactly your reasons.  Haven’t had the opportunity to use it as such yet, but should this winter.

Re. karo step baffles, don’t forget that karo is tunable!  If you feel the down will slide down the sides too readily, you can make the vertical baffles longer towards the sides, thus reducing the size of the openings through which the down can move in that direction.

Also: https://backpackinglight.com/search/?q=delta+karo

tldr; triangular cells need fewer baffles and one person reported good down stability with an easy mod – I haven’t made anything w/ down yet.