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Author Topic: DIY synthetic overbag Thinsulate query  (Read 1125 times)

Online Moondog55

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DIY synthetic overbag Thinsulate query
« on: October 12, 2016, 02:42:14 am »
Assuming I get to make another winter trip to North America I'll need some more warmth if I head to Canada
We got some Pre-packed Thinsulate from a local fabric store [ the Australian equivalent of Jo-Anns ] and while I have no idea what it actually is, the stuff is labelled as mid -loft.
Very LW either 60GSM or 80GSM and about 4 to 6mm thick [3/16 -> 1/4inch ]

This time I want to make a Gerry Cunningham/ Big Agnes style overbag with a wide pad sleeve but no insulation in the bottom and a short side zip

My last overbag was made using a single layer of 85GSM APEX and it was just warm enough to add 10 degrees to my set-up but it was quite heavy and bulky due to the insulation on the bottom
As this stuff needs to be quilted to a layer of scrim every 200/300mm we want to minimise the amount of work involved and I am wondering if 2 layers will be enough
3M were not able to help me and the three possible candidates have very different Clo values

Any thoughts?

Yes I could buy APEX but we already have this here

Offline Bothwell Voyageur

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Re: DIY synthetic overbag Thinsulate query
« Reply #1 on: October 12, 2016, 02:55:15 pm »
I believe that regardless of whether it is down or synthetic that is the air within the insulation that keeps you warm, so it is the total amount of loft that will count. If you know how thick the top half of your previous overbag was then you'll likely need the same on this one.

Personally I would just make it into a quilt and not worry about the pad sleeve.

You could put a drawstring at either end to assist in creating a foot box.
www.canoepaddler.me.uk for canoe tripping and winter trekking photos and fireboxes

Online Moondog55

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Re: DIY synthetic overbag Thinsulate query
« Reply #2 on: October 12, 2016, 04:22:27 pm »
Tried the overquilt
I am a restless sleeper and I need something to keep me centred on the pad

Offline scoutergriz

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Re: DIY synthetic overbag Thinsulate query
« Reply #3 on: October 12, 2016, 05:31:08 pm »
rather than quilting two layers, you could go old school and use the shingle method. Cut strips about a foot wide (width isn't important, but keep them all the same) Sew a strip on the TOP edge along the bottom, overlap the next by 1/2 and sew the top again, and continue all the way up. Now go back and hand sew your top sheet on JUST catching the insulation with the needle -do not sew through the insulation, you're just keeping the top sheet in place. You now have 2 layers with minimal compression and no cold spots.
Another way is to sew the insulation the same way to start, but don't overlap. sew a second sheet identical, lay them top to top, and mesh them together- Flip one layer up, pull over and flip the other under it, and continue until they're all meshed together and sew the edges- less hand work, but you're relying on the friction of the insulation to keep it all in place.

Online Moondog55

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Re: DIY synthetic overbag Thinsulate query
« Reply #4 on: October 12, 2016, 07:46:57 pm »
Never thought about using the shingle method with Thinsulate but I see no reason why I can't apart from the extra work involved it is the same amount of stitching.
On another forum somebody suggested layering a minimum batt of APEX between 2 layers of this Thinsulate but the lightest APEX I can source is 85GSM and that sandwich would be seriously warm
I seem to remember REI doing  sleeping bags like this back in the 90s

Offline Bothwell Voyageur

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Re: DIY synthetic overbag Thinsulate query
« Reply #5 on: October 12, 2016, 07:52:48 pm »
You should probably check that Thinsulate can be used in the shingle method. I think that insulation used that way has to have very long fibres to avoid simply pulling apart.
www.canoepaddler.me.uk for canoe tripping and winter trekking photos and fireboxes

Online Moondog55

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Re: DIY synthetic overbag Thinsulate query
« Reply #6 on: October 12, 2016, 08:55:15 pm »
It can be if you use a scrim I think
Finding UL scrim here is hard but we did manage to get some a short while ago, just enough to one summer bag tho

Offline 300winmag

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Re: DIY synthetic overbag Thinsulate query
« Reply #7 on: November 20, 2016, 08:49:32 pm »
If you make an over-bag with Thinsulate or Climashield it needs a zipper across one end (foot is best) so it can be opened and frost shaken out.

A synthetic over-bag is a good idea B/C it can collect most of the condensed (then frozen) moisture from the main bag, keeping the main bag drier for more days.

My idea of a good down winter bag is one with a down DWR treatment like Dri-Down or Down Tek. my new LL Bean bag has Down Tek.

OR just use a VBL inside the main bag.  :D

Eric B.

UPDATE: Just received my LL Bean -20 F. down bag a few days ago. Got i.e. in a double sale for $269. Down from $419. (and that was the price tag on the bag when I got it). It's well made with attention to important details like face and neck collar drawstring closures. Plus it has Down Tek, a good down DWR to resist moisture absorption. I would not buy another down bag without a good DWR. I do love my Western Mountaineering 3 season Megalite bag but it doesn't need a DWR on the down here in the dry Nevada and western mountains for 3 season use. Winter down bags are another story.
« Last Edit: January 07, 2017, 12:33:49 am by 300winmag »

Online Moondog55

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Re: DIY synthetic overbag Thinsulate query
« Reply #8 on: November 21, 2016, 01:33:31 am »
Why the zipper at the foot? I find it just as easy to turn it inside out and shake even with a sleeping mat in the sleeve.
VB works but then I can't wear my down parka [ my VB shirt has died; maybe I should make another one] and I use my Goretex bivvy over my down bag and inside the synthetic so moisture in my down isn't that much of a problem but even if it was I have been using Nikwax for 30 years or more on my down gear Most of my gear actually

Offline 300winmag

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Re: DIY synthetic overbag Thinsulate query
« Reply #9 on: January 07, 2017, 12:36:07 am »
Moondog,

The zipper allows access to the Climashield insulation so the frost can be shaken off the insulation and out and not stay in the overbag.

Eric B.

Online Moondog55

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Re: DIY synthetic overbag Thinsulate query
« Reply #10 on: January 07, 2017, 12:51:37 am »
I've not ever had that problem but then I've never slept in -45 either but why would a zipper make any difference when the shell fabrics are so breathable?
At -25C the frost if any sublimates out when warmed or exposed to the sun or at least is my experience so far

Online Moondog55

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Re: DIY synthetic overbag Thinsulate query
« Reply #11 on: March 30, 2017, 06:11:27 am »
OH!
Do you mean so that the two layers of the overbags shell can be separated?
I'm not sure I know how to do that so if you have any links showing how I would really appreciate it