EVA foam sandwich

[simon t]

Has anyone attempted to make a thin foam sleeping pad case?  Not sure if this is silly but it makes sense to me.

I’m thinking of 2 sheets of Zotefoams EV35 taped together on the bottom and 2 long sides with some kind of overlap at the top opening… basically like a giant foam pillowcase.

My thinking is that by having full coverage in 3mm or 2 mm foam on all sides you’ll reduce the radiative losses from the side of the pad and the exposed head end as well as 360 degree pad protection and an increase in R-value.

In the event of a pad failure, you have 6mm of foam which you could put your bag and spare clothes inside.

In an emergency situation, you could wriggle inside and use it like a bivy.  Waterproof and insulating… but zero breathability.

EV35 for a regular wide pad would be about 270g in 3mm.  Based on estimates I found here, potentially add 2.8 R-value, but perhaps more in real life because of the reduces side losses.

Would add a bit of bulk but could be a good cheap way to upgrade an existing pad for winter.

 

Any suggestions for a suitable tape to bond the sheets?

 

Silly or smart?… there is usually a fine line.

[Roger Caffin]

It would be a disaster if you want to use anything like CCF, anything which can’t breathe. You would get massive condensation inside the foam. This is not a prediction; it is experience.
Been there, tried that!

Cheers

[simon t]

Roger,  You mean in the case of jumping inside the foam case?… which is kind of stretching the use case tbh, more a desperate last option if your shelter failed in snow or rain.  The primary use would be to bump up the insulation of your pad and provide additional comfort and protection for your pad.

[Dustin V]

Simon, are you thinking of encasing the foam sheets in a cover? I could imagine the top sheet getting tangled underneath you as you move around.

[simon t]

Apologies, Dustin, I’ve not explained myself adequately.   Imagine a standard pillow case but made of EVA foam (like thinlight) and big enough to fit your whole inflatable sleeping pad inside.

Construction would be 2 layers of eva foam, joined on 3 edges (2 long, 1 short) with some kind of strong adhesive tape. and a pillow style envelope/overlap closure on the unbonded edge.

[Roger Caffin]

Ah – to encase the air mat?
Well, that’s feasible of course. In practice, many of us have a 3 mm CCF pad under our air mats to protect the air mat from spikes on the ground and to keep it dry in the snow. So the Q is whether a 2nd layer of CCF is worth the extra weight? I have not tried that.
Or would the extra weight be better used as more down in the quilt?

Cheers

[simon t]

I’m still on my starter cheap uninsulated inflatable.  When I was first out below freezing, I had a ccf below the pad but I could feel the heat loss through the pad.  While the ccf was below, I was heating the air in the pad but the area of the pad not under the quilt (such as around my head) was losing all that heat. I switched the ccf mat to above the inflatable, which was a big improvement.

Even in expensive insulated pads that reduce air movement, I wonder how much heat is lost around the edges and the exposed area around your head? Encasing could be a bit of a force multiplier as well as improved comfort and pad protection.

With a theoretical increase in r value of at least 2.8 for circa 270 grams of foam (regular wide), that’s on par or better than the r value per grams of high end pads and I’m sure covering the edges will improve the performance of your pad.

There is the added bulk relative to a high end pad but it does give you a solid back up for pad failure with 6mm of foam+ deflated pad + all the soft things you can stuff inside the foam thingy.

[SIMULACRA]

During certain times of the season I’ll carry two pad lengths (squared)of 1/8″ Zote CCF, along with my inflatable. One for the bottom of the Uber-lite, one for the top. I’ve tried just on the bottom and just on the top. Out of those two, just on the top works better for warmth. I also tried 1/4″ just on the bottom with better success. I’ve found, that on the bottom and top, with the inflatable in the middle, works best. 1/4″ vs 1/8″?  1/4″ packs bulkier so it has to be rolled. 1/8″ can be folded and put inside the backpack. The two 1/8″ also end up being slightly less weight than the 1/4″ by itself somehow. If you move around a lot in your sleep the top CCF pad is going to squirm around a bit. Does need re-adjusting at times. As for merging the two to create a pita sandwich for the inflatable to go inside? -Yeah maybe. Wouldn’t work well with my packing system, so I wouldn’t do it myself.

[Justin W]

More of a side note.  But if you want a cheap source of wide, but thin, and large/bulk amounts of EVA foam, look at floor underlayment insulation.  And it usually has a foil/IR reflecting scrim on one side.  I had a big roll of that sent to me for quite reasonable compared to more normal sourcing.

And if you put the two foiled sides together, facing each other towards the center (and to the pad), then any areas where the pad doesn’t touch the foil, will reflect some IR.  But there won’t be any IR reflecting where the pad directly touches the foil (or where the foam edges touch each other).

The idea would be ok for say serious cold weather use where one is using a pulk or the like, but it will be a lot of volume for more regular trips/backpacking.

[Author]

Posts