Bottomless Bivy

[James Cavan]

During the colder months especially I use a very thin evazote mat 2m long by 0.75m wide to augment my torso length prolite 4. It occurred to me that the bottom of the bivy stayed bone dry on the mat and I only needed the bivy to protect from a little misting and brushing against the walls of my single skin shelter.

Here are a couple of interpretations I whipped up in sketchup quickly.

By entering the bivy from beneath weight could be saved by not needing zippers as the hole could be kept snug with an elastic hem or lightweight draw cord.

I realise that this design would have limitations by not being able to use directly on the ground but if you use a groundsheet anyway then why carry a second?

Any gaping holes in the design (Pardon the pun) I'd love to hear them or suggestions how it could be impoved.

Ta, James

[John S.]

misread your wording thinking you have no pad where the hole was.

[Ryan Smith]

I like your thinking.

Ryan

[John Donewar]

James,

Quite an intriguing idea!

This is what would be called Thinking outside of the "Bivy".;-)

The way that you describe entering your bivy is the same method that I use to "don" my top quilt.

I pull the quilt over myself, insert my feet into the footbox, sit up and put my head through the drawstring cinched / snapped together opening and then lie back down. Just a little side to side rolling is all that is required to "tuck" the quilt under my body.

Am I doing the math correctly? When I convert .75 m to inches I come up with approximately 30" in width for your pad. Is this correct?

With that kind of width staying on your pad during the night shouldn't be to difficult.

Party On,

Newton

[Terry Trimble]

James,
Thinking out of the box on this Bottomless Bivy . Getting in out would be hell like fighting your way out of wet paper sack in less you make the head end and foot end less than 18". So you can slip your feet and head in easily then you have to tuck each side under you.

I would think instead of a hole entrance just have a bivy blanket with 24" head and foot area only to slip your head and feet out of have over large sides that hang down on each side . Kind like getting under the blanket of your bed.
Terry

[James Cavan]

Newton – Yes the thin pad is 30 inches wide! Some might consider it excessive but it gives me some wiggle room to get comfy on the ground! Plus i can put things head torch and other bits in easy reach in the night out of the dirt and wet.

Terry – Ideally the edge underneath should be as small as possible, or alternatively like you say a blanket type affair. The downside I can see to that would be wind creeping under the edge – maybe a drawcord around the hem would have the desired effect of bringing it all in or used as a blanket.
There's maybe a more accurate idea of the bottom opening

[Daryl and Daryl]

bivy

Link above shows a bivy made by Steve Evans. (scroll down page on right) It has a single 36" zipper centrally located for getting in and out of bivy. If you turn his bivy upside down the entry could be used as you are contemplating.

I've fooled around with this design a bit on my one person tent. I'm not very flexible and find that a 4' long opening is a lot easier for me to use.

[R]

I just finished a center zip bivy (thread coming soon!).  Along the way, I thought of doing something like this, w/ the opening on the bottom, but instead of a big cut-out like the illustrations above, making it a slit, as you would for a zipper.

Well, I just unzipped my bivy, turned it upside down, stuck my pad in the foot end and gave it a try.  It’s actually not that hard to get in and out of.

Sit in the middle of the pad and stick your feet in, pull it over your head, and lie down.  Now roll over and pull the end of your pad in.  Then if you extend one arm forward to tension the length of the bivy, rolling from side to side will allow the edges of the opening to get pulled under the pad.  Getting out is just the reverse which ends up being simpler to execute.

All that fabric under the pad should create a pretty good seal against weather and bugs,

 

 

[Russell Lawson]

I like the idea. I am fixing up my bivy at the moment and this gave me some ideas.  Generally only use my bivy like you when it is cold and wet out. My only idea would be to not have bug netting on the face so you can breath outside the bag, reducing humidity within.  There are not to many bugs during the winter anyhow and head nets to me are more free than mesh on the forehead.  Also by making your bag a giant stuff sack of sorts, with a cord lock entrance hole at the head, as well as your bottom hole.   You could enter two ways in case obstructions make exiting the bottom difficult.

My last suggestion is to maybe put a flap on the bottom hole, connected to the feet side.  It will weight more and might bunch up or defeat the purpose of having a hole. but i really love my bivy for the reason of not needing a ground sheet.

Hope your design works out as you want it!

 

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