UL Silnylon Bivy

[DanShell]

For my third sewing project I made myself a silnylon Bivy.

Im not 100% why other than I thought it would be a nice project to keep extending my sewing knowledge or ability and who knows I may even use it one day

Actually at 149 grams I will do away with the emergency blanket in my first aid kit and keep this instead. (thanks to the bush walk.com member for the suggestion).

Im not certain of the nylon ratings but the base uses a waterproof silnylon approx 1.3oz which is quite thin but I drenched a towel and knelt on it on the bathroom floor using the silnylon as a barrier and no moisture came through so Im confident it will do the job for what ill ever use it for.
The top is made from a water resistant breathable nylon and I used quite a bit of mesh over my head. The whole thing is zipped right around the top and a third down both sides, so access is easy. Although zipping it up once in it isn't as easy as Id like but it is a bivy, so its quite a confined space.

I think if I was to use it as a part of a sleeping system on a hike it would be under my tarptent or under a tarp of some sort and Id most likely still use some sort of ground cover. I will probably give this one to my son or wife to use and make another one that is slightly longer and larger as I feel a little cramped in it. I made it to suit my mat so it definitely keeps me on the mat but in hindsight I could have made it larger. I might sew some more tabs into it so I can tie it up in the tent and keep it off me a little, that may help with the cramped feeling.

As usual, sorry about the poor quality phone pic.

Attachments

bivy1.jpg (55.14 KiB) Viewed 10357 times

[perfectlydark]

That looks good! Do you have any suspension in it to.keep it off your face?

[DanShell]

That looks good! Do you have any suspension in it to.keep it off your face?

Not yet, Ill sew some tabs into the top of it so I can tie it up off my face. I put one down near my feet although not necessary really. I wanted to finish it so I could work out exactly where to put the tabs near the head.

[perfectlydark]

Good idea. I like it, good project!

[walkon]

What is the rough cost of this

[DanShell]

What is the rough cost of this

Hmm good question, without checking exactly I'd say it was less than $50.

[andrewa]

Condensation issues probably forthcoming....unless you have a sleeping bag that is cold enough that you don't sweat at all....

Bivy bags have all sorts of scientific issues attached to them. You need a vapour gradient. If you have a well insulated sleeping bag, the water vapour going through the outer layer is going so slowly it won't get through any fabric, breathable or not. If you have a crap sleeping bag, and you are cold, then there is probably enough vapour gradient to allow an outer layer to transfer it.

Focus on other projects!

A

[DanShell]

Condensation issues probably forthcoming....unless you have a sleeping bag that is cold enough that you don't sweat at all....

Bivy bags have all sorts of scientific issues attached to them. You need a vapour gradient. If you have a well insulated sleeping bag, the water vapour going through the outer layer is going so slowly it won't get through any fabric, breathable or not. If you have a crap sleeping bag, and you are cold, then there is probably enough vapour gradient to allow an outer layer to transfer it.

Focus on other projects!

A

Thanks, I have no doubt you are correct. But I'm still happy I made it, if for no other reason I am gaining sewing experience

Im going to be over 1000m this Saturday night so I may give the condensation a run....or Ill put my son it and let him test out the dampness

[walkon]

Go for it Dan, it's better to have more doers and have tried in this world. When I tried to work out the condensation issues and getting the bivy off my face and feet I ended up with a tent. Lol
Still think that I should have made it!

[ElvenCraft Gear]

+ 1 for the condensation issues.
If you put a double skin in the roof , inner use an untreated ripstop (15-20 denier) and it will absorb the moisture and wick it to the outside if you design the side vents properly. You can even get a ultra fine mesh weave ripstop if you need more ventilation.(I use this in my double skin tents)
Use a 20-30 denier (1.3gsm) silnylon as the outer skin/tarp and you should be pretty dry in all situations.