DIY Bivy/Hammock

[slumhest]

Hi,

I am thinking about a hammock design that can be used as a bivy when trees are not available. I am considering a three-layer design where the bottom layer is slightly larger than the middle layer to create an insulating air pocket, and I hope that this will be enough for me to let the underquilt stay at home? There will be a velcro opening between the bottom and middle layer so I can slip in a sleeping pad when used on the ground.
Middle layer is low-weight parashute nylon, and top is breathable PU-coated nylon with a bug-net "window".

The design is for use under tarp both as bivy and as hammock.

Please see attached drawing.

I am considering the following fabrics:

Top:
Nylon, PU-coated, breathable, 100den, 80g/sqm

Middle:
Ripstop parachute nylon, 100% nylon, 40g/sqm

Bottom:
Groundsheet, Nylon, PU-coated, 90 g/sqm


Please give me your input on fabric, design and what else comes to mind. This is by far my biggest DIY project, so I would like as much input as possible before spending my hard earned money.

Thanks,
Christian

[bowl-maker]

lawson blue ridge might be a good place to start to get an idea

[VictoriaGuy]

Interesting idea.

Q: If you will be sleeping under a tarp in any case, do you need a waterproof top layer on your bivvy? (I am a bit sceptical about 'PU-coated breathable nylon, but that's a different issue.) Why not just put your hammock (with bugnet) on the ground sheet, under your tarp?

Q: If you are using this as a hammock, you will be sleeping on the side that's waterproof/breathable with the mosquito netting? Aren't you concerned with 'pulling' on the netting and tearing it?

BTW, about leaving the UQ at home because you have an air space between the bottom layers....I don't think you will find the air space to be a good insulator. (Otherwise, we wouldn't have insulation in our house walls?)

[SwinginIt]

MollyMac Gear already sells something like this. You can check that out for ideas.

[bowl-maker]

Interesting idea.

Q: If you will be sleeping under a tarp in any case, do you need a waterproof top layer on your bivvy? (I am a bit sceptical about 'PU-coated breathable nylon, but that's a different issue.) Why not just put your hammock (with bugnet) on the ground sheet, under your tarp?

Q: If you are using this as a hammock, you will be sleeping on the side that's waterproof/breathable with the mosquito netting? Aren't you concerned with 'pulling' on the netting and tearing it?

BTW, about leaving the UQ at home because you have an air space between the bottom layers....I don't think you will find the air space to be a good insulator. (Otherwise, we wouldn't have insulation in our house walls?)

Actually, my house walls are insulated with air. However, the inside and outside of the wall are 3/4' T&G hardwood, and they used a reflective barrier inside the wall. Just sayin'

[gmcttr]

Get an uninsulated air mattress/float like the ones used in a pool and use it to sleep on 40F ground. I promise you will have a very cold night.

Your "insulated air pocket" might get you down to 65F....on a calm night.

[slumhest]

Thanks all,

Air is a great insulator as long as it doesn't move, but as discussed in this thread (I just found now) it seems like the air pockets does not completely prevent the air from moving.
I am not interested in bringing a sleeping pad for the ground and an underquilt for hanging. I have a bike-packing trip across the Alps in the planning so weight and bulk is an issue here.

The setup will primarily be used in the danish summer (down to 10'C/50'F at night) so maybe the semi-dead air would isolate enough?

Q: If you will be sleeping under a tarp in any case, do you need a waterproof top layer on your bivvy? (I am a bit sceptical about 'PU-coated breathable nylon, but that's a different issue.) Why not just put your hammock (with bugnet) on the ground sheet, under your tarp?

I am also sceptical on the breathability, but thought it could be handy so I maybe could leave the tarp and just bring a poncho...

Q: If you are using this as a hammock, you will be sleeping on the side that's waterproof/breathable with the mosquito netting? Aren't you concerned with 'pulling' on the netting and tearing it?

I was actually planning on sleeping between layer 2 and 3 as when used as a bivy to keep out the nasty mosquitos

[slumhest]

Get an uninsulated air mattress/float like the ones used in a pool and use it to sleep on 40F ground. I promise you will have a very cold night.

Your "insulated air pocket" might get you down to 65F....on a calm night.

That bad? :-(

The design is beginning to fall apart... in that case I am glad I didn't spend the money on fabric :-)

[VictoriaGuy]

I am not interested in bringing a sleeping pad for the ground and an underquilt for hanging. I have a bike-packing trip across the Alps in the planning so weight and bulk is an issue here.

Why would you need an underquilt? Lots of hammockers use pads.

I've never found that 'multi-use' items work very well. Sleep IN a bivvy sack, sleep ON TOP of a hammock, etc.

You are going to be bike touring? A poncho doesn't work well when biking....
As long as you don't get 'silly' a bit of extra weight will not be a killer on a bike.
IMO, you wouldn't need more than (if you want to go rough and ultralight, and hammock - all of which don't make a lot of sense for European bike touring, to me....):
Hammock with bugnet
Pad
Tarp with some poles
Light sleeping bag or top quilt
Small groundsheet

If you are going to be tarping/tenting/on the ground for a (large?) proportion of your trip, wouldn't you be more comfortable in something like an Akto (3lbs) with a light inflatable pad and a light sleeping bag? You could always throw in a light simple hammock to use on clear nights....

If you want to DIY, then something like one of the DIY Shires 'Tarptents' could be a possibility.

Will you be using any public camping grounds? You may want a bit of privacy - some of the Euro campgrounds I've seen are very crowded.

Anyway, it's an interesting project. What is your planned route?

[gmcttr]

If you want to pursue your general design, make the hammock body a double layer without the air gap, slip the pad between the layers (as many do) and let it be your insulation whether you're on the ground or hanging.