So I am putting some thought into a SUL kit for summers here in the SE. My main goal is to keep the cost down and the versatility high.

I am thinking that the cheapest tarp would be a 5'x8'(ish) tarp using 2nds silnylon from DIY Gear Supply. Coming in at about $20 for everything I need.

The problem with this though is that most people seem to favor using a bivy for a tarp this size, especially for splash protection. However, in my mind, adding a bivy will cost weight and money, most importantly money. My thought is that I can add the splash protection right into the quilt, like the cuben fiber Enlighted Equipment quilts.

I don't want to make the whole quilt out of waterproof material because it is far too hot for that, but I was thinking a liner out of 1.1oz breathable nylon and a shell that has a strip of nylon about 28" wide down the center with the sides of it being made from silnylon.

I've never seen anyone use silnylon on a quilt, just cuben. Is there a reason for this? It shouldn't add much weight over nylon, I suspect.

Does anyone think this just won't breath well enough? I haven't used a quilt with non-breathable fabric before, so I am just trying to get some thoughts.

Putting a silnylon shell on the outside almost guarrantees that you will get a lot of condensation inside the quilt. This is why no-one ever does it.

Cheers

would it be breathable enough? probably not.

You could make the tarp a little bit larger and/or give it some shape for extra coverage. Sounds more comfortable than wrapping yourself in silnylon.

or, make a bivy out of tyvek and a driducks poncho. super cheap, super light, super weather resistant.

Will this be a down quilt? I assume so, since you say you are shooting for SUL. I see no problem with your proposal to construct the outer shell with a breathable strip down the middle and silnylon around the edges, as long as you design the liner the same way, but with a smaller breathable strip. Something like the image below (black is silnylon, red is breathable nylon) should work fine.



I've considered a design like this for a double quilt for my girlfriend and I, to protect the quilt from wetting out at the edges from contact with the wet (condensation-covered) wall of our cuben Hexamid Twin.