Bushwalk Australia

I recently came across this groundsheet while looking for a new summer pack at Appalachian ultralight, it looks simple and light weight bathtub floor. I was thinking of making my own out of Sil-Poly, for use with my cat tarp, is there a reason why more people don't do ground sheets like this. Something I am overlooking?

I presume it's using shock cord on the corners. Sounds a nice idea, but I'd still make sure it is a tub floor, which that one doesn't appear to have. All well to have everything dry when the thing is set up and you're not in it, but better still if it stays dry when you're in it!

Z packs stuff hexamid a are a bit like that - Cuban floor "suspended" inside netting inner. Works well, as long as it is suspended, but I have had a damp night when the edge of the floor got too low, and water ran in. Not happy, but still like the tent a lot.

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I thought with sil-poly it might stretch enough the bathtub would form itself?

That looks like a great design. Nothing new, but your right it's not particularly common. Wilderness Equipment have sold suspended tub floors as an option on their shadow tents for decades. Same for Black Diamond Megamids.

I used to regularly sleep under a mid or tarp with just a plastic ground sheet. Provided your tarp is big enough It's actually quite rare for their to be enough water for it to run over the top of a ground sheet. Of course this would depend on a variety of factors.

If the edges of the ground sheet are still suspended when you are lying in it then it wouldn't matter if the ground sheet was really a three dimensional bath tub shape or not.

possibly it isn't popular because once you are on that sheet everything will move towards you .
Before I go to sleep I can have several items around me (water bottle,torch,glove,hat,clothing,reading material) that I would not want to be right against or under my mat.

Obviously it's a compromise some UL users are willing to accept.

I usually put my pack at my feet and was thinking a small pouch near my head would solve the wandering equipment problem for a small weight penalty.

That said I have only had one occasion where I have needed a bathtub inner tent and that was caused by to poor site selection after arriving late. Since I started using just a sheet of window insulation I have been a bit more careful.

This also seems like it would be more annoying to couple with a mosquito net.

Personally I would do it properly if you are going to the trouble of making a groundsheet. Creating a bathtub floor is exactly the same as creating the one in the photo above. All it requires is a little more fabric and remembering to make the folds for the vertical corners as you hem the material. They save small items going awol in the night and not making it into the pack in the morning and we all have ended up in poor pitch at some stage.