The lack of a bathtub floor is one of the chiefest comparative drawbacks of tarp camping vs tenting. I have been toying with this idea for some time. I used to usually collect some suitably lengthed dead branches and drape the edges of the tarp over them on the appropriate uphill side if rain threatened to inundate the ground.
I played with various means of suspending the edges of the tarp with mitten hooks attached to the tarp. This works but is awkward and slow with my arthritic fingers, then I thought, what if I made an inflatable tube which circumnavigates the tarp? I thought this was a genius idea till I Googled it and found someone else had already been there before me. https://www.esvocampingshop.com/en/air-barrier-tent-ground-sheet-inflatable/ Imitation is the sincerest form of flattery. I did come up with the idea independently though. Theirs is quite heavy and only really suited to car camping not hiking.
Before I ever looked to see if there was such a thing I was thinking mylar or silnylon (both possibilities still – further experimentation needed), then I hit on the DIY packraft site I posted about here: http://www.theultralighthiker.com/new-diy-pack-raft/ and realised they could supply the materials for the tube and valve and that I could simply sew this to the edge of my 1.3 oz/yd2 silnylon tarp then seam seal the join.
Unfortunately the lightest heat sealable material (eg from http://www.seattlefabrics.com/nylons.html) is (I believe) 3 oz/yd2. I would need a tube 22’ long to circle double (7’ x4’) groundsheet. If I wanted the tube to be 2” in diameter, this would mean the tube would be in excess of 11ft2 or 1.3yds x 3 = 4 oz plus the 1.3 oz/yd2 silnylon 3yds x 1.3 = 3.9 Total 7.9oz or approx 240 grams. Good, but too heavy. If I can make the whole thing out of silnylon the first figure will become (1.3 x 1.3) 1.69 oz giving a total of 5.6 oz – or approx 160 grams. Much better.
A silnylon dry bag seems to hold air quite well though it is not designed to, so I suspect that if I glue up a tube of silnylon it will serve quite well, even if I have to add additional silicon as in this post: http://www.theultralighthiker.com/waterproofing-tent-floors-and-ground-sheets/ The thing is people use the heat sealable materials because they need strength, but with this ground sheet, the inflatable barrier does not have to take any stress, so glued/welded silnylon might work well.
Why not try it yourself, and get back to me?
PS: This groundsheet will go very well with this tarp:
http://www.theultralighthiker.com/poly-tent-by-the-ultralight-hiker-on-the-cheap/
http://www.theultralighthiker.com/make-your-own-tarp-or-hammock/
http://www.theultralighthiker.com/henrys-original-tarptent-tarptent-for-2/
I realise this inflatable tube could be added to my Holeless poncho to make it into a better groundsheet: http://www.theultralighthiker.com/hole-less-ponchoshelter/ eg for my http://www.theultralighthiker.com/the-deer-hunters-tent/
PS: As with my other design ideas, feel free to make one yourself but if you want to manufacture them I would appreciate some credit.
Brilliant concept, using an inflatable rim. I think I’ll try making one and see if it is workable regarding function and weight. It would be fairly useless if it weighted
a kg. Thanks for the interesting blogs.
Greg
Thanks Greg. Good luck. Getting suitable lightweight heat fusible material will be the trick. If you source some under 2 0z/yd2 please let me know. Cheers, Steve.
What about something like 3mil poly tubing that they use in the packaging industry. If your ground sheet is polycro you could just glue it in places. Seal one end of the tube and just clip the other. 4mil would probably hold up better, but would weigh more.
Just found your site, great articles and ideas. Fun read.
Thank you Brian. A very good idea. I will try it. And thanks for the support. Cheers, Steve.
Interesting idea, but why do you want inflatable over just fold the edges up and sew them or clip them (if you want it temporary)? With your skills I think it wouldn’t be hard for you to create a bathtub groundsheet – so I’m guessing you are thinking of some advantages that I’m not realising.
It would just set up so much more quickly than fiddling with pegs and string.