WARNING: Long winded post ahead!! :)
Hey All,
New member here, and I've been lurking/learning for a couple months now! My main reason for beginning the journey to "ultra light" is so that I can minimize my pack load while elk hunting in the backcountry, but still maintain full functionality. This'll also come in handy on overnighters and fly fishing trips, as smaller/lighter gear makes everything more enjoyable. I'm in college currently, so $$ are in short supply, but time is not as scarce. I figured I stood to gain the most from lightening my shelter, as I'm using all my gear from my time in Boy Scouts. My 2-man tent weighs 6.5lbs fully decked out (ouch!) and around 3.25 lbs at the absolute minimum (fly, poles, stakes). So I began looking into tarps! I have my eye on a Borah Gear tarp, as they seem to be reasonably priced and functional, but I didn't want to take a 50+ dollar plunge without having done tarp camping before.
Enter the 3 mil Poly Tarp. I took some inspiration from this thread: http://www.backpackinglight.com/cgi-bin/backpackinglight/myog_3mm_plastic_tarps.html#.VaCrSPkTHYB
Then I started thinking about what I could do to make things better!
1. Find a better type of tape!!!! Duct tape and Gorilla tape have a tendency to slip in this application because the load is mainly in shear, and the thick layer of adhesive has very little surface texture to bond to. Gorilla tape especially is meant to bond to all sorts of rough stuff (pottery, wood, that kinda thing) and so smooth poly is gonna put a lot of shear force on that adhesive layer, which will result in slipping. Others had mentioned packing tape, and that is definitely a step in the right direction! I thought why not take it even further, and use a fiber reinforced tape! That way I have tons of tensile strength as well as tear-resistance. A quick Google search yielded Scotch Extreme Tape. Which is packing tape with a super tough adhesive, and vertical and horizontal fiber reinforcement. BINGO!
2. Ditch the grommets!!! Grommets tend to concentrate forces in bad places, thus cutting/tearing through fabrics and failing at inopportune times (e.g. pouring rain) Again, Scotch Extreme Tape to the Rescue! I made some loops out of the tape by folding it in half, then joining the ends with another piece. Needless to say, try as I might, I couldn't pull it apart (likely around 80-90 lbs tensile load). I think I've found a stand in for Grosgrain webbing!
Oh, and did I mention that the tape weighs under 2 grams per foot? Try that with Gorilla tape! I did some tensile tests on some versions of guy-out points with an 8 pound static load and some poly material. There was no poly deformation or tape slippage of any kind over about 6 hours- until I decided to see exactly what it could handle (about 18-20 lbs? maybe more, of shock loading before stretching to critical failure). Needless to say, the tape is ROCK SOLID, and the poly material is by far the weakest link, and plastically deforms significantly before critical failure, which is good.
For this tarp, I'm using 3.5 mil (0.0035" thick) painter's poly drop cloth. I know 2 mil would be more ideal, but the 3.5 was what I had around. Final weight on the tarp came to about 25.7 ounces with guylines and reinforcements for and 8X10 tarp. A tad heavy, I know, but a far cry from the nearly 60 ounces of my tent (in its' lightest form!!).
Without further ado, here's what I came up with! (hopefully the pics come out OK- not sure yet how this site likes to scale 'em)
Figuring out how to get a decent pitch:
Minimal deformation on the ridgeline reinforcement:
Plenty O' Room Inside:
Packs up decently small!
Basis of the corner tieouts:
Adding reinforcement:
Reinforced leading edges (going down from ridgeline to corners):
In short, I think with the 3.5 mil plastic and possibly excessive reinforcement, this thing is a little more "bomber" than it needs to be! I think with 2 mil plastic and more judicious use of the reinforcing tape (i.e. keep reinforcement on ridgeline and leading edges the same, lighten up corners and especially side tie-outs) I could likely get a very light and fairly durable tarp for not much money. I think the plastic was about $10, the tape about $8 (still have enough left over to patch any kind of puncture, tear, or burn), and the braided mason's line (guyline) about $3. I have enough plastic to make 2 more 8×10 tarps as well…
There was no deformation near any of the tie outs, and I got everything pretty taut and cinched down, so I think the Scotch Extreme Tape is a win! Also tried it on some fabrics like uncoated nylon, and it stuck great to those as well! Gives me some ideas for Silnylon… :)
I think all my goals were met for this project, so I consider it a success! If y'all see anything that could use improvement, please don't hesitate to let me know!! I love making improvements for a better end result!
I hope you found this at least somewhat informative! Thanks for taking the time to read :)
Logan
