Polycro Tarp Tested!

[Matt Swider]

Hi Michael, still wondering if you or someone can point me to the details of the how to for this type of shelter. I know you started with a 7'x10' piece of material and cut it down to 6'x9'. What I don't know is how big did the shelter end up being? Must be less than 9'. How did you know where to make the cuts to end up with a shelter with squared off ends? I was hoping to find a reference which helps one transition from a flat sheet to the three dimensional object you created. If that was in the video I missed it I guess. The word template comes to mind, but not sure that is the best description of what I am seeking. thanks for any help, Matt

[Michael Ray]

Actually, mine have all been simple rectangular tarps. In theory I could also pitch it A-frame, flying diamond, etc but I only reinforced it and placed the tie-outs specifically for half pyramid, which in my view provides the best stability and coverage. So, yes, once you pitch a rectangular tarp in half pyramid, the ends will angle inward at the open side (part of the protection I was seeking). Also note that I would lay at a diagonal within it, not straight across the open side (as it would be too short). If you truly want squared off ends once pitched, just realize it will change if you change the peak height, how high you pitch the corners off the ground, etc. Simple geometry can be used to determine what dimensions you need. You would end up with a flat tarp shaped like an isosceles trapezoid.

[Matt Swider]

Thanks for the response. I looked at the video again, and it was not obvious that the sides are not square. you are right they certainly don't need to be square, I just assumed so. You know what happens when you assume . . . . Making this just got a whole lot easier. I think I will try this before graduating to something more complicated. Matt

[Michael Ray]

Just set mine up real quick (and you're right I did make it 9×6 rather than 9×7) to get some pics that may help. Please note I pitched this extra high (just over 48") for exaggeration. I put in 2 stakes where the front corners would have been if flat on the ground (my head's shadow is on the left one). There is about 19" from the stake to the corner once pitched this high. :)

[Michael Ray]

I'll also admit my inner engineering geek. I made paper mockups of various tarp shapes (1" = 1') with a block of wood shaped to represent me in my bag on my pad to see how cramped things may be and how well the ingress/egress may work. That's why I settled on half pyramid for me. It would be easy for you to do the same and come very close to the dimensions you need for the pitch height you prefer. Mine is normally 44-45" unless it's real windy. ETA: my original did have bug netting with a zipper and all. Worked great. This one obviously doesn't. It was a real pain to sew through the tape I used to hem the original. I'm hoping the nylon sail tape may not be as bad for that with proto #3 though I may leave it off. Will be back in the Winds again but hope to be bug free by mid-Aug.

[Matt Swider]

Wow! Thanks for all the detailed explanation, pictures and your time. It is very clear now. Again, another assumption was the sides would be parallel to the ground, which makes the sides come in a bunch more. But now I see that they are not parallel. I was thinking of taking a big tarp I have and experimenting after work tonight with pole height vs the sides. I will likely still do that, but I now see the answers in your posts. So it looks like you first built a half pyramid in spring 2012. Is it still holding up well 3.5 years later? thanks, Matt

[Michael Ray]

If you see my reply to todd above, you'll see I've hardly gotten to use this version (polycryo) unless both boys are on the trip with me (they're in the Lunar Duo then), which hasn't happened much and only local. Maybe 5 nights total so far not counting some testing. FWIW, I noted when I set it up today that even though it's just been in my basement 99.5%, the double sided tape provided with the kit that I used to hem the edges is yellowing. I could still use my first version (LDPE) with the netting that I used for my 2010 and 2011 trips. If you look back at those videos you'll see I had to repair it from my dog damaging it before I ever even got to use it! Since I don't get to get out much, that one has maybe 24 nights, including one storm in the Winds. I would expect one to last for at least 100 nights barring some kind of failure from fire sparks, falling limbs, excessive winds, etc. The nice thing is most failures should be easily field repairable if you take some tape along. I did have to repair an attachment for the "door" I had made for my original one that I only used during that one storm (wind had shifted 180 for the second onslaught). ETA: link for my LDPE construction details Said I had tested it for 14 days so it must have more like 36 nights on it.

[Matt Swider]

funny you mention the door repair, as I am definitely wanting something with a bit more coverage. Where I am, rain is not usually an issue. But when it is, then the winds can be pretty unpredictable, and having an open side would be a bit dicey. Although maybe then I could just lower the pole down and reduce my exposure that way. I saw how you installed a removable door in your first video, that is another idea to consider. Glad to hear that the tent is fairly long lived, thanks for the feedback. Matt

[Matt Swider]

I am planning out this project. I finally read through the entire thread, but my mind is a bit of a blur now. I am planning on using the 1.5 mil heavy duty material from Duck. I am considering not hemming the sides, as it appeared that some folks did that and were successful. I did see one person who had side failure and did not hem (I think?), but I am not finding that post now. Tape: lots of types mentioned, thinking of going with the 3M 2120 that Michael likes. I do plan on using this on the ridge lines for a half pyramid style tent. Grommets: I will get some tape and test, but I am thinking of just using doubled over gorilla tape, might try to find a small tube which the line will go through. Line – I have a bit of 100# kevlar cord I will use here. Open to any feedback to materials/techniques not previously mentioned (especially hemming and tie out points), or just your $0.02 thanks, Matt

[David Gardner]

I now use 3M transparent duct tape (2120) instead of sail repair tape. The sail repair tape does appear to be stronger, but I've had a couple of tie-outs come off and I can see creep in other locations. I haven't had any failures with the 2120 either from lack of adhering or lack of strength. Michael, if you want to try the sail repair tape send me a PM and I'll send you a roll.

[David Gardner]

Matt, I don't think doubled over gorilla tape will be enough in place of grommets. The line will likely tear through from hole unless you use a washer or tube to spread the forces. I use 7/8" nylon washers with a flattened side. Cheap, easy, and packs well. I'm using Tenacious Tape for the tie-out in the picture. I actually prefer it over the 3M 2120 for its adhesion and it is very strong. Plus it's cool because it's clear like the tarp. But as noted below, it's ridiculously expensive. You get 20 inches for $5, and you need about 80"-100" of tape to do a tarp, depending on the number of tie-outs and reinforcements. [edited to add comments about tenacious tape]

[Michael Ray]

I think Matt was intending to make loops of tape rather than poking a hole through it. The latter would definitely not work without a washer, etc. The former should be fine unless Gorilla is weaker for some reason than 2120 in that regard.

[Matt Swider]

Yes, I am intending to make loops, not poking a hole. I am not against the washer idea, but it is just on more piece of material. I think I may have some old arrow with hollow shafts that could be the tube I pass my line through. This is another part also, but would spread the stress on the tape better.

[Richard May]

So I'm prone to lazy solutions to problems. :-) I have this sheet of material from when I thought I'd use it as a ground sheet (decided on full length pad instead) and decided to do a quick and dirty test. What would happen if I simply made a tarp tie out point with just a piece of cord? Of course the material probably couldn't handle this in any meaningful way. So to re-enforce the tie out points I used patches of Tenacious Tape I had lying around and then bought some patches of their new Flex Patches because I didn't have enough tape. The patches are $7 a pair!! Each is 3×5 inches so I cut them in half for the tie out points. Just the patches costs more than the polycro. I have to laugh at this. I am not very good at pitching a tarp with a ridge-line. I've always used silnylon without one. It was surprisingly tricky. Any pointers? These are the results. I probably could have pitched a little taughter, but my lack of experience got the better of me: . . . . .

[Matt Swider]

So I began my tarp today, only got as far as hemming the sides wiht the included double stick tape.  I purchased a heavy duty 7’x10′ duck brand which is 1.5 mil thick.  Just the material hemmed weighs 8.8 oz, nearly as much as my hexamid solo, albeit much bigger.  Was wondering about just using loops aof tape instead of washers, like this:

re read a bit of this  thread and saw at least one person thought it ought work out fine.  Next question is the ridge line.  I don’t recall if anyone has built and tried a version without reinforcing the ridgeline?  My original plan for this tarp is a simple a frame dining fly, but I would be interested in pitching it as a pyramid as well for an overnight shelter.  having multiple ridgelines seems like a bit more work  and weight than I would prefer.  Also, I think someone used a permanent piece of line as a substitute to a tape ridgeline, did I get that right?  Wondering if anyone would explaining the attachment meting or that, as I don’t do well reinventing the wheel.

thanks, Matt

[Matt Swider]

Next step complete.  I changed a bit from the idea above, using pieces of drip line hose for the guy line attachment to the tarp.  Also used this on the ridge line, and just ran an continuous tape ridge line along the 10′ center line.

Picture of typical corner guy line attach

Picture of typical side attach

Picture of ridge line attach

Weight is up to 10.6 oz, a bit of a hog but for a dining fly for several people not terrible.  I hope to pitch this in the yard tomorrow to see how it all goes.  Still need to add guy lines and pitch a tarp for the first time in my life.  Pictures of the set up tarp when it happens

[Matt Swider]

Got the tarp set up today, finally done!  Spent way more time than I originally imagined, but it was a fun process and I learned while doing it.

Would like to leave it set up for a few days, but overnight will have to do for now as I need my trekking poles for a day hike tomorrow.

[David Gardner]

Related thread on the way I build polycryo A-Frame tarps here.

[Michael Ray]

<span class=”profile-data”>@sbslider</span> Just refound this thread again since all subs were lost after forum conversion. Looks like you did well on your tarp. How are you liking it?

[Matt Swider]

Well, I had fun making it but I have not yet used it for any camping.  I guess I have not gotten over the common fear of “what if”, and I also bought a hexamid.  I may be bringing this along on our high sierra trail hike this summer though, that would be a great trip to experiment with it.

[Michael Ray]

I figure the chances of me having to bail because of tarp failure I can’t fix are quite slim. Fear tends to be heavy, but hard to argue if you already have cuben. I guess in that case it’s expensive. LOL.

[Matt Swider]

The hexamid is definitely expensive, its my mid life crisis sports car.  ;-).  But if I take the tarp and it fails (or I do) I can squeeze into my son’s contrail with him worst case.  Or kick him out of it and into one of his buddies tents.  Plan A is to cowboy camp as much as possible anyway.

[Michael Ray]

Hitting 50 next year myself so I’ve contemplated such a “sports car” but can’t bring myself to do it for as little as I get to head west.

Back to the topic, I was going to test the polycryo I had since I knew there was some that was NOT very good (ie, groundsheet that hardly lasted on one trip), but was pleased to discover I still have a Duck patio door kit so that will be proto #3 for me. Still plan to go with mostly nylon sail tape for this one just because.

[David Gardner]

Michael, let us know how that sail tape works out. I stopped using it after I noticed some “creep” and a couple of tie-outs pulled off.

I’m finishing up a new tarp for a High Sierra trip in three weeks. 12.5′ x 83″ with zippers at the ends which turn it into a floorless hexagonal tent. Will post pictures after the trip.

[Michael Ray]

I can say proto #3 is much heavier than proto #2 that was made with the standard Duck kit vs the Heavy Duty one. #2 weighs 174 g with guyouts attached. #3 weighs 247 g without guyouts. It should be able to take more abuse though so I’m not concerned by that. I already know one thing I’ll change with proto #4 next summer and that is either going back to just loops for my tieouts or getting larger OD plastic washers than I had a couple years ago so I can put some flats on them as David does. So final specs:

• 184 g – 110″ x 74″ (279 cm x 188 cm) of Heavy Duty Duck window film
• 4 g – large metal washer to use as grommet for hiking pole (could use plastic but didn’t have one)
• 1 g – 9 plastic washers for tieouts (3/16 ID)
• 10 g – 5 shock cords loops (10″ of 1/8″ dia I think)
• 48 g – nylon sail tape for ridgelines and in combo with 3M 2120 for tieouts

XL Neoair (uninflated) for visual reference of coverage

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