Polycro Tarp Tested!

[Nathan Meyerson]

I see from this post that most people have run a ridge line through the entire length of the tarp, rather than using ridge pull outs. Is there any concern of abrasion on the film from running an full ridgeline?

Hoping to get one of these made.

[David Gardner]

Nathan,

I have not had any problems with abrasion of the film from a ridge line cord.

David Gardner

[Pete Staehling]

>>"I have not had any problems with abrasion of the film from a ridge line cord."

I'd be curious if anyone had problems due to NOT using a ridge line? Not saying that is the case here, but I like to avoid weight added to avoid a problem that has never occurred.

[Michael Ray]

> I'd be curious if anyone had problems due to NOT using a ridge line?

Not yet, but I have always reinforced any ridgelines with tape as a precaution as I expect it would stretch some over time. I don't know if that would really be a problem or not.

[David Gardner]

> I'd be curious if anyone had problems due to NOT using a ridge line?

Pete, I would personally not use the tarp without a ridge line cord. The ridge line is subject to significant forces, especially tension. The one thing polycryo is vulnerable to is tearing, and for just a couple of grams (I use 1 mm 150 lb. dyneema cord) you can virtually eliminate that danger. Also, the ridge line cord, when properly constructed, takes all the stress off the tape-to-tarp connection at the ridge line. Plus, the ridge line cord holds the A-frame shape of the pitched tarp and keeps a nice taut pitch in side winds.

[Nathan Meyerson]

David, in your experience are tarp-tape connections at the ridgeline necessary, in addition to a ridge line cord? Don't they fulfill redundant purposes?

[David Gardner]

Nathan,

They are not redundant. If you just run a ridge line cord the tarp tends to move on the ridge line in winds and sag in the middle all the time. You can see this in the first picture in this thread. I actually run three cords for the ridge line. One between the tarp-tape connections at each end to nylon washers folded into the tape, then two separate cords at each end from the washers for tying out. Thus the center portion can be kept taught between the tarp-tape tie outs, and considerable tension can be put on the ridge line cord(s) without putting any significant tension on the tarp itself.

[robert van putten]

I just add washer-grommets right in the center of the tarp where I want the ridgeline to go, and pass a Loooong cord through 'em. The grommet goes through the tarp itself.

I use a long cord because I prefer to tie off to handy trees instead of stakes and sticks or poles. It is much faster, stronger and easier to pitch this way.

In use I tie off my ridgeline and sorta scoot the whole dang tarp back and forth to where I really want it, then stake out the edge cords to hold it in place.

One concern about doing it this way is water running down the ridgeline and dripping under the tarp in heavy rain. Short little bits of hanging string near the ridge grommet will catch and deflect these drips.

[robert van putten]

I still have one of my tarps set up in the woods near my home. It has suffered damage but not from the cords.
I've had trouble with both my duct tape tie-out and the double sided tape that comes with the window kits and used for hemming coming undone. Cold, snowy conditions take the "stick" right out of many adhesives.

Because I'm not going to blow three times as much coin on special tape as I did the plastic sheeting itself, I've started using gorilla tape which holds better and isn't to expensive.

Can't get away without another polycro tarp picture….

Polycro winter camp! Extra big tarp set up lean-too fashion.

[Aaron Sorensen]

Spent the day making a polycryo tarp from 2 large GG polycyro sheets.

I just used the parts I had available.

I did order the suggested nylon repair tape that worked like a charm.
It is nice and light and can be moved if it not placed correctly.

I wanted a 12" height at the center of each end but sometimes what works on paper doesn't work when it all come together.
I can either use 3 stakes in each end or use a 42" stick (plan on this most of the time). I'll need another stick in place where the trophy is.

I still need to add a tie out to the center of the front entrance.
The front is just taped without cutting any excess what so ever.
The back-side is cut along the pole then taped. It didn't come out as strait as I wanted but it also had to follow a curve which was really hard to actually cut correctly.

I don't have my scale. No idea where it is. The 2 polycryo's weigh 7.3 ounces and the pole about 4.5.
I don't think I added any more than 2 ounces with everything done to it. so hopefully it will fall in under 13 ounces?

I also still need to add a few inner loops with gorilla tape in order to hold the pole in place so it will probably end up at 14 ounces, however, this tarp is HUGE.
40" high, 60" wide and the beak comes out another 25" or so.
There is probably a good 50 cubic feet of usable room under this tarp.
Less than 1 ounce per 4 square feet works for me.

I'll take more pictures once I get it set up outside.

[Aaron Sorensen]

Finally got the tarp out and set up.
Of course as soon as I did, the dog thought it was play time and ran right through, breaking it in 4 different places.
I fixed it but will have to strengthen a few corners or replace some tape before it's done.

The only thing that needs to be fixed other than the above is the front beak needs about 3 inches (tapered) taken off each side from center.
I'll also need to use stakes on the corners instead of the pole or a stick.
This will tension each side much better than what you see in the pictures.

There is plenty of room for 2 inside.
This is more for me and 2 dogs. I just hope they learn that clear doesn't mean you can walk through it.

I'll get the final weight up when I get hold of a scale.

[Michael Ray]

> Of course as soon as I did, the dog thought it was play time and ran right through, breaking it in 4 different places.

LOL. Our dog did the same when I had setup my first tarp prototype. Being LDPE, it may have been easier to repair the major tear. I still used it for several weeks worth of nights, including storms.

My latest tarp I wasn't as pleased with because the tape didn't seem to stick as well for some reason. I had to fix a couple corners that pulled off under tension after a while (using shockcord loops). Same LDPE and 3M 2120 tape I used before (but maybe I used less). Even the nylon sail repair tape didn't stick that well (I had used it first). I'll try again with longer pieces of tape next time.

[Franco Darioli]

Aaron,
The first good wind gust will tear it apart.
Take a bivy with you as well.

[Aaron Sorensen]

The only reason this doesn't look taunt at all is because I need to stake out the corner end pieces.
You just can't pull anything tight the way it is. As soon as you do pull a corner tight, it become very taunt.
I also have a lot of slack in the beak because it needs to have 3" taken off each side.

After all of this, I will not be afraid of wind gusts at all.

My dog got a running start and absolutely smashed into the tarp.
In the end, this will hold up to the wind. Maybe not 25+ gusts, but for 90% of my outings, it will be just fine.

[Justin Baker]

So it definitely won't hold up to a charging bear…
You should also be worried about the more likely event of a charging marmot. They can get pretty fat and aggressive.

[Franco Darioli]

Aggressive , moi ?
we will see about that!

[Aaron Sorensen]

I can only imagine a charging bear when you see it coming at you the whole way.
No, surprise, you're just crapen yourself the whole time watching it come toward you.

[Greg Mihalik]

I used a .34 oz cuben tarp for my first JMT.

I was explicitly told to camp "below treeline", in the trees, and out of the wind.

The fabric itself has always been strong enough.
It's the seams and guy points that have been problematic.

[Aaron Sorensen]

Thanks.
Since thats what gave out on me with the dog, I'll have to strengthen them some.

[Dale Wambaugh]

Franco, you left out the "frame" for the photo :)

[David Gardner]

Just came up with a new idea for my polycryo tarps. I doubled over some duct tape along the ends and stitched in zippers. Also put in two more tie outs about 4" from the base at each end. When zipped and staked it forms a nice hexagon 7.5' long x 4' wide. Vent holes in the peak at each end. Ends overhang slightly for a nice eve effect over the vent holes and zippers. Sheds wind better in every direction.

Pitched open

End zipped closed

Side view of zipped end

Base of zipper

Vent hole

With sleeping bag and G4 pack

[Dale Wambaugh]

Great idea to sew onto duct tape. Two other avenues for ends:

– check out the hammock tarps with end doors. Some have separate flaps that are added and notably without making a seam on the diagonal. The other method is to fold at a side stake line and cross the overlapping ends over. Those flaps can simply be folded back when not needed. You can use just one door to aid ventilation.

– the Borah Borahgami tarp uses one triangle that can be folded over to make a door when in a-frame mode. The open seam uses Velcro. You could try stick-on Velcro dots on your tarps.

BTW, I think these polycryo tarps have huge potential for use as SUL hammock tarps. They would need to be 10'-12' long.

[David Gardner]

The trick for me is using a single 7' x 9' sheet, the largest I can get. I've tried adding flaps, but have not found a way that I that is sufficiently durable even after adding several ounces of tape. Here's how I used to close the ends:

BTW, I have stopped using nylon sail repair tape after several of the tie-outs let go. Now I'm using "Tough" 3M duct tape. And I don't "hem" them anymore with the double-sided tape that comes with the window kits, because it also fails. We'll see how this new tape holds up to winter weather…

[Stephen Parks]

"And I don't "hem" them anymore with the double-sided tape that comes with the window kits, because it also fails. We'll see how this new tape holds up to winter weather…"

Do you hem at all? What brand of double sided tape were you using? In reviews only the 3M DS tape seems to be universally liked (using the stuff for actual window insulation, that is).

I've been fascinated with this tarp idea ever since the first post, just haven't gotten around to making one yet.

[Stephen Parks]

"Here's how I used to close the ends:"

That looks like the "seam" would see more peeling load than shear. Peeling is harder for tape to deal with (as I'm sure you know).

If you wanted to make ends of separate pieces, could you tape them onto the outside of the main body, a few inches back from edge of the body panel? That way when you pulled the end piece closed, you would be wrapping it down around the taut edge of the main body. The tape would be in shear. And when you wanted the ends rolled back, they would rest neatly on the outside of the body. At least that's the way it looks in my head. If I had some time I would work up a scaled-down prototype.

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