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Polycro Tarp Tested!
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John Donewar
(Newton) - MLife

Locale: Southeastern Louisiana
Re: Polycryo Tarp Tested! on 02/16/2012 17:30:02 MST Print View

D,

Just curious if the cord down the center of the ridge line is necessary.

Do you think that it might do just as well pulling on the tie outs directly and stressing the polycryo material itself verses supporting the material with the ridge line cord?

Party On,

Newton

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Re: Polycryo Tarp Tested! on 02/16/2012 17:57:15 MST Print View

I wouldn't do that long-term with this material unless it was reinforced with tape.

Dan Johnson
(Seattle)

Locale: PNW
Re: Re: Polycryo Tarp Tested! on 02/16/2012 19:01:37 MST Print View

John:

I'm sure you could just use the tie-outs and omit the ridge line cord but I wouldn't want to rely on the material for too much. I feel much better knowing that the stress isn't put on the tarp for that long of a section. I'm sure it would work to just use the tie-outs but the structure feels much more sound with the ridge line. I've had it sent up in my yard for a while and even with the breeze doesn't seem to phase it.

My wife said I can make another one and this time I'll be using the bear minimum tape needed as to not go overboard and increase the weight for little to no gain.

Franco Darioli
(Franco) - M

Locale: Melbourne
Polycro Tarp Tested! on 02/17/2012 14:03:59 MST Print View

"Ah, is that where they get cryo from?'
Well I just assumed that ....
The original function of that film was to coat window glass to protect it from cold weather, hence the cryo bit.
Cryo , usually a suffix, comes from the Greek word kruos meaning very cold/frosty.
But you are correct, it is possibly the most misspelled name of a product
(along with Thermo Rest and variants)
Franco

John Nausieda
(Meander) - MLife

Locale: PNW
Re: Polycro Tarp Tested! on 02/17/2012 14:33:10 MST Print View

I'm fairly certain that Polycryo is the same wrap used to package meat in American supermarkets where it is a very large continuous sheet on a long roll. Handles freezing well.

Gregory Petliski
(gregpphoto) - F
re: on 02/17/2012 14:44:36 MST Print View

"Interestingly, I just searched and it seems that polycryo is slang for CLP solely within the BPing community (originating from Gossamer Gear, of course). I found no other references. Ironically, the URL for the GG webpage uses polycro."

What does CLP stand for? I too could not find Polycryo outside of Gossamer Gear, whats it called if you went to a hardware store?

Franco Darioli
(Franco) - M

Locale: Melbourne
Polycro Tarp Tested! on 02/17/2012 17:14:20 MST Print View

http://www.acehardware.com/family/index.jsp?categoryId=1259828

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: re: CLP on 02/17/2012 20:34:18 MST Print View

CLP is my abbreviation for cross-linked polyolefin, which is what this stuff is though there are MANY varieties of that as well. That makes me wonder how different it may be between brands.

Polycryo seems to be a word Gossamer Gear made up.

Window shrink film or window insulation kits are what you would commonly find it as. So the southerners will need to order it most likely.

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Re: Re: re: CLP on 02/17/2012 21:21:15 MST Print View

Some of you materials scientists out there ought to give us a list of these modern materials with chemical name, common name, and relative advantages or disadvantages of each, maybe something like "tougher than generic polyethylene," other names.

Start with:
Cross-linked polyolefin, Polycryo, ...
... Dyneema...


Thanks.

--B.G.--

drowning in spam
(leaftye) - F

Locale: SoCal
Re: Re: re: CLP on 02/17/2012 21:44:45 MST Print View

Yep, I couldn't find it at my local hardware super store.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Re: Re: re: CLP on 02/18/2012 06:57:16 MST Print View

Yeah, I can't imagine window insulation would be high demand in SoCal. :) There are a variety of kits in a variety of sizes that you can order - 3M, Ace, Frost King, Duck, ... (5000+ hits in Google Shopping)

will sawyer
(wjsawyer) - F

Locale: Connecticut
Re: Polycro Tarp Tested on 03/13/2012 11:19:50 MDT Print View

Hi Dan,

I'm making a very similar tarp (nearly identical) and I'm wondering how you attached the ridgeline to the tarp at the edges (or if you did at all). I am planning on tying on a very small loop to the tarp and then using a friction knot on the loop to grab the ridgeline cord. Also, a big thanks for all the testing you have done, it has been a huge help with my project.

Dan Johnson
(Seattle)

Locale: PNW
Re: Re: Polycro Tarp Tested on 03/13/2012 13:53:05 MDT Print View

Will

I'm stoked that you're building a tarp too! For my ridge line I simply ran the cord under the tarp. For the ridge line tieouts I made a small hole (just like the rest) so that I could run the cord thru it. This I thought was definitely needed since I was affraid that the isolated stress from the cord would tear the Polycryo fairly easily. Because the cord had to go thru the hole in the tieout it rested the cord stress on the burly Gorilla tape. After building it and setting it up I wish I would have added ridge line tensioners to tighten the material along the ridge.

And of course we'd all like to see pics! Plus if you could weigh your tarp for us that'd be sweet. I can't find time to find a scale to use or else I'd weigh mine :(

Also what size is yours?

will sawyer
(wjsawyer) - F

Locale: Connecticut
Re: Re: Re: Polycro Tarp Tested on 03/13/2012 16:13:40 MDT Print View

I think the tensioners will help a lot, I have it set up inside to test (strung between two posts of a bed), and with a bit of tension across the tarp there is little stress between tarp and guyline, except at the reinforced edges.

I used a 84" by 110" sheet, is was labeled for 'outdoor use' and cost a dollar extra. It also did not include the hairdryer shrinking in the instructions. Either they expect UV from the sun to shrink it on windows, or this might be a non-shrinking version. I 'hemmed' all the edges with the included double sided tape and used gorilla tape for the guyline attachments (total of 12: ridgeline, four corners, three on each long side).

Dennis Park
(dpark) - MLife

Locale: San Francisco Bay Area
Re: Re: Re: Re: Polycro Tarp Tested on 03/31/2012 14:28:39 MDT Print View

any updates on the research or photos of newly made poly tarps?

Dan Johnson
(Seattle)

Locale: PNW
Re: Re: Re: Re: Re: Polycro Tarp Tested on 04/02/2012 21:38:48 MDT Print View

@Dennis

So far mine is holding up nicely so nicely I haven't needed to make another. My site selection techniques have improved drastically since using this material but it's paid back more so in it's low cost and low weight. I have been thinking of making a 6x8 for more "emergency" situations though.

Chris Martin
(hope_for_gorilla) - F

Locale: Finger Lakes
I made one too on 04/03/2012 08:26:00 MDT Print View

polycryo tarp

Did this yesterday as my first MYOG project. Hemming the edges was very finicky; toward the end I found that it's much easier if you tape down the whole tarp taut first.

My tie-outs are gorilla tape wrapped around heat shrink tubing. I didn't read the thread recommending nylon washers until later. Fortunately, the $7 window insulation kit included enough polycryo for me to make another one!

Dan Johnson
(Seattle)

Locale: PNW
Re: I made one too on 04/03/2012 13:36:19 MDT Print View

Lookin' good Chris! What size did you make?

Chris Martin
(hope_for_gorilla) - F

Locale: Finger Lakes
polycryo tarp on 04/03/2012 20:21:24 MDT Print View

The kit came with a 62" by 210" sheet, so I cut that in half to make a 62" by 105" tarp. I'm considering the first one just as practice. Now that I know how to make neater hems, and found the thread suggesting nylon washers as grommets, I plan to use the other half to make a better tarp with more tie-outs.

The hardest part is just keeping the cat away while I work with crinkly plastic and string, essentially her two favorite toys.

Michael Ray
(topshot) - MLife

Locale: Midwest
Another Polycryo Tarp! on 04/12/2012 14:38:53 MDT Print View

So after over a year of waiting, I finally decided to pull out one of my large pieces of polycryo/cross-linked polyolefin (aka window shrink film) and make "Prototype 2" of my half pyramid. I wasn't able to pull it off in time for my recent trip with my boys, but I have Scout training this weekend with some good storms and winds in the forecast.

I had already had in mind a few design changes and I incorporated others from Dan's research and threads the past couple months - using the supplied double-sided tape to "hem" the edges and nylon washers instead of loops of tape for my tieouts. So here is the first pitch as barebones as it gets.
Polycryo tarp
I bought a pack of 50 nylon washers at Fastenal for $2. They were too small for my trekking pole tip at the peak so I just used a metal washer I had. Detail of the pole connection.
Detail of pole connection
Cross-linked polyolefin is known for being tricky to adhere to and I can tell the weatherproof adhesive on the 3M 2120 tape does not stick as well to it as it did to the LDPE so I used more tape than I would have otherwise. That may also make adding netting without sewing a challenge if I do that again. Here is a view with a full-size pad in it, where I'm playing around with differing peak heights and how far out the sides are pulled.View with pad
It took about 3 hours, which included cutting the size down to 6' x 9', taping all edges, taping the 2 ridges, adding all the tieouts and running to the store for washers.

There are a few things I'm still not decided on yet.
1. Adding shockcord loops to some or all 4 corners as I did on #1. This material isn't as stretchy as LDPE so it takes much more force to deform (though I had reinforced the LDPE with tape pretty well). My gut tells me it should be fine without them.
2. Adding tape down the center. I was forced to on #1 since that was a seam, but it did seem to keep the pitch tauter. The LDPE would deflect a fair bit in the wind. I may compromise and add a tieout a couple feet up from the edge.
3. I may add a bit more tape on some tieouts as I get a better feel for how the forces act on the material. For now I distribute the load perpendicular to the "ideal" force, but I've already seen where I don't always pull the front corners from close to 45 degrees. I may also need to change to the Gorilla Glue tape if 2120 does not hold long term.
4. Put the pole washer just a wee bit farther out from the edge so it's not on as much an angle.

Specs: 6' x 9' (finished size about 1" shorter because of the "hem"), total weight with the tieouts and washers but without guylines - 150 g (5.3 oz). FYI, the tieout tape and washers (9 plastic and 1 metal) added 22 g.

Thoughts on improvements?