Polycro Tarp Tested!
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Ultra Magnus
(Ultra_Magnus) - F
Re: Another Polycryo Tarp! on 04/12/2012 15:14:23 MDT Print View

I think that's a pretty impressive weight for such an inexpensive shelter.

Have any of you guys tested these shelters in any kind of significant wind? Could they stand up to some 30mph gusts? How long could it hold up to strong winds w/o failing?

BM

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Re: Another Polycryo Tarp! on 04/12/2012 15:51:31 MDT Print View

My LDPE version has seen 30-35 mph gusts. I'd expect it to be noisy but last indefinitely. I'd assume the same performance from this material. We were supposed to have 35 mph gusts at training but they just say winds up to 20 mph and not as much rain now. Bummer.

todd harper
(funnymoney) - MLife

Locale: Sunshine State
Another Polycryo Tarp! on 04/12/2012 20:39:00 MDT Print View

Cool shelter Michael!

I'm gonna build mine soon. These are awesome.

Dennis Park
(dpark) - MLife

Locale: San Francisco Bay Area
Re: Another Polycryo Tarp! on 04/12/2012 20:52:04 MDT Print View

Could you add a photo on how you taped the tie outs along the sides? (I guess this request would apply to all of you who have made a poly tarp.) I'm trying to figure out if the washer has to be taped off of the poly as in the photos from the poly testing thread or can the washer be placed on the poly and then taped into place. Thanks.

Dan Johnson
(Seattle)

Locale: PNW
Re: Re: Another Polycryo Tarp! on 04/12/2012 21:53:52 MDT Print View

@ Dennis:

You might be able to get away with putting the washer on the Material itself and then taping it down. The biggest worry I see is that the material is not very tear resistant (non at all really) so once it has a hole it is so much more susceptible to complete failure.


I recently got a new job (yay for me!) and i now have access to a scale. Today at work I weighed my Polycryo tarp and it came to 10.8oz. And that is with a crap load of heavy cordage and excessive tape used on all the tieouts. Also it is 7'x9 in size. I have no doubt that my next one (which will be smaller in size) will be sub 6oz if not less.

Dennis Park
(dpark) - MLife

Locale: San Francisco Bay Area
Re: Re: Re: Another Polycryo Tarp! on 04/12/2012 22:02:11 MDT Print View

Very nice! Keep us posted on your next model. Close ups of the key points and weights are always appreciated.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Re: Another Polycryo Tarp! on 04/13/2012 06:12:44 MDT Print View

Dennis,
I think you could do it either way. It would be a little cleaner putting them within the hem, but I would still add tape in both directions. I don't think the material would continue to tear because of the tape but that would be a good test for you to do. :)

FYI, I have one long piece of tape, containing the washer, that runs parallel to the ideal force direction, looping from the top of the material to the bottom of it. The "loop" is either an 8" piece for corners or 5" piece for secondary points. Then I added 2 perpendicular pieces on the top and 1 on the bottom. I used only 1 on the top in general for the LDPE version but the 2120 doesn't stick as well to this material so I thought the 2 extra pieces were good measure.

I just went out and took these before the sun rose. I found it interesting that ALL the places where there was tape had a film of condensation. You can see where I wiped the hem in this pic. You can also see I'm not pulling at exactly 45 so I made add a couple other pieces of tape to distribute the force better.
Corner tieout
Here is a side tieout. It's also the only place on my "hem" I had a major wrinkle. This was the last side I had done so it wasn't taped down at all (I removed the tape holding the corners down tot he floor as I went). I was also going too fast. :) It's a bit easier if you can keep the material taut.
Side tieout
And here is the only other condensation. Granted it didn't have my respiration to deal with but it also had no groundcloth and the back is essentially pitched to the ground.
Condensation

Dan,
I'm surprised your's is that heavy. You must be including guylines and stakes?

Dan Johnson
(Seattle)

Locale: PNW
The weight is all in the Tape on 04/13/2012 07:05:06 MDT Print View

@ Michael

Being this was my first tarp I experimented with I used a "butt load" of tape. And it doesn't help any that the Gorilla Tape that I used is insanely heavy. Not to mention that because of all the "over engineered" guy-outs I made it doesn't pack up very small due to the tape not folding very well. My packed size for the tarp and guy lines is the size of a nalgene. And my 10.8 finished weight does include the guylines. I'm using cheap cordage from REI that is pretty thick/bulky/heavy so I'm sure that's not helping me.

My overall weight for my 7x9 tarp, guylines, stakes, and ground cloth come in at 20oz. Keep in mind I'm not useing the lightest stakes either.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: The weight is all in the Tape on 04/13/2012 07:50:47 MDT Print View

It didn't look like you had used more than 1 large piece per tieout. As long as your guys are, I bet they're at least as heavy as the tape. Anyway, for reference, my Prototype 1 (LDPE) weighed 21.8 oz with everything, incl netting W/ zipper, ground cloth and stuff sack. That was a 6' x 8'.

I'm not sure I'll like trying to sleep with a headnet (or just a hat for that matter). I really liked taunting the skeeters in Wind Rivers through my netting. :) Keeping the annoying buzz away from the ears may be worth the weight penalty to me, but I'll give it a go without for a while.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Re: The weight is all in the Tape on 04/13/2012 10:34:40 MDT Print View

I actually had a failure point this morning. One of the washers ripped out of the tape (the very corner I took the picture of earlier). I did get pretty small washers (3/8 OD I think) but this tape has worked well for me in the past. Now I know I must add another layer of 2120 tape around the washer. You might not have this issue with GG - just something to watch.

Edited by topshot on 04/13/2012 10:35:38 MDT.

Mike Oxford
(moxford) - MLife

Locale: Silicon Valley, CA
Washers on 04/13/2012 17:09:59 MDT Print View

I wonder if Tyvek Homewrap strips would be better for mounting the washers than the tape .

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Washer failure on 04/13/2012 19:43:08 MDT Print View

Frankly, if it doesn't hold now, I'll just go back to my loops of tape. They don't look as elegant, but they worked. I will theorize it failed because I folded the tape right against the washer rather than leaving some space on the side where the force is applied. When I added my reinforcement layer, I did it that way, leaving maybe 1/8". I think I may try a subjective test of tieout design. I wish I had a fish scale.

As it turns out, the training I drove over 90 minutes to attend was canceled and they failed to notify me. Grrr. So I pitched in the backyard again, purposely the wrong direction so it should pop open like a parachute. Supposed to have some decent winds and gusts Sunday.

Michael Ray
(topshot) - MLife

Locale: Midwest
Tieout tape failure tests on 04/14/2012 15:16:44 MDT Print View

I wish I had a fish scale or similar to make this more objective, but I played around with some different tape combinations to see how much force it would take for them to fail.

Tieout tape failures

You can see that only 2 had not failed at the point I decided the pain in my hand of pulling on the Triptease (didn't use a glove or wrap it around a rod) was likely more force than it would normally take. I'm sure it was over 40 pounds. Interestingly the one I judge the best was just the tape loop (2nd from L) I'd been using all along. I normally use half that width (far L) so it doesn't bunch as much, but I also normally make it with 8959, which is stronger than 2120, and then cover it with 2120 for UV protection. The far left was just a single layer of 2120. The loops are technically double layer to prevent sticking, but only a single layer contacts the material.

The second best (6th from L) was what I have on my tarp now after the failure from the other day - one loop butted against the washer and a second layer that leaves 3/16-1/4" on the force side of the washer.

The worst one was how I started - one loop butted against the washer (3rd from L). It was pretty much tied with a single loop that left 3/16-1/4" on the force side (5th from L). Next came 2 loops butted against the washer (4th from L). Finally, the GG tape took a bit more force (maybe another 10 pounds?) to compromise. Both were pretty similar on whether the loop was butted against the washer or left a gap.

Edited by topshot on 04/14/2012 15:18:04 MDT.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Another Polycryo Tarp! on 04/16/2012 10:31:22 MDT Print View

Video added
Notice my comment, too. :)

Donald Krug
(hyKN) - M

Locale: Northern, Kentucky
tarp testing on 04/17/2012 19:38:36 MDT Print View

Thanks for the video. Now I see what you are (were?) doing with the washers. I made a tarp of this material for hanging over my hammock. I only had it out for testing once and there was very little wind. I will try to get it out for more testing soon.

I saw your comments about the failure and am wondering just how much stress this will take. I'll let you know if I learn anything in my testing.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: tarp testing on 04/18/2012 06:04:18 MDT Print View

I'm pretty sure the corner that had originally failed before the video (see further up this thread) went first. I discovered I'd repaired it with only a single layer with a gap (5th from L in the pic) so it was one of the weakest designs. Even so, it took some pretty serious gusts before it went.

Once that went, I bet the peak went since I'd butted the washer against those pieces of tape and it had also been pulling out from the backside as you could see in the video.

If you look at the short followup video, you can see I fixed the angle issue at the peak with a larger ID. At this point I've decided to stick with the washers rather than replace all the tieouts with loops of tape. I may go back to loops with Prototype #3 if I have any more issues, but I think I've learned enough now to know how to make the washers work. I definitely like a washer for the pole connection (similar to the grommets on my Lunar Duo).

Others have suggested placing the washers within the hem itself for a cleaner look like a generic blue tarp with grommets. I believe the reinforcing tape would need to be different in that case. For one, the washer would only be captured by it on one side (sandwiched against the polycryo). Knowing tape doesn't stick as well to it, I think it would be easier for the washer to slide under force. Thus, I'd be wrapping at least a couple layers of tape around the edge of the hem to stop the washer once it made it that far. I'd likely put it very near the edge to start though since if it does slide the polycryo would then have a small tear in it. That's just my expectation though. I haven't tested it and don't plan to as I prefer my method.

Daryl Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: Re: Another Polycryo Tarp! on 04/18/2012 09:02:33 MDT Print View

Michael,

Thanks for all your experimenting and sharing. Very helpful.

Daryl

Ultra Magnus
(Ultra_Magnus) - F
Re: Re: tarp testing on 04/18/2012 11:32:29 MDT Print View

I've been thinking about this and maybe round washers are not the hot ticket. Your tape folds over the washer, and the edge of the washer concentrates the load at that middle point of the folded over tape- a point load, if you will. What might work better would be a rectangular washer. Take some kind of semi rigid plastic, maybe a section from a milk jug or something similar, cut out a square the that matches the width of your tape, and sandwich that in your loop of tape. Maybe fold the plastic piece in half, doubling its thickness... I dunno- just thinking out loud. But either way, the straight edge of the plastic reinforcement would spread the load across the whole width of the tape, and you'd have more area of adhesion between the tape of the reinforcement increase the amount of load carried in shear.

I'm better at coming up with ideas than I am at explaining them, but I hope that makes some sense.

BM

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Re: Re: tarp testing on 04/18/2012 11:56:22 MDT Print View

You are correct that that would help. Perhaps buying some larger OD washers and grinding off one side would be a simple solution. I don't think a milk jug even doubled over would be stout enough. The plastic should be harder.

Michael Ray
(topshot) - MLife

Locale: Midwest
Re: Tieout tape failure tests on 04/18/2012 16:02:24 MDT Print View

I have a little data to share now on the tieout failure tests since I was able to borrow a cheap fish scale.

The worst case started deforming around 10 pounds and busted in the 15 range. The best of the ones I had done previously managed about 40 before breaking on a single attempt but repeated pulls to 30-35 would eventually cause it to go.

I did a few other combinations. I doubled up some GG and it held to the 50 lb max of the scale. I doubled up the loop and it held repeatedly at 40-45 but gave out at 50.

Then I made a single loop of the 3M 8959 that I had used on my previous tarp and it held 50 repeatedly. I suspect it would also fair better using washers since it's essentially high-grade strapping tape.

So what would I do different knowing this? Prototype #3 will likely go back to using 8959 for the actual connection point of the tieouts. However, it must be covered with 2120 to provide UV protection or it will disintegrate like normal strapping tape. GG could be used but it is not as strong as 8959, is heavier and it just doesn't look as nice. :) Maybe I shouldn't be so vain. LOL

While it's difficult to determine just how well the forces are distributed via the tieouts, you can at least guess that if you can accommodate at least a 3" section that it would take at least 25 lbs to break the tarp material based on the thread we had a couple months ago. So if my tieouts don't break until 50+ lbs, I shouldn't have to worry. Ryan's Storm Resistance article (when will Part 2 ever come out???) says, "Generally, moderately stormy conditions (snowfall equivalents of several inches through a night, or wind loads induced by 30-40 mph / 48-64 kph winds) can transfer up to about 40 pounds (18 kg) of tension force to guylines and stake-out points for most solo shelters." So I should be good to go there, but the article also states, "a significant mode of failure of ultralight shelters, especially those that employ low-stretch fabrics such as Cuben Fiber, is the shelter’s inability to be staked out tightly at high enough loads that induce a good distribution of tension evenly across all fabric panels. (emphasis added)" I think the saving grace here will be that the material does have a little give.

As an aside, one other point that I noted in the video but not here - the "catfish dropline" I got at Walmart held repeatedly at 50 so it would be suitable for some guylines. I don't know if it would work with linelocs or hitches though as I just tie a bowline on each end. But it's cheap, lightweight, braided nylon twine.