"The key is just to know the limits"

D,

I agree with your comment. I want to have a good idea when something is going to break, tear or come apart. I can then add a margin of error or prepare for the eventuality of the failure in the most weight/cost effective way. Your tarp is perfect for this because we all know it is at the very edge of failure now or in the eventual future. But when will this failure occur and what will be the weakest link that gives first? Inquiring minds want to know. For me it is like watching a serial movie.

The area where I've gone the farthest with this "testing the limits" strategy is my myog backpack. I keep going lighter and lighter on my way to the eventual breaking point. The fabric, for example, has gone from 6 ounce pack cloth to 1.9 ounce nylon to 1.1 ounce nylon with no failures yet. Next version will be out of M50 nylon which weighs about 3/4 ounce per square yard. Regardless of the outcome I've already concluded that most packs are way overbuilt fabric wise. Most of us aren't scrambling over abrasive granite or running through thorn bushes.

Keep up the good work. I've purchased a season ticket for your adventure.

Daryl

Just as an example of how expensive Lowes and HD are on stuff like those washers...

This is probably not the same washer exactly, I can't tell what the ID of that washer is but here is something not too far off at Fastenal...

http://www.fastenal.com/web/products/detail.ex?sku=11107626

They are $0.042 cents each so 100 of them would cost $4.20 cents. Lowe's and HD probably charge $1.99 or more for 4 of them. My brother and I build 4x4's and we use a lot of grade 8 bolts. The first time we discovered Fastenal we realized that for the cost of 1 grade 8 bolt at Lowes and HD we could typically get 10-25 of that same bolt at Fastenall. Some of the smaller stuff at HD and Lowes that came in bags of 2 with the nut and/or washer we could get 100 of the same thing at Fastenall for the cost of 2 bolt/nut/washer combos at Fastenal. It is ridiculous what they charge you in the hardware department at big box home improvement stores. Heck most everything is way too high. I have found the same thing with a lot of their chemicals like insect stuff where you pay X for one small can with a couple ounces of X spray and you can get a 20 gallen drum of the same stuff at a do it yourself pest control store for the same price.

(rant over)

Regarding length of time until failure. I recall another thread or article saying the tie out tape will slip from the tarp fairly quickly (ie less than 7 days). The solution was to put some staples through the tape. This could also be a difference when using Gorilla tape.

DJ you are an inspiration. I'm a tent sleeper and this thread has given me a method to experiment with a tarp.

> Regarding length of time until failure. I recall another thread or article saying the tie out tape will slip from the tarp fairly quickly (ie less than 7 days). The solution was to put some staples through the tape.

Staples? I'd never do that. Tape should be fine if you use something that is UV resistant. Gorilla Glue tape seems to be. 3M TRANSPARENT Duct tape is. Normal duct tape is not.

You could sew the perimeter of the duck tape then seam seal it maybe. Might be overkill.

I really liked the idea of sandwiching the washers between a folded hem on the edge of the tarp. I would be curious to know how the strength would compare. Possibly with a glued hem.

NOT a fun experience. :) Really gums up the needle so you need to clean it about every foot. I had tried to do my shelter totally without sewing. That is easy without netting, of course. The tape wouldn't hold the netting though so I sewed it on. My next test with netting will use silicone or an adhesive to bond it to the LDPE or CLP.

The taped washer inspired me to try this as an option.







The photos above show a 2" wide piece of clear Frost King tape folded over at each end 2". One end has no reinforcement. The other end has a small .3gram piece of vynal from a notebook enclosed within the tape. A hole was then punched in each end with a paper punch. When I hung weights from the item the unreinforced end tore with 14 lbs of load.

I then made a new piece of tape with reinforcements at each end and tested it. The reinforcements held but the tape started elongating at about 19 lbs. Ended test. Photos below.





Conclusions

Washer or washer like reinforcement is very effective. Same conclusion as D. The technique I used could be used with any piece of stiff plastic scrap that one has. No need to buy washers.

Edited by lyrad1 on 02/18/2012 07:54:39 MST.

Just wanted to make a note on the weight of the Gorilla Tape. According to the manufacturer, the 2" wide roll weighs about 0.66 oz a yard, and being such a tough tape, I'd take the ever so slightly heavier weight knowing that your tape ain't going anywhere.

Edited by gregpphoto on 02/17/2012 14:58:31 MST.

Thanks for getting the weight for the tape! Now I can calculate even more...

I did the math with those numbers for the gorilla glue for my tarp and it seems that I used about 84" of tape @ .66oz a yard equals about 1.539oz. When you put it that way it doesn't seem like very much weight at all, but it does seem like a heck out a lot of tape!!!. I mainly notice it when trying to pack it up. The tape doesn't bend very well once folded over and it makes the tarp much bigger when trying to store it after use.

After my strength analysis I now can determine that I'll only need 52" of tape. That makes the total tape weight drop to .953oz which is a 38% reduction in weight if my math is correct.

Wow, I've read other threads here recently on the polycro tarp you've made. Love the idea! I have a couple ideas on what to do with the polycro I got form home depot a few weeks ago.

I'm thinking I'd like to make either a bathtub floor groundsheet for use with y poncho tarp so I can pitch it higher during rain. Or I'd like to make a beak for use with half pyramid pitching. Maybe it would be possible to combine the two idea to create a bathtub floor groundsheet with a long flap on one of the sides that could be tied up for rain protection. That probably makes no sense to read... but I guess I'll just have to try to make it and post pictures in a new thread one day.

Thanks everyone who contributed to this thread. Very useful stuff!

Just in case anyone wants to know, I found that target was selling patio door insulation kits for only $2.98 in their clearance section. It's now even cheaper to build something out of this stuff!!! I bought a couple just cause I couldn't say no to the price :)

That's even better than the $4.50 clearance ones I got at Walmart last spring!

A quick note for anyone attempting one of these, make sure the washers you use are robust enough. I was going to use pieces of a milk jug since that's what I had on hand, but in testing some tieouts under repeated stress the cord cut through the milk jug washers and gorilla tape.

In short, use tougher plastic or the store bought washers.

-David

Anyone have any pictures of a tarp from polycryo? Size of tarp and weight?

Steve

Searching does wonders

Thanks!! I'll be sure to search before any reply in the future!

Steve

"Note that the standard Polycryo thickness is 12 microns = 0.000472440945 inches"

Wait..What?

Where the heck does this "standard" come from??

.47 mils is standard?
Seems like extra thin stuff to me.

Dennis brand window kits say .6 mils for the interior stuff ( 15.24 microns ) and 1.2 mils for exterior film ( 30.48 microns ).

I can't tell how thick the Frost King kits are, but have found one reference on their web site that mentions outdoor kits with 1.25 mil ( 31.75 micron )film.

Dan Johnson, what source are you using for the stuff you are testing, and what is everyone building their tarps from, the thin indoor kits or the possibly twice as thick outdoor kits?

( Edited because I got my darn decimal point in the wrong spot)!

Edited by Bawana on 02/18/2013 15:25:41 MST.

I'm using the Frost King Interior large patio door kit.

I'm surprised!
The thin interior stuff is stronger than I figured it would be.
I can't help but wonder how strong the probably-twice-as-thick exterior kits are.