Poor man's Cuben or "Polycryo" on Roids? Proof of concept model

[Diane “Piper” Soini]

I made a reusable shopping bag out of fused plastic grocery bags. https://www.instructables.com/id/Fusing-Plastic-Bags-the-eclipse-way/ I forget how many layers it was. It was sewable with a sewing machine and it came out very strong. I imagine it would be very difficult to make something like an 8×10 tarp out of shopping bags. I wonder if you could fuse layers of polycryo similarly.

I also wonder instead of fish netting sandwiched between the layers for strength you couldn’t just use a layer of wedding veil netting or the larger holed netting used for ballet tutus.

[Anonymous]

Hi Diane,

Nylon Tulle is fairly strong and tough for the weight, but unfortunately it stretches a lot under load. For this application, one needs a very, very, very low stretch material such as Spectra/Dyneema or Kevlar.

I’m expecting with using thicker Kevlar cord, in combination with fabric to fabric silicone bonding and sewing, and using Membrane Silpoly, that the prototype is going to test extremely well against a non reinforced Membrane Silpoly mini tarp.

My hypothesis is that the reinforced mini Membrane Silpoly is going to be able to take many times the weight at each of the guy out points than it’s non reinforced version (especially since the cord will be MUCH better secured this time).

Thank you for chiming in. And cool project about the grocery bags.  I’ve tried bonding polycryo with an iron at low setting, but once you get just slighty too hot, it starts to shrivel up very quickly.

I have wondered if you could bond polycryo to UHMWPE fabric using a hair dryer.  If you can control the heat better, theoretically they should bond at a molecular level via heat since they are a similar material (Polycryo being a cross linking between polyethylene and polypropylene, and UHMWPE being polyethylene).

If one could do this, then one could make EXTREMELY tough (tensile wise at least) and lightweight tarps and tent material at low weights, if you use 50D Dyneema or Spectra cloth in a loose weave.  But it would be expensive.  More expensive than DCF because there would be more Dyneema/Spectra material in it.

[Winston W]

Anyone try this stuff?

https://www.sailrite.com/Dura-Skrim-2-Patterning-Material-74

[Anonymous]

Have not.  It’s pretty heavy stuff at 2.7 ounces per square yard.  Wouldn’t make sense to use by itself. It could be used as reinforcements on a polycryo tarp in strips, but you would most likely have to use tape to connect them, and to me, tape is not a preferred method since it loses a lot of adhesion strength at low temps.  And if going that route, it would just be easier and make more sense to use reinforced tape like George mentioned earlier.

Hypothetically, it could be bonded to polycryo via heat, but the less surface area of reinforcement, the more tricky it will be to do so well, since when it comes to heat polycryo is very sensitive and finicky.

[Paul French]

Justin,

Very interesting ideas. Sounds like  you are near a break thru. Although I got ill a couple years ago before I was able to make a prototype, I was going to use 1/2″ wide Filament strapping tape  $7 ( https://www.amazon.com/dp/B01M04L0HW?aaxitk=DxKDrFC3W-0gCPoBsd4n8A&pd_rd_i=B01M04L0HW&pf_rd_p=9420597b-7dad-4cbd-a28d-7d676ac67378&hsa_cr_id=6112179080101&sb-ci-n=productDescription&sb-ci-v=1%20Roll%201%2F2%22%20x%2054.6%20yds%20(12mm%20x%2050m)%20Bi-Directional%20Fiberglass%20Reinforced%20Filament%20Tape%2C%20Strapping%20Tape%2C%20for%20Heavy%20Duty%20Packing%2C%20Steel%20Bundling%2C%20Wrapping%2C%20Palletizing    ) and 1.88 ” wide -40 F duct tape $10

(  https://www.amazon.com/dp/B07GRJ8L55/ref=sspa_dk_detail_4?psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExRVpFVEw4U0xEQ0xJJmVuY3J5cHRlZElkPUEwMDY0NjU4MkUzSktTMVFDVUhaVCZlbmNyeXB0ZWRBZElkPUEwMTczNDc5MjVESEU3UEVYNjFQQiZ3aWRnZXROYW1lPXNwX2RldGFpbDImYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl ) on top of the Filament tape. I was only planning on one thickness of 1.5 mil polycro  $10

(  https://www.amazon.com/Duck-Strength-Insulating-120-Inch-284352/dp/B015PY2BTS/ref=sr_1_4?crid=1PBTFA7HHYILE&keywords=duck+max+window+kit&qid=1565489575&s=gateway&sprefix=duck+max%2Caps%2C163&sr=8-4    )

George,

What were  the as dimensions and mils of  polycro sheet that you used?

How far apart did you space your pull outs?

Please, if you do not mind, tell us how your final product worked out and any lessons learned to save us the same learning experiences.

I have thought about this for years so I am curious.

Thanks for your efforts, gentlemen.

Paul

 

 

[Paul French]

Winston,

I followed your link. If that material is only 2.7 oz per square yard 7′ x 9′, please check my math, would be  about 6 yards weighing about one pound. Sure would be labor saver.

[Craig B]

Hey Justin, before you attach the ends of the cord/fishing line to the edges, you should soften and squish them flat.  It will make any connection between the cord/sheet much stronger, whether you stitch them or bond them.  You distribute the load that way to a larger surface area so each individual point within that contact area does not need to support as much force.  You can soften the ends of the cord/line using any flame like a lighter or torch.  An Iron might work.  Soldering iron will, but set fairly low.  Then you have to squish it very quickly once you take the heat away.  I generally have to do it several times before I manage to spread it out enough. And of course be sure to get a good attachment of those tabs to the reinforcing edge as well.

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