RSBTR Cuben Weights

[Hoosier T]

So I noticed they have .8 oz/yd2 and while I’m familiar with the composition of the usuals (.51, .74, 1.0), I wasn’t too familiar with the .8 stuff. I started looking, then I found a couple things that have me crazy confused. The .74oz cuben that is typically sold (Zpacks for instance) is ct2k.08, correct? More dyneema with same mylar as .51. So then I got excited because I though maybe the .8 stuff could have the thicker mylar layers (.18). However, the associated model numbers on the RSBTR site suggest the opposite. Do they have it listed incorrectly or is their .74 oz/yd2 cuben really ct1k.18? Which would mean it’s not the same as the .74 from Zpacks which I know for a fact to be ct2k.08. Additionally, the .8 oz/yd2 cuben on their site is listed as ct2e.08. Why does it have an e instead of k and why is it .8oz instead of .74 like ct2k.08?

[Hoosier T]

@kcbaker-2

Can you provide any details? I would love to pick up <1oz cuben with .18 mylar layers but it has proven difficult to find, or so I thought.

[Hoosier T]

Also, when reviewing cuben charts it looks like ct1k.18 typically weighs .75 oz/yd2 and ct2k.08 indeed weighs .74 oz/yd2. .74 is listed as the offering on RSBTR but the hyperlinked product code indicates it’s .75oz/yd2 ct1k.18.

[Pierre Descoteaux]

The 0.18 has a doubled ”K” mylar layer. The ”E” is a different mylar layer than the ”K”. The ”E” is lighter than the doubled ”K” layer while more resistant than a single ”K” layer. Time will tell if it is more durable since my myog tent has some of both.

I hope this helps.

[Hoosier T]

Thanks Pierre, although I’m already familiar with the anatomy and nomenclature (with the exception of E vs K) but I was hoping someone could provide a deeper explanation of E vs K. And if someone knew if RSBTR has these labeled correctly. I have read about 1k.18 (thicker mylar than the usual 1k/2k.08, which is what I want) but always known it was hard to find. RSBTR has their .74 indicated to be just that even though I believe 1k.18 is actually .75. Anyone have any input here?

[Matthew / BPL]

This thread has confirmed that the nomenclature of the various cuben materials is very confusing to me.

[Pierre Descoteaux]

Last time I tried to get some cuben ”E” thru rsbtr they had labeled it correctly. I’d assume it is not a mistake. For the weight, it is impressive!

[Kyle Baker]

I think our 0.74 oz needs to be updated to reflect a 0.75 oz weight, but all the DSM product codes are correct. The 0.8 oz (CT2E.08) is one we’ve sold for a while, but it’s been hard to get for some time now. Glad to finally have it back in stock.

I believe the 0.8 has increased mylar making it a more robust version of the 0.5 for tarps, shelters, etc. The 0.74 has increased spectra/dyneema content, making it more abrasion resistant and well-suited for floors and such. Obviously it can also be used for shelters though.

And ditto on the confusing nature of said nomenclature.

[Matthew / BPL]

 

Double post because of 502 error. Sorry.

[Matthew / BPL]

Kyle,

A table or clear explanation of the different materials would be awesome on your site. I’ve considered building some projects with cuben but I can’t get past the material choices so I haven’t built anything.

Hoosier,

Your videos on YouTube are very instructive and have made me think more about building a project with cuben.

Perhaps there is a partnership opportunity for the two of you? You could be the next Fronkey, sponsored by RSBTR.

Just thinking out loud here…

[Hoosier T]

Matthew,

I wish I could take credit for those videos but those are not mine. The videos I have linked in my cuben build thread were from an author named Leshy. I’m not sure who he is or if he is a forum member but his videos are wonderful and helped me a lot on my shelter build. The cuben options are generally pretty easy to understand. The value before the k or e (i.e. 1k or 2k) indicates the dyneema content and translates into tensile strength. The value after the decimal represents the thickness of the mylar and translates into abrasion and puncture resistance (not exactly this simple but this is a good guideline). The .74 listed on RSBTR also happens to be Spruce Green, the same as the .74 sold and used by Zpacks. It is ct2k.08 meaning it has much more tensile strength than the commonly used .51 cuben (ct1k.08) but the same mylar. I would really like to be certain that the .74 from RSBTR (Kyle said it’s actually .75 which would be ct1k.18) is in fact correctly labeled as ct1k.18. This weight of cuben is not common at all but would be amazing for a UL floor. It would have the same dyneema content as .51 (tensile strength not critical for a floor) but would have thicker mylar making it great for a floor. It’s just so coincidental that it’s also spruce green, like Zpacks, which makes it harder to believe that it’s not actually ct2k.08. Lastly, the .8 is still a mystery to me. The numbers (ct2e.08) would indicate that it has the same composition as typical .74 cuben but it’s heavier. So the difference has to be in the e. Pierre says the e is lighter than k. That’s counter to what the numbers would suggest. If normal ct2k.08 (high dyneema with thin mylar) weighs .74oz/yd2 and ct2e.08 has a lighter mylar layer then why is the finished weight higher at .8 oz/yd2?

While all of these variants may seem “close enough” that they will all provide roughly the same results, that’s simply not the case. If I were to order the .74 assuming it was labeled correctly as ct1k.18 (same dyneema as .51 but with heavier mylar) for the purpose of a floor, it could be catastrophic if it were not exactly that. If I built ct2k.08 into a finished tent as the floor, it would have extremely poor abrasion resistance so it’s critical to know exactly what each is composed with.

[Matthew / BPL]

Ah. Thanks for the clarification on the author of those videos.

[Pierre Descoteaux]

Hoosier, not trying to split hair but I was comparing the cubens that I have experience with! In this case, ct2k.18 vs ct2e.08. The 0.8 is lighter and its puncture resistance is slightly higher. To me this makes the ct2e.08  a better alter native to the ct2k.18 and there’s nothing counter intuitive here. I’m not in the know for your 0.74 vs 0.75 dilemma as I did not use either of them.

[Derrick White]

e versus k

 

a few years ago I was told by a Cubic Tech representative that e is a more durable mylar than k.

that may be helpful.

 

 

t

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