Cuben Fiber really stronger than steel?

**drsolarmolar** · 01-12-2017, 22:50

Recently I started a thread in the Warbonnet section of the manufacturers forum inquiring about damage to tarps caused by Ridgerunner spreader bars (titled "Spreader Bar Damage"). In the responses to that thread, two or three people mentioned their cuben fiber tarps had been damaged by spreader bars.

Due to the crazy amounts of snow we've had the past week, work has been really slow and I've had quite alot of time to surf the Internet. I went to Ripstop by the Roll and was looking at all the different fabrics including cuben fiber. I noted in the product description that cuben fiber is said to be "15 times stronger than steel." Now I'm not a materials expert, but wouldn't something "15 times stronger than steel" be practically puncture-proof (if not bullet-proof)? In what respect is cuben fiber stronger than steel? Apparently it isn't to pokey things.

**Speedogomer** · 01-12-2017, 23:20

If you took a piece of steel as thin as a cuben fibre tarp, you could probably poke a hole through it with your finger.

**gunner76** · 01-12-2017, 23:25

While cuben is very strong for its weight, it is not bullet proof. I have a couple of cuben Hammock Gear Tarps with doors ( got them before the price went crazy ) and love the fact that they are 8 oz vrs 20 oz for a normal winter tarp with doors. If I am backpacking more than one night, I take the cuben.

**drsolarmolar** · 01-13-2017, 00:12

Originally Posted by gunner76

While cuben is very strong for its weight, it is not bullet proof. I have a couple of cuben Hammock Gear Tarps with doors ( got them before the price went crazy ) and love the fact that they are 8 oz vrs 20 oz for a normal winter tarp with doors. If I am backpacking more than one night, I take the cuben.

I wasn't meaning to imply CF was literally bulletproof. But when a claim is made that something is 15x stronger than steel I would expect it to be pretty tough. I was wondering in what regards it's stronger. Could you lift a car with a CF tarp?

It certainly has an advantage when it comes to weight.

**Rushthezeppelin** · 01-13-2017, 01:08

Strength =/= abrasion resistance. Similar concepts with climbing ropes. They are strong enough to hold a truck but are susceptible to severe abrasive forces. Granted they can take some abuse but it's best to try and minimize abrasion (especially under load) when at all possible. This is just down to extreme difference in hardness between the two surfaces involved. A rock or the end of a bridge suspension rod are hard. Materials made from plastics like climbing ropes or cuben fiber are not hard. The hard material will thus abrade the softer material.

**Kalle Mandelstam** · 01-13-2017, 02:55

From Wikipedia (UHMW): "Since steel has a specific gravity of roughly 7.8 [UHMW <1], this gives strength-to-weight ratios for these materials in a range from 8 to 15 times higher than steel" [...] "and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel."
Link: UHMW/UHMWPE

The fiber IS pretty **** tough... I don't know if it's the fact that the actual fibers used in Cuben are so thin that the abrasion damages the fabric more than if the same weight and thickness were made of thicker fibers. I mean, once a fiber breaks it has zero strength and it takes longer for a thicker fiber to break from abrasion than a thinner one.

**dscotthep** · 01-13-2017, 07:38

It would be really helpful if you started by defining what you mean by "strength". An engineer is gonna want to know a material's ultimate strength, it's yield strength, and it's modulus of elasticity. Then he'll want to know how the material is being loaded (tension, compression, or shear).

Once those variables are defined, we can figure out which is stronger: cuben fiber, or steel. (The answer, of course, is "it depends"

)

Comparing cuben fiber to steel seems like an apples-to-oranges comparison to me. When was the last time someone tried to make a tarp out of steel? Or a wide flange beam out of cuben fiber? Why not compare it to nylon, polyester or cotton? That's what tarps have traditionally been made of.

**Caminante** · 01-13-2017, 08:24

Isn't cuben fiber made by laminating UHMWPE in polyester films? If so, comparing cuben fiber to steel is totally different from comparing UHMWPE to steel. To say that cuben fiber fabric is x times stronger than something else, you'd want that something else to be steel fibers of the same size as the UHMWPE laminated in the same polyester films (I'm not sure that exists). As a mental exercise, it would seeming be quite possible for a spreader bar to wear through a super thin fabric made of super thing steel fibers embedded in polyester laminate.

I think it would be more accurate to say that "the UHMWPE used in cuben fiber is x times stronger than steel of the same size resulting in a fabric that is extremely durable for its weight". I don't know much about cuben, but it seems like it would be quite strong in terms of not tearing under force (such as a tight tarp tie out or ridge line), but more susceptible to abrasion as that would wear away at the polyester laminate.

Just spitballing.

**mikeholczer** · 01-13-2017, 08:46

"Stronger than steel" is clearly a marketing phrase, which while likely true, does not mean what the average layperson thinks it means.

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**Firesong** · 01-13-2017, 09:04

I personally heard that for the first time when they were comparing steel to dyneema winch lines. Comparing the same diameter lines... hence the stronger than.