Cuben fibre poles (theoetical post)

[Anthony Britner]

Any idea if this would be possible? I gather that fabrication would be the same as with carbon poles, that is, a sheet of "C"* fibre wrapped around a round metal form to create layers held together by epoxy resin. *"C" refers to both cuben and carbon fibres.

a lot of infomation I seem to find suggests that the regidity of carbon comes from the fibre however, considering that the carbon is highly flexable until the epoxy is applied suggests that is the resin that gives a carbon pole it's regitiy whilst the carbon increses the overall strengh of the epoxy by acting as a binding over a wide area.

Therefore, should cuben be wrapped around a suitible form and coated with a suitible epoxy it should in theory be capable of forming a pole. it should be noted that whilst it is theoretically possible to create a very light pole from Cuben, how the strengh of such a pole would compare on a weight for weight basics to a carbon pole or even an alloy pole is debatable.

If I'm talking nonsense please say so!

[Dale Wambaugh]

Good for you to think outside the box, but I think most composite materials are porous so they are evenly saturated with whatever glue is being used. Some materials may not stick to the epoxy well and delaminate,so that would be my first test. The raw carbon fiber is very light stuff and thicknesses that compare to Cuben are very light indeed.

Industrial processes to make carbon fiber shafts are very good at getting the dryest matrix possible and that is a big challenge. I don't know how you could get a vacuum setup to pull all the excess out.

Laminated backpack stays or frame sheet would be interesting too. Then you can graduate to an epoxy/Cuben kayak and paddle :)

[Jake D]

that is what i was thinking.. not porous so no where for the epoxy to go. i think of Carbon fiber as mini re-bar.

plus you COULD make carbon fiber poles thinner and lighter but the strength would not be there. i mean CF arrows are like 5mm diameter. i'm sure poles now they are made of quite a few layers.

[Diplomatic Mike]

I think that the future is in airbeams, for the lightest poles. Fabric technology will need to improve, but i feel that is the way to go.

[Ron Moak]

There would be little upside to a Cuben Fiber pole. Unlike Carbon Fiber, Cuben Fiber is not a fiber but a brand name. The plastic sheets that are used to stabilize the inner layer of Dyneema Fibers would prevent any bonding between the Dyneema and resin.

An interesting pole might be one where layers of Carbon Fiber and Dyneema Fibers are uses together or the Carbon Fiber and Dyneema Fibers are woven together. Again, there could be all kinds of issues with bonding between the resin and the Dyneema Fibers.

Unless you've got a good Chemistry degree, not much of a project for a MYOG'er.

---

Air Beam technology comes and goes over time. Nemo tried to revive it in their early days. While they still carry some air beam tents, none were on display at the OR show. Interestedly, Kelty did have and air beam family tent with a daily contest on who could blow it up the fastest. I bet on long odds on whether we'll see there again next year.

[Anthony Britner]

Ok so maybe not epoxy resin. I see that the "hysol" adhesive that is so popular for bonding cuben is a polyurethane adhesive therefore a polyurathane resin would be the main choice for such a project. rather than epoxy.

Cuben could be used to create an ultralight airbeam tight, but it would require pretty thick cuben to reduce the risk of failing. which would negate the weight savings.

I do think that it would be instresting to see if making cuben poles will event be possible, let alone to what degree they work.

unfortunately I don't have the finances to attempt such a project right now but if anyone wants to give it a go feel free (be sure to remember that as it's my idea I'll take 70% of the profits ;)

[Diplomatic Mike]

Nobody seems to have pushed airbeams very far.
Modern fabrics, and plastics, are very light.
I think there is a long way to go in this field.

[Anthony Britner]

The airbeam aspect is intresting. My thoughts on that would be that cuben airbeams would require a thicker cuben to minimise the risk of puncturing as much as possible as a puncture would be a critical failure of the structure. Assuming a 5cm diameter airbeam even the strongest cuben would only weigh 13g/linear metre a smaller diameter would not just be slightly lighter, but would be quicker to inflate due to the lower volume.

[Ron Moak]

Puncture would be the least critical item with Cuben Fiber. It's the gluing that makes Cuben Fiber air beams impossible. All air beams are created using heat sealable materials to fuse the layers together. Without it you can't get a reliable seal. Gluing would just be too slow, too expensive and too unreliable to be used in a commerical setting.

[Anthony Britner]

"Gluing would just be too slow, too expensive and too unreliable to be used in a commerical setting."

A valid point as for a commercial setting it is not nessersary cost effective, hence why cuben products from the limited number of that have taken the plunge big manufactuers tend to be sewn not bonded.
But, for MYOG such an aspect is minor if not none-exsistant.

[John Almond]

Wouldn't the interface between the foot of the beams and the ground be the real issue, though? The abrasion there is the Achilles' heel of Cuben, from what I understand; the facing material used for Cuben is not particularly abrasion-resistant.

Would gluing another face fabric over the Cuben at the footing be practical/useful? Or would it cause issues with the footing staying in place? Hrmm…

[Ron Moak]

I'd bet $100 that there isn't a single MYOG'er on BPL or any other outdoor forum that can make a cuben fiber air beam that's strong enough to hold the pressure needed to make a useful air beam. I don't believe I can and I've got the stongest cuben seam technology available today.

Another point is that for air beams to be functional they need a fairly large diameter. The smaller the diameter, the greater the pressure needed to remain rigid. More pressure equals more robust heavier materials and tighter tolerances.

In the end there is no free lunch.

[Anthony Britner]

Personally I do not think that a cuben airbeam tent would be impossible to construct. BUT I do think that it would be a highly complex project which if there is even the slightest error in the cutting and especially the bonding of the cuben then any such error could have a drastic effect on the structural stability.

[James Marco]

Cuben "cloth" is actually constructed of various reinforcing threads. Commonly spectra, carbon or kevlar. In between the reinforcment threads is really nothing more than pressure bonded layers of plastic membrain. You would be far better off simply taking a reinforcing fiber, like doped carbon or even kevlar, and then applying a more or less standard epoxy resin. Otherwise you end up with a plasic pole reinforced with threads.

It is the engineering that really gives a hiking staff strength. Round is of course the strongest. I would suggest some nano-tubes in the construction, but these remain fantistical in price at this time.

[Jason Elsworth]

I think there has been some attempted MYOG cuben sleeping mats.

[Oliver Nissen]

With critical tolerances required for strong and airtight seams, this would be way beyond a MYOG project. But someone please prove me wrong!

These aren't fields I have expertise in, but I'd imagine circular knitting, scaled up rope braiding, or continuous carbon fibre pole technologies might someday be used to create air-impermeable high-tensile tubes that could be used for air beam tents.

This would minimise need for sealed seams, and avoid their associated problems. I suppose using such air beams would be way more expensive than carbon fibre poles, but weight far less than the Heimplanet air beam tent for the same convenience.

[Anthony Britner]

"I think there has been some attempted MYOG cuben sleeping mats."

correct, and IIRC it was taped so the majority of bonding methods appear to work to create an airtight structure in cuben as long as the cuben chosen is strong enough to withstand the stresses applied to it (I believe this was made out of 48g/M2 cuben)

To make cuben airbeams I would 1st attempt to get scraps of cuben of different weights approx 1m by 30cm wide and form the tubes. a bicycle pump with a pressure scale would be used. and each tube would be tested to failure This would help to determine what weight of cuben would be the best comprimise for such a project. bearing in mind that the pressure the tubes undergo in the test is likely to be greater than that needed to support a tent.

[R]

I happen to be tinkering w/ airbeams w/ the intent of using cuben. I just finished a proof of concept bladder using .5mil plastic painter's drop cloth. I was able to get an air-tight seal (submerged in water, negligible pressure applied) at the ends using double sided office tape.

Next prototype will be with a polycro bladder in a tyvek pressure sleeve. This is the equivalent of a bicycle tube inside a tire. The tube is fragile and only provides a gas impermeable membrane. The tire provides all the strength, durability and shape.

I don't see any reason cuben will NOT work. As mentioned, Nemo Equipment produces a line of air beam tents. According to their engineering page, a 2" diameter beam at 8psi is stronger than a typical aluminum pole. According to that page, a desert to arctic temperature swing only produces a 2psi change in a 2" dia volume and their design burst pressure is 20psi.

(http://www.nemoequipment.com/airsupported_technology)

So let's do a little math:

Nominal pressure: (8 lbs / in2) * (2" dia) / 2 = 8 lbs / in
Burst pressure: (20 lbs / in2) * (2'" dia) / 2 = 20 lbs / in

That's now a linear inch along the length of the tube with the force applied across the seam down the length of the beam. The lightest cuben avail. (CT0.3K.08) lists at 35 lbs/in. So there's no question the material can withstand the pressure.

1oz cuben is considered durable enough for ground cloth. A ground cloth is subject to far more abrasion and puncture risk than any part of the tent canopy, where the poles live. 1oz cuben has a tensile strength of at least 100 lbs/in, so even if your seams are only 20% material strength (!), that's still adequate. (Worth noting: polycryo is also a favorite ground cloth material due to puncture resistance.)

Preventing a puncture at the foot of the beam is as simple as using a double layer of fabric and possibly putting a small disc of plastic in the bottom. Several options come to mind to keep the ends of the pole from shifting: guy loop, velcro, suitable pocket/sleeve in the tent/fly wall, actually sew the sleeve to the tent.

Now a little more math:

1 oz / yd2 cuben = 0.00077 oz / in2
0.45 oz / yd2 polycryo = 0.00035 oz / in2 (I weighed a piece from my local hardware store but didn't verify the dimensions)

2" dia * pi + (2 x 1/4" overhang on the seam) = 6.78in
6.78in * (0.00077 + 0.00035) = 0.0076 oz / in

In comparison, Fibraplex carbon poles list at 0.011 oz / in. Obviously, this ignores the additional weight of ferrules, ends and bungie for carbon, and seams, valves, pump, and end re-enforcement for the air beam. But it does establish a ball park weight savings of ~30% over carbon at a considerable savings in cost.

And anybody that's ever relied on a bicycle knows that a flat is hardly the end of the world :)

[Sam Farrington]

Rene,
There are some blithe assumptions, like one oz Cuben being adequate for groundcloths, but the pole tubes are going to be off the ground, so that should not be a problem, especially with the protection you suggest.

All would depend on the bladder, at the weight you want, being sufficiently strong and durable to assure against rupture, deterioration and leakage. Don't buy the flat bicycle tire analogy – a collapsed tent in a storm at night can be totally grievous.

I'm now working with carbon poles made of Gold Tip 5 layer wrapped arrow shafts that weigh about 1.3 oz per every four feet, including ferrules and light shock cord, and require significantly more pressure to break than Easton carbon FX or .344 ALU tent tube. Can you beat that weight with the bladder, valve, Cuben cover and close to ground protection? And even so, will it be stronger than both the Easton .344 and FX? (Plus I won't have to pump) What do you think?

Admit that the carbon will not bend into a tight arc like you possibly could do with a sewn tube and bladder. That's why Roger Caffin's tents use the elbows, I believe.

[Roger Caffin]

Thermal bonding Cuban to Cuban is possible. The machinery would be expensive – Cuban doesn't have a real lot of competitors after all. You would have to wind the Cuban tape around the former pretty tightly to get sufficient bonding. Mucho $$$

But the biggest problem is likely to be getting the rigid former out from inside the curved pole afterwards. And THAT is why we don't have curved CF tubing yet.

(And why I use elbows, as Sam said.)

Cheers

[Roger Caffin]

All that aside, the real reason (imho) why air beams have not been successful in the field are the need for very high air pressure to get the required strength.

First, you need a serious pump. That is heavy.

Second, the amount of air in a tube is quite small, so ANY small leak causes a quick loss of pressure. At 2 am in a storm, that is not good.

Cheers

[R]

I'm taking Zpack's product line as a reference on the ground cloth.

Bladders don't require any tensile strength, just gas impermeability. Inflate a spare tube outside of a tire if you're curious.

Your 1.3oz/48in = .027oz/in which is 3.5x my per-in. figure for a cuben air beam before the extras (and 30% heavier than a similar Fibraplex). Over a single 8' pole, that gives me 1.87oz to work with. My .5mil proto bladder used a soft valve made from the same stuff as the bladder. I adapted the design from one of these: http://www.amazon.com/gp/product/B004C2RKHS/ref=wms_ohs_product http://www.youtube.com/watch?v=N2ynODlH7UA – jump to 8:30. The pump will be equivalent in construction to the final beam assembly and function like Nemo's pumps – inflate a bag, then squeeze it with your hands or apply body weight to it. It may well be a wash on a single pole structure, but will probably be lighter for multi-pole. The only thing I'm still grasping at straws on is how to attach/detach the pump from the beam. I could use Nemo's valves, but I could probably do lighter. So far I've made one failed attempt at using the threaded bits from a plastic soda bottle.

I can't speak to bending strength, as Nemo hasn't posted numbers, but if an airbeam collapses under load, say from a sudden gust of wind, it pops right back up at full strength the moment the load subsides. Carbon/alu polls don't. And yes, of course, you trade dealing w/ an inflatable pole for dealing w/ a rigid pole at set up and tear down.

Like most gear, there's pluses and minuses to it, and it's ultimately personal. With a little luck, I'll have the chance to form an opinion based on experience.

[Sam Farrington]

It was understood that the strength will come from the Cuben, not the bladder, but Roger raises a good point: To get the strength from the Cuben, you have to bond it to itself to somehow create an inflatable sleeve (with the bladder inside, yes).

PET/Mylar is a bear to bond. Warmlite tried for years to laminate it to other materials and gave up. CT has done so, but reportedly only with a very expensive,
propietary heat-based (read 'autoclave') process. That's what holds the mylar layers together over the Dyneema.

Many have found that you can bond the Cuben to itself well enough to join panel sections of a canopy, and to add tie-outs; while others (i.e., Lightheart) feel some sewing and taping is needed with the bonding. In either case, those bonds are primarily for shear strength. For an inflated tube, I suggest you are dealing with peel strength. Sorry, but don't think you will be able to do it. And how much extra weight is going to be added just for the inflatable sleeve alone (you can do the rest of the shelter with the Cuben)- very negligible. Suggest you use the best quality nylon, treated to reduce stretch. There are many varieties available through the sail cloth and paragliding industries. Good polyester would stretch even less on the warp and weft, but is heavier, not as strong or durable as nylon, and very hard to find coated and light. Some of the polyester sail cloths, or model-making cloth like Icarex, might do it; but the nylon is a softer material unless intentionally given a "hard" coating, and would probably be easier to work with and tailor to the curves/arcs you want for the inflated "pole."

[Jordo _99]

I'm very excited to try this with the next few tubes I puncture (or some old ones). Just need to figure out how to properly seal the ends (turning it into a pole instead of a donut) and finish my tent before I can test them out. Would be awesome to tour with some old bike tubes (that would use the same pump that I'm already carrying)

…While I do think that putting some kind of boot on the casing where it touches the ground would be helpful, I don't see it being very likely at all that it would puncture.
Most ULers that I've met/seen are meticulous on clearing their camp site since they already use fragile materials…so I'm not sure what is going to be hard about clearing a 6' circle where the beams might sit or not swinging around sharp objects that would puncture a shell/sidewall anyway.

What excites me about this isn't that it's a better option to carbon poles (I don't think it is) but that it's packing would be much easier to deal with…at least for touring I'm not keen on the idea of poles. Also, by using a system similar to a compression sack you could alter the poles for different pitches on the fly which could be another advantage.

I'm still not convinced that air beams are viable or even better than carbon yet…but it's exciting to think about, especially if you're into cycling and touring.

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