Ultralight Cot with Cuben fibre Material.

[Michael B]

I putting a Cot together and am trying to make it as light as possible . I want my wife to join my on my adventures but she has a lifetime of Bike racing and a few Bike crashes along the way so sleeping on the ground is not top of her list.. Mostly High Sierra trips so hammocks arent a great option .

I picked up pieces from LL ( Nylon feet,  .380 OD 7075 T-6 cross tubes) and now am planning the final steps.As I am light I can get away with 4 legs instead of the 6 usually employed.

Is using Cuben fibre 1.0 or 1.43 for the cot material an option  ie. will it safely support a person’s weight (me 150, wife 125, not at same time ) There will be two Al 7075 T-6 side rails threaded thru sleeves on the Cuben Fibre . Crossbow feet with Struts clip to it.

My estimate for finish with 1.43 Cuben is 1# 10 oz. I figure I can leave the NeoAir XL mat at home (13.1oz)  so i’m only  adding  less than a pound. realize that is a still substantial  but would love to have my wife with me !!

Is Carbon fibre worth the expense and how much weight would it really save

Can I get away with lighter/ Smaller side rails ??

Love any suggestions

Mike

[Jon Fong / Flat Cat Gear]

Cool idea, it would help to see a sketch.

[Anonymous]

Really should line the Cuben with some .67 UL DWR nylon at the very least.  Cuben’s main weakness is lack of abrasion resistance because of the thin mylar film.  Lining it with woven nylon will help to extend the life of the cuben (a lot), which is a much more expensive fabric than the nylon.

If you go with the 1 oz/yd2 Cuben, you could use the 1 oz/yd2 Robic (ripstop nylon) from RipStop by the Roll as a liner.  While a bit heavier than the above nylon first suggested, should be a lot stronger and more durable.  Seams are a weak point on cuben fiber.  I would roll the two fabrics over together at least a couple of times and then sew–this will give some strength and durability to the seam, as it won’t be a thin layer of mylar taking all the stress. Don’t use a super tight/short stitch either, about half way between the shortest and longest stitch settings should work better.

Btw, i’ve found that the Easton Nano Al tent poles are just big enough to put a common sized carbon fiber arrow shaft in.  You would have to put epoxy on the carbon fiber arrow so it doesn’t react with the Al, and to help keep it stable inside the Al tube.   The combo of these very light materials, would make for a VERY strong and VERY durable composite material.

[Ken Thompson]

Have you seen these ?

[Michael B]

KT have seen them and actually what I am basing it all on . Luxurylite sells them and most of the bits. Thars where I got the feet and cross members. .His design is very clever and well thought out. Was trying to get weight down below the 2 # point . That why i was asking about the Cuben Fibre cloth.

Thought I could make composite versions of the feet but dont think the weight savings would be much (epoxy resin versus Nylon). Imagine I could make them a little smaller ??

 

Mike

[Ken Thompson]

It is a good design that is also comfortable.

[Todd Stough]

Since cuben doesn’t breathe why is that the fabric of choice?  Wouldn’t one of the light weight nylon or polyester fabric work better?

Also how can you leave the sleep pad at home, what will insulate the cot?

[Ben H.]

Check out this thread:

https://backpackinglight.com/forums/topic/32956/

Because of the way cuben fiber fails it may not be a good material for a cot.

[Michael B]

Im not sold on Cuben Fibre and did read the article about CF hammock (ouch) and am open to all suggestions. Breathability may be something to consider but how breathable is a  Neo Air pad. I m looking for 3 season at this point but imagine a Closed cell foam 1/8″ would take care of colder nights. I even toyed with the idea of a 850 fill Down comforter attached to underside for insulation. wouldn’ be compressed so you probably wouldnt need much ( <1/2 a 40 F quilt  = 5-6 oz)  and it could double as cold weather wrap?? 

Im open to any and all ideas…

Thanks Mike

 

[Franco Darioli]

This may not be your case but some tents will not accommodate a 24x72x4.5 cot or not be practical once a person inside a sleeping bag is on top of it.
(inward sloping walls)

[Ben H.]

I agree on breathability.  I’m not sure why breathability would be an issue.  If your air pad is breathable you’re going to have a long cold night.  I’m really not a fabric expert so I can’t give you much advice.  There should be more fabric experts lurking around chiming in though.  I’m guessing you want something reinforced so that tears don’t result in failures.  Since the luxurylite fabric is design for a 300 pounder, it seems like you should be able to get a lighter fabric to work… I’m just not sure what that is.

[Michael B]

I have a YAMA cirriform with bug net , fits fine . cosy but fine. Sent an email to guys at Ripstopbytheroll

about  1.6 oz HyperD xl to see what they think

Mike

 

[Ryan Smith]

Can’t help you on the carbon fiber, rail size, etc questions. Maybe Roger or Sam can chime in since they have quite a bit of experience in that area.  For the fabric, I would forego the cuben merely because you can get nylon or polyester which will support your weight at the same weight or less, and it will be at 75% less cost. RBTR has 1.0oz Robic nylon that supposedly will hold upwards of 300lbs with with minimal stretch which would be both cheaper and lighter than 1.43oz cuben.  There are also some 40d nylons in the 1.5oz range that will work fine.

Ryan

[Michael B]

Thanks,  Justin at RBTR recommended the 1.0 Robic XL  and as it comes in 68″ width  I can shorten my cot a bit  (im 5’5″ ) so that will work great .  I did all sorts of variations on CF versus 7075 vs Easton Nanolite and it ends up making very little difference once you cut CF to size and add ferrules etc.

Seems the fabric will make the most difference from 5.5 oz (stock thermarest weight ) to 1.5 or so . Will start there and mess with struts/ rails  as I go .

thanks again

[Ken Thompson]

Wouldn’t a thick inflatable pad be as comfortable as a cot?  I find them as comfortable as a bed at home. A hammock is still the most comfortable.

[Michael B]

Hammock would be great but most of use will be high country Sierra , not to many trees up there.

Pad may be as comfortable for many but My wife has a hard time with them unless it was a 2 ” memory foam..no Im not going to offer to carry it for her….

[Anonymous]

I received some of the new Robic 1 oz/yd2 fabric from RBTR today.  I tried ripping it along the selvage seam edge (usually a weak point on fabrics) and nada–just the slightest hint of stretch.

Robic has really good air permeability, though for a cot that might not be a good thing (a little air permeability would be good though, especially in warm temps).  So far, i’m impressed with the weight to strength ratio of Robic as well as it’s CFM level.

In cooler temps, you’ll want to put some thin Evazote or similar foam on top.

[Michael B]

Well,finished the cot with the <span class=”Apple-style-span”>1.0 Robic XL fabric, quite impressed with myself . Alas it has too much stretch and I hit the ground or cross members. If I add the second Aluminum cross member to the most supportive assemblies total weight is back up to where it was with the original material and 2 less x members. Still I did get it down under 2 lbs. I know you are gasping but now i don’t need a ground sheet or a pad so Im only 3/4 lb worse off. . If I shorten it to 64 inches Ill shave off a few more ozs.</span>

It more for the fun/ myog  factor but it will get some testing this next week.

[Anonymous]

I’m a bit surprised that it has too much stretch, as some folks have made hammocks out of it, and have reported that it does not stretch as much as most other nylons–more specifically that it stretches only slightly.

Curious why you went with the Al poles over the carbon fiber?

[Michael B]

In a hammock it probably doesn’t matter but in the cot if there is stretch you feel the supports. Aluminum  cross members actually are more rigid than the Carbon fibre ones . I bought them both and tested it Carbon is lighter but actually flexes more . I think short of going to Titanium or something like that the weight is as low as you can go frame wise . the cot fabric weight  can probably come down a bit but material can have virtually no stretch in it to make it work

Fun trying anyway….

[Anonymous]

The Easton carbon fiber poles are designed with flex in mind, since they are being used as tent poles for their intended purpose, but other carbon fiber poles/tubes can be much stiffer than the Al tubes. Golf shafts and the like come to mind.

Also, you can pour or spray expanding foam into the carbon fiber tubes to further increase stiffness at not much weight increase.  Thats what i did with my Easton carbon fiber tent pole frame for frame backpack.

[Steve Chan]

 

You might want to consider using a heavier, polyester fabric instead of nylon – it has much lower stretch, but also lower maximum weight it can support. There is the 1.4oz PolyD that Dutchware sells:

http://dutchwaregear.com/polyd-1.4.html

RBTR also sells a 1.6oz Polyester Ripstop:

http://ripstopbytheroll.com/products/1-6-oz-polyester-ripstop

Both fabrics are well known to have less sag/stretch. And at the weights you gave, they should be fine.

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