I admire your curiosity and determination, a b. I think your perspective on the feedback you've recieved seems right. Discussions like these can get tense when people disagree, but the result is often productive.

To be realistic, you haven't busted any myths yet, and you're not going to be able to commission Ron Bell (MLD) or Tim Marshall (Enlightened Equipment) to build a cuben raft. If you want to prove that it can be done, you'll need to do it yourself. And I'm not shooting you down. I actually think that we all could learn from it.

The US Air Force did a test to see if any of the existing Cuben (Mylar) materials would reliably hold air. Their application was portable recon drones. AB concluded Yes and they concluded No. We will soon know who is "All Wet".

Edited by richard295 on 11/12/2012 21:18:07 MST.

I don't want to shoot the idea down but here are some thoughts.

I really think it comes down to how much money you are willing to risk on a project that might or might not work out well. If you want a light packraft for flat water I'd suggest a feathercraft. On the other hand if you really want to try a cuben raft and are willing to pay for it go ahead. Here are some ideas.

1. Try making a nylon version first. There are several advantages to this
-You make any mistakes on cheaper material
-You can try the nylon raft out and make sure you are happy with the design
-You have an extra raft so you can invite a friend along.
2. I'm not sure I'd bother with hybrid cuben. My understanding is the outside absorbs some water which means the raft will be a lot heavier as soon as you get it wet. I doubt there would be any advantage to hybrid cuben over regular nylon.

I was not aware of the feathercraft raft until Luke mentioned it. These are the specs of the lightest rafts from each of the current packraft manufacturers (according to the manufacturer's websites):

1. Supai Adventure Gear Canyon Flatwater 2: 1.5 lbs, $300
2. Flyweight Designs Flytepacker: 2.2 lbs, $300
3. Alpacka Scout: 3.2 lbs, $525
4. NRS packraft: 4.8 lbs, $525
5. Feathercraft Baylee 1: 6.5 lbs, $1200

Does anyone know of any other manufacturers making packrafts? All vinyl (non-fabric) boats (like the Sevylor Trail Boat) are omitted from this list. The venerable Curtis raft is excluded from this list because it is only available second-hand.

A 30D nylon packraft, although very fragile, could come tantalizingly close to the 1lb mark, I'd wager.


Edited to add a couple boats to the list.

Edited by ckrusor on 11/13/2012 16:17:34 MST.

.

Edited by Ice-axe on 01/09/2013 20:37:00 MST.

I kinda hesitate to get involved here, but if you really want to push the envelope, buy some 30d heat sealable nylon. Cuben is expensive and will not hold air. Aside from Richard, who knows more about fabrics than 99.9 percent of people on this site, you have several other people saying it's not a good idea. I'd trust a neoair (or hell, a cheap Target air matress) 100x before I'd get in a cuben raft, and I've used cuben quite a bit. If you're going to do it just because people are saying you shouldn't, then I guess godspeed.

I'm definitely thinking make a raft, just maybe a bit different. MYOG packrafts have been tried by one or two people but I don't think the idea has been fully explored. I also wish someone would do a better job of documenting the experience (might make a good BPL article).

Some things I'd think about...

-Cuben vs. Nylon (the weights really aren't that different) Durable cuben isn't much lighter then nylon. Given its stretch Nylon might actually be more puncture resistant then cuben.
-Weight Savings vs. Durability. If you go from .75 oz cuben to 1.4 oz cuben or similar nylon you increase durability a lot and I really don't think the weight game would be that much, maybe 3-6 oz. You will NOT feel that extra weight in your pack, especially since you'll have a PFD, paddle, etc.

Two other ideas

1. packrafts were not noted for their good performance on big rivers, lakes and bays. I'd read up on the newer models and what makes a good flatwater raft if you plan on doing rivers in this thing.
2. Another area for creative weight savings might be the other gear used for pack rafting. PFDs and paddles might be a good area for some creative projects (please wear a PFD when you use your creation, I've swam in big rivers and its no fun).

Regardless of what you make I hope you take good notes and have a good time. I'll look forward to hearing from you.

Why not try a cuben PFD first? A lot less material. Would be stressed to a similar degree holding you up. Two pieces and an inflation valve. What do you think?

Edited by kthompson on 11/12/2012 21:41:31 MST.

First of all, let me take a moment to say I'm glad to be able to post again. YAY!

I love the idea of a cuben raft. I'm an avid packrafter. However, I don't think a cuben pfd would be equal to the stress and pressure to which a raft would be subjected. Unless you sit on it and ride it down a river................

Edited by toesnorth on 11/12/2012 22:45:15 MST.

True, but it would be a way to see if it would hold air long term. You could stress test it easier than a full size boat. Thinking weights and swimming pool here.

Iceaxe,
What about combining a couple of small neoairs for flotation in a outer cuben sleeve. That would allow your flotation portion to have dual use. On a related note, I just made a bunch of cuben items over the last couple of weeks. I made new food bags to replace the 1.5 zpacks bag that went on my PCT hike. The new sacks were 100% waterproof but when I filled the old sacks up with water there were dozens of tiny holes in what appeared to be a very serviceable food bag.

Finally, I'm an engineer but can relate to your comment about the motivation of being told it can't be done. In a former life I invented a casting process using aluminum molds. After doing scale up I called a major AL manufacturer to make sure that the alloy that I was using was optimized. I was told by the experts that what I had already accomplished couldnt be done. I guess the experts were wrong.

Sounds like you have a new adventure planned. Look forward to hearing the details. Or you could tell me to go f off! :)

GG man, would never tell you to do that! It is your enthusiam for life that is an inspiration to me.
Your idea of a sleeved floatation raft is quite interesting. May not save any weight but would be a hybrid approach with built in safety of multiple chambers. Thanks. Hey Ken, your picture just reminded me of that hand drawn picture from Colin Fletcher's book. He used just such a PFD to cross rivers.. He also used it as a hat! Thanks PP and all. I will be sure to share pictures of the launch in my local resevoir.. It could be pretty hilarious.. Perhaps the first cuben submarine.

For big rivers, what about one of these offerings?

http://www.gaboats.com/

I think the in-elasticity of cuben would be a major problem, but no harm trying (save to the wallet).

The lightest rafts I'm aware that are currently available are the Flytepacker and the Supai Adventure Gear Canyon Flatwater 2. They appear to be fairly equivalent products.

I would save your money. The PET version of cuben fiber is NOT air-tight at all. Sure it might be the day it comes from the factory but after a little use pin-holes form and it will leak air.. An air molecule is much much smaller then a water molecule and is the reason it works decent for drybags but not so good for air-tight structures. All that said, when I was making dry bags I had Cubic Tech make me an airtight CT5K material using a 1 mil Weldable Polyurethane Film on both sides. It was EXPENSIVE ($30+ meter), Heavy (5.5oz sq yard) and had to be welded at a super low temp due to the Dyneema fibers. If you left the material in the sun for a long period of time it would weld together by itself. All and all it was pretty a cool material but needed some tweaks. It would of made a good drybag material but not a good packraft material as a 1mil film is still very thin for an air-tight material. From what I understand 2-3 mil is the minimum and if you went this thick you might as well use an off the shelf 70d or 200d TPU material since the film/coating weight would be the same. Good Luck : )

Been following this a bit but figured that everyone else had pretty much covered it...

I like that you're willing to try something new and push limits....However, this just seems pricy and time consuming for a result that almost certainly isn't going to accomplish much other than being able to say "told you I could do it" (It will probably float but it's not going to wear/age well at all and will be prone to failure).

By all means, if you have the time and money, go for it. I'd love to see it...I'm just confused as to the intention of using cuben against the overwhelming recommendations against it. If it were me, I'd be paying a bit more attention to all the red flags people are waving so it makes me wonder why you're so adamant about using cuben anyway.

so...why stick with cuben when the responses are heavily against it?

David, thanks for mentioning the Supai boat. I wasn't aware if it. I learned about two new packrafts in this thread (the Supai and the Feathercraft mentioned by Luke). The Supai is 11 oz lighter than the Flytepacker, making it the lightest packraft available (that I know of) by a substantial margin. I might consider buying one of these.

.

Edited by Ice-axe on 01/09/2013 20:41:50 MST.

So simple, makes you wonder why no one has come up with the same concept before.
One small problem I have is visualising how you are going to get into that raft so that the sides become "rigid"
BTW, keep in mind that the air inside those balloons can cool down pretty fast once in the water.
Anyway this has inspired me to have tacos tonight.

Ah! You argued earlier in this thread that cuben is not as prone to leaks as people think, ab, so I assumed that you were considering using the cuben as an airtight barrier.

I think your plan to use an inflatable bladder inside a cuben envelope is much more promising. Is this the basic design you had in mind (below)?



I had thought of making a heat-sealable nylon packraft/kayak in roughly that design, too. It seems that it might track better and have better speed than a conventional packraft. I think it would still be nearly as wide as a packraft at the widest point, though (in the middle, where you squeeze between the tubes). It has occurred to me that lower drag might be achievable with a large central tube with two small lateral tubes, but at the cost of much less stability:



I made a down-filled inflatable sleeping pad for my wife a while ago using the bladder-in-envelope design:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=56903





The thin, heat-sealable polyurethane film that I used for the bladder weighed about 1.2 oz/yard. I definitely would not use anything thinner. It is a tough material but it's fragile at that thickness. The envelope was M90 nylon taffeta, but I considered using cuben (and Steve Evans suggested it in the thread). However, according to my math, replacing the nylon envelope with 0.51oz cuben would only reduce the weight by about 15%, because the majority of the weight is from the bladder material. The bladder needs to be larger than the outer envelope to prevent it from being under any tensile strain when it is inflated. If you use the same bladder material I used and 1.4oz cuben, the weight of the material becomes nearly the same as heat sealable 30D nylon (2.5-3oz/yard). You can only improve upon 30D nylon from a weight standpoint if you use an ultrathin bladder material and/or a lighter weight cuben (like the 0.74 oz stuff).

Don't forget to add a (fabric?) vent somewhere (probably at least two) on the cuben, so air can escape from between the cuben and the bladder while you're inflating the bladder.

Edited by ckrusor on 11/13/2012 22:59:20 MST.