Cuben Air Matress…

[Gary Boyd]

I'm starting a new thread as the previous thread discussing this topic started out as a discussion of PE inflatables and soda bottle valves. The goal of this project is to make Cuben a viable material for use as a full size inflatable air mattress weighing in at 6 oz or less.

One thing that I realize about Cuben as a material is that while durable for it's weight it is still delicate and must be treated with care.

My current idea is to use 3M 9485PC tape as a bonding agent, and use a Thermarest repair valve attaching it with the hot bond agent supplied with it. If neccesary I will use SeamGrip or Aquaseal to backup and bonds.

I just made my initial prototype, here is a picture, I'm using a clothespin to seal off the one small hole I left in the seam to inflate. I'm using a standard soda straw to inflate this prototype.

I did make one gross error in judgement trying to use a potato chip bag clamp to clamp it shut, I did not notice that the clamp was serrated, and so it is causing leaks. I do need a strong little clamp to seal my second prototype.

After applying the tape I applied about 20 lbs of pressure across the mat deflated for approximately an hour. The bond is strong, and I believe the material would give way before the bond does even in peel.

I think the method of taping should be fairly important in this project, and I will discuss it in more length when I have it right.

I should add that I wouldn't consider using an air mattress made out of Cuben without a CCF foam pad or other ground protection underneath. A GG 1/8" pad should be included in the 6oz weight that is the goal of this project.

[Ashley Brown]

I'm watching your project with great interest…!

[Gary Boyd]

Thanks Ashley, and I welcome comments and ideas as this is all new to me. I want to thank Steve, Scott, and Roger for their help in the initial thread. I'm still pondering whether I should have tried Steve's Hysol method or Scott's Aquaseal, but I can try that if the 9485 fails.

The first inflatable seamed to do pretty well, save the small surface holes I punched in it with a serrated edge. It held air fairly well. I did notice a great deal of adhesive seapage which worries me, as I just assumed the adhesive tape would stay in it's place and not screw up my chambers.

I just made the second prototype and it proved to be a little more challenging. I think I was rushing because my tape lines on this one are just horrible. I'm going to let the adhesive cure over night in the hopes that I wont suffer from the adhesive problem again. I also added a straw valve to this one that I SHOULD be able to just tape off after I inflate it. Nothing fancy yet on the valve.

The biggest problem I face right now with the taping is trying to get everything placed just so when I'm ready to put the two pieces together. I'm going to have to be more patient with the tape, and perhaps just start the removal of the backing in one corner and only remove it as I place the sheet in the proper place.

This one ain't going to look as pretty, but it will hopefully be a step in the right direction.

[Scott Van Doeselaar]

Gary,

Looks interesting so far. Some questions for you:

Is the seam between chambers just taped together?

What do you mean be "adhesive seepage". Tape adhesives have a tendency to creep slowly over time. There is a strong intitial tack but under constant load it will slowly come apart. These joints are going to be under constant load for many hours. Still though I am anxious to see how it comes out.

[Gary Boyd]

That's correct the seam in between the two chambers is taped. The reason I decided to give this tape a shot is because 3m says it has great peel strength. I figure I'll let this one cure overnight and see how well it does under a load in the morning.

What I mean by seapage is that the tape itself is 1/2 inch and after messing with the inflation and deflation the adhesive began to spread from the seams. I really think I didn't give it enough time to cure. I wish there were better instructions for this tape though, they don't give specific time frames for how long to keep the seam under pressure.

We'll see in the morning how well it does, if I didn't screw it up so bad that it won't inflate. I really did a bad job on the taping this time around.

SIDE NOTE: I did not mean it to end up looking like a BPL pillow, but it did end up that way.

[Scott Van Doeselaar]

Gary,

Tape typically doesn't "cure" as a bond does. It should generally be full strength as soon as it is put together. Exposure to heat, vacuum and UV will tend to change the adhesive properties. Generally this will make the joint stronger. I don't think you will see much difference with overnight pressure applied.

Scott

[Gary Boyd]

So Scott, do you think something such as Aquaseal or Hysol would perform much better in peel? Or are you saying that trying to form seams in peel is a lost cause? Surely there has to be some bonding agent that wont fail in peel.

[Gary Boyd]

I'm currently performing a 3.5 lbs load test on the "pillow" I made. After two hours it seems to be doing fairly well, but I still think I'm getting leakage from the valve because I don't have a good closure system for such a modest valve. Right now, with a built-in straw valve, I'm simply folding the straw over and clipping it with a clothespin. I'll take pictures after an initial 4 hour test and see how the seems look. I realize the average human head is somewhere in the vicinity of 10 lbs so I will be attempting a 10 lb test at some point in time and see what is doing. I think maybe the use of a higher weight Cuben will eventually be in order even if I can get the tape to work, otherwise the thing may only be good for half a season.

[Steven Evans]

Nice! The original prototype looks promising! I wouldn't mind an SUL pillow either. :)

I never knew about the Thermarest repair valve…that solves all the problems with sourcing a valve. It would probably be better to manufacture a small plastic piece for the valve to screw into, just like on a thermarest mat…but that's your call.

I have used the 9485 tape with mixed results. I find it to be weaker then the Hysol adhesive, but Roger Caffin has used it and swears it bonds dead strong so maybe I didn't use it properly…FWIW, I remember him mentioning that the bond does get stronger after a few days but can't seem to find where he stated that. Maybe he can chime in.

[Gary Boyd]

Good to hear from you again, I too am eagerly awaiting word from Roger on the his use of 9485. After 4 hours the pillow had deflated enough so that the head would be touching the ground. I found a pinhole leak in the material at the seam, but not the seam itself, although I have found noticable peel in the middle seam. So it appears you and Scott were correct. Although after applying pressure to it again I was able to recover the 1/2 seam. A picture of phase 2

After attempting to use it as a pillow for about 5 minutes the pinhole in the corner material reopened and it began deflating again. I'm wondering if doubling over the seam material onto the inflatable would provide a stronger seam, sort of like a felled seam?

It does appear that CT1K.08 is not durable enough for this application and should probably go up to CT2K.08. I'm sort of glad now that I just ordered a couple of yards from rockywood instead of going the whole 9 yards (literally :P)

[Gary Boyd]

So I've been messing around with this darn pillow and I discovered something interesting. I busted the seam between the two chambers and now there is only a perimeter seam, but instead of deflating now I can apply as much pressure as I can muster with my arms and I cannot break the seams. I don't understand, but I'm taking a guess here. I reread the instructions on the 3m tape and it states the the bond increases as a function of time and temperature. I'm coming up on 24 hours for this pillow and the perimeter of the seam (not even the full seam) is the only part of the seam that has remained intact the entire 24 hours. I plan on sleeping on the pillow tonight and seeing if holds up.

[Scott Van Doeselaar]

>So Scott, do you think something such as Aquaseal or Hysol would perform much better in peel?

No I agree that the Aquaseal and Hysol will not be as good as the tape in peel. I would try adding some low heat to the tape joint overnight. Maybe in the oven at 150 to 180 F and see if this helps. It would be great if there is a way to stop the creep. You could also leave it out in the sun for the day.

[Scott Van Doeselaar]

Gary,

You inspired me to patch the holes in my trial tube. I also found something to plug my valve. I was holding air so I tried to do an aggressive pressure test. I attempted to stand on it. It would definitely have to survive this as a sleeping pad. I sprung a leak and it does not appear to have been the seam. You may have noticed just how thin and delicate the plastic layers are on cuben. The selvage on this has about 1 inch of the two outer layers. This plastic is not very strong by itself. If you take a close look at the structure of the material there are small gaps between the spectra fibers. I may have burst at this location. It sounds as if you may have had this type of leak also.

I have patched the holes again and will try again tomorrow.

[Gary Boyd]

Scott I don't believe that standing on a single tube is a required weight testing, simply because your entire weight should never be on a single tube. It would be distributed over many. I think this kind of testing would cause failure in several inflatable air mattresses on the market as there would not be enough volume for the air to find somewhere else to go. I think for a single chamber somewhere up to 20 lbs should be reasonable.

That being said I did some unrequired testing myself last night which didn't enable me to test sleep on the pillow. I punched the pillow inflated, and, of course it popped. I wish I hadn't had done that, because I do believe it would have stood up to a nights sleep. I was able to repair the seams by simply pushing it back together, but I think once the seam is broken it will continue to fail. I think I'm going to make one more with the tape allow it several days to "cure" under the heat of a lamp and see what the resulting bond strength is. I've been in such a hurry to test the things that I don't think I've really given the tape a chance to form it's full bond.

[Dustin F]

The bond continues to get stronger for a couple of days. I left my projects sitting for an entire week before use.

[Gary Boyd]

Thanks Dustin, which you would have arrived a couple days ago ;)

[Adam Kilpatrick]

Gary, did this project ever progress any further from here?

Cheers,

Adam

[BlackHatGuy]

Might want to try sending him a PM since he hasn't posted to BPL in four years.

[Steven Adeff]

I was thinking doing this to make a pillow at first, then possibly a full pad.
my concern is mostly that it would not provide much insulation so would really only be best as a summer pad, or perhaps combined with a space blanket for reflected radiation "insulation".

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