Inflatable arches

[drowning in spam]

Has anyone have some experiences and advice they could share?

I've been thinking of two options. The first would have the tubes directly bonded to the tent shell. The second would be to build the tubes separately and install them a lot like traditional tent poles.

The main benefit is the potential to build a free standing tent or add space to an existing design without having to carry stiff poky tent poles in my pack.

So…

Does the heat sealable fabric need to be cut to allow for the curve? I assume nylon fabrics may stretch enough to eliminate wrinkles, but what about non-stretch fabrics like cuben fiber?

What valve would be best and where can they be purchased? I'd like something that can either be blown up by mouth (pool floatie valve?) or uses a valve that's compatible a pump that's also used with an air mattress…preferably Kookabay. Actually, I need some valves first so I can at least experiment with cheap home improvement plastic sheets.

[Roger Caffin]

Sounds EXACTLY like a Nemo tent to me.

> Does the heat sealable fabric need to be cut to allow for the curve?
Yes, and it ain't easy.

cheers

[drowning in spam]

It would only be like Nemo tents in that it would be inflatable. Afaik, they don't have a freestanding inflatable tent. One design I'm thinking of would rely on a trekking pole for propping it up and the inflatable portion for structure. One other crazy idea I've had is using inflatable double walls for insulation.

I'd love it if it were as easy as bonding a couple x-strips together to make an inflatable crossing pole replacement for dome tents. If that works, I'd try other things. I still need cheap valves. These would be perfect if I can get them cheap.

http://www.holeeplastics.com.tw/manufacturer/22622/22622.html

[Jerry Adams]

I've thought about that

Thermarest valves might work http://cascadedesigns.com/therm-a-rest/accessories/valve-repair-kit/product
although there's a piece outside of that that the valve inserts into that would also be good to get

topic about air mattresses might be helpful
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=24850

[Colin Krusor]

I don't want to discourage anyone from experimenting, but I thought I'd point out a couple of potential obstacles.

First, you won't be able to inflate it by mouth. Nemo beams use 6-9 psi and you'll never achieve more than 2.5 psi with your lungs. This might suffice if the beams are 4" in diameter, but then the weight becomes prohibitive. You'll need the pump.

Cuben will develop pinholes. Polyester film has a flex fatigue problem and tiny ruptures eventually occur at the creases. Large cuben kites for surfing sometimes have inflatable cuben leading edges but they use a polyurethane bladder in a cuben sleeve. This is the reason that a durable cuben inflatable sleeping pad isn't practical.

Heat sealable nylon will be at least triple the weight of the carbon or aluminum poles that it replaces. Also, in order to withstand the required pressure (particularly in the sun on hot days), the seams will need to be in shear, which will require a curved tubular jig.

The advantages of inflatable structures are only fully realized (rapid deployment, small packed size, low weight) when the structures are very large (field hangars for aircraft, large field hospital tents, etc.). In small structures you don't get much benefit from this kind of design.

I think this idea is only tenable if you use a bladder-in-sleeve beam design, higher pressure (10-15psi), and small diameter (2") commercially available seamless sleeves (polyester or nylon). You could use a presta bike valve and a mini (less than 2 ounce) bike pump.

[drowning in spam]

Colin, thanks. As to the mouth valve, that's to keep costs down while checking designs.

Does it really need to be in shear? I would think that air pads see high pressure when being used, and aren't those in peel? Dynamic loading could still be a problem.

[Vick Hines]

Colin has all the problems nailed. The best work-around I can think of is to use lightweight plastic tubes inside nylon tubes. The nylon tubes would not have to be sealed; their purpose is to provide shape, structure and strength. This would save the weight and construction problems of using heat-sealed nylon seams, and would make repairs easy and simple: just pull out a leaky tube and replace it with a sound one. Or stick some tape over the leak.

[Eric Fredricksen]

It seems like even balloons (like the ones for making balloon animals) inside a nylon sleeve might work fine, possibly single-use. With the nylon providing strength, the rubber providing airproofness.

But maybe that's crazy.

[Roger Caffin]

> I would think that air pads see high pressure when being used, and aren't those in peel?
Some of those may be in peel, but I have seen reinforcing strips inside the seams on some.

It ain't easy, which is one reason the big names haven't done it.

Cheers

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