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# Electret Tent

Self-supporting with no ropes, poles, or air pressure
 (+14, -1) [vote for, against]

An electret is a manufactured thing which is analogous to a permanent magnet. Instead of being magnetic, though, it contains two separated and opposite electric charges. Electrets come in various sizes and shapes, and have a fair number of uses, including microphones in cell phones. Here is another:

Think about the fabric known as "corduroy", which has rows and rows of small ridges. Let's pretend this is an enlarged cross section:
_n_n_n_n_n_n_n_
and let us focus on one "unit" of those ridges:
_n_
Suppose that we make this corduroy out of electret-stuff, and the left side of that cross-sectional bump is given a positive electric charge, while the right side is given a negative electric charge. In stead of drawing bumps I will now use + and - symbols:
_+-_
Well, if we now consider two charged bumps, there are two ways they can be oriented to each other:
_+-_+-_
_+-_-+_
In the first case the two bumps electrostatically attract each other, and in the second case they repel. It is that second case that we want to use in our overall electret corduroy:
_+-_-+_+-_-+_+-_-+_+-_-+_+-_
Every ridge repels the adjacent ridges. From this fabric we construct our tent. It can be manually scrunched down into a big wad when we want to transport it, but when released, it automatically self-repels into a tent.

Almost certainly there is a limit to how large an object can be made using practical electrets. The bigger the tent, the more mass is being lifted against gravity, and the stronger the electret charges need to be. But for an ordinary pup tent or slightly larger family tent, this should be workable (and almost indistinguishable from magic).

 — Vernon, Jun 17 2005

Some Electret phenomena http://www.keelynet.com/electret.htm
Looks like a fair amount of "fun" potential, there. :) [Vernon, Jun 17 2005]

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Annotation:

<pictures catenary arch with spaces> Cool!
 — Shz, Jun 17 2005

What would it sound like when it brushes against itself?
 — Shz, Jun 17 2005

electret?
 — po, Jun 17 2005

It might look like a tent, but what would stop it from blowing away?
 — phundug, Jun 17 2005

This is a fun and brilliant idea. Would it work? If you take two electret discs (maybe cannibalized from old mikes), will one tend to float above the other electrostatically in the same way that two magnets might?
 — Basepair, Jun 17 2005

Don't you need electret bumps on both sides of the fabric to keep it from repel-curling up?
 — FarmerJohn, Jun 17 2005

 [Pa've], since electrets are often plastics, this tent will probably weigh about the same as others of the same size.

 [phundug], I did not say that stakes were not needed. Although if you get enough gear inside the tent after letting it expand, you might not need them, anyway.

 [Basepair], the strength of static electric charges is indeed a critical factor. I am indeed assuming that enough can be done for this Idea to work.

[FarmerJohn], I was envisioning the corduroy on the inside of the tent. Repulsion then leads to expansion. However, if the static electric charges on the inside are not quite enough for the tent's mass, then I could see using charged corduroy on the outside as well.
 — Vernon, Jun 18 2005

Nice!! ++
 — sartep, Jun 21 2005

Is corduroy waterproof?
 — andrew1, Oct 04 2005

[andrew1], ordinary corduroy is just a cloth fabric, so, NO. But I only referenced it here because of its shape; the material here is mostly plastic.
 — Vernon, Oct 04 2005

 Rather than _n_n_n_n_ :

 Concertina, thusly:

 From this (only more compressed): /\/\/\/\/\/\/\/\

 To this: ____________________________