segunda-feira, 28 de maio de 2012

Super Duper Ultralight Windscreen

Great article by http://ultralighter.blogspot.com Super Duper Ultralight Windscreen: "Super! Duper! Foldable! Crinkly!

Aluminum (a.k.a. 'aluminium' foil.)



My stove thinking appears to be so subtle that no one has ever asked me about my windscreen.


Stove and pot support (quiescent phase).

Most people, when they see my stove and cook pot, just stand there and drool, and not in a good way. None of them even understand what a windscreen is.

Anyone who has ever asked me anything about any of my equipment or how to backpack lighter has just ended up arguing with me about why it's not possible to do anything different than what they are already doing. This is yet another good reason to avoid people.


Still life with pot.

And those who do use alcohol stoves always have a big, clunky windscreen that leaves at least the top of the pot exposed, and usually a lot more. Leaving any part of the pot exposed wastes huge amounts of energy.

I decided a long time ago that if I'm going to waste energy, it won't be by carrying more fuel than I need, it will be wasted on carrying beer. And I'm so cheap that I've never carried beer either, other than from the store to my car to my kitchen, where I guzzle it indoors, in private, away from flies.

Right off I want to say that my kind of windscreen is not the Absolutely Perfect Thing. She's in the other room and no, you can't see any pictures, so don't even ask.


Folding foil's edges.

Fails:
  • An aluminum (or 'aluminium' for you kinky types) foil windscreen is horrifically sensitive to heat. Let flame lick it even once, and that spot brittles up and gets crumbly. Then you get a hole there.
  • Folding, unfolding, refolding over and over will eventually fatigue foil, and then you get cracks and tears.
  • It's easy to tear, even at the best of times, especially if you are a doofus.*
  • Wind. She blows, eh? and can disappear your unwatched windscreen and carry it away for a hat.
  • Not sexy. (But then, probably, neither are you.)


Done folding. All smooth.

Scores:
  • If you burn the inside of your foil windscreen you've made it too small. Make it bigger and try again.*
  • I used one of these screens for 10 days straight, twice a day, and it was still working fine.
  • Sure it's easy to tear. Get a life.
  • Wind, so pay attention. Unfold the thing and put a couple of small stones inside, and put a few on top while you're cooking. If that isn't good enough, you're a doofus and picked a dumb place to cook.*
  • If it's not sexy then no one will come over and ask dumb questions while you're trying to cook supper and catch up on your scratching.


Finished, with ends stapled together.

How To:

I have a small pot. It's a 16-ounce (475 ml) aluminum measuring cup which cost $5.95. It weighs 1.8 oz (50 g). I use it to heat water which I pour into my feed bag, and while that's brewing up I heat more water for tea. That is, each hot meal is done in two steps: food and then tea. I let my stove burn out and then fill it again for the second burn. After a while you get to know how much alcohol you need, so you don't waste fuel letting the stove just sit there and burn until you get tired of watching it.

I use standard 12-inch wide (305 mm) foil, either standard weight or heavy weight. (Who cares anyway?) Using three layers is generally right. The finished screen weighs around an ounce (28 g), depending on weight of foil and how much gets used.

I shoot for an approximate diameter of eight inches. Figure you'll need around 3.25 times your target diameter when you measure out the foil. So if I need a screen eight inches in diameter, I measure around 25 inches and end up about right. More is way, way better than not enough.


Lots of room inside.

The counter top where I live is about the right width, so I measure out the width, in foil, and then do it twice more, ending up with enough foil to make a three-layer-thick windscreen.

Three layers gives me strength enough for at least a week's use, and is heavy enough to resist tearing, and the resulting screen is not quite so likely to blow away. I always carry a second windscreen in my possibles bag, and think in about 10 years have needed it once.

OK, so you have the foil measured out.

Now (using my measurements, for example) start with a 12-inch by 75-inch continuous piece of foil, then fold it over until you have a piece 12 inches by 25 inches, and three layers thick.

Next, fold the edges. I use about 1/4 inch, folded over, and then folded over a second time. This strengthens and smooths all the edges.


Top scrunched down.

After that, I take the side of a pen (or my thumbnail) and crease these folds to get them as flat and tight as I can.

The next step is to staple the two ends together, forming a cylinder. Done.

To use, put one hand inside, and use your other hand to fold about 1/5th to 1/4th of the cylinder over on itself (see photos), leaving as small as possible a hole in the top to serve as a flue. Too big a hole and you get wind blowing in there, and the hot gases leave too fast.

Put water in your pot, fuel in your stove, light the stove, put the pot on its stand, and carefully lower the windscreen over it all. Wait until the stove goes out.

Since you can't see anything, you can (cautiously) move your hand over the flue hole to judge whether heat is coming out, and how much.


How it looks while running.

This windscreen has several cool aspects:
  • First, it blocks the wind better than other windscreens, because it covers everything.
  • Second, heat inside the windscreen reflects off its sides and top and bounces back into the cook pot, increasing efficiency.
  • It folds up to almost nothing, in whatever shape is handy at the time.
  • It's cheap and easy to make.
  • It can be as light or heavy as you want.
  • Once you are done cooking you can simply leave the stove and windscreen undisturbed until you are ready. I cook tea this way, and it stays hot for 10 or 15 minutes. Covering the top hole after the stove goes out adds to heat retention.
  • You can control how much air gets in at the bottom by putting a couple of small stones under one side, or by crinkling the foil at the bottom. If setting up on sand you'll need to do this to assure that the stove has enough air. Basically, you never have to worry about the stove getting too much draft.


Folded for carrying.

When I'm done, I fold the windscreen and wrap it around my cook pot. When using a larger pot I have room enough to put it inside. With the cup I use, I get the stove and pot support into it, but there isn't enough room for the windscreen, so this is a minor annoyance. This particular cup does not have a lid either, so I use another piece of foil.

The main items to watch are that the stove flame does not touch the windscreen, and to be careful folding and unfolding. Other than that, this is fairly doofus-proof.


Warning 1: Anyone trying this MUST use a reflector under the stove. More aluminum foil is fine. Without a bottom reflector, I've set the ground on fire more than once (back in the old days), and besides that, using a bottom reflector increases efficiency even more. You get a huge amount of heat bouncing around inside this thing. I've also, when cooking with the stove on a flat piece of wood, set that on fire too, so watch it.

Warning 2:
Be extremely careful about touching this windscreen while the stove is burning. In time you learn which parts MIGHT be safe to touch, but parts of it are always insanely hot when the stove is running.


* If you are interested in attending my new professional doofus training, give a hoot.

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