I've got an article on windscreens in particular and stove fuel economy in general in the August edition in Seattle Backpacker's Magazine: http://seattlebackpackersmagazine.com/2011/08/02/three-times-the-fuel.



I've written a blog post that goes with the article. The blog post discusses a few windscreen alternatives, including some that may not have occurred to you (they didn't to me): http://adventuresinstoving.blogspot.com/2011/08/windscreens.html

HJ

One thing I've used in the past is one of those aluminum foil pans you buy in supermarkets. It is heavier than roll foil but not as heavy as the MSR windsreen which I really like to use. The upside is that it costs considerably less too!

The bottom reflector screen is a good idea. Many many years ago I had an old bluet propane bottle stove that I wrapped with one of those Coughlin metal wind screens and it got too warm to touch. After noticing the heat, I immediately shut it down and let it cool off. Then I swore to myself to never let that happen again! Sending myself "into orbit" was not an intended practise!

I like the Tyvek kite screen. If the Tyvek ever gets hot enough to melt then you KNOW you wrapped it too tight to the stove to begin with! (melt at 275*F or 135*C, burn at 750*F, 400*C). The way it was shown however means that it block some/most of the wind but a fair bit still gets to the burner which will mean some fuel waste.

I read deeper into the following article - the oven bag material seems to be even better suited to being a wind screen material than Tyvek. Being almost clear, it won't be a reflector, just a wind blocker. And the extra idea of creating a roof is something else I never thought of.

I've used those before as a windscreen, and they work well.

The material that MSR uses is about 36 gauge, maybe 34 gauge. About 40 gauge seems like a nice, light compromise thickness.

The radiation shield/heat shield is what makes a windscreen on an upright canister stove workable. Absent that heat shield, you run the real risk of overheating the canister. However, in cold weather, yank that heat shield out of there. You want a little heat feedback in cold weather. In fact that heat feedback might be really essential. A windscreen is just a really good idea overall... just don't ever let your canister get hot to the touch.

The kite screen is a brilliant idea. It's a little "fiddly," but I imagine some people will really take to it.

With a bit of experimentation, I bet you could come up with something that would work in the worst of weather. I often carry plastic sheeting in my backpack for use as raingear, a ground cloth, etc. Having some Tyvek or oven bags in your pack could turn an outing disaster into a "no big deal" -- a real ace in the hole.

HJ

Excellent post, Jim!!
Why didn't I know about your stove blog before this?

-Blast

Thanks. I'm always trying to combine science and practicality. Hopefully I succeed once in a while.

All those shock waves in your youth (and adulthood) have taken their toll?

I've got my blog which has both specific stove reviews and also a lot of general posts as well as a series (now four) of articles at Seattle Backpackers Magazine. Guaranteed cure for insomnia.

HJ

Very nice article, Jim! I would never have thought of the kite one, either.

But I am curious about one thing, and I've seen it other places, too. I have always been under the impression that a windscreen is to deflect wind, but some stoves are completely wrapped (and some quite tightly) around the stove, with no air vents.

Doesn't a tight wrap around the lower part of the stove cut down on available air for combustion? Am I missing something here?

Sue

Sue,

That's an astute observation. The real answer is that it depends on the stove, the fuel, and the conditions. To really get it right takes some testing with monitoring equipment.

However, there are a few generalizations we can make:
1. You do want some clearance between the side of the pot and the windscreen. Normally a finger's width or so is fine. The ideal situation is where warm air is flowing up the sides of the pot between the windscreen and the pot. This warm air flow adds (some) heat to the pot and is referred to as a "flue effect." Generally, you do not want the windscreen to be tight up against the side of the pot.

2. You do want air to enter at the bottom of the windscreen such that the flame isn't starved. Most windscreens aren't so air tight that the flame gets starved, but it's actually not a bad idea to have a row of small holes punched in the windscreen along the lower edge of the screen. You can achieve the same effect by setting the windscreen on top of some small rocks. The thing to avoid is "sealing" the windscreen at the base by piling up dirt or snow or something. In the case of upright canister stoves, setting the windscreen (if it's the self standing kind) up on rocks has an additional benefit: Cool air entering at the base of the windscreen can help prevent canister overheating.

The above generalities will have to be tailored to your stove and your conditions. On a really windy day, you might have to really close up that windscreen tight and maybe even seal it with dirt along the base on the windward side. On a fairly still day, you might need to open up the windscreen a bit so you have two fingers width clearance around the pot and also set the windscreen on small rocks. Observing the flame can be helpful here. If you can see the flame getting buffeted by the wind, then you probably need to do more to exclude wind. If on the other hand the color of the flame looks as though the flame is starved, you'll need to open things up a bit.

HJ

Thanks, Jim!

I have had to adjust windscreens, but never had to close one completely. I think I read somewhere that an alcohol stove that burned with plenty of air produced less CO than one that had a tight windscreen around it. I don't know about other stove fuels.

I was wondering if I was missing something that was obvious to everyone else.

Sue

CO really isn't a big concern unless you're cooking in a tent or indoors, but if you're cooking in a tent or indoors, you don't have to have a very tight windshield.

HJ