QuietStove.com

Monday, April 8, 2013

Canister Stoves and Wind

I got a note from someone recently:
Hey Jim,
I'm really enjoying your adventures in stoving website.
I'm new to canisters, obviously, so I'm trying to play catch-up. I'm sure this is answered somewhere on BPL or on your website. But would you mind answering these 2 newbie questions?
1) Can the flame on a canister stove get blown out by the wind?
2) In your experience, is a windscreen valuable on an upright canister stove?
This is assuming the windscreen shields the canister from the heat source instead of reflecting the heat towards the canister. thanks for your advice and experience on this topic and others.
Yes, a canister stove absolutely can get blown out by the wind. Some Scouts were camped next to me when I was out doing some stove testing of the new 1.0L MSR Reactor. They took great interest in the Reactor when I explained to them that it was the most windproof upright canister stove, remarking "our Jetboils were blowing out on our last trip in the San Jacinto Wilderness."  And the Jetboil is actually more wind resistant than the typical upright canister stove.

Now, as to the second part of your questions, "is a windscreen valuable on a canister stove?" In a word, yes -- and for more reasons than just to keep your stove from actually blowing out.

First and foremost of course you want to prevent your stove from blowing out, but that's actually fairly rare.  Good site selection should prevent most full blow outs. 

Second, though, you want to prevent the wind from shifting your flame. You want that flame well centered under your pot. Take a look at this photo:
A flame shifted to the right by a very slight puff of wind
Notice how a light breeze has shifted the flame to the right. Where is the heat going? Well, it's not fully going into your pot. And what happens in a heavier wind?  Heavy winds can really play hob with your flame.  A windscreen can significantly reduce flame shifting.

Third, the windscreen helps trap heat. The flame heats the air that surrounds it. That hot air will help transfer heat to the pot, particularly if the windscreen channels the hot air up along the sides of the pot. Remove that windscreen, and the hot air gets dispersed by normal air circulation or wind.  Notice how in the photo below that the hot air around the flame is completely free to disperse into the surroundings. 
A very exposed, unprotected flame.   Note how the sides are completely open.
Lastly, the one time you really do have to worry about your flame getting blown out is on very low flame settings.  Using a windscreen allows you to use a low flame without having your stove blow out altogether, thus giving you greater control over your cooking. 


Why a windscreen?
You want to use a windscreen to
  • Prevent your stove from blowing out
  • To keep the flame centered (i.e. prevent flame shifting)
  • To trap the heat near the pot.
All of the above contribute to greater efficiency, faster speed, greater control, and, in higher winds, the ability to cook at all.

What kind of windscreen?
Ah, that's all very well and fine, Jim, but what kind of windscreen should I use?  Well, first, do NOT use a full 360 degree windscreen on an upright canister stove. An upright canister stove is a canister stove that screws directly into the canister (sometimes also called a "top mounted" canister stove).  If you fully surround the stove, you could trap so much heat that you overheat the canister and cause an explosion, which could have severe if not deadly results.

Here's a windscreen that I've found useful:
A windscreen made of quadrupled heavy aluminum foil.  Note the partial opening to prevent overheating.
Note that in the photo above that there is snow to the left of my stove.  It was January when I took this photo and I'm atop an 8,000+ foot/2400+ meter peak.  The gap I left in the windscreen is fairly small, which is fine for such a day.  ALWAYS, ALWAYS, ALWAYS monitor the temperature of your canister with your hand when using a windscreen with an upright canister stove.  If the canister feels hot, take immediate action to prevent overheating.  Open up the windscreen, turn down the stove, or even stop cooking if need be.  DO NOT allow the canister to overheat.  That would be, um, bad.  Bad as in a potential stay in the the hospital -- or worse.  Note that every manufacturer says not to use a windscreen in any form for this very reason.  I think a windscreen is reasonably safe if you consistently and frequently monitor the canister temperature with your hand, but keep in mind that you are going against the manufacturer's recommendations.  Nothing prevents a serious accident but you and your good sense.  The benefit though is of course significantly lower fuel use, faster cooking, and in some cases the ability to cook at all.  In significant winds, an upright canister stove may not be able to bring water to a boil at all, no matter how hard your try, without a windscreen.  The lawyer who wrote the warning on your stove probably didn't have to worry about that.  You do.  Windscreens are reasonably safe if you are diligent but potentially deadly if you are not.  Fair warning.

An aluminum foil windscreen made from multiple sheets of foil.  
The windscreen in the above photo is made out of heavy household aluminum foil of the type you can get at any grocery store.  I use three or four sheets folded at the edges to hold them together.  Note that it's light and needs to be braced with rocks in heavier winds.  It's not super durable, but will hold up for multiple weeks worth of hiking with reasonable care.  I fold mine in half lengthwise, roll it around a water bottle, and put the resulting bundle into a bagel bag for protection before putting it in my pack.
My windscreen rolled and wrapped, ready for packing.
Crafter's foil, also called tooling foil, of about 36 or 38 gauge is more durable.  I've found crafter's foil available on eBay.  Titanium foil is better still, albeit pricier.  Some have used aluminum roofing flashing to good effect although flashing is a bit heavier.

Note that you need a screen of sufficient height to accommodate the sizes of canisters you will use.  A 110g canister is far shorter than a 220g canister which is in turn far shorter than a 450g canister.  A windscreen for an upright canister stove on a 450g canister is so tall that it's frankly a royal pain in the posterior.  I'm not sure I can really recommend the above shown type of windscreen with a 450g canister.

Naturally, there are a lot of other ideas beyond the simple windscreen I'm showing here.  I address some of those ideas in a another blog post:  More Windscreen Ideas

Al foil as a windscreen
GOOD
  • Cheap
  • Easy to get
  • Easy to work with
  • Light

BAD
  • Needs to be braced with rocks in moderate to high winds
  • Not all that durable (but not all that bad either with reasonable care)

It's cheap, easy, and available, so experiment away. If you find it's not working for you in terms of durability or stability, then by all means seek out tooling foil, flashing, or titanium foil.

I hope you find this helpful,

HJ

4 comments:

  1. If I had my choice, I'd just as soon find a sheltered place to set up my stove. Since that isn't always possible, I do carry some of the foil and I have made a windscreen fro aluminum flashing that wraps around my pot. I kind of like flashing. It's heavier than foil, but it's heavier duty than foil. It's not hard to cut, using a sharp knife and a straight edge, it's common and it's inexpensive. All this aluminum sounds more like a heat shield than a wind screen. I wonder it there isn't a high temperature fabric that could be used instead of metal? Some fabric, aluminum rods and some bull dog clips might make a pretty good wind screen.

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    Replies
    1. I saw the kite screen, which is fabric, but I was thinking of something more compact.

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    2. Hi, Bill,

      That's a fascinating idea about fabric. Perhaps it would be really light weight (although the foil one shown here is pretty light). Have you ever seen an Outback Oven? Google it some time. They make a "hood" out of a fabric. The hood comprises the upper part of the oven.

      HJ

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    3. Regarding "fabric" type windscreens, have you ever checked out Nomex 410 as a possible material? Some people also use carbon felt.

      HJ

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