Windscreen suggestions

[John Gelack]

I recently purchased my first alcohol stove, and now I need to make a windscreen for it.I was wondering what is the best material to use. I’ve heard of people using aluminum foil,but I would prefer something a little more durable.I could use a foil oven liner or aluminum roof flashing, which seems like it would be the most durable option,but I’ve read about windscreens that were made from roof flashing turning brown and warping. Although the discoloration would not bother me, I would think a shiney windscreen would help to reflect some of the heat back to the pot. The warping is more of concern to me, but I’ve read that baking the windscreen in a oven will prevent this. What would you recommend. Also, would it be better to put ventilation holes all the way around the bottom of the windscreen or only half way around it. If the holes were only on one side of the windscreen, the side without holes could face into the wind and the stove would still be getting air, or would the lack of extra ventilation holes choke the stove. Maybe two rows of holes could be made on one side to avoid this. I would really appreciate any advice. Thanks John

[Vick Hines]

Take a deep breath and stop thinking so hard about windscreens. The short answer is, forget about flashing, use oven liner, forget about holes, just notch the bottom edge of the windscreen.

The long answer is:
MSR windscreens are made of soft aluminum of the same gauge as oven liner. Either the MSR windscreens or homemade ones of oven liner or cooky sheet will last for months of continuous use and years for most of us. That’s enough durability.

Oven liners and cookie sheets feel crinklier than the MSR windscreens because they are impact hardened during the manufacturing process. You can soften them by heating and quenching. The process is called annealing. In a darkened room, heat the aluminum until you see the first florescence – the dim red-brown called ‘cherry red’. Immediately quench it in cold water. If you get it too hot, it will burn through. That will let in too much wind.

Flashing windscreens are heavy enough to serve as pot supports. If you are not going to use the windscreen to support a pound or more of water, there is no need to use flashing.

The reason flashing browns is that it has a thin coat of varnish. Fumes from the burning varnish are highly toxic, so sand the varnish off before using the flashing.

RE: warping. If you are not making a flashing pot support/windscreen, this will be irrelevant. But the annealing process described above will prevent warping. You can use the varnish as a heat indicator — with good ventillation — and quench the flashing as soon as the varnish moves from light brown to a blacker brown. After quenching, sand the varnish off completely. It is easy to see after you char it. The reason for doing all this is that new flashing is impact hardened just like oven liner. That means it has lots of built-in stresses. Uneven heating releases these stresses unevenly – so the piece deforms. Annealing releaves the stresses.

Vent holes: Don’t waste your time with holes. Just cut notches around the bottom of the windscreen. They will move more air; they will shield the burner better; they will not weaken the windscreen; they will let the screen fold or roll up easier; they are easier and cheaper to make. You can spend a lot of time, money and effort on vent holes with minimal benefit. In the first place, they only work well with flashing – because it is so thick. You could punch vent holes in oven liner, but then it won’t fold or roll up well.

Holes must be large enough to overcome the boundary layer effect. The first 1/16 of an inch inside the circumference of the hole is dead air. In other words, a hole less than 1/8 inch in diameter will not pass much air except under pressure. It doesn’t take much pressure to move air through the hole, but a bigger hole will be much more efficient. It’s a sliding scale sort of thing. 1/4 inch is about minimum. Now then, drilling a hole 1/4 inch or larger in flashing is hard enough. It is just about impossible with lighter material. You can punch it, if you can find a punch big enough. Why bother? Just notch the bottom.

If you notch the bottom, the concern over which side to put the holes in becomes a non issue. The notches are on the ground where friction against the ground reduces the effect of the vagrant zephers. There may be rare conditions where the wind creates a problem, for example, if the stove is set up on a rounded boulder that entrains the airflow along its surface. Then a few strategically located pebbles – or just moving the stove (duh)- will take care of the problem.

[Douglas Frick]

I agree with Vick. I made my windscreen from an EZ-Foil oven liner. It’s 7″ x 30″, which is way too big, but it only weighs 1.7 oz and it fits around anything. I folded over 1/4″ of foil on the top and bottom to stiffen it up a bit and soften the sharp edges. I use two or three big paper clips to hold it in a circle. I didn’t punch holes or cut notches; I’ve found that since it usually sits on an uneven surface that there are plenty of air gaps underneath (or I can always stick a small rock under one side to hold it up a bit). I also didn’t do any annealing, sanding or anything else to it. After being formed and rolled several dozen times it has become nice and wrinkly, and there are no discolorations or burns on it. In order to make it so long, I cut two long 7″ strips, folded two ends together, then stapled the fold. It’s holding fine, but unless you use a big pot it’s unlikely you will need to make one longer than a single strip of oven liner.

[Jay Ham]

I just finished writing an article on making a windscreen from oven liner material. The article has gone through our editorial process and is scheduled for publication on March 1st.

When using oven liner material, you can punch the holes using a paper hole punch. Also, try to make it nearly as tall as the pot and close fitting, to maximize the heat transfer. The article gives details on how to achieve this.

Jay
MYOG

[John Gelack]

Thank you for your responses. I was originally leaning towards using flasking for my windscreen, but after reading your posts I’ve decided the oven liner would be a better choice. I really like the idea of cutting notches in the bottom of the windscreen, it would be easier and seems like it would allow for more ventalation. I am looking forward to the upcoming article on windscreens. Thanks again for your advice. John

[Michael Fite]

Last year I had some old lightweight Alum flashing, an hour to kill and decided to finally try making that perfect windscreen I've been dreamming about for so long. ;-) Well, functionally it turned out great. But it weighted as much as my Ti pot and MSR Pocket Rocket together! And was very hard to roll it to fit inside my pot. So, forget the flashing. Also, I can't recommend alum foil. Even if doubled or tripled up, still too flimsy. Use an oven liner or a disposable alum cookie sheet. Juuuuuust riiiight.

[John Donewar]

John,

Take a look at this MYOG windscreen. Mine weighs .85 ozs and fits inside of my MSR Titan titanium mini kettle.

belt buckle windscreen

Party On ! 2010

Newton

[Keith Selbo]

John,
With all the windscreens mentioned, even the slightest breeze will cool your setup and drastically reduce its efficiency. I was disappointed to find that with a simple aluminum flashing windscreen I was using 30% or more fuel to boil 2 cups of water on a hike this spring than I did when I tested my stove in my unheated garage. Back to the drawing board.

Now my windscreen is my blue Wal-Mart sleeping pad. Being tall and long, you can put a lot of space between it and the stove and still the keep breeze off the entire cooking setup so heat loss is near that of still air, and no extra weight!

[Author]

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