Let there be more stove windscreen discussion

[Matt Swider]

So, I am getting my gear organized for a four person cook group for an upcoming trip.  Because it is 4 people, and we are going as a boy scout (alcohol stoves prohibited), I am planning on using a Kovea Spider stove and a lager aluminum pot.  I have been thinking of ways to maximize efficiency to minimize the fuel containers we bring, and this is thread, as the title suggests, is about wind screens.

I was trying to decide what sort of windscreen to make, and am focuses now on a simple aluminum foil screen that covers most of the side of the pot.  In searching about holes cones, etc, I came across a video by Zelph that showed a marked difference between holes in the windscreen and an windscreen held off the ground by 3/4″.

Now I realize that this windscreen is targeted at an alcohol stove, what I am wondering is how much, if any, real efficiency difference having the windscreen elevated 3/4″ versus a ring of holes (1/2″ or so) around the bottom perimeter would make for a isobutane stove / flame.

thanks, Matt

[Ken Thompson]

nm, I see you managed to get your post edited.

[Matt Swider]

The Kovea spider is a remote canister stove, I probably should have stated that in the OP

[Ken Thompson]

 

Flame On!

[Pigeon]

Have fun, Matt. :)

I just bought a Kovea Spider and plan to use  aluminum flashing, or at times maybe a Caldera Cone. I did some reading (but my memory is failing me), did anyone out there suggest you do need airflow for fuel efficiency with a remote canister? Could there be an issue of overheating some part of the stove and causing premature wear?

 

Regarding the holes you may punch in the windscreen, you’d need so much open area of multiple sizes holes to approach the amount of air passage you’d get from the raised windscreen. It seems like wasted effort and prone to fall apart.

 

[Bob Shuff]

Kovea Spider is a great stove.  I found problems with a tight screen  and not enough intake holes.  Check out FlatCat Gear. He has at least two windscreens designed for that stove.

Mine is like the Snow Leopard, made from Ti sheeting.  The gap where the screen is suspended above the ground solved the sputtering issue.  More holes would probably get you there, but this is such a simple and elegant solution.

[Mario Caceres]

I’m fairly new to the Kovea Spider and in general I really like it.  I’m pretty impressed how you can put the flame really low which great for simmering or dry baking.  I only had an issue with that stove a few weeks ago when I used it in my Ausangate Trek (Peruvian Andes) when the stove keep making some spattering noises.  Ausangate trek was at 16K elevation so not sure it that had anything to do with that as I have not been able to replicate those noises here back in the U.S.

Anyway, back to your question about screens.  I like the Vari-Vent from trail designs.  The way to adjust the air inflow is very clever and you can customize it depending in which direction the air is blowing.  It also works with different diameters of pots.  I have modified one of the vents so It can easily accommodate the hose from the remote canister.

 

[Matt Swider]

I have looked at the Flat Cat kovea spider windscreens, but my pot is rather large, and none of those would fit.  I think the more I think about it the paperclips on the bottom of the foil would do the trick.  Maybe an extra gram, but an fully intact windscreen that will hopefully last for the 16 cooking meals planned.

 

[Matt Swider]

Hey Duke, at first I was wondering about the extra heat around the spider also, but the bit of looking around that I did showed that was not a problem.  I am also considering a aluminum flashing wind screen, as I have the material already.  I know that the flashing is a bit of a pita to roll up tightly, as I have made a cone out of flashing for my kmart grease pot.

Also thinking of either a home made foil, or the vari vent one that Mario just recommended.  I like that aluminum material, and would not have guessed that fooling with the vents would have been worth it, but it sounds like Mario really likes it.  Looks like the 6 3/8″ inch one would work for my stove/pot setup, and I think the weight was comparable to the flashing I am thinking of using.

So raising the cone of a solid cone, or maybe the vari vent, or . . .

good food for thought.

[Matt Swider]

wow, when I looked at getting the standard windscreen from trail designs at , 6″ I was gong to pay more in tax and shipping, about 1.5x the cost of the item.  Guess I will keep looking . .

[Matt Swider]

Well Duke, you inspired me to try the aluminum flashing version, and it seems like it will work out fine.  I thought it would not fit easily into the pot, but I was wrong.  The weight is 2.6 oz, a bit more than I hoped for.  Also found a malleable aluminum one on ebay for $8 shipped, at 1.4 oz may go with that one, still deciding.

[Mario Caceres]

Matt, if I were you I would contact them and see if they can ship you the screen in a flat envelope via 1st class mail.  That should be less than a couple of dollars.  Tell them you don’t need the screen shipped in a roll but flat  (They may need to fold it a couple of times so it fits in a regular manila envelope but that should be no problem.  The material is very pliable and lightweight)…. Not sure how flexible Trail-Designs would be to accommodate such request but in the couple of times I have contact them for some information they have been very responsive and customer oriented.

[Rick M]

I bought a Ti windscreen from China off eBay for ~US$6 delivered. Arrived in 2 weeks. Attaches with a clever magnetic snap button. I use it with my Caffin stove and Esbit Ti wing. Couldn’t be happier.

[Roger Caffin]

One can be hugely complex here, or very simple. I favour the latter.

This windscreen works just fine in the bush and in the snow. You will note that it is very easy to adjust the stove with this windscreen. It can take two micro-stakes at the corners to hold it in place against the wind.

A detail for snow use: a small amount of radiation is being allowed to hit the canister, to keep it slightly warm. This is very useful in the snow. But do not let the canister get too hot to touch – ever.

(Yes, this is my new Vortex Burner Winter Stove in use in the Alps. It was for morning tea – a bit windy and cold at the time.)

Cheers

 

[Matt Swider]

Thanks for the tip Mario.  I thought about doing just that, but could not find contact info on their web page.  Looked just now and it was very easy to find.  Guess I was tired last night.

thanks, Matt

[Matt Swider]

Hey Rick, I have a titanium windscreen, but it is too small for this pot.  I looked at others on ebay and did not find one large enough.

[Matt Swider]

Hey Roger, that is simple and functional.  I had a completely enclosed design in mind though, as I don’t need to perform any adjustments to the stove, other than at the remote canister.  I am speculating that the completely enclosed design is more efficient than one side open as you show.

[Roger Caffin]

Ah, but the opening lets you check the flames and lets quite enough air in, while not causing too many drafts around the pot. And it warms the canister up too.
All I can say is that I have been using something like that for years and years. It works fine for me.

Cheers

 

[Matt Swider]

I can’t argue with that Roger.  I must say, that I do feel a few tests coming on here . . . .

[Matt Swider]

So I did two tests.  First was with a windscreen completely enclosing my pot with a small, unmeasured (1″ or less) gap around the sides, and around an inch at the bottom to let air in.  Flame set pretty low for efficiency, boiled 1 liter refrigerated water in 29 minutes, used 17 g fuel.  Second was the same setup except I had the windscreen on the ground, and had one side open like Roger’s picture above.  Flame set pretty low for efficiency, boiled 1 liter refrigerated water in 26 minutes, used 17 g fuel.

Conclusion:  for this test setup, the completely enclosed windscreen had no significant effect on efficiency, don’t bother.

[Jon Fong / Flat Cat Gear]

Unless the wind was blowing you might not see a differences between the two setups.  I would image a 3-5 mph wind ( at ground level) would show a difference. My 2 cents.

[Roger Caffin]

I would image a 3-5 mph wind ( at ground level) would show a difference. 

I haven’t seen much difference myself, assuming the windscreen goes at least half way up the pot, sits well on the ground, does a 3/4 wrap at about 25 mm from the pot – or roughly something like that.
I find the stakes holding the windscreen in place to be very valuable in getting a good set-up. If there is a lot of wind the stakes become essential, but then the windscreen still works fine.
On the other hand, I find that a low windscreen tends to be rather ineffectual. At least half way up the pot seems important.

Cheers

[Mario Caceres]

Matt, thanks for doing these tests.  As Jon pointed out, If you did them in your kitchen or in an area with not wind that would explain your results.

There is an interesting article in the BPL archives about windscreens designs.  Not sure if you are a member and have access to this article.  Basically in this article the author suggests a gap of 1/4″ to 1/2″ between the screen and the pot to have any effect.  You mentioned in your testings you used about 1″ so that large of a gap would not create any “chimney effect” to improve the efficiency of your set up.  The article mentions “…The primary functions of a windscreen are to break the wind, create a calm zone within the cooking system, and channel heat from the burner to the cookpot”.  Clearly if you are testing in your kitchen the first two functions won’t apply but the third one should still work (assuming the proper gap).

[Matt Swider]

Unfortunately, I am not a member who is able to access the articles.  I wonder if anyone has done a test with varying uniform distance from pot to windscreen to see how the efficiency is affected.  I considered during my testing to try and carefully adjust the windscreen to about 1/2″ all the way around, but realized that I would never do that on the trail.   And even if I did, likely someone in my cook group would disturb it at some point, so it did not seem to be practical for a non-fitted windscreen.  But that does bring up the idea to modify my present one to be able to fix the diameter, and hence create at least an approximate uniform gap around the pot.  But really, to make it uniform each time it is set up one needs something like a cone IMO.

I was testing outside, but it is just not very windy where I live presently.

[Roger Caffin]

I really don’t think the gap is critical.  Going from 1/4″ to 1/2″ is not going to alter the heat transfer rate to any signifance extent. Add to that the problems of getting an exact separation in the field – which in practice you will never manage, and it is all a waste of effort.

On the other hand, having the windshield HIGH enough up the side of the pot will prevent the wind from moving the flames sideways, and that is really what matters.

Try using some micro-stakes to anchor the windshield. That works really well and is very little hassle. It also allows some fine tuning of the gap. When I was cooking on sheet rock the stakes were tricky, so I threaded them through the holes and sat a few small rocks on them outside. That worked as well.

Cheers

 

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