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SGT Rock
2007-04-15, 12:18
I know I have a thousand things I am trying to catch up on around here on the site. But here is one simple on I have been wanting to do since I read about the stuff in Iraq.

I went to Lowes and got some of that Oatey flame protector cloth to make a pot cozy that would also help trap in some of the heat from the stove when you use it. My plan was to make the cozy so that it would fit tight around the pot and form sort of a ring to maintain the heat under the pot. It didn't work out exactly like I planned, but it does seem to work. What it appears it does is it works better as a windscreen and pot cozy. Field testing will show - but I think something like this could work with many stoves and pots.

Photo #1 - the material
Photo #2 - the cut parts
Photo #3 - the cozy around the pot. It is "sewn" using trip wire. Note that the part that will be the bottom is on the top to help hold in some of the heat and can be used as an insulated pot holder.
Photo #4 - the pot of water boiling
Photo #5 - A peak at the flames inside. Something I realized is I don't need to make air holes, just use some rocks in camp to create a small air gap under the cozy/screen.

Follow up post coming...

SGT Rock
2007-04-15, 12:21
I had to post like this since there are only so many attachements per post...

The weight of the screen/cozy is 29 grams (about 1.05 ounces) and it is flame resistant to something like 2500F. Here is a picture of the bottom/top in direct contact with the flames from the stove:

JAK
2007-04-15, 13:23
I wonder if you could use it as a hobbo stove / cozy just by itself as well as a wind screen / cozy when using the alcohol stove. It would get messy I suppose, but if you run out of fuel its an option.

SGT Rock
2007-04-15, 13:29
I have thought about that. I think (this is just opinion) that if you needed a hobo stove you could probably get by better with just a pot stand like the tipod and sticks - at that point the windscreen could just get in the way more than help...

I could be wrong.

I also realize I am probably not the first person to try something like this. I tried something similar with some aramid fiber many years back - but it seemed to catch fire and didn't seem to work so well.

TeeDee
2007-04-15, 16:55
I have one of those.

One thought about it as a cozy: it is supposed to be made of ceramic fibers I believe. Still I am very cautious about what I get in my food. If these would have any tendency for the fibers to come loose and migrate into a pot, it probably wouldn't do any harm immediately, but enough of anything like that surely wouldn't do you any good.

Just something to think about and look closely.

SGT Rock
2007-04-15, 17:02
Says it is made out of carbon based woven materials, whatever that means.

See, I knew I wasn't the only one. How have you used yours?

JAK
2007-04-15, 17:22
Could you make a sandwich out of that stuff and muffler tape?
Would that make it better, or just heavier?

SGT Rock
2007-04-15, 17:24
Well I suppose you could, but I don't know why you would want to use this stuff for that. If you are doing boil-in-bag cooking there are a lot of cheaper materials to use that do not have to be flame resistant. I did think about the muffler tape thing for the inside though to work as a reflective layer.

dropkick
2007-04-16, 01:54
How much was the material?
I want to build a new cozy.
My current cozy is made from a car sunscreen and I've always been uncomfortable with it around too much heat.
Was thinking of buying a ironing board cover and making one out of it, but haven't settled on anything yet.

SGT Rock
2007-04-16, 08:55
it was $15 for a sheet.

incognito
2007-04-16, 12:00
I know I have a thousand things I am trying to catch up on around here on the site. But here is one simple on I have been wanting to do since I read about the stuff in Iraq.

I went to Lowes and got some of that Oatey flame protector cloth to make a pot cozy that would also help trap in some of the heat from the stove when you use it. My plan was to make the cozy so that it would fit tight around the pot and form sort of a ring to maintain the heat under the pot. It didn't work out exactly like I planned, but it does seem to work. What it appears it does is it works better as a windscreen and pot cozy. Field testing will show - but I think something like this could work with many stoves and pots.

Photo #1 - the material
Photo #2 - the cut parts
Photo #3 - the cozy around the pot. It is "sewn" using trip wire. Note that the part that will be the bottom is on the top to help hold in some of the heat and can be used as an insulated pot holder.
Photo #4 - the pot of water boiling
Photo #5 - A peak at the flames inside. Something I realized is I don't need to make air holes, just use some rocks in camp to create a small air gap under the cozy/screen.

Follow up post coming...

Did it work as you thought concerning the heat retention under the pot and in turn heating the water faster or useing less fuel?

$15.00 is a high price for a windscreen/potcozy

The material is highly absorbant. It is porous. It will get wet and stay wet for a long time if let to air dry. If you use your burner to dry it, that will be a wast of fuel. If you get wet food product on it, cleaning it will be chore. A pot boiling over onto it will mean cleaning headaches.

In some areas it's hard to find rocks to be used as air entry ways. Better to make holes.

Many people cook their food and then take it off the burner and put it into a cozy to further the cooking process.

All things considered, I would not choose to use the material for a pot cozy.

SGT Rock
2007-04-16, 12:16
Well I haven't tested it yet and I haven't decided if I am going to use it full time yet. This is more of a play toy at this point.

Can't find rocks?

Lanthar
2007-04-16, 13:01
There is a thing called flame resistant silicone foam that I've had in mind for the same thing. You can get it from CS Hyde Company <www.cshyde.com> , it feels kind of like neoprene but withstands way higher temps and is flame resistant. I gotta dig my sample out and stick on on my SP600 (there is one that comes with an acrylic adhesive - samples were provided as 2in squares) and see how it resists flame on a regular basis...

It's been a while since I've looked at prices though... it's definitely more expensive than neoprene...

incognito
2007-04-16, 14:10
Well I haven't tested it yet and I haven't decided if I am going to use it full time yet. This is more of a play toy at this point.

Can't find rocks?

That's right, in some areas like I said. Some areas are sandy and have been cleared of all rocks by those that use ground cloths under their pads, etc. Not all people are using hammocks as you well know. Sleeping, walking, kneeling on little rocks feel like boulders. These boulders are tossed as far as possible from where we set-up for the night. Who wants to go looking for them to put under a pot cozy only to find them under foot after their use?

After thinking on this a little bit, I've come to the conclusion that it is best not to use a cozy on any pot during the heating process. It has been determined that flames going up the sides of a pot are beneficial to to the transfer of heat to the pot and on into the water. The more you can transfer to the water, the more efficient. The plumbers cloth prevents any heat from entering the sides of the pot.

I'd like to ecourage all that read this to feel good about flames up the side of the pot to transfer heat to the water.

SGT Rock
2007-04-16, 14:35
So what you are saying is I may have to look for rocks LOL. I don't see that as an issue if I decide to play with this. I've been a lot of different places and climates and I have never been unable to find a few small rocks ;)

Actually as for how it was determined that flames going up the sides have benifit, I tend to belive they don't have that much benifit. And this is why:

1. There is only a finite amount of heat being generated when the alcohol is burned. For a half ounce of alcohol it is about 240-250 BTUs total depending on what the mix of ethyl and methyl is. Now if you take it as a given that water from a creek is going to be at about 50F, that means to get a boil 16 fluid ounces of water at about a thousand feet, you are going to have to put at least 166 of those 240-250 BTUs into the water. This was the whole reason the BTU was invented - as a standard measure of how much of any given fuel was needed to raise the temperature of a pound of water one degree. If some of those BTUs are wasted on the side because the air flows out and up - then that is wasteful to the fuel efficiency of the stove. An aluminum winsdscreen is a sorry way to retain that heat into the system since the screen absorbs some of that heat and then radiats it out.

2. Often people think of heat wrong. Heat won't magically transfer, what happens is that energy build up or relases. Heat energy is finite and heating something to 200F and then expecting everything in contact with it to also be 200F is not how it works. If you have an object at 200F and contact it to the water, then the water heats and the object cools as the heat energy tries to balance. So anything that can take some of those potential BTUs for the pot and wasts them radiating or holding that heat energy reduces the efficiency of the system.

3. Some stoves do not achive boild because they burn too low and the heat released from the pot/water leaves that to the air as it tries to equalize with the surounding air. Trapping that heat in the pot as it warms would be benificial. If you could insulate the top and sides of the pot, then hold all potential heat energy under the pot and keep it from radiating outward you may have a slower boil, but again, you can make the most of the heat energy produced.

As for the plumers cloth windscreen - their is an air gap up the sides because you really do need the air flow or the flame won't work, but I don't like the side flames because of how wasteful of the BTUs they are. I have tested some side burners where the pot rests directly on the stove and the flames go up the sides, and have found them to be consistantly less fuel efficient than the same sort of stove design with the flames starting by striking at the center of the pot with the majority of the flame being under the pot itself. Heat raises ;)

Anyway. I strongly encourage people wasting fuel up the sides of their stoves to think about that.

incognito
2007-04-16, 16:30
As for the plumers cloth windscreen - their is an air gap up the sides because you really do need the air flow or the flame won't work, but I don't like the side flames because of how wasteful of the BTUs they are. I have tested some side burners where the pot rests directly on the stove and the flames go up the sides, and have found them to be consistantly less fuel efficient than the same sort of stove design with the flames starting by striking at the center of the pot with the majority of the flame being under the pot itself. Heat raises

Today I wrapped the plumbers cloth around a pot. There is no air gap that exists after being wrapped. You must have done something special to create it and did'nt let us know about it. Having said that, the cloth is preventing heat from being transfered through the sides of the pot. Your photo clearly shows that any heat will go out from under your windscreen and travel up as your clearly pointed out that it does rise. As it travels up the outside of the plumbers cloth, it is insulating the pot from the heat traveling upward.

I have tested many stoves and burners of different design that allow flames to go up the sides and have found them to be consistantly efficient. I am refering to the type that the flames strike at the center of the pot with the majority of the being under the pot itself. I had not made mention of side burner in my previous posts. I'm refering to all types of stoves. If there are flames going up the sides of the pot they present heat to the pot. The water in the pot will absorb some of that heat as it is being conducted through the walls of the pot.

There is not a stove made that doen'st have heat rising up the sides of the pot. Grab all that you can!!!!!

You mentioned side burners that the pot sits directly on the stove. Thats good. Makes me think of the "SuperCat" Highly efficient!!! 1/2 ounce of fuel, boils 2 cups water in 4.5 min. Bam!!Bam!!Bam!! just like that. The heat is up into the pot/water just where we want it. Now to the other extreme, like you mentioned:

3. Some stoves do not achive boil because they burn too low and the heat released from the pot/water leaves that to the air as it tries to equalize with the surounding air.

I'm testing a commercially available stove that seems to have that exact problem that you mention. Can't get it to boil in the field. Burns low and slow. Everthing has to be just right, and even when you think you gotit, failure, no boil.


Trapping that heat in the pot as it warms would be benificial. If you could insulate the top and sides of the pot, then hold all potential heat energy under the pot and keep it from radiating outward you may have a slower boil, but again, you can make the most of the heat energy produced.

Now your talking the "The Holy Grail" of backpacing stoves. I can see you're trying to achieve that and I wish you well. The way Lanthar is going, it looks like he's going to beat you to it. Right Lanthar?:biggrin:

TeeDee
2007-04-16, 16:32
Says it is made out of carbon based woven materials, whatever that means.

See, I knew I wasn't the only one. How have you used yours?

Under my wildwood wood burning stove. It avoids leaving any telltale marks. No way to tell that the stove was even used.

oops56
2007-04-16, 17:07
Check this out Incognito a piece of birch fungus cut in half a cat food can and grill. The water only got warm you think i need a windscreen:bandit:

http://i33.photobucket.com/albums/d52/oops62/stoves%202/th_fstove.jpg (http://i33.photobucket.com/albums/d52/oops62/stoves%202/fstove.jpg)

SGT Rock
2007-04-16, 17:10
Today I wrapped the plumbers cloth around a pot. There is no air gap that exists after being wrapped. You must have done something special to create it and did'nt let us know about it. Having said that, the cloth is preventing heat from being transfered through the sides of the pot. Your photo clearly shows that any heat will go out from under your windscreen and travel up as your clearly pointed out that it does rise. As it travels up the outside of the plumbers cloth, it is insulating the pot from the heat traveling upward.

Well I am still not sure of that. If there is an air gap between the pot and the screen, I can't see how the heat is traveling outside the plummers cloth, the air intake is under the screen in a small gap (air holes do the same thing) and then the chimnee of the stove is the screen. So the air starts at the bottom, combusts with the fuel, and continues to raise, not go down.



I have tested many stoves and burners of different design that allow flames to go up the sides and have found them to be consistantly efficient. I am refering to the type that the flames strike at the center of the pot with the majority of the being under the pot itself. I had not made mention of side burner in my previous posts. I'm refering to all types of stoves. If there are flames going up the sides of the pot they present heat to the pot. The water in the pot will absorb some of that heat as it is being conducted through the walls of the pot.
Well I like to test the extremes to find out what is what. So if I test a stove that only shoots flames out the side and they do not achive boil with the same given amount of fuel as a stove that has the flame hit at the center bottom, that must mean that side flames do not warm as efficiently as bottom flames. Right.

So if bottom flames are better, and side flames are not, the the more flame you keep under the pot, and the less flame you get on the side of the pot, then the better the stove will be. Right.

If you agree with that, then if you can build a stove that keeps all the flame under the stove and not on the side, that would be a good thing. BTW, this is one of the things the jet boil does. Otherwise they would be burning and melting their cozies LOL.



There is not a stove made that doen'st have heat rising up the sides of the pot. Grab all that you can!!!!!

You are right, but you can minimize the excessive use of less productive flames. Here is a logic test - take a quart of water in a pot and put it over a canister stove. Now turn it on at max volume and measure run it to a boil (test with a thremometer, not by site, these things can trick people). At the end of the boil, measure fuel usage.

Now do the same thing, except run it at about 1/4 throttle.

Which one used more fuel.

Where did that extra heat energy go based on observation.



You mentioned side burners that the pot sits directly on the stove. Thats good. Makes me think of the "SuperCat" Highly efficient!!! 1/2 ounce of fuel, boils 2 cups water in 4.5 min. Bam!!Bam!!Bam!! just like that. The heat is up into the pot/water just where we want it. Now to the other extreme, like you mentioned:

I'm testing a commercially available stove that seems to have that exact problem that you mention. Can't get it to boil in the field. Burns low and slow. Everthing has to be just right, and even when you think you gotit, failure, no boil.

Oh come on, lets not play games. You are talking about my stove LOL. I thought we were all stove geek friends here, so no hidden agendas. I think you do good things playing with stoves, and in a lot of ways we have things to share here, not shoot each other up trying to be "right".

But anyway, I have seen the cat stoves do the exact same thing in field conditions because they burn fuel very quickly. Went through a whole ounce once and barely achieved boil. It made lots of flame though. Shot right up beside the pot. Plenty of side flames but never got to boil.

Whas it me or the stove?

If it was me, what went wrong.

If it was the stove, what went wrong.

Now if I can get my Ion to boil in the same conditions with the 1/2 ounce of fuel that I couldn't get a fireball of a cat to do with one whole ounce, and so can others. Does that mean you are doing something wrong with your ION LOL.


Trapping that heat in the pot as it warms would be benificial. If you could insulate the top and sides of the pot, then hold all potential heat energy under the pot and keep it from radiating outward you may have a slower boil, but again, you can make the most of the heat energy produced.[/QUOTE]

Now your talking the "The Holy Grail" of backpacing stoves. I can see you're trying to achieve that and I wish you well. The way Lanthar is going, it looks like he's going to beat you to it. Right Lanthar?:biggrin:

Exactly. I am talking about achiving the maximum fuel potential. Tweeking the things to make it work and make it efficient at any level. I know I am going to try things that don't work, don't work like I planned, or work better than I thought. If I came up with a bunch of reasons why things wouldn't work before I tried them, then they would never work because I didn't try them. Simply poo-hooing what you see picture of or read about without even testing it is sort of an odd way to form an opinion don't you think LOL.

Test, play, and learn. That is where the fun is.

incognito
2007-04-16, 19:40
Check this out Incognito a piece of birch fungus cut in half a cat food can and grill. The water only got warm you think i need a windscreen:bandit:

http://i33.photobucket.com/albums/d52/oops62/stoves%202/th_fstove.jpg (http://i33.photobucket.com/albums/d52/oops62/stoves%202/fstove.jpg)

Don't use a windscreen as long as you're doing it on your workbench.

Look at this photo and you may get an idea (woodsurvival.com/survival/fire/tinder/tinderfungus/spolypore/part2.html)how to use the conk fungus.

(woodsurvival.com/survival/fire/tinder/tinderfungus/spolypore/part2.html)

Storm is a friend of mine. Here is a photo of him, (woodsurvival.com/survival/fire/tinder/tinderfungus/spolypore/part3.html) looks like me.

(woodsurvival.com/survival/fire/tinder/tinderfungus/spolypore/part3.html)

When I click on the links they don'tgo through, so use the info in parenthasis to log-on.

SGT Rock
2007-04-16, 19:49
I couldn't get those links to open, hmmmmm.

JAK
2007-04-16, 19:53
I would agree that you want to concentrate heat on the bottom, but that combustion air then moving up and around the sides can give some additional heat transfer, and you maximize this 'waste heat recovery' with a wind screen, and perhaps even more with an insulated wind screen. Making the gap smaller can have some benefit, as long as it doesn't reduce flow excessively. Another potential source of heat loss is too much combustion air, which could be corrected by ensuring the wind screen goes right to the ground and then tuning the inlets at the bottom and the gap on the sides of the pot. For slower heating, insulation with the ground might be worth the weight, especially in winter, and an insulated lid also. Keeping the weight of all the components is important also, not just to keep the weight down, but so it doesn't steal too much heat. Not so important for the pot as the other components that might heat up more and not get a chance to release their heat to the water later, the wind screen for example. It would be interesting if the wind screen could be insulated and be quickly adjustable to provide just the right gap when serving as a wind screen, and then instantly switch to no gap when serving as a cozy. Just some more random thoughts. With wood stoves the priorities are a little different as it is mostly smoke and mess you are trying to minimize, rather than excessive heat loss.

SGT Rock
2007-04-16, 19:58
I would agree that you want to concentrate heat on the bottom, but that combustion air then moving up and around the sides can give some additional heat transfer, and you maximize this 'waste heat recovery' with a wind screen, and perhaps even more with an insulated wind screen. Making the gap smaller can have some benefit, as long as it doesn't reduce flow excessively. Another potential source of heat loss is too much combustion air, which could be corrected by ensuring the wind screen goes right to the ground and then tuning the inlets at the bottom and the gap on the sides of the pot. For slower heating, insulation with the ground might be worth the weight, especially in winter, and an insulated lid also. Keeping the weight of all the components is important also, not just to keep the weight down, but so it doesn't steal too much heat. Not so important for the pot as the other components that might heat up more and not get a chance to release their heat to the water later, the wind screen for example. It would be interesting if the wind screen could be insulated and be quickly adjustable to provide just the right gap when serving as a wind screen, and then instantly switch to no gap when serving as a cozy. Just some more random thoughts. With wood stoves the priorities are a little different as it is mostly smoke and mess you are trying to minimize, rather than excessive heat loss.


Good points JAK. And with that keeping the weight down - if you add 8 ounces of weight into a system to save 3 grams of fuel per boil - then what is the point? That is something I have had to balance as I try to figure out how to scavange the BTUs.

SGT Rock
2007-04-16, 20:02
This link worked:

http://wildwoodsurvival.com/survival/fire/tinder/tinderfungus/spolypore/part3.html

JAK
2007-04-16, 21:06
Check this out Incognito a piece of birch fungus cut in half a cat food can and grill. The water only got warm you think i need a windscreen:bandit:

http://i33.photobucket.com/albums/d52/oops62/stoves%202/th_fstove.jpg (http://i33.photobucket.com/albums/d52/oops62/stoves%202/fstove.jpg)Really cool picture. Great flow visualization.

Lanthar
2007-04-17, 13:16
Good points JAK. And with that keeping the weight down - if you add 8 ounces of weight into a system to save 3 grams of fuel per boil - then what is the point? That is something I have had to balance as I try to figure out how to scavange the BTUs.

Yup, that's always the balancing act. Of course, as you've said before if you can re-use that 8ozs as your cozy, your net increase isn't nearly as high...

BTW - As an aside, I'm really enjoying watching your transformation into a thermodynamicist, complete with terminology and everything ;)

Skidsteer
2007-04-19, 09:40
Good points JAK. And with that keeping the weight down - if you add 8 ounces of weight into a system to save 3 grams of fuel per boil - then what is the point? That is something I have had to balance as I try to figure out how to scavange the BTUs.

I played with this idea (http://www.whiteblaze.net/forum/vbg/showimage.php?i=11895&catid=favorites)some last year, Sarge. I'll be very interested to see what you come up with.

Sgt.Krohn
2007-04-20, 12:10
Rock - I really gotta give you some photography lessons ;-)

also- we should just quit attaching photos to your server space (would save a ton of bandwidth) and teach everyone how to re-size their images, upload them to Tinypic and them drop them into their post with image tags [img]

from my instructions on TexasKayakFisherman
~~~~~~~~~~
RE-sizing photos & posting them
~~~~~
The first thing you need to do is to make sure the photos aren't too big to post. If you don't have any kind of photo editing program - one of the easiest methods is to use this webpage
http://www.lan-lord.net/photo_resize.aspx
Remember to save the new smaller file as a new different name or you will corrupt your larger original file

Once you have a smaller/640pixel file saved to your desktop you can load it into your post by going to
http://tinypic.com/
and upload the new re-sized photo file and upload it to TinyPic's website. Once the photo has been uploaded you will see the new URL for the photo posted in three different ways. The one you need to use for the image to post in your message is the middle one where you see the URL surrounded by "image" [img] tags. Highlight then copy & paste that line onto it's own line in the body of your post and your image will appear in with the text.

SGT Rock
2007-04-20, 21:49
Yup, that's always the balancing act. Of course, as you've said before if you can re-use that 8ozs as your cozy, your net increase isn't nearly as high...

BTW - As an aside, I'm really enjoying watching your transformation into a thermodynamicist, complete with terminology and everything ;)
Am I at least getting some things right? I have been trying to learn this stuff through discovery learning and some internet research. Not the most efficient way of doing it.

JAK
2007-04-21, 09:41
Actually I think discovery learning of project based learning is the best way to learn applied science or engineering, perhaps the only real way. You gotta be will to get your hands dirty, and do a little math now and then, but the main ingredient is to be driven by curiousity and need. Most of the old timers, James Watt and Thomas Newcomen and so one, they were both mathematicians and mechanics. Watt studied math then instrument making. I think Newcomen was actually blacksmith first, and then a preacher maybe, but anyway you get the idea. Those were the good old days though, for curious individuals wanting to tinker like we do, but in a big way.

Lanthar
2007-04-21, 10:40
Am I at least getting some things right? I have been trying to learn this stuff through discovery learning and some internet research. Not the most efficient way of doing it.

As JAK said though, not the worst way of doing it either. You've always had an intuitive (at least I presume it's somewhat intuititve) grasp on how heat flows, lately though it seems you've been using more 'scientific' terms rather than layman's terms. :albertein

One correction though, heat doesn't actually rise. :wink: Heat moves unilaterally in all directions.

Hot gases will rise, however, due to their lower density than cold gases (causing the cold gases to drop in the same space). Therefor, if your burn rate is low enough, it would only be cold gases dropping out underneath your windscreen. I don't know if this makes sense with words but if you made a taller stand you COULD wrap the insulation tight around the pot (extending down past the bottom of the pot but down low enough to cover the burner). Then a short Al windscreen would protect the burner from wind and you'd have more than enough oxygen for the flame. Keeping the burn rate low enough, you'd create a nice bubble of warm / hot gases right under the pot that, when an idividual gas molecule had given up enough heat (making it now, cold) would drop out of the way for more hot molecules to take it's place.

How to gauge whether it was working? Do you see flames poking out around the bottom of the CF windscreen? Burn rate is way to high or the bubble size is not large enough. No flames? Put your hand down near the bottom of the CF screen, can you feel heat coming out from around it or does is seem cool? If it seems coold, then you're trapping pretty much all of the BTUs in that bubble (if you remember reports of jetboil owners being able to put their hand near where the burner / flux ring exhausts... same kind of subjective test).

However, I suspect this will get you into the realm of, as you said "adding 8 oz to save 3 oz". But, if you can get it to work then you can back off to start tweaking that ratio.

On immediately benefit of the insulated windscreen is that you can get it very close to the pot without it absorbing any of the heat from the rising hot gases (I presume the CF material has a relatively low thermal conductivity). Allowing you to wrap it tighter to the pot and increase residence time of the hot gases against the pot (due to restricting how much space there is and not letting them get away, only hot gases in the film area - directly against the pot - will actually transfer heat while moving up the sides... well, some will transmit due to radiation, but that's less effective).

sailingsoul
2007-04-21, 23:49
I've just spent 1/2 hour trying to find a link posted a few months back. It was a video on a stove developed in africa with and insulated fire box. In explaining the design it was stated that there was a space between the top fire and the bottom of the pot. Thus alowing a higher temperature. I remember that point because i was supprised that the hottest point wasn't in the fire. Does anyone recall the link.

sailingsoul
2007-04-21, 23:57
The reason I asked is because a stove like the rocket uses and insulated fire box. Has anyone applied that aspect in design to an alcohol stove?

SGT Rock
2007-04-22, 09:16
Well if this works, then this would be an insulated fire box.

SGT Rock
2007-04-22, 09:24
As I recall, some of those heat shields Nasa uses are made from carbon.

JAK
2007-04-22, 15:44
The other reason they say heat rises is because convective currents are much stronger to or from a horizontal surface if the hot is under the cold rather than the other way around.

The fire is the hot spot, the insulated zone in the rocket stove is to complete combustion at high temperature before transfering heat to the pot. If you allow a wood fire to contact the pot you get better heat transfer, but less complete combustion and more soot. The other reason for the rocket zone is to generate draft, which is neccessary to drive the convective heat transfer from the gasses to the pot. Because of something call Reynolds Analogy, the heat transfer in the boundary layer is proportional to the friction in the boundary layer, so you want to reduce friction everywhere else, but there is no way to avoid friction where the convective heat transfer occurs, so you need to generate the draft. It helps if the wind screen is insulated, not just to reduce heat loss to the environment, but also to reduce the friction against the wind screen. Interesting eh. Anyhow, a fan can be used to provide the draft with less height, but height can also be reduced by putting the chimney before the pot, for higher temperatures and more draft for the same height, as long as the chimney is insulated, and then insulating the wind screen also. It does makes for a more awkward stove, but I think if you could keep is small enough you could keep it light. A smaller wood stove needs to be better insulated though. The hobbo approach is simpler and lighter, though less efficient - bigger fire, let the volatile gasses burn off, then cook with the coals. One million hobbos can't be wrong.

Here are the rocket stove links. Good info for all wood stoves, and all stoves in general. Some of the principles apply to all stove strategies, whereas some of the principles only to the rocket stove or similar strategies.

Discussion of Design Principles:
http://www.repp.org/discussiongroups/resources/stoves/Still/Rocket%20Stove/Principles.html

Power Point Presentation:
http://web.mit.edu/ats/Documents/lesotho%20refresher%20oct%2005.ppt#12

Detailed but easy to read Design Manual in pdf format:
http://bioenergylists.org/stovesdoc/Pcia/Design%20Principles%20for%20Wood%20Burning%20Cooks toves.pdf

Here is a video on a camping rocket stove. It's long, but very detailed.
Looks heavy, and not that insulated, but at least its more than an idea.
I would like to see it made smaller, with more ceramic wool and less metal.
A true rocket stove would have a windscreen also, with a very narrow gap.
http://video.google.com/videoplay?docid=797446823830833401

sailingsoul
2007-04-22, 23:46
Thanks jak, great info',,,,,Oh pooh!! I just spent 20 minutes typing a responce and lost it!!!! I HATE when that happens, Oh well. In a nut shell , I have seen a different link months back. (like Dec.) When I find it I'll post it. SS :captain:
P.S. And Yes Sgt', carbon (& graphite) is used by Nasa for thermal insulation

Lanthar
2007-04-23, 11:32
Last night on my drive home, I was thinking about how this could probably be used to make a rocket stove... JAK weren't you working on one in the past? Is this carbon stuff that SGT Rock found more or less dense than the ceramic wool you're thinking about using?

Skidsteer
2007-04-23, 18:43
Last night on my drive home, I was thinking about how this could probably be used to make a rocket stove... JAK weren't you working on one in the past? Is this carbon stuff that SGT Rock found more or less dense than the ceramic wool you're thinking about using?

Plumber's cloth (http://www.whiteblaze.net/forum/showthread.php?t=16053) is similar in texture and density to felt.

A 1/4" x 9" x 12" sheet weighs 1.65 ounces.