The Evolving Backpacking wood/alcohol/solid fuel Stove- 2012 edition

I think I have finally come close to my version of the perfect home made backpacking wood stove.

Uncle Tom's Home Made Wood Stove
Uncle Tom’s Home Made Wood Stove

In 2007, I started my thru-hike of the Appalachian Trail with a wood stove.  For that trip, I disassembled an older version of the Sierra Zip Stove , replacing the inner chamber with a modified titanium Sierra cup from REI, and ditching the old heavy base plate in favor of a Lexan replacement, with the addition of three Coleman folding legs. It weighed in around 9 ounces.  The stove worked fine, but the Lexan base did not hold up (it cracked).  I replaced it in Hot Springs, N.C. where I bought a simple Etowah alcohol stove that held up well for the remainder of the 2,175 mile  walk.

But my preference for using a wood backpacking stove led me to sign up for a stove building workshop at Snow Walkers’ Rendezvous in November of 2007.  The workshop was put on by Don Kivelus, of Four Dog Stove Company. You can view all of Don’s products here: Catalogue.    Don sells a titanium wood backpacking stove, the Bushcooker.   I viewed the stove at his vendor table and when I inquired about purchasing one ( for $120) , he told me that I could buy his used demonstration model for $60, but then Don encouraged me to take his Sunday morning workshop for $10 and make my own low cost version.  I had a blast with the workshop.

We each made our stoves out of one 1-quart paint can, one 1-pint paint can, 6 sheet metal screws and and six 1/4” bolts. No special tools were needed. We used only a can opener, knife, and screwdrivers.  I have a video of that stove in use on YouTube , that has over 38,000 hits to date.
I used the stove throughout the 2008 backpacking season, and felt it could be improved.

For the last week I have been making and testing stoves.
The finished stove, including windscreen, weighs a mere 5.7 ounces.  I filled the inner can with 2.9 ounces of air dried wood, scraps really, from around my wood pile.  On 12/21/08, the air temp was a crisp 17 degrees.  I was able to rolling boil a pint of cold tap water in 8 minutes and 45 seconds from touching off the birch bark tinder with a match.  I removed the boiled water, made a pot of tea and then checked the stove at the 20 minute mark and could still see a small bed of coals glowing inside.  NOTE:  I did not add any additional wood after the stove was tindered. There were occasional gusts of wind as well.  I plan to take along a sheet of aluminum foil to use as an emergency  windbreak.

The most interesting finding about this new version is that it did not have to be tended.  The first stove required me to frequently remove the cook pot in order to add additional wood.  This one has been redesigned to allow adding wood without removing the cook pot, for example if you wanted to simmer for 10 minutes or so.  But I never needed to add any additional wood.

I also revisited an older fire building technique. This stove burns from the top down. I packed the stove with 2.9 ounces of wood, lit it from the top, and forgot about it.   Flames exit the top inner holes in this stove after the burn is halfway done.

At our summer camp,  we have a older commercial wood stove that operates under the same procedure, brand name Tempwood .  It was marketed in the 1970’s as a downdraft model. You load it with wood and kindle the top, just like this little stove.  The Tempwood works just as advertised.  There are disbelievers out there that are adamant that any backpacking wood stove can’t be a true downdraft unit, but doubters can check out the data/diagrams on the Tempwood, play around with this stove and decide for themselves.

Construction  Details:
Outer Can– 1 quart paint can, bottom removed and 1/2 “ holes drilled along base. I bought my can for $1.70 at Lowe’s.  You can use old paint cans as well, just clean them out, or throw them in a fire.  I didn’t drill all the way around,  but left untouched a 4” side of the can. You could do just half the can, in case you wanted to block wind, and add more holes later if you wanted to.   A #1 Irwin Unibit cuts through these cans quickly , but a regular drill bit is also OK.  It is easier to drill out the side holes on the paint can if you remove the bottom after you drill out the holes.

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Inner can – best choice is a Progresso soup can, 1/4” holes drilled through bottom.

Bottom of inner can with 1/4# hole pattern
Bottom of inner can with 1/4″  hole pattern

Any 20 oz. can works as well, such as DelMonte or Dole crushed pineapple.  Drill out a ring of 1/2” holes on the top of this can, about 1” apart and centered about  1” below the top of the can.

Friction fit the inner can into the paint can.  Keep pushing, and you will feel it lock.  I suspect you could use high temperature JB Weld to cement it in, but it functions with the press fit.  For long term use, I secured the fitment by screwing through the top sides of both with three 1/2 sheet metal screws.  No drilling required.

The pot stand I made was constructed from a large can of canned chicken with 3/8”  holes drilled and the use of tin snips.  I fit it into the groove of the paint can for stability.
Morning coffee anyone?

[Editor’s Note, 7/14/2012]I made two modifications that retains a 5.7 ounce stove weight. The first minor mod is with the attachment of the inner to the outer can, using three small nut/bolt/washer assemblies, rather than pot rivets. The other change is with the inner can. I substituted a standard 1 pint paint can for the soup can, cutting out the base with a standard rotary handle can opener. The lid is discarded. The pint can is reversed for insertion into the quart can, with the bottom now the top, and remember to drill a row of holes below the “new top” before securing with either sheet metal screws, pop rivets, or little nuts and bolts. Instead of using the old pint can lid as a base for the firebox, a new part is cut resulting in a 3 and 1/4″ diameter piece of metal stock.

Base

Here is a diagram of the cutting pattern.

cut pattern for base

Thin sheet metal stock could be used for these finned assemblies that could be cut with metal shears and then bent with a pair of needle nosed pliers. I was fortunate enough to have an extra titanium fin assembly that Don Kivelus gave to me that fits the 1 pint can perfectly. It drops right in through the top and does not have to be secured. Not many of us have sheets of titanium lying around, but the advantage of titanium is that this will be a lifetime part. The rest cheap cans will rust and have to be replaced, but not the titanium fin assembly, which can be moved into the replacement stove, if ever necessary. I have burned out my original firebox after 4 years.

I was able to get a boil from 2.7 ounces of wood, with 16 oz.of tap water just before the 5 minute mark, lighting and building from the bottom, quickly adding dry wood. Granted, it is 90 degrees out, rather than the 17 degrees during the original tests. I was not using a wind screen.

The addition of the finned base plate appears to bring additional burning efficiency due to the vortex created by the air moving upward into the burn chamber. On 7/25/12 I received confirmation from Don Kivelus about the improvement in efficiency using the finned grate .  Here is what he sent me:

Kivelus installed his “fan grate” in the “Bush buddy” and found it improved the performance by 10-20%.
His results, as follows:
16oz water, 80 degrees F, SP900 pot /with lid
1 oz wood dowels/ 3 cc alcohol
4DS quick burn technique- [The quick burn technique -> stack your fuel wood in a random fashion in your fire pot to just below the top holes, then dribble 3-4cc alcohol on the fuel. Light, place pot, walk away and let food cook !!!]
No fan grate:  4 minutes 50 seconds = 200 degrees / no rolling boil achieved

Fan grate installed: 4 minutes 50 seconds = 207 degrees/6 min. rolling boil @ 212 degrees

Another big advantage to using the 1 pint, rather than the soup, can for the burn chamber is that the shorter vertical height allows enough height to place an alcohol burner cup under the stove. Find a small metal cup that holds 1 oz of yellow Heet or denatured alcohol- fill it, light it, and then after a few seconds place the stove over the burning cup, carefully! If you have never used alcohol for boiling, do this in the dark the first time, so that you can see the flame pattern, which is invisible in strong daylight. Also be very careful of spilling the fuel. I highly recommend taking along some alcohol so that you have a backup when you can’t find dry firewood, or just want to quickly get water boiling at the end of a hiking day. I was able to get 16 oz. of water to boil in 5 minutes, 10 seconds.

You can also use solid fuel tablets ( Hexamine), sold as Esbit or Coghlan’s fuel tablets. (Two Coughlan’s = 1 Esbit). Just light and drop into the burn chamber.

[For those of you who live in the midcoast Maine area, I’m scheduled to conduct a workshop on building your own backpacking stove through FiveTowns Adult Education on Tuesday night, 6 PM, October 16, 2012. $10 materials charge.]

A brief video of the stove in action.