All aluminum flat bottom Foster’s cans

Looks great, David!

I'd be interested in the burn efficiency data vs the rounded bottom can.

How do you seal the two cans together? With some adhesive or just pressure fit? If just pressure, are you concerned about the can eventually leaking as it eventually acquires some wear & tear, dents & dings? If adhesive, are you concerned about it leaching into the water being boiled at all?

Jonathan,

I'll do some comparison burns if I get a chance before 8/18, when I head back to grad school.

At present, the cans are sealed together with a press fit. I did a few boils on the kitchen stove, no leaks. I'm taking one with me on a trip to the Sierras next week, to see how it holds up. Long term, it might be vulnerable to wear & tear, etc., but I won't know until I've been using it for awhile. If it starts to leak at some point, I'll probably just make another one.

On the other hand, I have acquired some "food grade" silicone sealant which I will probably try eventually. My understanding of "food grade" means that it does not contaminate the food. But my preference is to not use sealant if it can be avoided.

Sorry I ever said that :-(

It looks super good new. It's looks change over a period of time due to greasy/oily hands, lime build up from hard water and then comes the natural oxidation of the raw aluminum.

In the 3rd photo it shows the radius of the can bottom on the left. That area is going to fill with water if not fully packed with silicone. No matter how tight you press fit the top into the receiver bottom, water will find it's way into the joint. At some point in time something is going to start growing in there. Fill it with silicone to be safe.

Yes, there are advantages to a flat bottom Fosters pot:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=93058

Thanks Dan. Good advice on the silicone.

I made one of these this weekend, and it turned out well. Thanks for the tip! Mine made a fairly loose fit so I epoxied it in place (silicone had cured in the tube). I probably could have cut the fosters can off in the straight section.

I make the cans differently now. I cut the can at the bottom of the straight section and stretch it a bit over an intact can, then slip the flat bottom up inside. Nice tight fit and only takes a tiny bit of food grade silicone sealant in the seam.

I also wire brush and sand all of the BPA plastic liner from the cans.

Wow, those really do become dog ugly after a while ;)

Those are some bold ridges in the can. Nicely done.

I haven't seen an eraser shield in use for a couple of decades now.

Where and how do you apply the silicone? I envision that you do it after inserting the flat bottom, applying a bead along the interface inside the can and working it along the gap so no water can work its way down. But that seams (pun intended) like a pain.

@Stephen:

I prefer to think of the cans as having a "rugged, industrial" look. But yeah, fugly except in a form-follows-function sort of way. They come out of the annealing process looking that way. I think it's variations in the aluminum oxide that forms on the surface.

Bold ridges = strong. Wish I could figure out how to do it without having to anneal the cans first.

Eraser shield: I'm old school. I've taken a few AutoCAD classes, but I'm working on a car project with variable radii arcs and compound curves and haven't progressed to the point where I can do those on a computer.

@Frank: Once I get the flat bottom started into the stretched can I put a very small bead of sealant at the juncture around the outside of the seam, then finish pressing the parts together and wipe off the excess sealant. Not difficult and pretty tidy.

So I had the top half of the cat food can still sitting there, and the Foster's can seemed unnecessarily tall, and a snap-on lid would be nice, sooo….

The photo shows it with two cups of water in it.

I had hoped for more rigidity with the cat food can top bonded on the beer can, but it isn't very stiff. It is plenty stiff for boiling water in and lifting it and pouring, but not as stiff as you would want for storage. Surprisingly, though, when I snapped on a plastic lid from an almond can, it becomes quite rigid at the top end. I guess you could just pop the top on the cat food can instead of using the safety opener, leaving the inner rim, and that would add some stiffness, but I don't think it is needed. Or you could just put the cutoff top of the beer can back on at whatever height you wanted after expanding it as you showed, though you wouldn't be able to use the plastic lid.

This is certainly not as nice as what you guys are making, but it is an alternative that most anyone could make. .80oz (.07oz less than with the original fosters top). The plastic lid from a BDA can is another .14oz.

Sweet! Great idea! I'll have to try that and add some ribs too, see how much that helps the rigidity at the top. Where do you get the snap on plastic lid?

Ha, at this point, the thing is more of an extended cat food can than a modified fosters can.

I used the lid from a 6oz Blue Diamond Almond can, but of course any lid that is designed for pet food cans will fit, and are available in the pet food aisle.

I've been meaning to get back to this thread. Here is my latest version. Not much different but I think the green cans with the horizontal design look better, along with a gold colored cat food can to sort-of match.

David, I suppose it is just differences in the local canneries, but for me the fosters cans slip easily inside the cat food cans, so I go with that. It would take a lot of stretching to get the cat food can on the inside.

You can't boil with the plastic lid, but you can use the cut-off lid from the cat food can for that. It stores neatly inside the plastic lid, or you might be able to use a rubber band to hold it on instead.

Pot: .73oz
Boiling lid: .16oz
Plastic lid: .14oz
Total: 1.03oz. Maybe I could cut off the pull tab and get it down to an ounce flat ;)
The pot volume is 600mL to the rim, could probably go a little shorter depending on how much water you use.

The top of the can seems stiff enough to me for use and for transport with the lid on, but the middle section is still a little susceptible to crinkling damage (I'm guessing here, as I've never used anything like this in the field). I carry a separate plastic cup, so it would be nice to find one that could go inside or outside of the pot to protect it. I found a pill bottle that I thought might fit the pot, but it is just a teeny bit too small inside. It would have certainly protected the pot, but weighed 1.7oz, so killed the benefit of the light pot anyway.

It would be nice to have some way to strengthen/protect the pot in an easy way that anyone could do. Anyone know of something that fits?

One thing I do is carefully cut out inside the rim of the plastic lid and it will snap on OVER the Foster's lid so you can easily carry both

Hmmm, I didn't have to modify the plastic lid at all. Here it is with the metal lid inside. It fits quite securely. Again, maybe a local difference.

Here is a can container made from two 1-liter soda bottles. 1.3 oz for a full size can, so maybe 1.1 oz for a cut-down can.

mine will do that too but the metal lid is tough to get out. Cutting out the center of the plastic lid, I can press the metal lid out.

Ok, I see what you mean now. You make the plastic lid into a ring it sounds like. This would reduce the ability of the lid to stiffen the top of the can by itself, but would still be fine with thermal lid inside. Thanks for the tip.