Short long copper aluminum Moulder Strips

[Jerry Adams]

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[Gary Dunckel]

What, Jerry?

[Jerry Adams]

Previously, there was a question about whether it was copper/aluminum or length of strip that was important for Moulder strip.

I’m mostly ignoring any personal offense that I didn’t intend.  This is just about how to achieve performance with the minimum weight.  And I don’t think it was ever well established how important length of Moulder Strip is.  And, for example, a Titanium Caldera Cone is still a Caldera Cone even though that is made with Aluminum.  If you make it with Titanium it weighs a little less but you can still extrapolate performance with Aluminum to Titanium.

I have four stoves:

Some are shorter, some taller.  BRS 3000 is 1.75 inches from the bottom to where the burner is.  Coleman F1 and Pocket Rocker are 2.5 inches.  Soto Windmaster is 3.5 inches.

A 4 ounce canister is shorter than a 8 ounce canister.  From where the stove screws on down to the fuel level (which increases as you use up the fuel in the canister).

I tested 3 configurations:

Long strip – Soto Windmaster with 8 ounce canister – the Moulder strip was 7 inches, 5.5 inches from where flame was to where the fuel level in the canister was – about twice the distance of first configuration.  I just tested a copper strip

Sort strip – BRS 3000 with 4 ounce canister – the Moulder Strip was 4.5 inches, 3 inches from where the flame was to where the fuel level in the canister was.  1 inch wide.  0.025 inch thick for copper = 0.47 ounces. twice as thick for aluminum = 0.37 ounces.  Aluminum has half the conductivity of copper so you need twice the thickness.  But it’s density is less than half so the conductivity per weight is a little better for aluminum.  (However the difference in weight is insignificant).

I measured the temperature of the canister with a LM335 sensor siliconed to the bottom of the canister.  I used a velcro strip to attach Moulder strip to canister = 0.1 ounce.

With the long strip (Soto + 8 ounce canister):

This was similar to my testing a year ago with aluminum.    The red line shows when the burner was on – starting at minute 0.0 and stopping at minute 3.0.  The temperature drops during the burn time – evaporative cooling exceeds the amount of heat coming down the strip.  When the burner is turned off heat continues to come down the strip so the canister temperature goes up.

This is sort of usable, but not very.  If I had a cozy on the canister maybe it would retain enough heat to boil water for my next cup of coffee.

With the short strips (BRS 3000 with 4 ounce canister):

The solid line is copper and the dotted line is aluminum.

They both worked about equally well.  The heat from the strip exceeded the evaporative cooling – the temperature increased during the burn time.  After the burner was turned off the temperature continued to rise, about 8 degree C more than starting temperature.  Especially if there was a cozy on the canister, it would retain this heat for my next cup of coffee.

My air temperature was 35 F which is where the cheap butane I was using starts to really slow down.  But, this should work well at much colder temperatures, especially if there was a cozy around the canister.  You would have to pre-warm the canister to start if it was much colder.  As has been discussed in previous threads.

There is a small difference between copper and aluminum.  With copper the temperature increased a little faster.  This would be an advantage because the canister will cool from evaporative cooling until the strip heats up next to where the fuel is.  Maybe that’s because the needle valve of the BRS 3000 was open a little more for the copper test.

On the other hand, the specific heat of copper is 0.39 J/gC, 0.90 for Aluminum a little more than twice as much.  If there is the same amount of heat flowing from the burner down to the canister, it will take longer for the temperature to increase down next to where the fuel is in the canister.

So, bottom line, Aluminum Moulder strip is insignificantly lighter weight, and performs insignificantly worse. I will try to never mention Aluminum Moulder strips again : )

But, what is significant, is to have the shortest possible strip – choose a shorter stove like a BRS 3000 and use a 4 ounce canister rather than an 8 ounce.

[Ken Thompson]

My Genuine Moulder Strip®️ is copper. As Moulder intended.

[Jerry Adams]

I will not suggest you switch to Aluminum

What stove and canister size do you use?

[Ken Thompson]

BRS 3000 and a 110 canister

[David Thomas]

“I have (only) four stoves”

Well there’s your problem, right there! – Hikin’ Jim

[David Thomas]

Love the sciencey graphs.  Thanks, Jerry.

I had been, inadvertently, testing Moulder Strips in extreme conditions (-15F, -21F) in their most favorable configuration (BRS-3000T on a 4-ounce canister).  To equal that with a taller set-up during Type 2 Fun, a thicker MS and/or a cozy might be needed.

One needs a Moulder Strip the most as the canister is almost empty (greatest distance from flame, lowest propane fraction).  In that usage, should we insulate the copper/aluminum strip from the steel of the upper canister with a strip of paper or cloth or duct tape or folded toilet paper – leaving only the bottom cm/inch of the MS contacting the canister?  Because heat conducted into the upper canister is lost to the environment before heating any liquid fuel at the bottom.  Or use a cozy – which has obvious, additional benefits.

[Jerry Adams]

If you put something between strip and canister up above, maybe it would push out the strip from the canister that much down below where the fuel is so would be worse thermal contact?

if you heat up the canister just above the fuel level it will slowly conduct through the steel of the canister down to the fuel.  Since it’s close enough to the fuel level maybe it will conduct fast enough to be useful?

it’s too bad the canister isn’t made out of aluminum rather than steel, that would be much better in cold weather (but would explode in warm weather).  It would be like one big Moulder strip

[Gary Dunckel]

Sir Moulder, do you care to offer your opinion here, or do you prefer to remain silent, as do I? I mean, why gild the lily?

[David Thomas]

Aluminum propane tanks are lighter than the steel versions.  They (and composite ones) are used in marine environments to resist corrosion, but I also see some being flown to remote locations in Alaska because the reduced air freight charges covers the added cost of the aluminum tank (over many uses).

A reusable (and Lindal-valve canisters are perfectly reusable, as you know) aluminum or titanium canister would be sweet.  I’ve fondled some aluminum hair products containers in the store and pondered if it could be adapted to a Lindal valve.

Yeah, in hot weather, heat radiated to the top of an aluminum canister would conduct down to the liquid fuel.

[Jeffs Eleven]

On a loosely related topic I used a wood stove (big cabiney- flat top one) in a cabin last weekend and was amazed how a 24oz Al pot boiled noticeably faster than my BPL 550.

I’ve known, but never I’ve never seen it head to head.

[Jerry Adams]

another loosely related topic is cooking people prefer aluminum or copper pans because they conduct heat better sideways.  If there are hot spots on your burner, the pan will conduct heat sideways so the heat is more uniform on the cooking surface.  You’re less likely to scorch your food.

with my Ti pot, if I have the burner on when cooking oatmeal, it invariably scorches where the flame is.  So I just turn the burner off before I add the oatmeal, but if I had to simmer something it would be a problem, although putting a small disk of aluminum under the pot would fix that.  Or copper

[David Thomas]

“So I just turn the burner off before I add the oatmeal, but if I had to simmer something it would be a problem, although putting a small disk of aluminum under the pot would fix that. “

I once had an automotive radiator over a 130,000 BTU/hour burner (for a remote hot tub on a caving trip) and the heat was too localized for the radiator (water in some tubes would boil while other tubes wasn’t getting heated.  A 6″ x 6″ metal plate would have been ideal (and I later used a railroad track plates that secures the rail and four spikes) but on that trip, I just used a flat rock.  It worked well enough as a flame spreader.  And I didn’t have to carry it in or out.

[Jeffs Eleven]

Ha! I forgot about that story.

 

I’m doing it wrong

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