FireMaple Petrel cup with Heat Exchanger test

[TooOld2Hike_EP]

Always intrigued by good engineering ideas, I bought - and tested - a FireMaple Petrel cup which has a heat exchanger on its bottom. (Like a JetBoil?)



When backpacking/camping, I put a cup, filled with 400 mL of water, on a stand and use Sterno to heat the water to rehydrate food in pouches.

It typically takes 8 minutes (warm outside temps) to 12 minutes (cold temps) to bring the water to a “boil.”

Boil in quotes because when I did the following testing, I found that water starts to bubble at 70 degrees C. It takes longer to become "hot." (Explains why my chicken chunks have been crunchy.) So I tested to 90 degrees C here, using a digital thermometer.

I poured equal amounts of equal temperature water into my old cup and the Petrel and put each cup on my stand, one at a time, over a low flame on a gas range. I timed how long each took to reach 90 C.


(You can’t see the air inlet holes at the bottom of my stand because you’re seeing the “wind” side of the stand.)

I didn’t change the (low) setting for the gas range during the experiment and approximated the flame from a can of Sterno.

It took 17 minutes for water to reach 90 C in my old cup. It took 8.5 minutes in the Petrel.

Some of that is due to the fact that the Petrel is a little wider than my cup. So it fits “snugly” on top of my stand, which doesn't allow heat from the Sterno to bypass the Petrel.

Still, the bottom line is that I can boil water faster using less fuel with the Petrel than with my old cup.

[LindaAnn]

How much does all this weigh???

My stove and pot (including lid) weigh 4oz total, and boil water very quickly. I’ve never timed it, but definitely less than 10 minutes. If I use my better stove, the combined weight goes up to 5.8oz, but it seems like the water takes about the same amount of time to boil.

[xsproutx]

@LindaAnn
Sounds like he's using Sterno which just doesn't get that hot really... combined with it being a "solid" fuel, you get all the benefits of being heavier while also performing worse.

[TooOld2Hike_EP]

5.7 oz for the cup itself.

There are videos comparing the heat exchanger cup on a stove to a Toaks. Having a heat exchanger is faster.

Physics says that the hotter the flame, the less difference in time to boil there will be. So for me with Sterno it makes a big difference.

The argument for those using gas stoves is that you can set your stove lower for the same performance and save fuel during a thru-hike. (IIRC, something like a 25% savings in fuel.)

A full can of Sterno weighs 7 oz.

For what little backpacking I do, it works for me.

But mostly, it was interested in the experiment.

[chumley]

@LindaAnn
I haven't done a deep dive in the YouTubes, but there's probably a thorough cost-benefit analysis on this already posted in a half-hour-long snoozefest video. The Sterno cans are just $2.50 apiece and burn for 4 hours. So even if it takes 6 times longer to boil two cups of water (Jetboil claims 100 seconds), and a $7 8oz propane tank boils about 8 liters of water (oh, wait, nevermind, that ends up more economical than sterno fuel).

If you have nothing better to do when you're sitting around camp on a pleasant 60-degree evening, the time to boil is irrelevant. If it's freezing and you want some hot soup or morning coffee, or if it's raining and you're cooking in your vestibule, time is more of a factor.

But when efficiency is not an issue, I would consider the cute little tealight candles. They last for months in the guest bathroom at my house, are much cheaper than poo-pouri spray, and IKEA sells 100 of them for $5. Two or three of them should boil water in an hour or so if you have some foil to direct the heat to your pot.

I don't know if these also come in citronella flavor, but if so, it might be possible to kill two mosquitoes with one match. Win. Win. Win.

[LindaAnn]

@chumley
When I’m hungry, the time to boil is very relevant. Weight and time are what I care about.

I would, however, like to see a bunch of tea lights fall out of your pack and roll all over the place. While I’m already eating my dinner.

[LosDosSloFolks]

@chumley
In my backpacking days I used, (and still have) a little Svea that burned white gas. It could boil a litre of water in under 7 minutes but it was heavy compared to what's available now. It was the top dog in the 70's.

[Alston_Neal]

@LosDosSloFolks
Nice article on your stove.
https://www.rei.com/blog/camp/gear-i-ho ... ping-stove

[LosDosSloFolks]

@Alston_Neal
That's the one. It's as loud as they say! Sounds like a rocket due to the pressurization of burning some fuel on the top of it prior to lighting.

[chumley]

@Alston_Neal What an enjoyable piece of literature! Perhaps there's hope for REI after all. The new marketing lady should abandon overpriced trendy retail clothing and gear, and transition to publishing!

[azbackpackr]

I still have my Svea stove, somewhere in storage.

[RedRoxx44]

Cheap ( 12 bucks) china stove from ebay and 3.5 oz fuel and my old titanium pot prolly 6-7 oz and takes less than 10 min for sure. Also has the auto ignition. I ending up getting like 4 of those stoves because I liked them so much and have one in my car camping kit, one for the backpacking and a couple of spares in case of breakdown or sand/ dirt exposure. The original ones have been in use about 10 years.

[Pivo]

@xsproutx
This is exactly why banquet workers use hot water in the chafing dishes/ banquet steam pans, using Sterno to heat the water would take too long, or never happen, and the food would be cold and unsafe to serve.

[xsproutx]

Yep. Sterno is great for keeping things warm but sucks at boiling because it burns something like 25-35 degrees below boiling. You can boil water with it with a lid and/or enough mass (which would take even longer) but you're fighting physics to get there basically. That's the main reason it's faster with his newer setup; the snugness captures more of the energy and increases efficiency.

[Alston_Neal]

One of the things that perplexed me about the Svea was although it was small and light, carrying the one gallon white gas can could prove to be annoying.

[LosDosSloFolks]

@Alston_Neal
Jesting aside, I had the coolest spun aluminum container for holding the white gas. The weight was basically just the amount of gas which varied on the # of days I'd be hiking. I wasn't a "grammer" when I backpacked but it was pretty light even with enough fuel for 7 days which was my longest trek in the canyon.

[TooOld2Hike_EP]

It works for me. I see ppl in videos with the cup/pot way up high on their stoves, resting on a small 3- point platform. Looks easy to tip over and burn oneself and/or set the forest on fire. (A LOT of people in videos using their setup surrounded by dead leaves.)

(Same concern when I see ppl leave their Sawyer on their Smartwater bottle in their backpack pocket. One drop of the bottle and the filter might crack open.)

This particular new cup has insets for the prongs of most stoves, which lowers the CG of the cup a bit and acts to capture the cup somewhat.

My can of Sterno is very stable, sits on the ground and not likely to tip over. Nice and quiet too. I start heating water before I inflate my sleeping pad, so it works out. Time/ability to boil has not been an issue. (Even in my first venture in February on LSM two years ago.) And with this new cup, my experience should be better.