[pct-l] Isobutane Canister performance

[Matt Signore]

That BPL article supports some of what Mary says.  However, the ability to
judge how many uses you have left in a partially used canister is where the
article diverges from what Mary believes.  As the canister is used more the
mix is less consistent.  So, you cannot use weight of a canister to judge
how many boils you have left.  Because it could be the wrong part of the
mix remaining inside the canister.  When you use the words "definitive
findings" I feel they should be definitive.  Also the amount of time to
boil water varies upon altitude.  So, yes there are even further
discrepancies.

"Only a Sith deals in absolutes" - Obi Wan Kenobi (Not that I am calling
Fireweed a Sith.  I just love the quote)



On Wed, Sep 11, 2013 at 12:21 PM, Dan Welch <welchenergy at gmail.com> wrote:

> Mary,
>
> I think anecdotal results have merit - especially when they largely jive
> with "lab test" results that have been conducted by others.  Roger Caffin
> and Will Rietveld of BackPacking Lite have published a number of articles
> on canister stoves and their efficiencies (including comparisons to alcohol
> stoves.)  Their testing is mostly under strictly controlled test conditions
> - so strictly controlled that they gave me pause.  As backpackers we don't
> operate under controlled conditions - but lab tests can still give good
> guidance for making decisions.  I just am much more comfortable when
> anecdotal evidence corroborates lab tests.  So thanks for sharing your
> results.
>
> Anyway, BPL has tested a number of canister stove rigs under different
> wind and temperature conditions.  Under calm conditions, they found a range
> of 10-15 gms fuel per L "boiled" (see their definition and partial test
> description below.  The article gives much more detail.) They too were
> using MSR cartridges and their findings can be reconciled with your finding
> of 6.1 gms fuel for 1 and 3/4 cup (equal to 14.7 gms per L.)
>
> That was for clam conditions.  They found that wind degraded this
> efficiency greatly.  In a 12 mph steady, controlled, wind, fuel use almost
> doubled.  But, consider that a 12 mph STEADY wind is pretty unusual AT
> GROUND LEVEL.  In this type of condition most people would be seeking a
> more sheltered spot for cooking, so I consider this extreme.  A good test
> for "worst case" conditions, but not something to judge fuel use by.
> Importantly, adding a windscreen recovered most of this lost efficiency.
>
> Notably, the JetBoil systems had the best efficiencies in calm conditions
> (~10 gms per L boiled) and the FUEL USE WAS LARGELY UNAFFECTED BY WIND.
> These articles are the reason I purchased a JetBoil.  The efficiency and
> lack of wind effect on the JetBoil has been borne out by my field tests
> (conducted in 3-season Smokies Mtns. conditions and Summer in the Sierras &
> Rockies high country.)  However, my records are nowhere near as
> "scientific" as the lab studies - but they are applicable in their own
> real-world way.
>
> Thanks again,
> Timberline
>
>
> Excerpt from Will Rietveld article (subscription required):
>
> http://www.backpackinglight.com/cgi-bin/backpackinglight/lightweight_canister_stoves_test_report.html#.UjCcaczD_IU
> "Tests were conducted at 6,650 feet (2,027 m) elevation. A 1.5-liter MSR
> titanium pot 6 inches (15 cm) in diameter was used for all of the tests,
> except for the Jetboil stove, which has its own pot. The pot and stove were
> cooled between test runs. Boiling was measured with a signaling digital
> thermometer at 199 °F (93 °C, the boiling temperature at 6,650 feet
> elevation is 201 °F; we measured at 199 °F to avoid the vaporization
> process) with the temperature sensor placed in the same position each time.
> Each test was repeated three times."
>
>
>
>
>
>
>
>
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-- 
Matt Signore
pcthandbook.com