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<div class="moz-cite-prefix">On 25/01/2018 11:16, Rick Walsh wrote:<br>
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<div class="gmail_quote">On 25 Jan. 2018 8:07 pm, "Willem
Ferguson" <<a
href="mailto:willemferguson@zoology.up.ac.za"
moz-do-not-send="true">willemferguson@zoology.up.ac.za</a>>
wrote:<br type="attribution">
<blockquote class="quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">I am
working on the user manual. Because of UI changes, this
includes replacing all the images in the section dealing
with the dive planner. I am trying to get the
recreational planner to work and I have a problem. See
attached image.<br>
<br>
If the initial cylinder pressure is not set, then the
planner provides a dive at the specified depth and
duration is determined by the NDL, limited by the
present cylinder size and initial air pressure. So I
select a 12 litre 232 bar cylinder and do not set the
initial cylinder pressure.<br>
<br>
1) The ceiling and profile do not approach the NDL
limits based on dive tables, even with GF=90/90.<br>
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<div dir="auto">Hi Willem,</div>
<div dir="auto">In the example you provide, the air NDL at 30m
is 13min with gf 35/75. This looks about right to me. From
memory the Buhlmann NDL (gf 100/100) is ~17min, and the PADI
and navy tables are 2-3 minutes longer. Reducing the gf to
35/75 would reduce the NDL.</div>
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<br>
I suspect this is not the complete explanation. The NAUI, NOAA and
US Navy tables all give the NDL with air at 30m between 22 and 25
min. With gf=100/100, Subsurface gives 16 min. In addition, the
profile does not get close to the ceiling at NDL. I suspect that,
with initial cyl pressure not specified, the whole calculation just
does not work. Forcing the bottom time to 26 min (gf=100/100) brings
the ceiling close to the profile which is more or less acceptable.
So that part of the planner works. But if the bottom time is
specified as much shorter than 26 min, the NDL also is much shorter.
There is a problem or bug there.<br>
<br>
Then there is the question of the use of GF with recreational mode,
since the Bühlmann option has been *de-selected*. Does this mean
that VPM conservatism can also affect the profile? I thing there is
a need for me to document the way thing work because the current
text is clearly not sufficient. I have a feeling the only difference
between a conventional ZH dive plan and a recreational dive plan is
the latter's ability to automatically provide a NDL profile, which
in this case does not work anyway.<br>
<br>
<blockquote type="cite"
cite="mid:CAF+v9Jtps2agtuZrGdfU92aOUbAieMkTB60uvtQRcc0zEE1LVg@mail.gmail.com">
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<blockquote class="quote" style="margin:0 0 0
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<br>
2) Even more important, at the bottom it says that the
dive requires 1245 litres of gas, more than is in the
cylinder. But this is wrong because the 12 litre 232 bar
cylinder takes 2784 litres.<br>
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<div dir="auto">That looks like a bug. I'm guessing the
calculation here assumes the starting pressure was zero. If
you don't enter a starting pressure, the planner should assume
cylinder working pressure.</div>
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<p>I would agree. The gas volume calculation is accurate. The
cylinder volume/pressure is lost somewhere.<br>
</p>
<p>Kind regards,</p>
<p>willem</p>
<p><br>
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