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    solo training vs firefighters training whats the difference

    I'm another 25 year veteran of the fire service and have been diving solo for somewhere around 10 years now. I started off in a rural volunteer department and ended up in one of the largest municipal departments on the continent, so I've done everything from 3 guys fighting a barn fire to a...
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    redundant air at less than 30'?

    One thought is that one will be more comfortable in an emergency with equipment that one is used to. So if you intend to carry one when below 30', then maybe it's a good idea to carry one above 30' too. Maybe even practice using it once in a while so it's a routine procedure in the unlikely...
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    familyman

    I think a line-of-duty death mitigates the loss somewhat. I am an avid motorcyclist, and have lost fellow riders and seen the effect of that loss on their families. I am a professional firefighter, and have lost co-workers and seen the effects of that loss on families too. In the latter...
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    Pony bottle - what size?

    Have a look at the spreadsheet I put together: http://www.scubaboard.com/forums/attachments/solo-divers/66656d1256070777-pony-bottle-what-size-ponybottlesizechart_v2_1.xls The spare air won't last long at any sort of depth. I understand they were originally developed to give crashed pilots...
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    average sac rate

    Interesting point. For air at room temperature I understood the difference at 3,000 psi to be about 3% for air compared to an "ideal" gas. At 4,500 psi, the difference climbs to 10%, IIRC. So it might be a factor for someone with HP tanks, but probably not so much for someone using conventional...
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    average sac rate

    Absolutely correct. One could liken it to driving a car, and watching the gas gauge. If you are driving your own car, you can glance at the gauge and decide if you have enough gas left to make a particular journey based on your knowledge of that particular car and how many miles you get to a...
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    ..Finally... I just did it!

    Congratulations. That's exactly how and why I ended up diving solo. Hard to resist all that water sitting right there whenever I'm ready for a swim. (BTW: it's called waterfront property because the dock is actually out front. The cars come in the rear of the property. Look at the...
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    Pony bottle - what size?

    I used 207 bar fill pressure for metric tanks. Volumes (in metric and SAE) for the various pony sizes were taken from the Catalina website. Attached is a version allowing for skipping the safety stop altogether. I hesitated to do this, as I don't want to encourage people to cut things too...
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    average sac rate

    I'm not an SDI instructor (or an instructor period) but may be able to shed some light on this: Technically, depth has no effect on your RMV. In that sense, it is a constant. It's not a true constant because it varies by rate -- you inhale X cu. in. of air per breath and Y number of breaths...
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    average sac rate

    SAC doesn't specify volume, pressure or mass for that matter. It's an imprecise term. I think pressure is a fair measure of consumption, and one that divers traditionally utilize (eg: Q."How much air did you use?" A."1200psi") -- provided the cylinder size is constant. The term RMV...
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    Pony bottle - what size?

    Ok, here's the second attempt. There are radio button options for Units of Measure, Time at Depth, Assent Rate, Stress Factor and number of Safety Stops. I added one more atmosphere of depth and any scenario that calls for a pony larger than 40 cu ft results in a call for doubles. The...
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    Pony bottle - what size?

    Good points. So as I see it, the variables (so far) might include: Conservativeness -- Cautious/Moderate/Confident (eg: time at depth; 1min/3min/5min?, assent rate; 1atm/min, 1.5 atm/min, 2atm/min?, normal RMV multiplier:x1, x1.5, x2?) Units of measure -- Metric/SAE Extra stop? and the...
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    Pony bottle - what size?

    Hey, if you can hold your breath for 5 minutes, I'm impressed! <lol> Seriously, the 5 minutes is a bit of a fudge factor, allowing for some time to deal with whatever the emergency might be. I picked that number based on other's experiences -- stuff posted on Accidents and Incidents, etc...
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    Pony bottle - what size?

    Actually, I used an Excel spreadsheet to generate the table above. If this works right, it'll appear attached to this post. If someone wants to add a metric table, feel free to modify it at will. I would suggest that the math be checked before it is hosted elsewhere. Just in case I made an error!
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    average sac rate

    Actually, PSI per minute was the way that I (and many others) were taught to calculate SAC too. Cu. Ft. per minute is more precisely referred to as Respiratory Minute Volume. So you're not weird.
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    Pony bottle - what size?

    How about a chart, based on maximum depth and Surface RMV? (I use the term Surface RMV advisedly, since there seems to be some confusion over the term SAC on this board.) Something like this: Solo Diver's Pony Bottle Minimum Size Chart: S. RMV .2 .3 .4 .5 .6 .7...
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    Pony bottle - what size?

    No apologies necessary. I didn't word things very well originally -- when I look at it again, it could certainly be taken that way. Anyway, I'm just throwing the suggestion out there for discussion. And yes, I like the idea of a sticky outlining all the pertinent considerations.
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    Pony bottle - what size?

    Understood -- and agreed. And actually the process you describe is similar to the one I used to settle on a 19 for myself. However, over the years the question of pony size seems to come up again and again. For one reason or another, not everyone seems prepared to delve into that level of...
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    Pony bottle - what size?

    Your answer got me thinking about gut feelings and rules of thumb. An oft-used rule of thumb is the rule of thirds -- the final third being the reserve for emergencies. In that vein, would it be reasonable to say that a good rule of thumb for the redundant emergency air supply is that a pony...
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    From the other side...

    A "license" is a permission to do something. It can be revoked. The PCOC card is a certification that (supposedly) you know what you are doing. Think of it this way: a person can attend a driver's ed course and get a pretty little certificate and card to present to their future insurance...
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