Jonathan once bubbled...
whoa someone upset Northeastwrecks this morning! not sure of my maths - is a 19cf the same as a 3l? if so then plenty to get you out of a recreartional, non deco dive. If you're into deco then about as much use as a wet fart in a bath.....
when I am doing single tank cold water dives or deep non deco single tank I always like me trusty 3l pony to be around
yes - three rgs total
gee up!!
Actually, it has some use on a deco dive. If you crack the valve just a little it might bubble long enough for someone to find the body.
Not sure about the size conversion. The conversion is somewhere in my DM books. I'll let you know when I find it.
As to the rest, I'm not upset (except that we couldn't dive this morning due to heavy seas). I will say that I found the comments regarding doubles to be inaccurate and essentially meritless, except for the comment regarding costs, which I found to be on the conservative side (I'm looking at somewhere in neighborhood of 3K for a complete doubles rig, plus the cost of obtaining the Trimix cert. that I'll need to take full advantage of them).
I do get concerned whenever I see one of those little Pony bottles attached to a diver. Some time ago, I was fulfilling one of my DM certification requirements by assisting at an AOW class. Once student insisted that her 19 cu. ft. Pony was an adequate redundant backup.
Rather than put this person at risk or make a scene in front of other students, I asked her to meet me the next weekend for a no-deco dive on the Idene (90 fsw). I asked to borrow her Pony for a demonstration. We planned a nice NDL dive.
Just before we started our ascent, I switched to the Pony. I maintained a normal (no more than 30 fpm) ascent rate hanging off the line in a nice horizontal pattern while breathing at a normal rate.
My SAC rate is not too bad. However, I did not have enough gas to slowly ascend and complete the safety stops that I had contemplated (1 at 30, 5 at 20). Instead, I ran short during the 20 fsw stop.
This was not a big deal because this was only a simulated emergency. I still had my own bottle and I had plenty of back gas.
Some might say that this wasn't a fair test because I imposed too many stops and for too long. However, my definition of a redundant backup is that I can make my planned ascent, including all planned stops (whether required for deco or not) without running out of gas. I don't want to chose between growing gills and blowing off my planned stops.
In addition, this simulation assumed that I could immediately ascend. Whie this is usually true in OW dives, what happens if you are on the far side of the dive site when you switch to the pony? I've noticed that many recreational divers don't carry lift bags or reels. That means (1) a free ascent that could be well off from where the boat is looking for you; or (2) trying to make it back to the ascent line on that little bitty bottle.
If I were going to use a Pony specifically for backup, I would make it large enough to ascend from depth at a normal rate with all planned stops. I would also plan on an increased SAC rate because the chances are fairly good that something has gone rather badly wrong if I'm ascending on a Pony and that might cause me to breathe more heavily than normal.
Finally, I would also plan on being able to buddy breathe the Pony on the entire way up. I say this because, if my buddy is worth a damn, he/she has stuck with me through whatever caused me to need the pony in the first place; and, unless the reason for my pony deployment is equipment failure, my buddy might also be out of air.
For that reason, I might suggest a larger Pony bottle. My dive buddy chose an Al40.
