Posted by Kendall Raine on September 12, 2001 at 11:02:36:
In Reply to: I have to respond to that... posted by Cabo on September 11, 2001 at 12:16:23:
Several thoughts, Cabo, about ponies. What follows isn't DIR doctrine, but common sense.
1) Back mounted ponies where you can't get at the valve and reg are a problem. They constitute and entnaglement issue. They can't be passed off to someone else. You can't shut off the valve in the event of free flow.
2) Slinging the bottle from the harness-left hip and shoulder-solves all these problems. You can remove the bottle to clear an entanglement or to pass of to another diver. Even in the event of a free flow, you can breathe from the free flowing reg by turning the bottle on and off.
3) Many ponies are simply too small. If an OOA diver can breathe 1.5 ft3 at the surface, that's 6.0 ft3 at 100 fsw or about 60 seconds' worth. A pony that size is simply a chance for an OOA diver to run out of gas twice-the same reason a Spare Air works for helo crews (for which it was designed) but is worse than nothing in diving. A 13 or 14 Ft3 bottle is only twice as much and so of little value. A 30 ft3 bottle actually starts to qualify as an effective bailout from a non-OE dive. Depending on the dive, you might want a 40. A Luxfer 40 is about 1.5 negative in salt water full-not enough to impede trim and balance.
4) Oher viable sources of redundancy include a buddy and a set of doubles with an isolator manifold.