Right now the pony reg is on a short hose on a bungee around my neck (like a DIR backup reg). I've practiced opening the valve and switching regs, but I'm sure that it will be a lot more stressfull in a real OOA.
I see. Now I understand better why you're asking this question.
I've thought about going with doubles when I go with the bp/w, but I believe I've read a couple of times that a doubles setup isn't recommended when diving in cold water with a wetsuit, due to the large amount of weight that I'd need to wear and not having a redundant buoyancy device (dry suit). Does that only apply to diving steel doubles?
Not necessarily. It does depend a lot on the tanks you use. If you made twins from AL-72s and used an aluminum backplate the chances are very good that you'll still need a few lbs of ditchable weight. There used to be a guy here called Genesis who did some experiments with twin AL-80's and an aluminum backplate + 5mm wetsuit and he was able to swim them up from 100ft IIRC.
As far as rundundant buoyancy, a drysuit is a good idea but you can get away with using a closed circuit safety sausage (deco buoy) as long as you still have some ditchable weight that you can jettison at the surface.
I'm not sure I understand the difference between redundancy and bail-out. In my mind they're synonymous for the type of diving I'm doing (basic OW). Can you elaborate? I'm thinking that if there's an event that requires the deployment of an alternate air source, be it a pony or an octo, by either my or my buddy, at that point the dive's over and we're headed straight for the surface in a reasonable, controlled manner.
Ok. Maybe the best way to explain the difference is with a scenario. Imagine yourself on a dive where you have *no* access to the surface because of an overhead. That can be a big deco obgligation, or in a cave or under ice, or near a busy shipping lane....something like that. In that situation, if your primary regulator failed and you needed to turn it off then you would go to your octopus. If you only have your pony, then you'd have 19cf of air left to get back to safety, even if there were 120cf of air in your "back-gas" that you can no longer access because of a single failure. In other words, when in this situation, you can't just switch to your pony and surface.
Redundancy says to make sure that you have two ways to access your back gas. This means two complete regulators (1st and 2nd stages) to access all the back-gas. The goal of doing this is to make sure that if your primary regulator fails that you can still access *all* your air and continue the dive..... In fact, you would call the dive, but getting back to the surface may involve a long swim under water first.....
Bail out has a different purpose. It assumes that you have direct access to the surface at every point during the dive and that you can switch to your redundant air source and surface in response to a failed primary. Continuing the dive (or exiting from an overhead) is out of the question because the air supply is too small...
Setting up for redundancy means you either need two tanks, each of which has it's own valve/attachment for a regulator or that you need one tank with a double valve with two attachments for regulators. The single tank version makes use of H and Y valves. They're called H and Y valves because of the form they tend to have. I attached a picture for you (see below). Top left is an H valve, top right is a Y valve and on the bottom is a double valve used for two tanks.
How to configure all this is a subject of some debate. Some famous people said that they think ponies are useless and now a lot of (internet) divers have adopted that standpoint and it gives rise to a lot of "pony vs doubles" debates. If you search on Scubaboard you'll see lots of them and it's a good idea for you to read through a couple to get the gist of the issues.
I personally think that a pony is sufficient for "bail out" (assuming it's big enough) but not for "redundancy". In your case, you clearly have it rigged for bail-out. I don't know if that's your intention, but if you're trying for redudancy then you need another regulator on your back-gas.
Still following? It's not just semantics, it's about in which situations your configuration could be considered safe and in which situations should shouldn't dive with it like that.
The last thing I should say about that is that all the redundancy in the world is useless to you if you can't reach the valves to close/open them. This is definitely a skill that needs to be trained and practiced.
R..
