Simple question about removing backup regulator
- Thread starter mcavana
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LeadTurn_SD
Contributor
+1 on a bigger pony. But heck, just buy the whole horse (30 or 40 cu ft) 
19 is "just enough" from that depth. It might or might not allow you to swim back to the anchor line. Probably not.
So, the reason I personally like 30 or 40 cu ft for the depth you are talking about is this:
"Rule of Thirds"
While not really necessary for all dives and in all situations, the "Rule of Thirds" as it relates to gas management is a very good safety rule to follow: 1/3 Out, 1/3 Back, and 1/3 Reserve.
With an Al80, you actually have about 77 cu ft of air. One third of that (in round numbers) is 26 cu ft. A 30 or 40 cu. ft. tank would "restore" the full amount of your reserve gas in the event of a total loss of your primary gas (tank on your back), and allow a normal return to your start point. A 19 cu ft will require an immediate surface. A 30 or 40 will allow you to return to the anchor line, then surface normally, and do a safety stop. It will be just as if nothing had happened to your main tank.
Best wishes.
19 is "just enough" from that depth. It might or might not allow you to swim back to the anchor line. Probably not.
So, the reason I personally like 30 or 40 cu ft for the depth you are talking about is this:
"Rule of Thirds"
While not really necessary for all dives and in all situations, the "Rule of Thirds" as it relates to gas management is a very good safety rule to follow: 1/3 Out, 1/3 Back, and 1/3 Reserve.
With an Al80, you actually have about 77 cu ft of air. One third of that (in round numbers) is 26 cu ft. A 30 or 40 cu. ft. tank would "restore" the full amount of your reserve gas in the event of a total loss of your primary gas (tank on your back), and allow a normal return to your start point. A 19 cu ft will require an immediate surface. A 30 or 40 will allow you to return to the anchor line, then surface normally, and do a safety stop. It will be just as if nothing had happened to your main tank.
Best wishes.
My understanding from what I read earlier in this thread was that a 19cf tank, even at 100 feet should be enough to get me to the surface at a normal rate, and allow a safety stop as long as I start heading up as soon as I start using it. Would you say this is correct? (I will of course try this out with plenty of reserve in my normal tank the first trip I take it out)
I understand the thought that I might as well get a bigger tank so I have it for when I want to do other stuff.... However I can honestly say that I really don't have interest in doing other stuff. I have no interest in the caves, or in penetrating wrecks, or even diving deeper. My interest is only in what I can do here locally... and that is 60 to 105 feet open water dives
That said, I don't think it would make sense for me to get a bigger tank. Bottom line though, if I change my mind in the future, and need a bigger tank for what I want to do, it won't be the end of the world to buy another bottle.
LOL after 80 posts in this thread I think it would make sense for me to remove my octo. With my new setup, diving where I am diving, the only situation I can possibly think of that would require the backup second stage on my primary tank would be if my mouthpiece came off the primary second stage... but really, the odds of that happening are pretty low... and I would probably decide to head up at that point anyway. 500 dives without an octo would be well worth heading up early for the one dive where my mouthpiece comes loose (using my pony to head up.)
Am I missing something here? What other possible situation would it be used? keep in mind I am diving solo. Nobody else down there with me. I have a pony bottle ready to go with its own 1st and 2nd stage.
You can breathe from a second stage without a mouthpiece on it at all. I tried it just to see if I could right around the same time I taught myself how to breathe directly from an aluminum 80. So even in the rare case where you forget to put a zip tie on your mouthpiece, or it spontaneously combusts, you still do not need an octo. As a matter of fact, when diving with a pony I cannot think of any situation at all where you would need two second stages on your back gas. If you happened to run yourself out of back gas, went to your pony, and another diver instantly appeared in front of you like in Dragon Warrior for Nintendo, you could still buddy breathe with him to the surface and share the pony. Your pony bottle regulator is on a 40" hose, correct?
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LeadTurn_SD
Contributor
Hi mcavana,
So you can compare, here are some height and buoyancy spec for various pony bottles I copied from LP:
Height (in.)
6 Cu. 13.8
13 Cu. 15.8
19 Cu. 20.4
30 Cu. 23.0
40 Cu. 27.9
Buoyancy Full (lbs.)
6 Cu. -1.5
13 Cu. -1.7
19 Cu. -0.3
30 Cu. -0.7
40 Cu. -2.6
You see the size and bouyancy between a 19 and 30 cu in pony are pretty similar, as is the price (I think the 30 cu in is only $5.00 more on LP!!). So underwater they will essentially "feel" the same, they cost the same, but the 30 gives you much more gas.
Is a 19 cu ft enough? I think so. If you've already bought (or ordered) one, don't sweat it. Just remember your Boyles Law, do the math, and you can determine how much is needed for any anticipated OOA situations.
Oh what heck, here is the math:
At 100 feet, you are at a smidge over 4 ATM. 19/4= 4.75 So, using 1.0 cu ft per min as a "theoretical" mildly stressed consumption rate, you have a bit over 4 minutes (at 100 feet) before you go OOA again. That gives you maybe 1 min to problem solve, then a direct ascent at a normal rate to safety stop depth, and maybe a brief safety stop (breath the tank dry @ 15 feet then surface slowly). It should be enough. Note that 1.0 cu ft per minute is the figure thrown around for an "experienced" diver that is stressed but still under good control. Many new divers breath 1.0 cu feet per minute or more when they are relaxed! If you are moderately "stressed" by going OOA, you can pretty much double your consumption rate, or more.
You'll need to get a good handle on your actual SAC and RMV to really know / understand how much gas you might need. It differs between divers.
I think the factors I've listed are why several of us recommended larger pony for the depths you are thinking about. But lots of folks have used 19 cu ft tanks in real emergencies from 100 feet (or more) and were fine.
And lots of folks have gone much deeper with no redundancy at all. But we got older and hopefully slightly smarter
Best wishes.
halocline
Contributor
The answer is not more air, it's better understanding of the risks involved, more trained skills in emergency avoidance and management, and subsequently better judgement. You could carry 100 cft in a large bottle, 4 extra 2nd stages, and you're still at 100 ft with no buddy support several miles offshore with no emergency O2. You could get snagged on something, or get sick, or have a runaway ascent, get caught in a current, maybe the guy in the boat takes a nap, all sorts of things.
It's risky, and of course air is a big part of it, although in this lengthy thread you've mentioned nothing about gas management. (If I'm not mistaken) You did ditch the spare air, which is a good step, but if you think that the absence or presence of an octo makes any significant difference on your safety in this situation, then I don't think you have a basic understanding of the possible risks.
Many, many recreational dive fatalities happen with plenty of gas left in the tank.
Try not to take these comments personally.
It's risky, and of course air is a big part of it, although in this lengthy thread you've mentioned nothing about gas management. (If I'm not mistaken) You did ditch the spare air, which is a good step, but if you think that the absence or presence of an octo makes any significant difference on your safety in this situation, then I don't think you have a basic understanding of the possible risks.
Many, many recreational dive fatalities happen with plenty of gas left in the tank.
Try not to take these comments personally.
Not taking anything personal! you are after all only trying to help.
Well, I have made one reference to air management in this thread... and that was when I said with a full emergency pony in toe, at 80 feet I will head up with no less then 750 psi left in my primary tank... and at 100 feet I will head up with no less then 1000 psi left in my primary tank. I honestly don't know what my consumption rate is but I would say it is pretty good. I usually head up from coming close to running out of bottom time before running out of air if that is any gauge.
As far as some of the other things you mentioned. No, we don't have oxygen. this may be something I look into the next time I have money. But one thing to consider here is the captain, an assistant dive instructor, who has completed the rescue diver classes is educated enough to handle most situations..
In the worse case scenarios, it is nice to know that we leave out of the mayport Jetties, home of the Mayport Naval Station, and Coast Guard Station. Point here is that if we ever needed emergency help, it would never be very far away. 75% of my dives are within 16 miles of the stations. (not very far considering the boats the coast guard uses... You know the one that looks like a giant inflated hull with 2 - 225hp motors on the back?! Those suckers must do at least 50mph in 3 foot seas.
I don't imagine a runaway assent happening. I figure the way this would happen would be when someone looses a weight belt. I have a weight integrated BC. That or an out of air situation, but that has already been covered.
Yes I could get snagged on something. Sure. I don't penetrate anything, so fishing line or rope would likely be the cause. I have a very high quality dive knife to deal that... and plenty of gas to sort things out. if at the very end of my dive at 100 feet I get caught up in fishing line stuck to the wreck for instance... I still have 1000 psi in my primary tank. Normally something like this should take me seconds to cut my way out of... but assuming it is the worst tangle, I would still have plenty of time to free myself before emptying 1000 psi... and still have the pony bottle ready to go if needed.
My dive buddy is NOT going to go to sleep. Trust me.
As far as getting caught in the current... If their is a strong current (which I have still yet to see here in Jacksonville) I would simply stick to the anchor line when I head down and up. A general practice when I dive solo is to stay very close to the ancho r anyway. Most of the wrecks are relatively small, so it isn't like I am going to get lost. As soon as I get down I check the anchoring. I make sure we are anchored as good as possible. Often times I will adjust or slightly move the anchor just to lower the chances of becoming unanchored. Sure we could become unanchored... but that is fine. One advantage to diving solo is there is only one bubble maker! The captain is easily able to keep an eye on my bubbles and where they are.
Lets say the boat does become unanchored as soon as I get down there and I don't see it happen. Well, the captain would stay with my bubbles. He has a windlass anchor, so all he has to do is push a button to pull in the anchor. If he were to somehow loose my bubbles, He would use his GPS and Fish finder to get back over the wreck, where he should in theory be able to find my bubbles again. I would not leave the wreck unit I started to head up. I have done plenty of accents without a rope so no problem there. Sure it is possible that if he is hovering over the wreck, the current could push me away from the wreck as I head up. using my compass, I can determine (while the wreck is still in site) what direction the current is pushing me. I simply gently swim against the current as I head up and as I do my safety stop. When I surface the boat shouldn't be far. Assuming he was with my bubbles he should be right there. If he lost my bubbles, because I swam against the current he still shouldn't be that far. That said if he is pretty far away, that is where my whistle and 6 foot long signal tube (that I take on every dive) comes into play. Also, the captain always has his very high quality binoculars.
What if the boat doesn't start? well this would be a possible with any open water dive from a boat. I put out my signal tube, stay calm, and hope for the best.... tooting my whistle every minute or so.
I know what you are saying though... there is always risk. But guess what, it is scuba diving. of course there is risk! walking down the street has risk! It is all about trying to reduce the risk as much as possible. Many of you consider having a buddy as automatically reducing risk. I do not share this same opinion.
You know how the point was made that the spair air was so dangerous because it was a false sense of security? Well I hate to tell be the one to tell you if you don't already know but a dive buddy can offer that same false sense of security. As statistics prove, There are a MANY situations where a dive accidents can and do happen when someone has a dive buddy. Don't turn your eye to the fact that a lot of those accidents would not have happened with a solo diver properly prepared with both training and equipment.
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