WetRocks
Contributor
N..but there are accounts of fatalities where A lack of SM proficiency was a likely factor.
Really? Do tell...
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N..but there are accounts of fatalities where A lack of SM proficiency was a likely factor.
Really? Do tell...
Then I guess I did NOT understand. If you intend to do only those guided cenote dives that every dive shop down there offers to OW divers, then stick with single tanks for that. I suspect your guide would scratch his head if you said you wanted to dive doubles for that kind of dive. If you're diving with a group--that is, unless you have a private guide--it's almost guaranteed that everyone else in the group will be diving a single Al 80.
I got confused when you mentioned having taken a cavern course and seeing others diving SM and BM.
Just a silly initial statement. The transition from BM single to BM is easier! ...period.
Especially if the diver in question was trained well and is in a Hogarthian / primary-donate configuration. (Which is a good idea, and getting more common)
Sure, some people will take to SM faster than others, but a much higher variability in gear, body types and preference is just a starting point. I know cave divers that have well over 50 dives (in SM) and are still tweaking their configuration, or swapping over to different brand/types.
I have seen well sorted out divers step into a set of doubles with minimal surface training and within 20m, look VERY good in the water.
**Now for the OP, I am not recommending either path, but getting some formal instruction is probably a good idea.
@swimmer_spe
1: "back in the day" which realistically was only like 5 years ago, we all had to figure it out ourself. You can buy sidemount gear from anywhere, those of us that started diving sidemount before it became a fad had to figure it out for ourselves. Steve Martin has the online video courses that are apparently very good. Servicing sidemount gear is no different than servicing anything else. Regulators are regulators, just because they have different hose lengths on them doesn't make it witchcraft, a bcd is still a bag with some valves on it and those don't really need to be serviced anyway. You can also contact Matt et al at Dan's Dive Shop in Toronto who teach sidemount. They're still a 5 hour drive, but for something like this, it's worth it if you are committed to sidemount.
2: I think you're still missing the important point that I made in that arguably too long post. The problem you have for cenote diving is that you will not have any more gas to stay down with doubles or sidemount because of the limitations of your certification. It is not until full-cave that you are allowed to use thirds of doubles. If you have a single AL80 you are allowed to use a third of that, or about 25cf. If you have a pair of AL80's whether on your back or sides, you are only allowed to use a sixth of that, again roughly 25cf. The extra mass will usually mean less penetration on the same air volume though with your high sac rate it may not matter much. You have to learn to maximize the gas that you have with you, not just band-aid the problem by carrying more.
Going to doubles at home is one thing if you want to stay down longer, but is it worth the cost of that class and the gear?
3: Very rough numbers. 120cf tank, assuming you left 500psi behind means roughly 100cf used. You said you're at 45mins now, and at 40-60ft you're SAC rate is around 1.0cfm. That's high. Typically you'll see around .6 which is around 70-75 minutes of dive time. 1.0 is what we typically use as a SAC rate for racing around in an emergency, .6 is considered "normal" for kicking around in a thick drysuit.
For a similar amount of money as the doubles course and gear, you can go take a course similar to GUE Fundies as mentioned previously which will teach you how to move efficiently through the water.
You need to be comfortable and relaxed before you go under. Every dive should start with a cold water treatment which is you breathing on the regulator or snorkel, mask off, face in the water. In through the mouth, out through the nose until you are relaxed enough that you can slow the exhalation down and stop/start it at will. In truly cold water it will often take over a minute. If you don't do that, you have an elevated heart rate from gearing up, getting into the water, floating around trying to get situated etc. and it takes a long time for it to stop. The mammalian diving reflex is a wonderful thing but to trigger it, your whole face has to be wet.
Gas switching in sidemount can be done as frequently or infrequently as you want, but to say "switch every 500psi" is putting a pair of needless gas switches in. You switch gas in sidemount typically at the maximum delta you are comfortable with from a trim perspective, and/or whatever is convenient for you. The bigger the tanks, the more frequent the gas switches because 500psi is a lot more mass out of a 149 than it is out of an 80. If that point is 500psi, which is convenient on an al80, then there is nothing that says you have to have one tank going first and the other playing catch-up. Breathe one 500, then the other 1000. Still have a 500psi gap, then breathe the other 1000 so you never exceed a 500psi delta, but you are minimizing gas switches. Have to think and ask for the why behind the what/how instead of blindly follow things that you hear.
There is still a learning curve for doubles, while I think the curve is a bit less steep for doubles, it is still there. Valve drills are no joke to start learning, and the trim profile definitely does change vs. singles. I find it easier to get started with doubles than sidemount because there is basically a single acceptable base configuration and the adjustments that you make from there don't really change anything major. In sidemount there are basically 3 accepted "base configurations" and those three are all very different than singles so it takes a bit longer to get sorted initially
OP here. What is a Hogarthian? I do have 2 regs, one in my mouth, and the other one is the one I typically donate.
Cons
The tanks are not manifolded so if you have a regulator failure, you lose access to the gas in that tank
@Caveeagle 50? Try 500 or more. Edd still tweaks his gear on a pretty regular basis and I'd bet he's over 5000 sidemount dives... I don't know anyone who is actually truly "happy" with their stage configuration yet...
2) Early on in this thread, I was told that, and now understand that. On the first dive, I should come up on half the gas I went down with. With the second dive, do I still use the 1/6 or do I do the 1/3s?