Essentials of Recreational or Essentials of Tech. Basically GUE Fundies Rec and Tech standard.
Tank configuration
- Thread starter swimmer_spe
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Essentials of Recreational or Essentials of Tech. Basically GUE Fundies Rec and Tech standard.
OP
swimmer_spe
Contributor
I don't want to become another statistic. That is why I would rather ask the questions here and learn before I decide on what to do.
You heavily snipped the post.
"Lorenzoid said: ↑
Then I would guess the "10-20 divers" you saw doing mostly SM with a few BM were not doing those guided cavern tours but rather were cave divers. You were fortunate to have avoided encountering the hordes of guided cavern divers (of which I have counted myself among). From my perspective, having been taken by my guide to some of the more popular cenotes for that, I saw a whole lot of single-tank divers with guides and a smaller number of dual-tank (I don't recall whether SM or BM) cave divers.
I have heard there are at least some cenotes that will allow you to do the cavern line without a guide if you show a cavern c-card, and I get the impression that's what you're considering trying. I don't know if they have other requirements for cavern divers, such as redundant tanks--whether BM or SM--but that seems like it would be prudent. As you may have observed, it's debatable whether every bit of the cavern line in every cenote even qualifies as cavern under TDI's definition without a bit of a stretch. I believe the guides are required to have the full cave gear, presumably as a safety net for their customers in single tanks. If some cenote will allow you to do the cavern line with your TDI cavern card, I have to believe redundant tanks--whether BM or SM--would be a given. So, if I now understand the situation correctly, I disagree with those who are advising you to stick with single tanks for self-guided cenote cavern dives."
I was referring to the fact that someone gets the fact that he understands that I should stick to single tanks, and that my observations.
I am not planning on doing a self-guided dive. I know my skills and experience are not where they need to be. As I aid,, I do not wish to become another statistic.
1) Yes, I live near Lake Huron, but it takes about an hour to get to a launch site. However, the local dive club usually dives local small lakes. AFAIK, no one local is teaching sidemount. No one local is selling sidemount gear. No one locally is servicing sidemount gear. If I am wrong, please help me find the resources I need.
2) Thank you for that, it does help me see the good. You also touch on the steep learning curve. I am not sure if I am ready for that curve, yet. This is why doubles are something I am considering as I do plan to take a doubles course, and there is someone locally who can do the course.
3) The depth was 40-60 feet when I dove the most, and I would last less than 30 minutes at first. How did I improve that?
1 - getting acclimatized to the water before going under.
2 - dropping about 10-20lbs. Depending on the dive, I was well over 10 lbs too much weight.
3 - learning my gear, and being comfortable with it.
4 - taking my time. If I already have a raised heart rate, I am sucking the gas.
The rest of your information is really helpful. I was assuming you switch every 500psi.
Regarding the learning curve, don't expect that backmount doubles is easier, only different. See for example
https://siriusdiving.com/reading-room/valve-isolation-protocols-for-technical-diving for a valve isolation drill. Those things are easier (or unnecessary) sidemount.
You could visit a sidemount test event and get some hands-on experience to see if this is for you. In general, you should have a lot of shallow open water experience with your gear before trimix class or cave class, no matter whether backmount doubles or sidemount.
https://siriusdiving.com/reading-room/valve-isolation-protocols-for-technical-diving for a valve isolation drill. Those things are easier (or unnecessary) sidemount.
You could visit a sidemount test event and get some hands-on experience to see if this is for you. In general, you should have a lot of shallow open water experience with your gear before trimix class or cave class, no matter whether backmount doubles or sidemount.
- Messages
- 20,562
- Reaction score
- 14,952
- # of dives
- I'm a Fish!
@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
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
Last edited:
Caveeagle
Contributor
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.
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.
- Messages
- 20,562
- Reaction score
- 14,952
- # of dives
- I'm a Fish!
@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...
L
You don't scare me!
SM does work best with certain personally types.
I'm only 50ish in and still sorting on the most basic level.
Not that dive 1 wasn't a wonderful experience...
Caveeagle
Contributor
Not trying to "scare" anyone. Just portray a realistic picture of the relative challenges associated with SM diving. I hear a lot about back and rotator cuff issues and th advantages of valves you can see. I acknowledge all that. ..but there are accounts of fatalities where A lack of SM proficiency was a likely factor.
I have a dedicated SM gear set and use it for dives where it makes sense. I still find BM doubles to be more appropriate for ~2/3rds of the dives I do.
Similar threads
