Discussion of best practices for advancing in cave diving (moved from A&I JB thread)
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I think 99.9% of people dive wet suits because I've been to Egypt on vacation a couple of times.
OP
I also see most people using bottomt mounted stages in sidemount. But there is no difference in drag if you carry topmounted or bottom mounted stages in sidemount. The most important thing here is that you carry them as sidemount cylinders.
In backmount, stages are less streamlined, absolutely true. It is almost not workable if you want to carry them as sidemount cylinders and want to dive in your cold water outfit with drysuit and gloves. But there is a big difference between absolutely not streamlined and as streamlined as possible. It is just physics. Ali cylinders float at the bottom when they get empty. So they tend to turn. You need to make the vertical distance between the boltsnap at the top and the boltsnap at the bottom as less as possible (like with sidemount). So start with the right rigging and put the boltsnap as close as possible to the band at the bottom. Also wear the best fitting harnas as possible with the D-rings in the right position.
Yes, they still will go up if they get empty, but not that much as sometimes you also see.
But remember, take the equipment that works for the dive. You don't do backmount dives in caves that only fit sidemount. There are also caves where sidemount is not the best option. It is easier to take 3 or 4 stage cylinders with you on backmount, especially if you don't use the DIR-method. With the DIR-method you can take extra cylinders on a leash, like you can do with sidemount. That is also an easy way to take extra cylinders. But yes, if they are full, they are dangling to the bottom. If they are empty, they hit the ceiling. So there are some disadvantages also. But I can also mention a lot of disadvantages for sidemount, and also for ccr and sm ccr. There are still dives that can be best made on a single tank (no caves of course).
And every cylinder, also in sidemount will give extra drag. Most people don't feel 1 stage cylinder, but start feeling the 2nd. Try to swim backwards with just 2 cylinders, then with 3, than with 4 and for sure you will feel the difference.
And I can tell you that my camera causes at least that amount of drag than an extra cylinder (in backmount). I don't feel it if there is no current, but as soon as there is current, you will feel it. But I still prefer to take my camera with me on cavedives that I make for fun. I am now used to it and feel empty when I don't take a camera with me.
And if you want to discuss the DIR-style way of diving, and you want to discuss it right, you must be open minded. There is not 1 way of diving best, also DIR is not always the best way, but even if you just use a part of it, that part can be used in other styles also.
Stages left and right is maybe not dir, but if I use my ccr, there is no longhose that can be a problem when using stages at the right side of my body. So where a 3rd stage will be on a leash in oc, in ccr backmount diving it will be on the right side. I also can rig my stages with my backmount ccr sidemount, where I cannot do it that way with a oc twinset. This has to do with the frame that is used by the rebreather and cylinders don't have that.
I also can explain why a 18/35 trimix is also still a DIR-gas, why EAN80 can be a choice instead of 100% sometimes. And there are good and bad divers found in every agency.
Even there are good divers found that took courses by bad instructors and vica versa.
In backmount, stages are less streamlined, absolutely true. It is almost not workable if you want to carry them as sidemount cylinders and want to dive in your cold water outfit with drysuit and gloves. But there is a big difference between absolutely not streamlined and as streamlined as possible. It is just physics. Ali cylinders float at the bottom when they get empty. So they tend to turn. You need to make the vertical distance between the boltsnap at the top and the boltsnap at the bottom as less as possible (like with sidemount). So start with the right rigging and put the boltsnap as close as possible to the band at the bottom. Also wear the best fitting harnas as possible with the D-rings in the right position.
Yes, they still will go up if they get empty, but not that much as sometimes you also see.
But remember, take the equipment that works for the dive. You don't do backmount dives in caves that only fit sidemount. There are also caves where sidemount is not the best option. It is easier to take 3 or 4 stage cylinders with you on backmount, especially if you don't use the DIR-method. With the DIR-method you can take extra cylinders on a leash, like you can do with sidemount. That is also an easy way to take extra cylinders. But yes, if they are full, they are dangling to the bottom. If they are empty, they hit the ceiling. So there are some disadvantages also. But I can also mention a lot of disadvantages for sidemount, and also for ccr and sm ccr. There are still dives that can be best made on a single tank (no caves of course).
And every cylinder, also in sidemount will give extra drag. Most people don't feel 1 stage cylinder, but start feeling the 2nd. Try to swim backwards with just 2 cylinders, then with 3, than with 4 and for sure you will feel the difference.
And I can tell you that my camera causes at least that amount of drag than an extra cylinder (in backmount). I don't feel it if there is no current, but as soon as there is current, you will feel it. But I still prefer to take my camera with me on cavedives that I make for fun. I am now used to it and feel empty when I don't take a camera with me.
And if you want to discuss the DIR-style way of diving, and you want to discuss it right, you must be open minded. There is not 1 way of diving best, also DIR is not always the best way, but even if you just use a part of it, that part can be used in other styles also.
Stages left and right is maybe not dir, but if I use my ccr, there is no longhose that can be a problem when using stages at the right side of my body. So where a 3rd stage will be on a leash in oc, in ccr backmount diving it will be on the right side. I also can rig my stages with my backmount ccr sidemount, where I cannot do it that way with a oc twinset. This has to do with the frame that is used by the rebreather and cylinders don't have that.
I also can explain why a 18/35 trimix is also still a DIR-gas, why EAN80 can be a choice instead of 100% sometimes. And there are good and bad divers found in every agency.
Even there are good divers found that took courses by bad instructors and vica versa.
Oh yes, totally simple! /s
Pretty much every cave student ever (in supervised conditions) has let go of a line when they shouldn't have. Months or years later, they are in actual low or zero vis, have limited experience in those conditions or have a whole mountainous cascade of problems accumulating... people drop or lose the line that's usually the final straw before they perish.
Underwater Tourist
Contributor
Yes, but thats the point of training. Swimming into a silt out shouldnt be even an event, a minor inconvenience at best. If there is one thing you can distil emergency cave training drills to: is to hold the line like its your life, because it is!
Maybe there was some other emergency that happened during the silt out and contributed to divers letting go of the line and not finding stages, but if it was just silt and nothing else, then its unfortunately on them..
It does make a difference in drag.
You can train till the cows come home. Stress in training is nothing like stress caused by a real life situation. Keeping calm when you actually find youself way up sh_t creek, is another story. The people that got into accidents also trained. Having many hours underwater (in caves) under your belt helps but people's bandwith still gets overloaded at some point.
That's why people should progress slowly over years rather than zero-to-hero rush through levels. It's better to run into issue early, in easy conditions rather than deep or in a cave.
It's better to have the first free flowing reg type thing happen in 40' of open water and not in 240' and 2 hours from the cave entrance... or while you've got youself stuck in a restriction and your stress level is going through the roof.
J-Vo
Contributor
JonG1
Contributor
Without going too far ot how easy is it to top mount sm cyls, is the reduction in drag really that significant?
J-Vo
Contributor
It's not a huge difference but I think it's noticeable. Depends on how it's mounted and on the position of the main tanks too though. I use dir-style rigging for the o2 tank I drop and hate swimming with that thing.
The top mounted stages also don't clutter up you chest area and I like that.
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