Deep Diving Gas Planning

[OldFNG]

Just a point to ponder Higher Altitude + Thinner oxygen level+ Maximum bottom time diving + being fairly new diver would anybody else be worried about narcing out at depth.

Oldfng I would agree with NWgreatfuldiver and rethink your plans and do a lot of altitude shallower dives building up to the deeper ones, just want to see you on the SB postings in the future

Very good point, one thing I had noticed about tropical dives is I didn't start feeling noticable effects until 110 to 120 feet, and 130 felt just like 120. I'm almost debating finding out when the local dive shop is doing a deep dive course and tagging along to re-evaluate how I feel at the various depths in a glacial lake. I defiantely need to do a number of dives to find out how I handle in the new environment.

 

[aquaregia]

100' in Fla was no big deal. 100' in Monterey was brown trousers time.

 

[dumpsterDiver]

Very good point, one thing I had noticed about tropical dives is I didn't start feeling noticable effects until 110 to 120 feet, and 130 felt just like 120. I'm almost debating finding out when the local dive shop is doing a deep dive course and tagging along to re-evaluate how I feel at the various depths in a glacial lake. I defiantely need to do a number of dives to find out how I handle in the new environment.

You won't have to worry about low oxygen levels at depth. I've never heard that narcosis is worse at altitude, but the depth and cold water can ring your bell.

 

[Randy43068]

OK, who's doing body recovery for this chap?

Seriously, get some experience with a mentor before trying all this nonsense.

 

[OldFNG]

OK, who's doing body recovery for this chap?

Wow, seriously? I made this post with the honest intention to start a discussion on the merits of my thought process before I begin my planning in addition to other sources.

I've already had it pointed out that my train of thought was flawed, so was that really neccessary?

 

[bleeb]

I made sure I bought cold water regs, and first stages. My planned dive profile for the first few months at about 2 to 4 dives a weekend will be first dive of the day to 80 feet with second dive to the 60 to 40 foot range.

This leads me to the assumption that I should plan as if I was doing a 130 foot dive in terms of gas consumption and plan for about 20 feet deeper than actual depth based on tables + use a computer based on the sections I've read and altitude training dives I have done.

In terms of gas consumption, I'm not entirely clear on what you're assuming, but you seem to be implying that the air usage on a cold 60' or 80' dive is similar to a warm 130' dive. (Maybe that's not what you meant.) If so, it seemed worthwhile to caution you that this could be significantly underestimating gas requirements. For the same depth, when going from warm water to cold, an air consumption increase of 2-3x wouldn't surprise me, especially in a newcomer to cold water diving. That's potentially a lot more than 130'. As others have commented, more experience in cold water at shallow depths would give a much better sense of how much things have changed.

 

[DaleC]

No it wasn't.

Hi Old FNG. I assume you are thinking of diving Minnie (I've been there myself).

Bob had some good info there so I would think about what he said.

Just some random thoughts if I may:

Don't assume anything about adjusted depths for altitude diving. There are specific tables that tell you the adjusted depths and Pg's for your calculations. A 130' actual depth dive at both 3000 and 4000' are off the chart (PADI tables) and thus deco dives. 120' actual depth is 134 and 139 respectively and again deco dives. Even 100' actual is 111 and 116 respectively.

You will not find yourself put into any sort of decompression load. You will put yourself there. Avoid this by planning your dive and diving your plan. If you do not have the knowledge at this point to plan such a dive don't do it.

Err on the side of conservative dives and stay away from the NDL's at this point. Thinking about deco in your situation is putting the cart before the horse. You are courting several elevated DCS risks that you need to learn to mitigate (elevation gain to dive site, cold, depth) and still need to refine your basic diving skill sets (and yes, I still am refining mine as well). Forget how deep you dived tropically, cold water is a completely different setting and the two do not correlate.

Are you using a computer? If so can it be altitude adjusted. If not you will be following an incorrect NDL profile and will have to use tables instead. Again, don't try to get away with fudging things. Altitude decompression theory is already something of a guessing game as it is.

Carry all your gas. As others have said, you can't always count finding cached gas and it is not a practice commonly employed in our neck of the woods (except for caves).

Learn about rock bottom calculations. Plan to reserve that amount in your main tank and have at least the same amount in your pony (if you go that route). Make sure your buddy is on the same page.

Lastly, hook up with some local divers. Calgary has an active community and several divers from that region post in the local "Western Canada" subforum here on SB. Stop by and post a thread to see who's doing what in your area. They will be able to fill you in on some of the SOP's for your specific type of diving.

Good luck!

 

[OldFNG]

No it wasn't.

Hi Old FNG. I assume you are thinking of diving Minnie (I've been there myself).

Bob had some good info there so I would think about what he said.

Just some random thoughts if I may:

Don't assume anything about adjusted depths for altitude diving. There are specific tables that tell you the adjusted depths and Pg's for your calculations. A 130' actual depth dive at both 3000 and 4000' are off the chart (PADI tables) and thus deco dives. 120' actual depth is 134 and 139 respectively and again deco dives. Even 100' actual is 111 and 116 respectively.

You will not find yourself put into any sort of decompression load. You will put yourself there. Avoid this by planning your dive and diving your plan. If you do not have the knowledge at this point to plan such a dive don't do it.

Err on the side of conservative dives and stay away from the NDL's at this point. Thinking about deco in your situation is putting the cart before the horse. You are courting several elevated DCS risks that you need to learn to mitigate (elevation gain to dive site, cold, depth) and still need to refine your basic diving skill sets (and yes, I still am refining mine as well). Forget how deep you dived tropically, cold water is a completely different setting and the two do not correlate.

Are you using a computer? If so can it be altitude adjusted. If not you will be following an incorrect NDL profile and will have to use tables instead. Again, don't try to get away with fudging things. Altitude decompression theory is already something of a guessing game as it is.

Carry all your gas. As others have said, you can't always count finding cached gas and it is not a practice commonly employed in our neck of the woods (except for caves).

Learn about rock bottom calculations. Plan to reserve that amount in your main tank and have at least the same amount in your pony (if you go that route). Make sure your buddy is on the same page.

Lastly, hook up with some local divers. Calgary has an active community and several divers from that region post in the local "Western Canada" subforum here on SB. Stop by and post a thread to see who's doing what in your area. They will be able to fill you in on some of the SOP's for your specific type of diving.

Good luck!

I'm very much assuming minnie, and as for assumptions I was going on assumptions for gas consumption. My general plan was as follows:

1) Set computer to the highest personal correction factor possible
2) Set altitude on computer to altitude for area
3) Plan for rock bottom and ensure I have plenty of gas
4) Carry a pony with enough gas to get me from max planned depth to surface while maintaining surface stops
5) Cache gas at safety stop depth with as atleast as much gas in the pony (simulated surface support of spare tank + weights dangled below boat as was done during my warm water deep dives(This was the contentous issue which started this thread and has been pointed out may be retarded)
6) Dive with local divers, assume gas consumption will double or tripple from warm water, get experienced divers to mentor on local SOP's
7) Do lots of local dives in training lakes such as chaparral until I'm sued to gear.

 

[rjack321]

I bet there's alot to see at about 1/2 the depth or less than you're postulating about diving in this thread. You might need to slow down to see though. Last time I dove a mountain lake (last March) there were hundreds & hundreds of rough skinned newts breeding in 20ft, those were cool. Go see those things for a half dozen plus dives. I bet you'll come back here with some more nuanced questions.

 

[OldFNG]

I bet there's alot to see at about 1/2 the depth or less than you're postulating about diving in this thread. You might need to slow down to see though. Last time I dove a mountain lake (last March) there were hundreds & hundreds of rough skinned newts breeding in 20ft, those were cool. Go see those things for a half dozen plus dives. I bet you'll come back here with some more nuanced questions.

I fully agree, the problem was I was assuming like minniwanka where most of the dives are advanced dives, 60 to 80 feet or lower. There is nearby two jack lake which is 40 feet on average and a perfect training lake. So from whats been said I'll be hitting up two jack for most of the rest of the season, or just lake chapparal which is 20 feet most of the time with exceptions going to 35 feet.

My goal is to try and log 4 dives a weekend for as long as I can during the season and then in the new year dive like mad.

On the question of the pony, I've been pondering the best way to carry it, sling it or just bracket mount to the back of my main tank. Advantage of slinging it is I can hand it off to my buddy if needed. I'm thinking AL40 (between 100 and 200$) + 1st stage ($100) + second stage ($100) + spg ($50) so 450 might be just the kind of protection from gear failure (not bad gas planning) I need.

Thoughts for the area?