100m air dive & workup, PG

[Tortuga68]

In the tradition of such popular threads as http://www.scubaboard.com/forums/advanced-scuba-discussions/345916-85m-air-dive.html and http://www.scubaboard.com/forums/technical-diving-specialties/297905-psai-narcosis-management-course-73m-air.html, I present my report on my 100m air dive

After spending a week here in Sabang, Philippines doing work up dives @ 30, 40, 50, 55, 65, 75 & 90m, this morning my two dive buddies and I completed a 100m dive on Joshua's Wall.

All dives were done with air as bottom mix in back-mounted doubles, and two deco stages per diver with 50% & 100% 02.

For the last two dives in the series we had support divers - for 100m we had one diver follow us down and level out at 75m, and another diver who came down the SMB line we deployed from 45m. Both support divers had the same equipment/mixes

The 42 minute run-time for the 100m dive was:

Descent phase: 4 minutes
Bottom phase: 4 minutes
Ascent phase: 7 minutes to first stop; 1 minute stop @36m, 1@33, 1@30, 1@27, 1@24, 2@21 (switch to 50%), 1@18, 1@15, 3@12, 3@9, 9@6 (switch to 100%), switch to backgas and 3 minutes to surface

Plan was cut on Decoplanner and run with bottom timer/watch

All the dives were great fun and went pretty much according to plan; most of them were blue water descents - on the final dive it was blue water until ~80m then the site features magically materialised, very cool

I remember the dives well, felt relatively clear-headed for most of them (the 90m dive was the one I felt most narc'd on) and happily I experienced no symptoms of either DCS or OT

Thanks to my buddies, support divers, boat men and shop crew for being part of the fun!

I will probably do a trimix course sometime next year, so it will be interesting to go to the same sites and see the difference the gas makes - better or worse

Feel free to ask relevant questions if you wish

 

[waterpirate]

Glad you enjoyed the experiance. IMHO that week of work up would have been better spent in full tri-mix. Is he hard to get in your locale?
Eric

 

[w ripley]

The problem usually doesn't come from short duration dives, but from longer dives that have some degree of complexity, such as penetrating. I find that as the complexity increases so does my need for a very clear mind, which HE has faithfully provided.

I remember a night penetration on air of a wreck's engine room in just 130 fsw and getting narced. It was a feeling that scared the hell out of me because I was in a dangerous situation and realized that I didn't have full control over my actions. My rule has been from that point forward just not to dive over 120 fws without HE and it has kept me alive for over 15 years.

Some people can diver deeper on air than others. However, the longer you dive, the deeper you diver, the farther you penetrate a wreck or a cave, the more you begin to try and reduce aspects of the risk to you, and for most of us that means diving what we believe are safer breathing mixes.

Diving deep air is a stupid, IMO, when there are prooven alternatives with a safer track record. How you dive is your choice; I choose not to dive deep air.

 

[deepstops]

Was there a purpose to the dive?

 

[Tortuga68]

Was there a purpose to the dive?

Yes, to go to 100m on air

Diving deep air is a stupid

Thanks for that insight

IMHO that week of work up would have been better spent in full tri-mix. Is he hard to get in your locale?

No, it's readily available. Using it for 30-65m would have been an expensive waste of time IMO

 

[alwaingold]

Bottom phase: 4 minutes

Wow, that sounds like a really fun dive.

 

[Pullmyfinger]

Tortuga,
Thanks for posting the details of your dive. Although I have no plans to dive deep air, my next planned step in training is tri-mix.
It is interesting to read what others are doing with deep dives on air.
It gives some data in terms of what's done in warm water on air.
I'm sure you knew you'd catch some flak for posting that here.
Thanks for the details of your dive just the same.

-Mitch

 

[Divin'Papaw]

Next week I start my workup drives. I wanna drive 100 mph for 4 minutes after consuming a fifth of Jack. Wish me luck. Should be fun.

 

[KMD]

In the tradition of such popular threads as http://www.scubaboard.com/forums/advanced-scuba-discussions/345916-85m-air-dive.html and http://www.scubaboard.com/forums/technical-diving-specialties/297905-psai-narcosis-management-course-73m-air.html, I present my report on my 100m air dive.

So in the traditions of all those previous "popular threads" I would normally get right into the this sure to be riveting and informative discussion on deep air but in the tradition of many new years eve events, I am in the process of getting liquored up and hitting the road.

 

[VooDooGasMan]

Tort, how much back gas did you return with on a 4 min BT, seems like 1/2 anyways.

I do 275' on al 80, no BT, just back up the water collumn. Yet i fly down as fast as I can and and only breathe to equalize, and no movement at all. I take in very little nitrogen on way down.

How do you descend, head up or down, I'm head down and streamline for speed.

Tortuga, I know that there is plenty to see in your dive profile, that is why I specialized in al 80 for travel diving, when time is so short at dive destinations.

You have done well on you air dives, and it will reward you in your travels where air is the gas you are given. Not only that, with the experience, you may save someone at those depths by getting to them quickly.

Keep the practice up and you will get better and better, good luck to you.



Happy Diving