Solo planning and execution

[Slamfire]

I am attaching a pdf of my log book page for this dive. There are 2 reasons for blocking out my number of dives and my number of underwater hours in the attached pdf:

1. I honestly don't know my real number of dives. I only started logging dives when I moved to Canada. I started diving 13 years before moving to Canada.
2. I do not want people using my number of logged dives as a benchmark -- "He's got x number of dives. I have slightly more. I should try this type of dive myself..."

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It seems that there is a wolf eel den in Whytecliff at around 140-130' no more than 5 mins swim northwest of the cut. I thought it'd be interesting to go look for it. So I planned this for the mission:

DIVE PLAN

145ft for 25:00 (27) on Nitrox 25.0, PPO2 1.347, END 136
70ft for 2:00 (33) on Nitrox 50.0, PPO2 1.559, END 32
50ft for 2:00 (37) on Nitrox 50.0, PPO2 1.256, END 20
40ft for 3:00 (41) on Nitrox 50.0, PPO2 1.105, END 13
30ft for 4:00 (46) on Nitrox 50.0, PPO2 0.954, END 7
20ft for 5:00 (52) on Nitrox 50.0, PPO2 0.803, END 1
15ft for 2:00 (56) on Nitrox 50.0, PPO2 0.727, END 0

DIVE RUN TIME: 56 minutes.
CNS Total: 26.7%
OTU's: 68

Time to Fly: 3.5 Hours

109.4 Cu ft. of 25.0% consumed.
35.3 Cu ft. of 50.0% consumed.
144.7 Cu ft. total open circuit gas consumed.

Descent rate = 60'/min
Ascent rate to 70' = 30'/min
Ascent rate from 70' = 10'/min

Descent rate is nominally at 60'/min but very rarely do I actually go down at that speed. Doing a slower descent rate just adds to the conservatism since you actually spend less time at depth. You just have to be aware that you will not really have the 25 mins of bottom time to complete the mission. It will be less.

I like to run the software with the last stop at 15'. That way, if the conditions are calm enough I'll actually do the stop at 10' and if the conditions are bad, I'll just add the last stop time to the 20' stop. Also, I do not like to have my last stop be my longest stop.

Another modification I like to make is to add a minute or two to the 70' stop, to exploit a little bit of that O₂ window.

I use Z-Planner because it allows me to put in my deep stops wherever I wish. I run a preliminary plan through V-Planner first to get an idea of where the deep stops would go if I were using VPM. Then, I put those deep stops into Z-Planner modifying them as described above. Sometimes, depending on the dive, I'll run a profile through an older version of DecoPlanner that allows you to see M-Value graphs for such dive.

CONTINGENCY PLAN

-Lost deco gas
145ft for 24:34 [ 27] on Nitrox 25, END:136ft
60ft for 01:10 [ 31] on Nitrox 25, END: 55ft
50ft for 02:00 [ 33] on Nitrox 25, END: 46ft
40ft for 03:00 [ 36] on Nitrox 25, END: 36ft
30ft for 05:00 [ 41] on Nitrox 25, END: 27ft
20ft for 06:00 [ 47] on Nitrox 25, END: 17ft
10ft for 16:00 [ 63] on Nitrox 25, END: 8ft

Nitrox 25 : 139.4cuft
Oxygen Toxicity - OTUs: 43 CNS: 19%

Plan is using Bulhmann GF 30/85. Ascent rate constant 30'/min all throughout the dive. Software was MV-Plan, but sometimes I use DecoPlanner. Results with either software are very close to each other.

EXECUTION
I did not find the wolf eel. I did not check the tides the day I went in and it turned out to be a pretty high tide day. So the wolf eel that I expected to be at 140' was probably more in the range of 150'. I did go down to 152' in a saw tooth like search pattern along the wall. But I was only exposed to the 150's range for half of the originally planned bottom time. Diving in the 150's range with 25% is starting to get a bit hot O₂-wise for my liking, particularly when I'm soloing in a multi level O₂ exposure dive. Then I went higher to 130's-140's range for the latter half of the bottom time just to average out a total of 145' for total bottom time.

When I was descending, at around 130' I stopped for a few seconds to relax, slow down my breathing and control narcosis. If it is more difficult than usual to clip back my spg to the hip D-ring, I am narced. Add to that the other usual symptons and you have a pretty clear idea when you should stop to keep it under control. After the relaxing, controlled breathing and refocusing, things got much better and I recovered my usual dexterity.

There was some wave action that day, so I just opted for doing my last stop at 20'. I extended the last stop 10 more mins than planned, just because I could and was in no rush to get out.

 

[sylpha]

am i missing something, why would you not check the tides. it's not just the height of the tide, but the change in tide causes current wouldn't you want to know that?

i check the tides for every dive i do, even if someone else is organising it, i like to know which direction the water is running before & after slack. My husband & I have a database for dives and we enter tidal information, both predicted & actual on each site.

i just don't understand why others don't check.

 

[kramynot2000]

Thanks for putting this up and too bad about not finding the eel.

 

[Slamfire]

am i missing something, why would you not check the tides. it's not just the height of the tide, but the change in tide causes current wouldn't you want to know that?

I would have to confirm with my logbook, but I estimate I've done at least 50 dives in this particular site. I've been under all sorts of tidal conditions here and frankly, I don't think it will present anything insurmountable or at least unadaptable. If you see the attached pdf, I do comment on the current. I did find an adverse current for a good portion of the dive. The effects this current had on the dive was a slight increase in my SAC rate for the entire dive -- from a usual .55 ft³/min to .614 ft³/min. For me, this level of exertion is still acceptable for decompression. As for gas planning, even though my average SAC rate is .55, I always make my plans assuming a SAC rate of .7 for the work portion of the dive and .6 for the deco portion. Additionally, I carry generous amount of gas, as you can see in the attached pdf. I was still able to follow my intended route without any deviation, in spite of the current. I came up the shore exactly where I wanted to surface.

Nonetheless, your point is well taken. It doesn't hurt to check on tides, all the contrary. There is a real danger when you start getting complacent with different aspects of diving. I used to check tides more diligently before. I will retake that habit. It is really easy to check for tides Mares, courants et niveaux d'eau | Tides, Currents, and Water Levels.