How anal is this?

[Jay Cohen]

My goals this Spring Summer is to continue to gain dive experience by diving as much as possible, in varied conditions and with as many experienced divers that I can find, beg, borrow, bribe……

With that said, I’ll be doing a bunch of April/May dive in local eastern Ohio quarries, with the intent of heading to the Great Lakes and a trip to North Carolina during the summer.

I really like the idea of planning a dive and understanding gas management, both of which are being discussed in my Intro to Tech course(doing for continuing ed, not planning Deco dives near future)., vs just jumping in the water and swimming around.

So how anal is this???

Plan A: Dive buddy says let’s kick out to the Tubes(max dept 60Ft), come back, we have 2800 psi, if one of us gets to ½ or 1400 before the other, signal, we’ll turn around.

Plan B: I say, well, Tubes sounds good, lets shoot a bearing, I estimate it’s 800 meters out about a mile round trip, since I want to surface with 500 psi in my tank, and I’m your back up air source, I’m going to keep 500 for you, since I know my kick cycle rate for 100 meters and my SAC for 60 feet, I’m going to estimate my gas usage, since I have my computer set for gauge mode, I plan to turn at 20 minutes, so rough estimates starting psi is 2800, plus 1000 for ending balance in tank, 3800 used, I plan to turn at 1900(not a factor for me, I'm on gauge mode) I would also consider the descent/ascent rate with safety stop.

I’m thinking by dive buddy is going to look at me like I’m crazy, since we’re in a rather controlled environment and a CESA is always possible. I know this might be over kill in a quarry at “only” 60 ft, but how do you practice gas management/dive planning, as you got to start somewhere.

Thanks in advance for any replies to this very newbie question.

 

[scubamama5]

Your numbers on Plan B quite confusing A mile round trip/ half mile just to get there. Black water navigation at depth?...Cool.:cool2:
Why not go with a simple rule of thirds ..one third out, 2 thirds back..?

 

[iztok]

When I dive quarry surface swim is always an option. It is not too far so plans are more relaxed. If we want to spend more time at depth (that one would normally do in true open water environment) and then just do a proper deep/safety stops and swim on the surface as we hit 500psi no problem.

Now if we want to practice dive planning then it is another issue.

 

[Steve50]

You have a quarry that is a half mile or more across?

 

[scubamama5]

Now if we want to practice dive planning then it is another issue.[/QUOTE]

What issue?? Lake, Quarry, Spring, Ocean, any water Pit..always plan your dives. Think up some "What If's"...what if this happens, what if that happens...
OP's post on Plan B...is

I've only been to two quarries: Dutch Springs and BainBridge..maybe quarries are bigger in Ohio??
Of course, I'd surface swim too, for pleasure divin'.
This Diver is training..and a black water Nav. is good training.
OP is tryin' to prepare for Tech, practice is good..dippin' in a black hole in doubles before jumpin' in deep, shows me, he's a concerned, safety conscious diver...just over thinkin' his dive plan re: gas management.

 

[muddiver]

Reference the attached document and Rick Muchison's gas management article: http://www.scubaboard.com/forums/basic-scuba-discussions/165474-backing-into-gas-plan.html

I did not analyze your dive plan, but I did note that you have actually considered planning your dive using the management of your breathing gas supply. I would try to find out what your Surface Air Consuption (SAC) rate is and use that to figue your underwater time as opposed to a simple and not very approximate rule of thirds method. You will be supprised at how much additional gas a normal dive requires to really be safe.

Good start, keep learning and diving.

Also, I personnally would swim out to the drop point on the surface to allow the use of surface navigation land marks. Using long distance landmarks on the surface is much more accurate than trying to navigate underwater, espacially in low visability conditions. But, it is a good exercise for you if that is the way you choose to dive.

 

[redacted]

Plan B: I say, well, Tubes sounds good, lets shoot a bearing, I estimate it’s 800 meters out about a mile round trip, since I want to surface with 500 psi in my tank, and I’m your back up air source, I’m going to keep 500 for you, since I know my kick cycle rate for 100 meters and my SAC for 60 feet, I’m going to estimate my gas usage, since I have my computer set for gauge mode, I plan to turn at 20 minutes, so rough estimates starting psi is 2800, plus 1000 for ending balance in tank, 3800 used, I plan to turn at 1900(not a factor for me, I'm on gauge mode) I would also consider the descent/ascent rate with safety stop.

Nothing wrong with detailed gas planning, especially when you need to determine if you have enough gas to do the planned dive. But if you mix up your pluses and your minuses, it could get you in more trouble than plan A.

 

[scubamama5]

Thanks Muddiver for finding and linking Rick Muchison's post! He went step by step nicely.
BTW..my math is simple, surely approximate... SAC rates vary during the dive, based on conditions, etc. Sure, you plan dive time... still gotta turn the dive at about a third in. (ok add 100#)
As you sit on a dock/chair/couch whatever, add some movement..helps to simulate a divein' SAC rate.
Good Conversation Here..again..Nice link Muddiver.

 

[Jay Cohen]

Muddiver, thanks for the article, it's printed and saved.

Guys, thanks for the comments, appreciate the advice and understanding attitude.