# Calculation questions and Planning



## BOHUNTER1 (Feb 18, 2008)

See how bad I look....I got my certs in Guatemala, Yeah....

I know we all are going to do this, dive into uncharted, untraveled waters one day. When you plan for the dives or just going diving, and the depth is UNKNOWN, but you know its less than 60 feet, how do you prepare or calculate your plan of attack. You are probably going to burn a complete tank when down also, so who knows an hour or two down and the depth is what??? We dont know. 

NO DIVE COMPUTER... Must figure with charts... and keep time. Pressure will let you know!

Since we dont know the depth and want to stay down a bit to venture around, we fill with up with Nitrox 32% for example. Beautiful day sun is high and water viz is nice and clear maybe 20 feet. Got my weights and fins, regs on BCD inflates check check, feet first. BUddy up and head down all good in da hood. As we reach the bottom and viz is better and water is cooler, we head out Due North, we tapped out at 53 feet. As we venture around we find ourselves up and down, terrain and obsticals. Up and down and finally find our depth now is just 35 feet. Checking guages and noticing the pressure has dropped and we are down to 1000psi and North of the Boat, we head back on Bottom again, remembering this is an actual downhill part of the floor, so we wind up into the deep 53 again and then comsume a bit more air in the return, we are under200psi now, and head up slowly. Hang on to the anchor rope for a few minutes for a safety stop then we reach the surface and get out for a spell and go over the dive....

Ok for the recreational no computer guy. When we do our Calculations on Surface intervals and pressure group, do we base this on the9 minutes at 53' or the possible guess average of the entire dive wechecked depth on. We know we hit this depth, but we were there for just 9 minutes, the rest of the54 minutes was all over... How do we figure this type dive. 

EAN of 32%

PO21.4 = 90 feet

PO2 1.6 = 107 feet

Our EAD on 32% is 47feet, rounded up from 53 feet to 60 feet

Dive planner at 47 feet gives us 80 minutes.

We were down 1:03 minutes So our Planner shows us "T" group after the dive if based on entire dive time. But we hit that hole for 9 minutes and was out of it.....Does this matter?

Ok lets say thats fine that way and we eat a biscuit and drink some water for45 minutes and gather up reload and bail off for #2 dive.... SI of :45 minutes total.

PG is "J"

We check planner and shows us 47 minutes NDL......

If we are following the planner and dive the 36 minutes and get out even if we touched 53 for such a short time, how do each of you figure this and how should we as average Joe Recreational divers out on the water preform these dives.

LOCATION IS WITHOUT DEPTH FINDER... For example lets say it was a canoe 30 miles offshore with 4 ' seas.... Doesnt matter folks we are trying to find out how long and if we are in danger or just a techncality issue... LOL

Thanks Hope I got my numbers right, you cant learn if you dont ask and its better to know before you screw up.

Steve


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## Telum Pisces (Sep 27, 2007)

All I know is that when doing calculations without a computer you must use your maximum depth for the whole dive. If you touched 53 feet, your whole dive was at 53 feet when you do your calculations. That's what's great about a computer. It is constantly calculating at your different depths.


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## Mike aka FishWerks (Oct 22, 2007)

> *Telum Piscis (8/21/2009)*All I know is that when doing calculations without a computer you must use your maximum depth for the whole dive. If you touched 53 feet, your whole dive was at 53 feet when you do your calculations. That's what's great about a computer. It is constantly calculating at your different depths.




Don't forget elements like; physical effort during the dive, physical condition of the diver, water temps (cold), recreational activity the night before (alcohol) ... these can cause an an increase in the nitrogen absorbed and dictate a change in the schedule used, in particular if you are at or near depth/bt which may require decompression.


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## FelixH (Sep 28, 2007)

If you want credit for the shallow portions of your dive, get a computer. That's what they're for. If you're running tables, you're supposed to calculate the total dive time at your max depth.


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## Clay-Doh (Oct 2, 2007)

Bohunter! I just read thru haf your post and got a headache!

Get a computer buddy!!!


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