It's time for some SCUBA questions

[Sdiver]

Originally posted by pulque
my wild-ass guess:

you are up a 5000 ft mountain, wait 12 hours so you have no starting pressure group, do a 60 ft dive that counts as an 80 ft dive, new pressure group of 'R', your 1:30 SI time is spent driving down to sea level which somehow lowers your pressure group to 'A' rather than 'C' (maybe excess off-gassing), leaving you with 5 minutes RNT and a maximum TBT of 35 for a 70 ft dive.

Okay you're kinda in the ballpark. But using words like "somehow lowers you PG to 'A' rather than 'C'." and "Waiting for 12 hours" to dive.....ahhhh NO.

Altitude is a factor.

When you've had enough torture, I might reveil the answer.

[pulque]

Originally posted by Sdiver
Okay you're kinda in the ballpark. But using words like "somehow lowers you PG to 'A' rather than 'C'." and "Waiting for 12 hours" to dive.....ahhhh NO.

I could not find anything out about altitude reverse profile. I discovered from the NOAA manual that there is a PG of 'D' upon arrival at 5000 ft, before the first dive. Thus my WAG that one might off-gas a bit by coming down the mountain.

When you've had enough torture, I might reveil the answer.

LOL. there are ways of making you talk.

[Roguish Lawyer]

How about an answer? Looks like Matchanu is busy elsewhere . . .

I smell chum. Have to investigate . . .

[Sdiver]

Very Well...I'll post an answer later tonite.

I'm just scanning now, before I have to blaze off to work.

[pulque]

still treading



signed,
AC #4

[Roguish Lawyer]

Yeah, let's get it together!

[Sdiver]

Sorry I'm late....the short bus got a flat and no one knew how to change it.

Anyway, where were we ??? Oh that's right, you guys want to know how it's possible to do two dives with a profile like this :

1st dive 80 feet for 30 min.
1:30 S.I.
2nd dive 70 feet for 30 min.
and not run the risk of coming up/down with a DCI

and the 2nd dive is the deeper dive.....

Well here goes.

Yes altitude is going to be a factor. I'll be using three (3) dive tables for this problem.
The first table is the TDAA (Theoretical Depth At Altitude) table
Second table will be the PADI RDP (Recreational Dive Planner)
Third Table will be, the standard Navy Dive Table (Just to show the contrast between it and the RDP)

Our first dive is going to be a Mountain lake at 7859 feet. Water temp is low to mid 40's. Our actual depth is going to be 49 feet.
We are going to round up both our altitude and dive depth.

8000 feet and 50 feet.

On the TDAA a 50 foot dive at 8000 feet is like diving at 67 feet at sea level.

Round that up to 70 feet.

Now we want to add 10 feet for it being a COLD and Strenous dive (water temp in the low to mid 40's) I don't care if you are wearing a dry suit, you'll still add that 10 feet, onto your dive profile.

So on this dive it'll be like diving at 80 feet. We dive for 30 minutes. Our Pressure groups after the dive are now:

PADI : R
Navy Table : G

We have a 1 hour and 30 minute Surface Interval, driving DOWN the Mt. to our next dive spot. Which will be a Natural Spring/Sink Hole, like the Blue Hole, in Santa Rosa, New Mexico.

After our 1:30 S.I., our new Pressure Groups are:
PADI : C
Navy Table : E

The Blue Hole is also at altitude. The altitude there is 3920 feet. Water Temp. is in the mid to upper 60's. Our actual depth is going to be 58 feet. Round up....
On the TDAA a dive at 60 feet at an altitude of 4000 feet is like diving at 69 feet at sea level. Round up....

70 feet for this dive.

On the PADI RDP, as a C diver your ABT (Actual Bottom Time) would be 28 minutes.
On the Navy Tables, as an E diver, your ABT is 26 minutes.

But we overshoot our ABT and are under for 30 minutes. So in order to complete the REST of the above question ***and not run the risk of a DCI*** we would need to do an Emergancy Decompression stop at 15 feet for 8 minutes.

So.....Original question.....How is it possible to do 2 recreational dives with the following dive profile:

80 feet for 30 minutes
1:30 S.I.
70 feet for 30 minutes

and not run the risk of coming down with a DCI and your 2nd dive is your deeper dive ?

Actual depths:
1st dive......49 feet
2nd dive.....58 feet

This is how your 2nd dive, is the deeper dive.

[Dozer523]

Loathe to start a new thread for this but maybe we need a SCUBA thread.
(There's a HALO one -- I can just feel the envy)
This one is for the bubble-blowers . . .

An USAF guy asks an Army guy:
"Why do Scuba divers always fall backwards off their boats?"

To which the brilliant US Army soldier replies:
"If they fell forwards they'd still be in the f@ckin boat."