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.
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
70 feet for 30 minutes
and not run the risk of coming down with a DCI and your 2nd dive is your deeper dive ?
1st dive......49 feet
2nd dive.....58 feet
This is how your 2nd dive, is the deeper dive.
Non Sibi Sed Suis
It's Good To Be Da King !!!! Just ask NDD !!!!