NAUI Scuba Diver 140 Decompression, Dive Tables, and Dive Computers E and do a 1 hour SIT, your new Letter Group is D. If you want to return to 18 meters (60 feet), align your arrow with the 18 meters (60 feet) depth in the D Group section. The longest time limit in the window is 31 minutes. To find your End-Of-Dive Letter Group for a repetitive dive, use the following steps: 1. Find your new Letter Group on the circumference of the baseplate and align the depth arrow on the disk with the deepest depth of your repetitive dive. For example, align your arrow with the 18 meters (60 feet) depth in the D Group section. 2. Read the bottom times from the center of the disk outward and find the first time that you do not exceed. For example, if you do a repetitive dive to 18 meters (60 feet) with a Letter Group of D and your ADT is 23 minutes, the first time you do not exceed is 26 minutes. 3. Look to the right of the window to see your End- Of-Dive Letter Group. For example, the End-Of- Dive Letter Group next to the 26 is H. The calculator design eliminates the AMDT. It also eliminates adding the ADT to the RNT to obtain a TNT. However, the answers are the same as those obtained from the dive schedules using the NAUI Dive Tables. Dive Planning with the Calculator You can use the NAUI Dive Time Calculator to achieve the same three methods of dive planning as you can using the NAUI Dive Tables: • Limit your bottom time to the maximum number indicated for a given depth and group. • Extend your surface interval to move to a group letter earlier in the alphabet. • Dive to a shallower depth. For example, you are a diver with a Letter Group of F and you want to dive for 25 minutes. You move the window back and forth and find that you can dive to 18 meters (60 feet) for 19 minutes or to 15 meters (50 feet) for 33 minutes. To avoid exceeding the Maximum Dive Time, you know you can dive no deeper than 15 meters (50 feet) and stay no longer than 33 minutes. You want to dive to 18 meters (60 feet) for 25 minutes, but cannot because you are a diver in Letter Group F. You need to determine the Letter Group that will allow you to make the dive. You also need to determine the minimum surface interval that would allow you to achieve that Letter Group. To determine the group that will allow you to make the dive, align the depth arrow with 18 meters (60 feet) in group F. Work back, one Letter Group at a time, realigning the depth arrow with 18 meters (60 feet) for each group, until you find a Maximum Dive Time of 25 minutes or longer. In this example, the first Letter Group allowing a Maximum Dive Time of 25 minutes is E. In some instances, the words DO NOT DIVE appear in the calculator window. This means that you have too much residual nitrogen to permit a dive at the depth selected for a particular Letter Group. You will have to extend your surface interval to dive at that depth, or dive at a shallower depth. Required decompression information is handled differently using the NAUI Dive Time Calculator than with the NAUI Dive Tables. A separate Decompression Timetable is provided. To use this table, use the following steps: 1. Look in the first column corresponding to the depth of your dive. 2. Look in the second column for your depth for the first time that equals or exceeds your ADT in excess of the Dive Time limit for your depth. FIGURE 5-18. THE NAUI DIVE TIME CALCULATOR ELIMINATES SOME CALCULATIONS REQUIRED BY THE NAUI DIVE TABLES.
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