Blog – Page 4 – Scuba Diving Overload

PADI RDP Tables 1 and 2 The last section of PADI’s Open Water Diver Manual or eLearning, covers how to use dive tables, also known as the PADI Recreational Dive Planner or RDP. By going through the theory, knowledge review and quiz, you will learn how to use PADI’s dive tables and how to find the minimum surface interval between two or more dives, how to find the maximum allowable depth for a repetitive dive, and how to find the adjusted no decompression limit for a repetitive dive. These concepts are extremely important as they allow you to plan dives independently without (over)relying on your dive guide. If you want to learn all these concepts quickly and easily, check out my post on How To Use PADI’s Dive Tables. I strongly recommend you do so before going through the RDP knowledge review and quiz. To complete the RDP knowledge review questions and quiz, you will need PADI’s dive Tables or the eRDPML. If you have not received those as part of your PADI Open Water Crew Pack, you can download them from the PADI website. Once you feel comfortable enough with the theory, you can start with the knowledge review questions and the quiz. Passing score for the quiz is 75%. If you get some of the questions wrong, or have difficulties in answering – that’s not a problem. This is one of the most difficult parts when it comes to dive theory. I recommend you review questions answered incorrectly with your instructor, or comment down below for more explanations. I am happy to help you out. If you are looking for answers and explanations to other PADI Open Water knowledge review sections, check out the following links: PADI OWD Section 1 Knowledge Review Answers Explained PADI OWD Section 2 Knowledge Review Answers Explained PADI OWD Section 3 Knowledge Review Answers Explained PADI OWD Section 4 Knowledge Review Answers Explained PADI OWD Section 5 Knowledge Review Answers Explained Let’s now turn to the Knowledge review questions: When using the Recreational Dive Planner (table or eRDPML), I should ascend (go up) no faster than __________ per minute or the maximum rate allowed by my computer, whichever is slower. Answer: 60 feet / 18 meters. In case you do not remember the ascent rate by heart, the answer is written directly in the second page of PADI’s RDP tables, under the “General Rules” heading. The maximum ascent rate is 18 metres/60 feet per minute. As a general rule, you should either follow your dive computer or ascend slower than 18 metres/60 feet per minute. The RDP Table and eRDPML allow me to see the relationship between Answer: depth and no stop time. Also in this case you can use directly the RDP Table to answer the question. Table 1 shows you the no decompression limits and group designation for a given depth. Table 3 shows you the repetitive dive timetable. Therefore, the Recreational Dive Planner shows you the allowed no stop time at various depths. I dive to a depth of 11 metres/39 feet and stay for 46 minutes. What would my pressure group (PG) be at the end of the dive? How to find you pressure group at the end of a dive Answer: K On the RDP Table 1, follow the 40 feet or 12 metres column down to a time of 48 / 49 minutes. Remember that in case the numbers we are looking for do are not in the RDP Tables, we always need to round up. Once you have located the time box (i.e. 48 or 49 minutes), follow that row across to the pressure group K. I have made a dive then stayed on the surface for a while. After this surface interval my pressure group is K. What is the maximum amount of bottom time available when doing a repetitive dive to 17 metres/56 feet? How to find the maximum bottom time available for a repetitive dive Answer: 26 minutes To answer this question, turn to Table 3 of PADI’s RDP Tables. You need to find the crossing point between the K pressure group and the depth (60 feet or 18 meters). The maximum time of bottom time available will be displayed in the light blue cell, indicating the Actual Bottom Time. After a surface interval my pressure group is D. I want to do a repetitive dive to 12 metres/38 feet for 32 minutes. What will be my new pressure group (PG) when I reach the surface? How to find your pressure group at the end of a repetitive dive Answer: N Start from Table 3, where you need to find the Residual Nitrogen Time where D intersects with 40 feet / 12 meters. That’s 25 (imperial) or 26 (metric). Add the Residual Nitrogen Time to the Actual Bottom Time of 32 minutes to obtain the Total Time. That’s 57 (imperial) or 58 (metric). How to find your pressure group after a repetitive dive (part 2) Turn now to Table 1 and follow the 40 foot / 12 meters column until you find a No Decompression Limit greater than 57 (imperial) or 58 (metric). In either case that’s 60, corresponding to pressure group N. I dive to 59 feet for 22 minutes. After a 30 minute surface interval, I plan to dive to 50 feet. What is the maximum allowable time for the second dive? How to find the maximum allowable time for a second dive Answer: 61 Starting from Table 1, you need to find the next greatest depth on the first row, that’s 60 feet. Move down the 60 feet column until you find the next greatest time, which is 23 minutes. Move on the right and you will find pressure group H. Move across in Table 2 until you find a time interval that includes 30 minutes. Follow that column down to find the pressure group at the end of the surface interval. That’s D. How to find the maximum allowable time for a second dive (part 2) Now, turn to Table 3, and you will need to find the intersection between pressure group D and 50 feet. You will then find 61 minutes in the blue cell, which is the allowed bottom time. I am planning to make two dives. The first dive is to 60 feet for 45 minutes, and the second dive is to 60 feet for 35 minutes. How long would I have to stay on the surface (minimum surface interval) to do these two dives safely? How to find the minimum surface interval Answer: 1 hour 4 minutes Starting from RDP Table 1 find the depth on the top row, 60ft, and follow the column down to the next greatest time, which is 47 minutes. Move on the right to find pressure group S. How to find the minimum surface interval (part 2) In a second step, move to RDP Table 3, follow the 60ft row across until you find a time in the blue box equal to or greater than 35 minutes. Once you have located it, follow this up to pressure group F. How to find the minimum surface interval (part 3) As a third and final step, go to RDP Table 2. You need to find the intersection between column F and Pressure Group S: the minimum surface interval is 1 hour and 4 minutes. I dive to 56 feet for 47 minutes. After a 30 minute surface interval I do a second dive to 56 feet. Losing track of time, I notice my bottom time is now 25 minutes. According to the General Rules, what should I do? Answer: ascend to 15 feet and stay there for at least 8 minutes before going to the surface, and not dive for six hours. The question is actually asking you to check whether you have exceeded the maximum bottom time and by how much. Start from RDP Table 1, follow the 60ft column until you find 47 minutes, moving across you will find group S. On Table 2, follow S to find 30 minutes (between 28-32 minutes) and follow the column down to L. Turn to Table 3, find the intersection between 60 feet and pressure group L. The number in the blue box is 24. Staying 25 minutes means you’ve exceeded your bottom time by one minute. The general rule is to ascend to 15 feet and stay there for at least 8 minutes before going to the surface, and not dive for six hours. A group of Advanced Open Water Divers plans to make two dives. The first dive is on a reef in 90 feet of water for 20 minutes. The group then remains on the surface for 1 hour. The second dive is on a wreck in 60 feet of water, with a planned bottom time of 30 minutes. What will be the ending pressure group after the second dive? Answer: Pressure Group S. This question is about finding the pressure group after a repetitive dive. Using the RDP Table 1, you should first find the depth on the top row (90 feet) and scroll down the column until the next greatest time close to 20 minutes. That’s 21 minutes. Move to the right and you will find the corresponding pressure group, M. Now turn to RDP Table 2, follow the M pressure group until you find the 1 hour surface interval. Move down along the column and you will find the pressure group after the surface interval. That’s D. Go to the RDP Table 3 and find the crossing point between pressure group D and the 60 feet row. You need the residual nitrogen time in the white box, which is 16. Add 16 minutes to the 30 minutes bottom time and you will get a total of 46 minutes. Now go to RDP Table 1, and follow the 60 feet column to the next greater time, that’s 47 minutes. Move right to find the pressure group at the end of the second five, that’s S. My buddy and I are planning to dive at a site where the water and air temperature are near freezing. We plan to dive to 60 feet for 30 minutes. What dive profile would we use when planning our dive? The general rule, as you can read directly in the eRDPML and RDP Table is that if you plan a dive in cold water or under conditions that might be strenuous, you should assume a depth 10 feet deeper than actual.