Today, as you can see, scuba diving is increasingly available to everyone, this result is due to the most important Educational Agencies, as is P.A.D.I. ( Professional Association of Diving Instructors ) that invest huge sums of capital in the search for new solutions that can contribute to the safety of the recreational diver.
With the advent of scuba diving computers, increasingly sophisticated and precise in the detection of data relating to diving, the famous and beloved tables (by the students) have lost some relevance in the life of the diver.
A good diver should know very well how to use the tables, also because in case our computer abandons us during a dive, with our beautiful table in the BCD pocket, however, we will be able to finish our dive and go back up in total safety without having to entrust ourselves to the good fortune that our distracted companion, has moved away or even lost … But this topic, that of the importance of the couple system, we will address it in another article.
Returning to the R.D.P. (Recreational Diving Planner) we said that it is important to know it, because it allows us to plan one or more dives in advance, thus offering us the possibility of organizing our holiday by planning in advance the diving plan we are going to do. The table provides us with different information and is divided into 4 steps on two sides. But let’s go in order and start with side 1.
SIDE 1> 1st Step: Example: let’s imagine we want to plan our 1st dive of the day at a maximum depth of -12 meters. and that we decide to dedicate a maximum time of 38 ’min.
Do not we have to do is slide your finger on the numbered bar at the top, from left to right Until we find the depth we desire or the one closest. (NB) in this case the depth taken for example is -12m but if it had been that of -15mt; -17mt and so on, as you can see, these data are not shown in the table. But for this no problem.
Here is one of the First Rules:
in the event that the desired depth is not in the table, It takes as reference the first data following the one requested by us. (-15mt? Takes -16mt; -17mt? Take the next one, – 18mt.).
the same rule that is used for depth, is also used for the time spent on the bottom. As you can see from the image above, once it determined the bottom time, we must always move your finger to the right, until you get to the corresponding value. In our example, the data value is “H“.
The value “H” is the membership group after a dive made -12mt for 38 ‘min.. This value is very important because it indicates how much Nitrogen we have accumulated in our blood and later we will use it to find out how much time it will be necessary for the nitrogen to be disposed of, even if not entirely, through our fabrics.
SIDE 1> 2nd Step:
It is important to know that the final or beginning group of a dive profile, the closer it gets to the letter “A“, the lower the nitrogen still held in our body. Always continuing with the dive profile taken as an example first, now we will see after a certain Surface Interval, in which Group the table places us.
Even in this case, the procedure is similar to the previous. Then continuing to the right, assuming we decided to do a surface interval about 30 minutes, slide your finger until you find it the numerical value that includes 30 minutes of interest to us. As you can see, the quadrant it contains has been taken as a reference value (0:29 / 0:37) and proceeding down gives us the “D” value.
What is this value indicating to us? The value “D” as a result of our immersion in -12mt for 38’minuti and a 30 ‘minutes of surface interval, shows us that we still have a quantity of nitrogen to be disposed of, which cannot be underestimated, in case you plan to do another dive, immediately following the previous one. This last “D” value will become the entry Membership Group for our second dive.
As mentioned at the beginning of this article, the PIR (recreational diving planner) is divided into two tables each composed of two different sections.
Before proceeding to illustrate how to use the “B” side of the recreational diving planner, let’s not forget the second important rule:
All repetitive dives (so immediately following the first one) they must be planned at a depth equal to or less than the previous one and in any case must never exceed -30m. of depth.
It is equally important that the minimum Surface Intervals are respected as required in the Table (SIDE 1> 2nd Step). Still on the subject of the Minimum Surface Interval, another of the important rules tells us:
If 3 or more dives are scheduled in one day or if even from the first, the final Group after any dive is “W” or “X”, the minimum surface interval between all those that will follow must be 1 hour.
If the final Group is “Y” or “Z”, the minimum surface interval between all those that will follow must be 3 hours. To continue we must transcribe the data of the profile in our possession. To do this, I used what is technically called a “square dive profile” and the data shown are taken from the SIDE 1 table> 1st Step and SIDE 1> 2nd Step.
To show you how important it is to respect Surface Intervals, we will continue to plan the second dive of the day, following the data obtained from the first dive profile.
SIDE 2 of the Recreational Diving Planner.
In the picture above, we have a series of letters in the top row starting from the left with the “Z” and ending at the right with the letter “A“. While outside the left side there are numbers in columns and refer to the depth of the new dive.
Continuing the planning I decided to use as an example, a repetitive dive, always at a maximum depth of -12 meters and for a bottom time of 38 minutes, so it is identical to the previous one. We find our new depth, on the table sidebar, in our case they are 12 meters and we let the finger slide until you find the intersecting angle with the final Group after the surface interval relative to the previous dive.
The box that I encircled you in “Red” shows us two values. Let’s see what they refer to:
The white box indicates the Residual Nitrogen expressed in minutes, still present in our blood. The Blue box indicates the Limit Time, beyond which we must not go with the second dive. Now look at the profile below:
(RNT) is the value obtained from Table 2. (ABT) is the current bottom time, as shown here on the left in the profile.
RNT + ABT = TBT
(TBT) is the theoretical time of our immersion. What is theoretical time? The theoretical time in our case (64 ’min.) is the amount of total nitrogen in our blood.
Although really the second dive lasts 38 ’min, in reality our blood has accumulated Nitrogen as if it were a dive at -12 m. for 64 ’min. This data will determine our Group after the second dive.
Retrieved on (TBT) we realized that the second dive is feasible. To get the final group of the second dive, proceed as follows:
Let’s go back to SIDE 1> 1st Step of the PADI Table.
From the box indicating -12 m. we go down with the finger following the column in vertical, until you find the value 64 min, or the one immediately following, in this case it is 66.
With the same procedure as the first dive, from 66, we proceed to the right on SITE 1> 2nd Step and we will get the final group, which in our case will be “O“.
As you can see, the Minimum Surface Interval, after the second dive regardless of the group to which it belongs, it must be 1 hour.
The second section of SIDE 2 of the RDP contains all the basic rules for safe diving.Warning: The Recreational Diving Planner may only be used by patented divers or under the supervision of a PADI Instructor.
Author: Francesco Cordone