Rainer
Contributor
On one hand you are quite correct, there's wiggle (that's what I called fuzzy at the start of but for repetitive diving (or anything outside of the aforementioned limitations), I feel that RD may be a tar-baby.
Could you *please* give an example of where it produces these super aggressive dive profiles for repetitive dives?
How many "technical" dives are you planning to do in one day?
I just ran *four* "typical T1" 150' 25 min bottom time dives through V-Planner (of course, 0 conservatism, we wouldn't want to deal with those "fudge factors" you so hate), each with a 2hr surface interval (what GUE and UTD recommend); 21/35+50%. Dive 1, on V-Planner (VPM - B), calls for 21 minutes of deco. RD would give 25 minutes between 70' and the surface, plus another 5 minutes of deep stops (so 21 vs 30). On V-Planner, dives 2-4 *all* call for 22 minutes (no extra time is added for each subsequent dive after the first). RD would give the same 25 minutes between 70' and the surface, plus an additional 5 minutes of deep stops. I'm having a hard time seeing how RD is less conservative. For shorter SIT, you should extend the deco with RD, just as you would do with tables. This is covered in the relevant courses.
Let's take some T2 examples. How about two dives to 220' for 25 minutes, with a 2hr surface interval (let's use the UTD 2:1 set point at 200'); 15/55+50%&O2. For dive 1, V-Planner gives 59 minutes of total deco, with 45 of those between 70' and the surface. RD gives 74 minutes total deco, with 60 of those between 70-0'. What happens with the second dive? V-Planner gives the exact same profile, except adds time to the final stop- an additional 7 minutes. That gives a total V-Planner deco of 66 minutes (52 between 70-0') vs 74 minutes on RD (60 between 70-0'). What happens with even *more* dives (as if anyone is really doing >2 T2 dives in a day)? Well, if you did the same dive a third time, V-Planner only adds an additional *one* minute to the final stop (still less conservative than RD). A fourth dive? Again, only an additional *one* minute (still less conservative than RD).
One of the main reasons RD is more conservative to start is that it allows, as the examples above demonstrate, for repetitive dives without making drastic changes to the schedules (though as the V-Planner profiles also demonstrate, repetitive dives hardly result in massive amounts of extra deco as long as a reasonable surface interval is observed).
In any cases, both RD and V-Planner are just generating profiles. You actually have to go out and dive to see how your body holds up. If either set proves too aggressive for your personal physiology, you *do* need to institute some type of "fudge factor" (i.e. add deco time). This is hardly a slight against RD or any other tables. Both can only give you a starting point that is conservative for most.
Hardly the "tar-baby" you make it out to be...