I agree with many of the posts above.
I think the time to move to doubles is well in advance of your first tech course. When I took Cavern and Intro Cave courses it was a few years post Advanced Nitrox and Deco Procedures courses that were in turn not done until well over a full season of diving with doubles and a long hose configuration.
The payoff was that I was rock solid in all the tech courses and did not have to devote any mental energy to adjusting to the skills required with doubles nor did I have any equipment/configuration issues as they had all been resolved long before arriving on site.
In contrast another diver in the cavern course had zero doubles experience and attempted to transition during the course which resulted in excessive task loading and one issue after another as he tried to come to grips with the configuration. It also meant he did not proceed to any portion of the Intro to Cave course and did not get the same bang for the buck on what was an expensive trip to Florida. In my opinion the instructor made a major mistake in encouraging/letting that transition happen during the course as the student would have been pushing his normal limits already even with a familiar configuration.
I think instructors who suggest delaying a trasition to doubles until a tech candidate is engaged in actual technical courses do those students a disservice. It does not take a rocket scientist to figure out how to dive a set of doubles and the extra gas is not going to get a diver bent or in trouble - that results from poor judgment not excessive gas.
It does help to have another doubles diver who is willing to mentor you in transitioning to doubles in a recreational environment and in making equipment selection/configuration changes as you move through the process.
I also agree that doubles can be very useful at recreatioanl depths. Some smaller boats, due to limited deck space are not very ammenable to allowing two sets of doubles on what is a recreational dive, but most could stretch it to a single set of doubles and a 30, 40 or even 80 cu ft stage as the foot print is not much larger than 2 AL 80's, and that small increase is offset by the lack of a need to swap tanks between dives.
In that regard it makes sense to do dive number 1 using all the contents of the stage (down to maybe 200 psi anyway - not bone dry) then switch to your doubles to finish dive one, while leaving at least half the total original gas (doubles plus stage) in the doubles for the second dive. You end up with slightly longer dives (still taking care to stay within the NDL's) with more reserve and much more redundancy while gaining experience with both doubles and stage bottles under the mentoring of your more experienced and better trained buddy. Then when you take that next step into a technical diving course, you have the basics already mastered and can focus on the contents and demands of the course.
I think the time to move to doubles is well in advance of your first tech course. When I took Cavern and Intro Cave courses it was a few years post Advanced Nitrox and Deco Procedures courses that were in turn not done until well over a full season of diving with doubles and a long hose configuration.
The payoff was that I was rock solid in all the tech courses and did not have to devote any mental energy to adjusting to the skills required with doubles nor did I have any equipment/configuration issues as they had all been resolved long before arriving on site.
In contrast another diver in the cavern course had zero doubles experience and attempted to transition during the course which resulted in excessive task loading and one issue after another as he tried to come to grips with the configuration. It also meant he did not proceed to any portion of the Intro to Cave course and did not get the same bang for the buck on what was an expensive trip to Florida. In my opinion the instructor made a major mistake in encouraging/letting that transition happen during the course as the student would have been pushing his normal limits already even with a familiar configuration.
I think instructors who suggest delaying a trasition to doubles until a tech candidate is engaged in actual technical courses do those students a disservice. It does not take a rocket scientist to figure out how to dive a set of doubles and the extra gas is not going to get a diver bent or in trouble - that results from poor judgment not excessive gas.
It does help to have another doubles diver who is willing to mentor you in transitioning to doubles in a recreational environment and in making equipment selection/configuration changes as you move through the process.
I also agree that doubles can be very useful at recreatioanl depths. Some smaller boats, due to limited deck space are not very ammenable to allowing two sets of doubles on what is a recreational dive, but most could stretch it to a single set of doubles and a 30, 40 or even 80 cu ft stage as the foot print is not much larger than 2 AL 80's, and that small increase is offset by the lack of a need to swap tanks between dives.
In that regard it makes sense to do dive number 1 using all the contents of the stage (down to maybe 200 psi anyway - not bone dry) then switch to your doubles to finish dive one, while leaving at least half the total original gas (doubles plus stage) in the doubles for the second dive. You end up with slightly longer dives (still taking care to stay within the NDL's) with more reserve and much more redundancy while gaining experience with both doubles and stage bottles under the mentoring of your more experienced and better trained buddy. Then when you take that next step into a technical diving course, you have the basics already mastered and can focus on the contents and demands of the course.
