Diving Safely Without A BC

[John C. Ratliff]

Thanks. I now think perhaps my instructor was exaggerating a bit.

I'm also thinking just about any freediver could do it without taking any breaths (unless the first one counts as 1 )

Please note, at least for NAUI, these were "minimum" requirements. The instructor was free to make the course more difficult, or longer, or add materials as long as the minimum was met.

SeaRat

 

[OldPhotog]

SeaRat, thanks for posting that history lesson. Fun to read and brought back memories. I learned from some crusty old UDT guy at our local "Y". Had to do most of it.

 

[george_austin]

Great point @John C. Ratliff - "free to exceed minimum requirements" I wonder if instructors are still free to exceed min req's? I would think they must be.

 

[dmaziuk]

I thought you'd like to see a historical perspective on skin and scuba diving skill requirements.

Heh. I find it mildly amusing that they replaced "220 yards" with "200 metres or yards" -- if you do 220 yards in a 25-yard pool you end up 5 yards out.

Looks like the brick requirement would be the most relevant to the thread's topic: if you can swim up carrying a 5-pound brick, you should be able to swim up carrying 2lbs of the regs and 3lbs in the tank (assuming no suit buoyancy etc. etc.) without additional buoyancy of the air cell.

 

[REVAN]

Interesting datapoint: I recently did a comparison between my streamlined kit and a stock single tank OMS BP with a 45 pound wing. My streamlined kit has no BC and some fairings to clean up the hydrodynamics of the tank. I measured an 85% reduction in drag as compared to the OMS kit using the same AL80 tank. Shedding all that drag feels very liberating.

I'm hoping to do a comparison with a standard tank and harness setup at some point as well, but haven't gotten around to it yet. Based on previous diving experiences, I expect it will be pretty good also, but won't have actual numbers until I do the tests.

PS - To be clear, those numbers are for the kit itself on a diver, but not including the diver.

Normalized data for the whole diver was measured as follows:
Cd (diver) =1.0 -> with mask, fins wetsuit and wt. belt
Cd (diver + OMS kit) = 2.0 -> adding the scuba equipment doubles the drag of the diver
Cd (diver + Streamlined kit) = 1.15 -> only slightly more than the base diver

I have a datapoint for a DiveRite harness with no BC and a single Al80 tank. I wrote it up in another thread.

Here's the link:

Okay folks. I did more swimming tests, this time using my DiveRite Transpack 2 and no BC wing. I have a 48" hose on my single regulator with the hose routed in a low drag configuration. It's the kit shown in part 4 of the article.

Normalizing the data to that of a freediver swimming with arms at the side, here is how it all breaks down:

Cd Freediver = 1.0
Cd Diver with Al80 in experimental streamlined kit = 1.15
Cd Diver with Al80 in DR Harness with no BC = 1.6
Cd Diver with Al80 in OMS BP/Wing = 2.0

As a kit and compared to the OMS BP/Wing:
Ditching the wing cuts the drag of the scuba kit by 40%.
The streamlined kit cuts the drag of the scuba kit by 85%

For the whole diver system:
Ditching the BCD wing saves 20% in total diver drag.
Using the experimental streamlined kit saves by over 40% in total diver drag.

Streamlining gear works and can make a really big difference in the overall diver's performance and level of relaxation and efficiency of air use.

 

[captain]

This was last March in Silver Springs, notice anything.

Dropbox link to Gene Page Photos Sea Hunt Forever Divers

 

[undrwater]

Yeah...but THAT looks dangerous! ;-)

 

[captain]

A few years ago, twin Navy non magnetic 90"s, DA Aquamaster and UDT vest.

 

[JamesBon92007]

Wow, the AquaCars are really cool! And six of them in one photo!

 

[Bob DBF]

Please note, at least for NAUI, these were "minimum" requirements. The instructor was free to make the course more difficult, or longer, or add materials as long as the minimum was met.

SeaRat

In a 1980 NAUI/PADI OW class that was brought to my attention, as I had been diving for years and was taking the class just to get a c-card. Not only was I held to a higher standard and given "extra" requirements, unless the instructors standards were met, no card would be given.

The same was true for the rest of the class, but I had no idea what the agency OW standard was in comparison to his. The drop off a 3 meter board with the gear in your arms, air off, and gear up on the bottom, successfull completion of freedive skills, 100yd kelp crawl in full gear after OW skills and dive, 30 min in open water not allowed to touch the boat after OW skills and dive, and so on. I know the guy that had to grab the boat had to come back and complete it after the rest got cards.

My understanding was that he dropped PADI because he could not make the card dependent on his requirements. I don't know if he could do that now in NAUI, if he were still with us and teaching. His class was made to produce divers that would be safely diving the NorCal coast.


Bob