Diving Safely Without A BC

[Shotmaster]

On air, bottom times were a lot less, so you had to be efficient, swimming with a lot of gear slows you down from drag. If you get the chance to hit some warm water, try a dive with just your tank and regulator, it is freedom! I grew up in Panama City, FL and diving in shorts, a T-shirt and a speargun was a blast.

 

[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

 

[Shotmaster]

Cousteau did it first. LOL

And that streamlined house was holding Triple Cylinders!

 

[REVAN]

I like my streamlining better.

My fairings are smaller. They don't cover the whole tank, just the parts that will benefit.

 

[cool_hardware52]

I recently did a comparison between my streamlined kit and a stock single tank OMS BP with a 45 pound wing.

Houston, we have a problem................

Tobin

 

[REVAN]

Please explain...

 

[Storker]

I'm pretty certain that Tobin is hinting that 45# is an unusually large wing for single tank diving.

Unless you need a lot of weight and most of it is attached to your plate, it's serious overkill and more drag than necessary.

 

[gypsyjim]

I'd expect somewhat different results, comparing drag with no bcd to dragging around an empty weather balloon.

 

[REVAN]

I'm pretty certain that Tobin is hinting that 45# is an unusually large wing for single tank diving.

On that, I completely agree. It's not something I would use, but it is not uncommon either. Someone did buy this thing and paid a lot of good money for it too. I'd say this falls into the category of, "this is what happens when someone is not taught about the penalties of drag and goes for what is popular and cool looking instead of what's best for the diving they will actually do". The wing is big, but atleast it was banded to keep it small when deflated, which it was for the test.

Drag wise, I don't think this is likely to be worse than something like this Mares BCD which is a very common product sold in many dive stores.

Hybrid Pure - B.C.D.s Ergo - Mares

 

[george_austin]

I read through this whole thread and I didn't see what I think is the primary answer for PADI's insistence on a BC with power inflator. It's the same reason they insist on ditchable weights; surface management. PADI really emphasizes the ability to stay positive at the surface, and for good reasons considering most of what they do is teach certification classes to people with little or no dive experience. I realize BC manufacturers don't certify their products as life jackets, most likely for liability reasons, but that's what they're most often used as for new divers and OW students. PADI cites some statistic like half of diver accidents happen at the surface in their OW classes....I'm not sure of the number, but that's the gist of it.

I personally think that all divers could benefit from doing some diving without a BC in terms of developing good swimming skills, weighting strategies, and breath control. In warm water, with a minimal wetsuit, double hose, and small neutral tank, I've gone on several no BC dives, it's really fun.

To answer your question about what circumstances it's safe to dive without a BC, my opinion is that it's safe as long as you don't need the surface support of a BC, and can swim your rig to the surface without a problem. So this might include shore diving where you can easily swim to shallow water, or boat diving with a float you can hang onto.

Got me thinkin . . I think the training philosophy nowadays is setting the bar so low that "anyone can do it" which facilitates all around income for the "industry" - IMO, nothing facilitates moving thru training as quickly as the "water wings"

When I was certified in 72, you didn't just walk into a shop and sign up to be a scuba diver. There was a little bit of a psychological evaluation by the staff divers before consideration. In my case, since I was a skinny 14 year old, the shop staff instructors agreed that I should get a skin diver certification from L.A. County Dept. of Parks and Recreation before I would be accepted into their NAUI Basic Scuba Diver program. I thought I was already a pretty accomplished and experienced skin diver and I knew I was a good swimmer but after a summer long L.A. County Skin Diver Program and later acceptance into a NAUI Basic course - of course I realized that those old Navy frogmen were correct in their evaluation at the beginning.

Of course nowadays some sensitive snowflake would file a lawsuit on a shop that hurt their feelings like those guys did.
It wasn't a guarantee by a long shot that you would progress from Week 1 to Week 2 and a couple people in my class actually did "ring the bell" and quit after Week 1. As well, after a review of your swimming and basic watermanship skills on Day 1, the Instructor certainly had the discretion to deny further training - no refunds. "Sorry, learn to be a better swimmer and come back next year"

I think some of those older guys kind of based their training methodology on their own UDT stuff and then added what they thought was going to add value.

I remember that you could have access to tanks, weights and regulators and a Mae West but if you didn't have a wetsuit or they didn't have one that fit you, you were diving in your swimsuit LOL. - which was great in the pool but in Laguna Beach in April and May is not so comfortable.

There was no one in the class who wasn't already a pretty accomplished skin diver, or "freediver" as they say now. I can't imagine some 60 year old grandmother just walking in then with no ocean experience and signing up. Nah.