JACKET vs. BACK INFLATE BCDs- which and why?

[djanni]

Why wouldn't a wing be nearly fully inflated at great depth with a heavy wetsuit and a full tank?

I can imagine losing 16# of neoprene flotation as the suit compresses and the tank still has 8# of air so even if the diver were perfectly weighted, they would need 24# of lift under these conditions.

If the diver is overweighted, the required lift would increase. That could be pretty close to the total lift of a 30# wing. Most BCs have somewhat more lift. Perhaps on the order of 35# of so. They might not be fully inflated but they are getting close.

As to how this affects the pockets? Beats me! I don't recall having a problem with my old SeaQuest ADVi jacket style BC but all I ever carried was dive tables and a slate. It probably wouldn't be a problem with a back-inflate BC but most of those have integrated weight systems and the pockets are often limited.

Richard

I guess a situation could be created where one might need a lot of air in the bladder. Your example; overweighted diver, great depth, heavy wetsuit and a full tank of air may create such a situation. Could be they're trying to bring up a heavy piece of metal too.

My comment was based on the evironments, wetsuits and depths within my diving experience. If the OP is going to dive in cold water wearing more than a 5mm wetsuit/hood and to depths greater than 135 feet then he should consider the tight pocket issue.

I was addressing the fully inflated comment and I never intended to put the OP at risk and if I did I sincerly apologize. I hope the OP reads this post.

 

[rstofer]

My comment was based on the evironments, wetsuits and depths within my diving experience. If the OP is going to dive in cold water wearing more than a 5mm wetsuit/hood and to depths greater than 135 feet then he should consider the tight pocket issue.

I was addressing the fully inflated comment and I never intended to put the OP at risk and if I did I sincerly apologize. I hope the OP reads this post.

I don't think the depth needs to be anywhere near 135. I usually think of 'great depth' as something in the 100' range. The truth is, I have never tried to measure my wetsuit buoyancy at depth. I do have some concern about the adequacy of a 30# wing as that is what I am using. OTOH, I won't be going that deep any time soon.

I started diving in SE Asia. Buoyancy control was never an issue. Nobody used wetsuits and, at most, people wore 10# of weight with 6# of buoyancy change in an Al 80 tank. Now that I dive in colder water (Monterey), I am very aware of the differences in buoyancy. My whole mindset needed to change. Now I view every equipment decision in terms of how it works in cold water at 'great depth'. Where I wear my weight, how much lift for the wing, how negative is the tank; all these things start to matter.

I seriously doubt that anything you said would have created an issue for the OP.

In the end, divers need to dive all kinds of gear and make their own decisions. Ask questions, get opinions, filter the info based on needs and make a decision. I still like my jacket BC. I'm diving with a BP/W but I haven't tossed the BC.

Richard

 

[cool_hardware52]

I don't think the depth needs to be anywhere near 135. I usually think of 'great depth' as something in the 100' range. The truth is, I have never tried to measure my wetsuit buoyancy at depth. I do have some concern about the adequacy of a 30# wing as that is what I am using. OTOH, I won't be going that deep any time soon.

Testing at a Florida University (I wish I had the original reference) determined that at about -165 fsw typical Neoprene has fully compressed.

The effects are non linear with respect to depth, partially due the material properties and of course ATA's are not linear with respect to depth either. The greatest % changes in pressure occur shallow, and the great swing in suit buoyancy does too.

Very few exposure suits are more than 30 lbs positive. If you suit is less than 30 lbs positive, and you are properly weighted a 30 lbs wing is sufficient. If your suit is more than 30 lbs positive, or you are overweighted a 30 lbs wing *might* be too small.

Tobin

 

[ae3753]

After my final PADI open water cert dive, I asked my instructor for some advice on buying equipment. He said that the only advice he wanted to give was DO NOT buy a back inflate BC, ONLY buy a jacket type. He said that he had seen too many beginners having trouble with back inflates. He said that they were harder to dump air from.
After reading this thread I am questioning his advice. I understand why the back inflates might give beginners problems at the surface, but they seem to be easily fixable. Could some instructors comment on this ?

This has to do with wing shape and size.

A properly selected back inflate will not be difficult to dump air from.

However, this is not what most beginning divers buy. When I was a newly minted OW diver, I bought myself a Zeagle Ranger - looked rugged, plenty of options, and big lift.

What I found out, as do many who buy an improper BCD (whether jacket or backinflate), was that it was not optimal for my diving. As a single tank, warm water diver at the time, I needed something with less lift and less bulk.

The larger wing and wider shape caused significant taco'ing around the tank, and required more active management of the bubble. Because jacket (or vest) BCDs do not wrap around the tank, this issue is avoided. You can still trap air in a jacket BCD, but not from the taco effect.

Both styles seem to range from dirt to gold in terms of price- and I've yet to find anyone note that one style works better or worse in certain diving conditions. I'm looking at purchasing the Mares Dragon BCD w/ airtrim. A buddy lent me his and it was extremely comfortable (albeit sized just a little big), and has all the bells and whistles of the best Zeagle. Please enlighten me with your input! Also, has anyone in here experienced any negative findings with the Dragon BCD which I should know about?

The Mares Dragon has all the bells and whistles, and that's exactly what I'd be concerned about. The 44#s of lift and mass may be unnecessary for your diving.

It is a matter of preference, but I like as minimal and streamlined a BCD as possible. For me, this is usually a backplate/wing set-up. The freedom of movement and lack of clutter makes me feel more in tune with the environment and ultimately more comfortable (less drag, less stuff on my chest and on my sides, etc.)

 

[djanni]

I don't think the depth needs to be anywhere near 135. I usually think of 'great depth' as something in the 100' range. The truth is, I have never tried to measure my wetsuit buoyancy at depth. I do have some concern about the adequacy of a 30# wing as that is what I am using. OTOH, I won't be going that deep any time soon.

I started diving in SE Asia. Buoyancy control was never an issue. Nobody used wetsuits and, at most, people wore 10# of weight with 6# of buoyancy change in an Al 80 tank. Now that I dive in colder water (Monterey), I am very aware of the differences in buoyancy. My whole mindset needed to change. Now I view every equipment decision in terms of how it works in cold water at 'great depth'. Where I wear my weight, how much lift for the wing, how negative is the tank; all these things start to matter.

I seriously doubt that anything you said would have created an issue for the OP.

In the end, divers need to dive all kinds of gear and make their own decisions. Ask questions, get opinions, filter the info based on needs and make a decision. I still like my jacket BC. I'm diving with a BP/W but I haven't tossed the BC.

Richard

I seriously doubt it too but I don't like to be preceived as a know-it-all, because I don't or highly biased and I certainly don't want anything I might say to end up putting someone in a less than desirable situation. My deepest is 135' (wouldn't call that great depth) in a 5mm. Properly weighted and probably with less than a full tank, if I had any air in the bladder it wasn't much, so that's been my experience.

Don

 

[offthewall1]

Find a BCD you like... while there are certainly some key differences between the two styles (and others have already shared that here... so I wont repeat) ... they both work... and so if you like one or the other, go for the one you feel comfortable in. It is more important that you are comfortable in your gear... not that you can be influenced by what others tell you you should have...

 

[SubMariner]

Personally, I like my Aeris Atmos hybrid:
- lots of lift
- best of back & (partial) jacket BC

Maybe when I get a couple of pennies to rub together I'll see how their female specific version performs.

 

[Sharktreat]

Jacket or rear inflate, its all down to preference. When I was getting my OW I used a rear inflate during all of the pool time and had no problem with it at all. During the OW dives I was unable to find one and was forced to use a jacket which I was frustrated about since I had gotten so comfortable with the rear. Long story short is I'm glad I got to try out both as it made it much easier for me to buy my rear inflate BC. I just prefer not feeling like I'm the filling inside a burrito. Really try both before you buy and make sure its a good fit!

 

[ivobj]

Rear inflate gives you better trim, leading to less drag and easiness to swim, and consequenses of that (less air consumption, etc, etc). Regarding confort, as many already posted, both can be very confortable, it's a personal choice.

There is another option, the Back Plat & Wing setup, which is even better to trim, gives you more flexibility to adjust wheight, let you remove in some cases all the wheight from the belt, and if well adjust eliminate tank bouncing and side rolling, this is my personal choice, specially because is the best to switch from doubles to singles just attaching an adapter, that also functions as the extra ballast needed when you move from steel doubles to ALs.

MY OPINION is that if you see yourself in the future diving double cylinders also, go for BP/W setup, if you intend to stay with singles you can choose between rear inflate BC or BP/W as well, but as before, personal preference, try to test before to see what you like.

 

[Dive Rite]

Hi JP,

What a great post! We get this question a lot, so I hope its alright if I provide some information.

The question you asked is about differences in operation or features.

One of the main features no one has mentioned is lift. A drawback of the Jacket style BCD is that the lift is typically dependent on size. An XL size diver may get 30 lbs of lift, but a XS diver may only get 21 lbs of lift. This is a huge disadvantage for those of us who are petite. A petite diver needs to carry the same weight tank, same exposure protection, etc. as a larger diver, but is offered less lift.

A BP/Harness style BCD means you get a harness customized to fit your stature, but the wing is standard in lift and doesn't change with the size of the diver.

Typically, about 30lbs of lift is ideal for a warm-water, 3mm exposure, aluminum 80 single tank diver.

You can peruse our online Solution Finder for customizable answers to this question and other frequently asked dive gear questions.

I hope this is helpful,
Kathleen

Ok, so I know the difference in the two styles, and the difference in operation. Unfortunately, I'm not real sure why some choose one, and some choose the other. Is it mere comfort, or are there factors I'm missing? Both styles seem to range from dirt to gold in terms of price- and I've yet to find anyone note that one style works better or worse in certain diving conditions. I'm looking at purchasing the Mares Dragon BCD w/ airtrim. A buddy lent me his and it was extremely comfortable (albeit sized just a little big), and has all the bells and whistles of the best Zeagle. Please enlighten me with your input! Also, has anyone in here experienced any negative findings with the Dragon BCD which I should know about?

Respectfully,

JP