Jacket inflate vs Back inflate

[EastTNDiver]

Here are my opinions, based upon my experiences:

1. I found that the jacket style BC which I rented pressed in on my stomach and waist when inflated, making it uncomfortable to breathe. Before anyone jumps in and posts "you must be fat," "you were overweighted," (neither is correct) or "you should hardly need to put any air into your BC" I will respond with "you must be a warm water diver and the OP is in California (not warm water)." I dive cold water. When diving a 7 mm two-piece wetsuit you will have considerable compression at depth (on the order of 20# for me), meaning that you need to put a considerable amount of air into the BC to keep you neutral. In my case, for the BC I was wearing, this lead to uncomfortable pressure on my waist and ribcage, making breathing more difficult. I am sure that jacket style BCs are great in warm water. However, in cold water I very much prefer my rear-inflate BC (Zeagle Scout).

2. I used to feel that my rear-inflate BC "pushed me forward." I now believe this to be incorrect - I think that my weights on my weight belt were incorrectly positioned (too far forward), the result being that the weight pulled me forward. Having repositioned the weights (including having moved some to my top cam band) I find that (with my rear-inflate BC) I float comfortably in an upright position with no tendency to face-plant.

And, not trying to be rude, but my response is you must be over weighted. If someone is adding enough air to a BC to squeeze them to the point of being uncomfortable and making their breathing more difficult, then they need to re-evaluate their weighting. It doesn't take 20# of weight to sink a two-piece 7 mm wetsuit, so how could it compress that much bouyancy out of your wetsuit. I dive deep cold water on a regular basis, and never have to add "significant" amounts of air to maintain proper bouyancy. In fact, I barely touch the inflator. I'm not arguing for jacket BC's, as I also prefer/use a back inflate, but just think your assessment in point #1 is incorrect, and that you might want to re-evaluate your weighting.

 

[cool_hardware52]

It doesn't take 20# of weight to sink a two-piece 7 mm wetsuit,

Not true.

Many 7mm suits are 18-24 lbs buoyant. It depends on the actual material used, the cut of the suit, the size of the diver etc.

A 7mm suit that's more than 20 lbs buoyant are routinely seen.

Go get one of the typical XL 7mm one piece tough as nails suit from the local rental rack, roll it up (with the hood and booties) and see just how much ballast you need to sink it.

Tobin

 

[EastTNDiver]

Not true.

Many 7mm suits are 18-24 lbs buoyant. It depends on the actual material used, the cut of the suit, the size of the diver etc.

A 7mm suit that's more than 20 lbs buoyant are routinely seen.

Go get one of the typical XL 7mm one piece tough as nails suit from the local rental rack, roll it up (with the hood and booties) and see just how much ballast you need to sink it.

Tobin

I guess my statement was a bit too blanketing in scope. My 7 mil wetsuit does not require that much weight to sink it. Nonetheless, I stand by my statement that if you are inflating to the point of restricting your breathing to maintain proper bouyancy...which I would argue is not proper bouyancy...then, you are overweighted.

 

[tbone1004]

ya, my 7mm john is about 24lbs to sink it... I weight check myself in a bathing suit and 500psi on each different bottle setup, and go through the weight checks like Tobin said for each of my wetsuits. No questions there. If I can't sink then it's something with me, not being under weighted.

 

[Crush]

I guess my statement was a bit too blanketing in scope. My 7 mil wetsuit does not require that much weight to sink it. Nonetheless, I stand by my statement that if you are inflating to the point of restricting your breathing to maintain proper bouyancy...which I would argue is not proper bouyancy...then, you are overweighted.

I have not looked at your profile, EastTNDiver, but your certainty, compounded by your being incorrect, leads me to believe that you are a new Instructor, or possibly an Assistant Instructor. Am I right? A more experienced person would not diagnose problems based upon an incomplete description on SB, or pronounce errors with such faith.

Here is how I am weighted: at the surface with my BC empty, if I inhale, I float. Next, if I exhale, I sink. The fact that I am doing this with a full tank would lead some to conclude that I am under-weighted since near the end of a dive my tank will be more buoyant. In reality if I do my safety stop at 15-20 feet at the end of a dive I am neutral owing to suit compression. I can do a slow, controlled ascent from the stop and, since boat traffic is not a problem, I am not worried about having to re-submerge in panic.

 

[EastTNDiver]

I have not looked at your profile, EastTNDiver, but your certainty, compounded by your being incorrect, leads me to believe that you are a new Instructor, or possibly an Assistant Instructor. Am I right? A more experienced person would not diagnose problems based upon an incomplete description on SB, or pronounce errors with such faith.

Here is how I am weighted: at the surface with my BC empty, if I inhale, I float. Next, if I exhale, I sink. The fact that I am doing this with a full tank would lead some to conclude that I am under-weighted since near the end of a dive my tank will be more buoyant. In reality if I do my safety stop at 15-20 feet at the end of a dive I am neutral owing to suit compression. I can do a slow, controlled ascent from the stop and, since boat traffic is not a problem, I am not worried about having to re-submerge in panic.

No, you are not right, and you seem to be taking it personally. I did not state that you personally do not have your weighting right. I stated that if you are weighted as such that you are required to inflate your BC to the point of restricting your breathing, then you are over weighted.

It also strikes me odd that you would sling such arrows, when in fact, you are checking/adjusting your weighting improperly with a full tank. Being positively bouyant at the end of a dive is not necessarily good...especially if you are positive enough that it gives you thoughts of issues with re-submerging. Take it personally if you wish, but you might wish to re-evaluate how you are checking/adjusting your weighting.

 

[Crush]

...then you are over weighted.

...being positively bouyant at the end of a dive...

Am I over-weighted, under-weighted, or both?

 

[cool_hardware52]

Being positively bouyant at the end of a dive is not necessarily good...especially if you are positive enough that it gives you thoughts of issues with re-submerging. Take it personally if you wish, but you might wish to re-evaluate how you are checking/adjusting your weighting.

mpetryk describes adjusting his weighting *exactly* as I recommend for new DSS BP&W users when diving with single cylinders and buoyant exposure suits.

There are many benefits to being "eyelevel at the surface with no gas in the wing and a full cylinder"

The impacts of a buoyancy failure are much more easily dealt with, and there will be less gas in the BC during all phases of the dive. Less gas in the BC makes buoyancy control easier too.

With a typical single cylinder holding ~8 lbs gas, and the typical diver using maybe 6 lbs or less re submerging is trivial, even more so if one understands that neoprene rebounds slooooowly.

If you have trouble swimming to 10 ft when 4-6 lbs buoyant you might want to look into some good quality free diving training.

Tobin

 

[master00sniper]

Wow, this is awesome. I started this thread with what I thought was a simple question, and hella (i'm from norcal, hella is a real word here) people are blowing up about this that and the other thing. Keep it going. Not only is it entertaining to read, but I'm learning as well.

If I may throw some questions in here, what does OP stand for? Also someone mentioned BC Cd's. What is that?

 

[Crush]

Wow, this is awesome. I started this thread with what I thought was a simple question, and hella (i'm from norcal, hella is a real word here) people are blowing up about this that and the other thing. Keep it going. Not only is it entertaining to read, but I'm learning as well.

If I may throw some questions in here, what does OP stand for? Also someone mentioned BC Cd's. What is that?

I believe that OP means Original Poster (the person who wrote the original post). I sometimes also use it to mean Original Post (the text). I believe that both are accepted, but I could be wrong.

BCs are buoyancy compensators. In the general sense, they include backplate with wings (BP/w) (or at least the wing ) as well as "jacket" or "vest" style compensators, and even the old-school "horse collars." In common usage on ScubaBoard (SB) BC usually refers only to the "jacket" or "vest" style buoyancy compensators. For many "BC" is a bad word - some of those who very much prefer BP/w refer to BCs as "poodle jackets."

BCD is buoyancy compensation device, which is the same as BC.