Rear Inflation - Face Down in Water

[PaulChristenson]

I'm not trying to be a smart***, but, how does a back inflate BC squeeze your guts?

OK...I'll be one...

That is when the Wing is between you and the plate...

 

[Blitz]

I have been diving a back inflate of some kind for years and have never experienced this "facedown" effect that I am always hearing about. I have dove bc's and backplates, warm water and cold and in none of those situations have I been pushed face first. What Lamont said about the AL tanks makes some sense, but I have dove those and can't remember that problem.

 

[diveman7683]

I have been diving a back inflate of some kind for years and have never experienced this "facedown" effect that I am always hearing about. I have dove bc's and backplates, warm water and cold and in none of those situations have I been pushed face first. What Lamont said about the AL tanks makes some sense, but I have dove those and can't remember that problem.

Even though you haven't had that problem, it exists. I see it a fair bit with students and new divers. Some ways we fix that is to lower the tank abit, add trim weights to the tank.

 

[Blitz]

I don't doubt at all that it happens, I am wondering about the mechanics. Like you said, trim weights, tank height. Is it more common with anxious divers? Stuff like that. I guess I am trying to get at the 'the reason' it happens.

 

[Damselfish]

I don't doubt at all that it happens, I am wondering about the mechanics. Like you said, trim weights, tank height. Is it more common with anxious divers? Stuff like that. I guess I am trying to get at the 'the reason' it happens.

Simple physics, if you've got too much weight in front and too much bouyancy behind relative to everything else it happens. Remember that peoples body shapes and compositions and other stuff are going to play into it too, so what isn't a problem for you may be for someone else. Your usual BI does not have a heavy plate in back. And if it's got WI pockets in front they are sometimes out from the body a little more than if you were wearing a weightbelt, which would make it worse.

A steel tank would help, but that's often not an option for people that travel to warm places that have only AL80s, pretty common. Even in cold water areas some people buy AL80s just because they're cheaper or because they haven't caught onto the weighting issues yet.

Maybe a crotch strap would help prevent someone from feeling they need to add more air on the surface, but only if the BC is actually riding up to begin with. I think a well fitting BC can and should stay put on it's own without needing extra straps as band aids. People suggest it often, but I don't think too much air is the problem most of the time. If the BC stays put and you still fill it way up, sure. But if the BC is up around your ears, the reason often given why people overinflate, the part that's out of the water isn't going to contribute floatation on the back side.

Anxious divers UW tend to hold extra air in their lungs they don't realize, which makes them need more weight to get down. On the surface that air would be pretty much in the center of things so I don't think it's really affecting the weight distribution. I suppose if they are carrying extra weight because of this, so need to inflate more on the surface, maybe it makes a little difference.

I got a BI a couple years ago and had trouble getting it sorted out at first. It doesn't ride up, I don't put much air in it and I'm certainly not anxious after all these years. My problem was weight distribution - when you dive tropical with 6 pounds it's pretty hard to split it up 4 ways! (I solved this by convincing myself 8 was better. So if I can get 4 2#s for the 2 front and 2 rear pockets I'm all set, though some places it's hard to get enough small weights. I've put an odd weight on the tank strap if I have to, but it's a pain. One of these days I'll get a pocket for when I have to do that.)

 

[cool_hardware52]

Maybe a crotch strap would help prevent someone from feeling they need to add more air on the surface, but only if the BC is actually riding up to begin with. I think a well fitting BC can and should stay put on it's own without needing extra straps as band aids.

"Band aid" is not an accurate description of a crotch strap on a Hogarthian Harness, it's a basic element.


Tobin

 

[Damselfish]

"Band aid" is not an accurate description of a crotch strap on a Hogarthian Harness, it's a basic element.
Tobin

I wasn't talking about harnesses. I was talking about BI BCs. If you need to add a crotch strap to keep a BC in place (that wasn't intended to have one) I believe it's a bandaid. Maybe a solution for someone, but still a bandaid.

 

[cool_hardware52]

I wasn't talking about harnesses. I was talking about BI BCs. If you need to add a crotch strap to keep a BC in place (that wasn't intended to have one) I believe it's a bandaid. Maybe a solution for someone, but still a bandaid.

Or maybe a sign of poor original design.

Tobin

 

[Damselfish]

Or maybe a sign of poor original design.

Tobin

yes, sometimes. A bandaid for a bad design, or a bandaid for poor fit, whatever.

 

[Scuba Jerm]

I tried a rear inflation BC yesterday and no matter how hard I tried, I ended up face down in the water. I usually use a jacket style and have herad that the back inflation unit is really good for trim.

Any thoughts on what I can do to keep my face out of the water on the surface. I prefer to swim on my back or rest on my back on the surface..

Thanx
Regards
Tom

Tom,

for that reason I like the Oceanic Outrigger BC. http://www.onestopscuba.com/catalog/product_info.php?cPath=26_32&products_id=53.

It's a bit more pricey than others out there but it is really comfortable and easy to use. Just my 2 cents.