Quick air dump from rear dump on horseshoe wing?

I have a DSS bp/w that I have about 10 dives on, slowly getting used to it. I also help out in my LDS's OW classes. I use the bp/w when I can during pool sessions to get some experience on it as well. Last night at the end of class I was doing some mental "what-ifs" and came across a problem.

We had all the students along the wall at the deep end mimicking the tag line on a boat as they exited the pool via the ladder. I was just kind of keeping them in line, on the wall, making sure they didn't bunch up, and keeping an eye out for problems. I'm inflated on the surface. I got to thinking, what would be the quickest way to get to the bottom of the pool (or down fast in open water) in an emergency? I figured I should go head down, and dump air through the rear dump, just as I would with my jacket BC.

After the students had cleared the pool, I gave it a try. When I got to the bottom, I could tell my air wasn't fully dumped, and was still positively buoyant. I turned head up, and dumped from the deflater. Quite a bit of air dumped out. I think what must have happened was that a lot of air was trapped on the opposite side of the horseshoe, at the bottom, and couldn't get out through the rear dump on the other side. I'm thinking that would not have been an issue with a donut wing.

How would this maneuver be best completed with a horseshoe wing?

http://www.scubaboard.com/forums/bu...ight-systems/196547-horseshoe-donut-wing.html This was a prior thread

as stated by evil_xander :

Horseshoe wings require a tad more effort to vent completely if you want to use only the bottom dump valve (it is left, on the internal part of the wing).

You first have to get the air to the highest point by elevating your torso, shoulders up, and then roll a bit to the right plus do a butt up so that the lower left part of the wing is the highest point. Basically, you shift air from right side all the way to the bottom left part of the wing. It does make a funny sound during the process. I'm sorry nobody yet filmed me do this maneuver as it does look like I have convulsions of some sort.

With donut wings, air moves also on the bottom arc, not only in the top arc, so it's somewhat easier to use only the lower left dump valve.

Not that it is much of an issue anyway, plus you always have the inflator dump valve, as with regular BC.



personally i still have a back-inflate bc that uses a horseshoe style -- i tend to use the shoulder dump along to get down quickly - or that and the inflator since some air will get trapped in the hose otherwise.

So it probably makes sense to use the inflator from a head up perspective to get a full dump, and to use the bottom dump valve for fine tune buoyancy? In my above scenario, I should have done a full dump at the surface via the inflator, and then turned head down to dive.

Slightly OT, but I'll ask here. On my jacket BC I've got the bottom dump on a pull cord, and the shoulder one I can either pull the inflation hose, or raise the hose up to vent. The shoulder also acts as a 'blow off valve' to keep a stuck low pressure inflation valve from popping the bladder.

Do wings work the same way? Can you vent by pulling the inflation hose? Do they have a blow off type valve? Or is it a model specific thing.

Inquiring minds want to know, and I'm not trying to thread jack ya.

Steve

Mine does not have a pull dump on the inflator hose. Note sure about other models. I believe all varieties of BCs have the over-inflation valve.

There is no good way to dump the other side of the wing if you are seriously head down. To empty the wing, you need to be head up and use the inflator dump.

I have never seen a good reason to submerge from a horizontal position, although I know some GUE instructors teach descending that way. It only works if you are sufficiently negative from your gas supply to overcome the buoyancy of the gas in the full pontoon, which, if you have had a full wing on the surface, means pretty big tanks or doubles.

it doesn't take much to be in a slightly head up angle (you don't have to be truly vertical). Air will seek the highest point, even if it is just fractionally different.... that puts the air easily expelled from the LPI...

TSandM:

I have never seen a good reason to submerge from a horizontal position, although I know some GUE instructors teach descending that way. It only works if you are sufficiently negative from your gas supply to overcome the buoyancy of the gas in the full pontoon, which, if you have had a full wing on the surface, means pretty big tanks or doubles.

Click to expand...

Can you say that part in different words? I guess the word I do not know in this application is pontoon.

PM sent

I'm using the word "pontoon" to refer to one side of the wing.