Vertical vs horizontal ascent/descents

[goldenbear01]

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A ScubaBoard Staff Message...

Split thread from

Diving at a reef wall with no bottom in sight..

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The biggest danger is for new divers who are overweighted and not paying attention - jacking with their gear or the like. When they finally look up, the notice that there's no one around them and their ears are starting to hurt from their rapid descent.

As pointed out by Mike Ferrara, that's the problem with people who are over weight, but swim head up, (instead of horizontally in trim), to keep their depth. When they stop to fix their gear, they sink.

newb diver here so i've never done a wall dive; i've been doing my descents w/my head up (i thought padi said that's the safest way to descend viz a viz equalization). should i change my descent do horizontal/head slightly down?

 

[Boxcar Overkill]

newb diver here so i've never done a wall dive; i've been doing my descents w/my head up (i thought padi said that's the safest way to descend viz a viz equalization). should i change my descent do horizontal/head slightly down?

There are two issues here:

(1) I was referring to swimming around in general. Some divers don't get their buoyancy right, and they try to control it with their fins by swimming upwards a little bit as they move forward. So rather than swimming in a prone position (horizontal) they are swimming at a 45 degree angle with their head up. The problem with this, (besides being a little bit harder to move because of the increased drag) is that when they stop swimming for whatever reason, the can't hold their depth and they start to sink. Often without even knowing it. So as a general rule your depth shouldn't be dependent on your forward motion.

(2) I personally descend horizontally, although I don't think it's that important. But I've found that most of the stuff you do is easier when you're prone, including descending. Here I have to give credit to the DIR divers for always pounding away on that point. I have to say that after trying it for awhile, I think they're right. You have to learn to dump air through your rear dump valve, (or at least I did on my setup) and there are a few other little differences. But it's a bit easier to move around and control your depth when "in trim". So I descend horizontally. But your not doomed to an early death if you find you don't like it.

There are other, more experienced divers that can chime in here. But that's my thinking on the topic.

 

[AirInHere]

I am working on my Divemaster and have been observing/helping with classes for a couple months now and have a simple observation that I think helps.

Most students are pretty nervous about what they are doing in the water. Decending feet first is just to enable the instructor to have one less issue to deal with regarding students not being able to descend for their certification dives. Forgotten weights, insufficient wieghts and other real issues need to be dealt with swiftly if half the class has decended already, head first descents that result in no air coming out of the LP inflator is a user error issue that can be avoided.

I see it happen every single class. I think I even did it once or twice.

Later on, you develop a better balance for bouyancy and can manage a horizontal decent pretty easily. (About the same time you manage to stop making impact craters when you drop down).

Regarding the vertical position of some divers.....If you wear a jacket BCD, then expect to trim vertically. Its what they are designed to do. Fighting that is counterproductive. BP/W are meant to float horizontally. If that is what you want, get a wing.

Neither one is more right than the other. Each is correct for its own design.

Many people love the upright positioning a jacket BCD offers. It also allows people to have a more natural field of vision for what they are used to experinecing.

BP/W will not only float you horizontally, they point your mask at the bottom of the ocean. You have to look straight up to see forward, and that is uncomfortable for some people.

Critical thinking about all your gear is important. Your gear is probably doing exactly what you paid for it to do.

Make sure you understand what you are paying for before you buy.

 

[24940]

Vertical ascents/descents are taught because it is easier than teaching a proper horizontal ascent.

If you are horizontal, positive buoyancy can be offset by finning. With a vertical ascent, this is not an option. This fact alone is enough for me, but there are several other advantages to horizontal.

Regarding the vertical position of some divers.....If you wear a jacket BCD, then expect to trim vertically. Its what they are designed to do. Fighting that is counterproductive. BP/W are meant to float horizontally. If that is what you want, get a wing.

That's just not true. Jackets trim out fine if you have the weight distributed properly. The instructor in the video below is wearing an off the rack poodle jacket. Looks pretty well trimmed, despite the fin skulling to keep the heavy fins from sinking. He looks just the same in a BP/W.

 

[Blackwood]

i've been doing my descents w/my head up (i thought padi said that's the safest way to descend viz a viz equalization).

That doesn't make any sense to me. Regarding equalization (as well as other things), you may run into trouble with overly quick ascents/descents.

Boxcar Overkill mentioned the increased effort due to drag of swimming in a non-prone position. That same drag helps us to control ascent and descent rates.

I can't think of a reason that vertical/head-up descents would be safer. Oh, well, unless people aren't taught to control their buoyancy. So I guess that's it.

 

[Boxcar Overkill]

Regarding the vertical position of some divers.....If you wear a jacket BCD, then expect to trim vertically. Its what they are designed to do. Fighting that is counterproductive. BP/W are meant to float horizontally. If that is what you want, get a wing.

Neither one is more right than the other. Each is correct for its own design.

With due respect, I disagree with this statement. While I dive a Bp/w, I know a lot of divers who use a jacket and they trim our horizontally just fine. It may be somewhat easier with a bp/w, but jackets can do the job just fine, too.

Blackwood and 24940 are spot on, I think.

 

[AirInHere]

I stand behind my remark about how the jacket style BCD position a person in the water. Of course a skilled diver can trim out a jacket style BCD. That is not being debated.

I am saying that jacket vs BP/W have inherent properties that must be considered when deciding to use either type of gear.

You should not treat them like they are identical devices, and you should not be surprised when they perform differently.

 

[Boxcar Overkill]

I am saying that jacket vs BP/W have inherent properties that must be considered when deciding to use either type of gear.

You should not treat them like they are identical devices, and you should not be surprised when they perform differently.

I wouldn't disagree with you if that was all that you had said. But you went further.

It's this part, particularly the bolded portions, that I disagree with.

Regarding the vertical position of some divers.....If you wear a jacket BCD, then expect to trim vertically. Its what they are designed to do. Fighting that is counterproductive. BP/W are meant to float horizontally. If that is what you want, get a wing.

Neither one is more right than the other. Each is correct for its own design.

(emphasis added)

1. I don't believe that it's counterproductive to swim in horizontal trim with a jacket style BCD, as you stated. In fact, I think it's a good idea. You probably won't die if you don't swim that way, but if the question is, "is it better for a diver with a jacket BCD to have Horizontal or Vertical trim?", the better answer is "horizontal."

2. I don't think that most jacket style BCD's were designed for vertical trim. It may be easier to have horizontal trim with a Bp/W, but I see no evidence that the manufacturers of jacket BCD's engineered them for the purpose of swimming upright through the water. By and large, I don't think that is there intended use.

3. I don't agree that "Neither one is more right than the other." Again, it's not going to kill you if you dive out of trim, (probably), but as a general proposition, it's not the better way to dive for either kind of BCD. Just how important it is depends a lot on what kind of diving you do. But I don't see how any experienced diver could argue that diving vertically in a jacket BCD is just as good as diving horizontally in a Bp/w. As a general proposition, that's just not true, whether one is talking about safety, mobility, control, etc. There may be exceptions, but I don't agree that is the rule.

So we'll just have to disagree.

 

[AirInHere]

I guess we will....

Regarding the vertical position of some divers.....If you wear a jacket BCD, then expect to trim vertically. Its what they are designed to do. Fighting that is counterproductive. BP/W are meant to float horizontally. If that is what you want, get a wing.

I have noticed that many students swim in a slightly angled position. They have their weight in the quick release pouches and a little near the tankbands. They level out horizontally when they take off swimming, but assume a vertical position as soon as their forward momentum is stopped. This is a natural position for a human body to be in and is comfortable for many people. Then they bend at the waist, kick their feet and assume a horizontal position to swim to the next point they want to stop at. You can maneuver weights around untill you automatically trim in a horiontal position with a jacket, but why fight its inherent properties? Buy a wing style BCD instead if you want to trim horizontally.

I do not think there is a concerted effort to make jacket style BCD trim vertically underwater. I do not really think the trim underwater has been given much consideration at all. I think the trim at the surface is given real thought. And you trim vertically in a jacket at the surface.

Neither one is more right than the other. Each is correct for its own design.
This is directed at the reality that there is no single set of gear that is perfect for every situation. Each persons skill level, intended dive site, intended dive profile and a million other factors influence their decisions. I intend on diving doubles at depths beyond recreational limits here in MoCal. My equipment choices are going to be very different than the choices of a person who intends to dive Ft Lauderdale, Florida's outer reef. And Same for someone travelling to PnG for a week of diving. Even if you decided to just dive a BP/W configuration, you would need different plates and wings for each of those areas. And each one could be the correct style for that region.

I guess we will have to disagree.....

 

[24940]

I have noticed that many students swim in a slightly angled position.

I've seen students descend on their backs. They have no control, initially. It's not a matter of fighting the bcd, it's about managing it.

You can maneuver weights around untill you automatically trim in a horiontal position with a jacket, but why fight its inherent properties?

Again, it's not a fight when your kit is configured properly. If your kit puts you into a vertical position, you are fighting to stay horizontal. Do you kick from point A to point B in a vertical orientation? Diving in any attitude other than horizontal is not efficient. If you are at an angle, your thrust is directed downward and forces you to be negative in order to maintain depth. Stop kicking and you sink. That's depth control not buoyancy control.

I do not think there is a concerted effort to make jacket style BCD trim vertically underwater. I do not really think the trim underwater has been given much consideration at all. I think the trim at the surface is given real thought. And you trim vertically in a jacket at the surface.

Designing a BCD around surface performance is like designing a car for parking lot performance. I have no prob staying vertical at the surface in my rig, but I'm usually flat on my back, either kicking to the site or just relaxing while I wait for my buddy. I don't know where you are getting the idea about these rigs being built for the surface, but here's a hint you might be on the wrong track: Trim pockets (found on most jackets) aren't there to make your attitude more vertical.

Even if you decided to just dive a BP/W configuration, you would need different plates and wings for each of those areas.

I'm getting the impression you have very limited, if any, experience with a BP/W. I've dived mine in Puget Sound, SoCal, Roatan, Hawaii and Oregon. Same plate, same wing. It's more an issue of transport than divabilty. Switching between steel doubles and singles requires a different wing, but the plate is the same.