horizontal ascents

[SparticleBrane]

One of the best demonstrations we use in our open water classes is a dive slate in the water.
If you take a standard dive slate and put it in the water, horizontally (parallel to the bottom), it well take a good while to sink due to the greater surface area presented to the water. If you take that same slate and put it in the water vertically it will almost immediately sink to the bottom.

While the doesn't seem like an incredible demonstration, it shows the power of proper positioning in the water and how much easier it is to maintain depth if you're horizontal vs. being vertical.

 

[JimC]

Cave divers tend to stay horizontal at all times no matter what. It is a trim configuration meant to avoid stirring up silt within the cave. It is a fairly critical cave issue.

Actually, cave divers go into whatever position is required for the cave profile. As a cave diver I put my self in the best position allowed by the cave (and my abilities and 'read') to reduce silting, eliminate cave damage and increase efficiency. That is often not horizontal.

 

[Soggy]

Nice horizontal trim in your avatar photo, Soggy. Looks good.

Photoshop is great, isn't it?

 

[nadwidny]

Not sure how much easier it is, but, I was told one reason we ascend horizontaly is to be able respond quickly to a buddy in need, toxing diver, OOG, etc., as opposed to a slower response, due to being verticle. One would first need to acquire a horizontal swimming position before being able swim to their buddy.

Chris

Those are possible side benefits of a horizontal ascent but the main reason is that the body decos out better when horizontal.

 

[nereas]

What if you want to move vertically? I'm thinking DCS Dome in Taj Mahal kind of vertical.

Then you press the trigger on your X-scooter and point it upwards, or do a barrel roll.

(All kidding aside, that is actually what you are not supposed to do.)

 

[FishTaco]

Those are possible side benefits of a horizontal ascent but the main reason is that the body decos out better when horizontal.

Hi Brian,
I'm not saying you're wrong, and it seems logical, just curious as to why you believe its the main reason. Could you direct me to a scientific study on the subject?

Thanks,
Chris

 

[ScubaMilo]

One of the best demonstrations we use in our open water classes is a dive slate in the water.
If you take a standard dive slate and put it in the water, horizontally (parallel to the bottom), it well take a good while to sink due to the greater surface area presented to the water. If you take that same slate and put it in the water vertically it will almost immediately sink to the bottom.

While the doesn't seem like an incredible demonstration, it shows the power of proper positioning in the water and how much easier it is to maintain depth if you're horizontal vs. being vertical.

Now I'm by no means an advocate of verticle ascents.
But the problem with your anology is your dive slate does not have a means of propulsion attached to the bottom of it.
So I think what Fishtaco was saying is it takes quite a bit of practice to become comfortable doing horizontal ascents especially in a dry suit.
Where as verticle ascents, any yahoo can pretty much hold a stop even without proper buoyancy control(by simply using their fins).
So in reality a verticle ascent could be considered easier by some.


I do not believe that horizontal trim makes much if any difference in the perfusing of inert gasses from the tissues to the blood.(or visa versa)
Due to this paragragh in the o2 window paper on the GUE website:

For practical purposes, liquids are incompressible and do not respond to changes in ambient pressure. Because of this, the sum of gas partial pressures in a liquid can be less than ambient pressure. Liquids such as blood and other body tissues will equilibrate only with the gas partial pressures to which they are exposed. On the alveolar side of the alveolar membrane, the total partial pressures must equal ambient pressure. However, on the liquid side of the membrane, the total partial pressures can be less, and in some areas may be quite a bit less than ambient pressure. The partial pressure that a gas exerts in a liquid depends on the temperature, the solubility of the gas in the liquid and the amount of gas present. Thus, if the amount of gas present and the temperature remain constant, the partial pressure of the gas in a tissue is fixed. If one gas is removed from a tissue, the remaining gases do not expand to fill the partial pressure vacated by the gas that was removed. Figure 3 shows total partial pressures for air breathing at 1 ATA from inspired gas to venous blood. Because of the decline in PO2 from alveoli to arterial blood, the total gas partial pressure in arterial blood during air breathing at 1 ATA is 752 mmHg, less than ambient pressure (760 mmHg). If PaO2 is lower than 95 mmHg (assumed in this example), then the total partial pressure in arterial blood will be less.

With all this in mind, I would lean toward the primary idea that being horizontal, makes you more readily able to deal with unforeseen or emergency situations.

I do not claim to be an expert on any of this, these are just my observations.

Milo

 

[texdiveguy]

Horizontal ascents are must more interesting while on your back in the water column. :mooner:

 

[Thalassamania]

I have learned a valuable lesson about doing horizontal ascents. However, this one happened on our way down at the start of the dive in the shallows (maybe around 10-15 ft).

I got in the water first, followed by my wife and my son and our DM (my son's buddy).

My son was having problems equalizing, so he would yoyo to go deeper and then go up a bit to relieve the pressure if he couldn't equalize. This was happening for about 3-5 minutes and he and the DM were in about 10ft. My wife signaled me to go see what was wrong and to help bring my son down.

Maintaining trim and a horizontal position, I got behind my son who was in a vertical position. The DM was also in a horizontal position to my son's right side.

Suddenly, I could hear a low rumbling sound and fear suddenly dawned on me--it was an approaching boat! I could see the shadow of the hull fast approaching us with the props at full speed. The DM and I understood what we had to do, so we grabbed my son and we pulled him down as fast as we could fin down. Fortunately, we got away from the props and we caught our breath at about 15 feet.

If the DM and I were in a vertical position, it would have cost us seconds to get into a horizantal position and I could only shudder to think what the outcome would have been like.

Lessons learned: Stay horizontal in descent and ascents. You are always in good position to respond to any emergency.

Hope this helps,
Hory

If you want to make that argument you need to be arguing for a vertical, head down attitude during ascent.

 

[SparticleBrane]

Now I'm by no means an advocate of verticle ascents.
But the problem with your anology is your dive slate does not have a means of propulsion attached to the bottom of it.
So I think what Fishtaco was saying is it takes quite a bit of practice to become comfortable doing horizontal ascents especially in a dry suit.
Where as verticle ascents, any yahoo can pretty much hold a stop even without proper buoyancy control(by simply using their fins).
So in reality a verticle ascent could be considered easier by some.

Any yahoo can do a vertical ascent, because they're used to being vertical all day long. None of us move around on our bellies all day so being horizontal takes a lot of getting used to.

The entire point of the dive slate is that it doesn't have propulsion attached. It shows how much easier it is to remain in a fixed location in the water column, not moving, by being horizontal as opposed to vertical.

See what I'm getting at?

I really wish I had a copy of the video...it's actually really good. You can let the horizontal dive slate get almost 3/4 of the way down the pool (takes a good while) and then put in the vertical slate and it will beat the horizontal one to the bottom.