THE "PERFECT ( being horizontal ) TRIM" HOAX

[BlueTrin]

Is there a documented test on the quantity of oxygen used between horizontal and vertical position ?

I don’t know if there is a test because you’d have to define what you want to test/study precisely.

But if you were to test that a guy in almost vertical trim is gonna require more effort to move the same horizontal distance on the ocean floor, surely you can see the finning at a 45 degree angle isn’t optimal?

I don’t think people are saying you should be in horizontal trim absolutely all the time, but if you move horizontally along the floor, surely almost people can see it’s efficient to be streamlined and fin in the direction you are trying to move?

 

[johndiver999]

Is there a documented test on the quantity of oxygen used between horizontal and vertical position ?

If you are not trimmed perfectly then it may require the diver to exert muscular tension in order to maintain a certain position. Often I hear people talk about keeping their butt and lower back tight in order to assist in good trim. If you are just drifting or hanging on a stop, then I would assume that the minimum amount of gas use would be inversely correlated with muscular tension.

 

[Jake 10]

If you are not trimmed perfectly then it may require the diver to exert muscular tension in order to maintain a certain position. Often I hear people talk about keeping their butt and lower back tight in order to assist in good trim. If you are just drifting or hanging on a stop, then I would assume that the minimum amount of gas use would be inversely correlated with muscular tension.

Will muscular tension increase oxygen consumption?

 

[Jake 10]

I don’t know if there is a test because you’d have to define what you want to test/study precisely.

But if you were to test that a guy in almost vertical trim is gonna require more effort to move the same horizontal distance on the ocean floor, surely you can see the finning at a 45 degree angle isn’t optimal?

I don’t think people are saying you should be in horizontal trim absolutely all the time, but if you move horizontally along the floor, surely almost people can see it’s efficient to be streamlined and fin in the direction you are trying to move?

The test : oxygen consumption by a diver in a horizontal vs a vertical position

 

[BlueTrin]

The test : oxygen consumption by a diver in a horizontal vs a vertical position

What would be the diver doing:

• doing nothing, just hanging underwater?
• moving a certain distance across the ocean floor?
• sitting on the bottom of a pool?
• … etc

You need to define the question to have a study.

 

[wetb4igetinthewater]

The test : oxygen consumption by a diver in a horizontal vs a vertical position

I think we can all apply common sense based on physics.

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I don't see anyone spending money on a study to show how people who exert themselves more will consume their gas faster.

 

[Jake 10]

What would be the diver doing:

• doing nothing, just hanging underwater?
• moving a certain distance across the ocean floor?
• sitting on the bottom of a pool?
• … etc

You need to define the question to have a study.

Let’s start with just hanging on the bottom working on buoyancy ,

 

[Wibble]

Is there a documented test on the quantity of oxygen used between horizontal and vertical position ?

I use about 0.8 litres of oxygen per minute when relaxed in horizontal trim; poking around inside a wreck, etc. Double that or more when task loaded or finning hard. Last dive was 2 hours duration and used 130 litres (43.71 bar of a 3 litre cylinder according to Shearwater)

The only time I'm vertical is when I've arrived back on the surface and waiting for the boat to pick me up. Descents are always horizontal as going down the shot line to the wreck. Decompression's always done horizontal a couple of metres from the SMB reel bouncing up and down.

The drysuit has a bubble of gas keeping me warm; anything other than horizontal means the legs squeeze and get cold. When vertical the drysuit will vent all the gas out of the dump and it gets harder to breathe.

The test : oxygen consumption by a diver in a horizontal vs a vertical position

I'd never be in a vertical position -- it's too uncomfortable, cold, affects diving, can't move around using fins... -- so can't help you with the gas consumption I'm afraid.

However, there's a correlation between good core skills and efficiency.

 

[boulderjohn]

Just a simple thought experiment. If you are hovering, your trim won't matter all that much in terms of energy use. But let's consider two divers swimming from point A to point B at the same depth.

• Diver A is at a 45° angle, so her/his kicking is propelling her/him upward at a 45° angle. Of course, s/he does not go up, and that is because s/he cannot do this and be neutrally buoyant--or s/he would ascend. So s/he must stay negatively buoyant and use some of that kicking to maintain depth. If s/he stops kicking, s/he will sink. In addition, the diver's body moving through the water creates a lot of resistance. The diver does, however make some forward progress.
• Diver B is swimming in horizontal trim. S/he is neutrally buoyant, so each kick pushes her/him in the desired direction. S/he can stop kicking and just glide at times without sinking because of being neutrally buoyant.

Which do you think will use more oxygen during the dive?

 

[BlueTrin]

Let’s start with just hanging on the bottom working on buoyancy ,

If the guys are good and don’t require finning for maintaining buoyancy, I doubt it makes much a difference in most conditions.

Don’t know if a study though …