Trim on Walls

[cwoco]

Much is made about the importance of horizontal trim when diving on the sea bottom, but I'd like to find out what position board members typically adopt on walls. To me, on a wall dive, horizontal trim makes no sense, as you are more exposed to the currents that typically sweep along the wall face.

Let's say you are diving along a wall, and a gentle current is sweeping from left to right. You are also moving gradually to the right. Along the wall, there are large occasionally large chunks of coral (fan or barrel) that pop out. What body position do you adopt for most of the dive?

1) Vertical, as if in horizontal trim but the wall is the 'sea bottom'. Chest facing the wall.
2) Horizontal, fins out in the current, head towards the wall - same as on the sea bottom. Chest is facing down
3) Horizontal and sideways, as if in horizontal trim, but the wall is the 'sea bottom', and head is to the left, feet to the right (or vice versa). Chest is facing the wall.
4) Horizontal and sideways, the sea bottom is downwards, head left, feet right (or vice versa). Chest is facing down.

Previously, I mostly used 1) and 4), but on my last couple of dive trips, have been trying 3). It's harder to do that when the rental regulators breathe rather wet when sideways or upside down though. I also occasionally have to push off the wall when the current pushed me in towards the wall or I approached a large, protruding coral.

On the most recent trip, I noticed that my DM who dives walls every single day would adopt 1), but had far, far less movement than me. He was able to hover almost motionless without kicking, even with a gentle current pushing him sideways, while I was bucking around deciding whether to face the current or go against it.

I surmised that this was probably due to a deeper understanding of the currents and his body control. Imagine your body is a sail. If you angle a sail correctly, you should be able to get the wind/water to push u in nearly any direction. This is how windsurfers can sail (indirectly) against the wind, by cutting left and right.

 

[Patoux01]

Horizontal, facing wall for me (2) . I want to follow the current anyway, but I want to be able to get myself away or to the wall. Since I don't master the sidekick, that's the only position allowing me to do it.
Unless playing games, I usually don't dive on my side, and certainly not for a whole dive.

 

[wKkaY]

3 and 4 if i'm cruising along the wall.If i'm looking at something closely, probably a combination of 2 and 3 to get into position, and (when appropriate eg if dead rock is available) poking the wall for support, with current behind me.

 

[Frosty]

cwoc--all of the above.Body goes into whatever position it needs to to see what I want to see.

 

[Doc]

Usually #3, but Frosty said it best.

 

[MikkelBC]

Imagine your body is a sail. If you angle a sail correctly, you should be able to get the wind/water to push u in nearly any direction. This is how windsurfers can sail (indirectly) against the wind, by cutting left and right.

Apart from being a diver I am also a glider pilot, and this is a common misconception that I hear a lot. As long as you are not propelling yourself in any way or holding on to anything, your body will float along at exactly the same speed and direction as the current. There will be no flow around your body and therefore no force to act on your body as if it were a sail. Sails work in the wind because they are attached to the boat which is "attached" to the water. A sail wouldn't work on a weightless boat floating in the air. The boat would just drift along with the wind. Just like a kite only works in the wind because it is attached to the ground with a string.

Sent from my Nexus 7 using Tapatalk 4

 

[RJP]

To me, on a wall dive, horizontal trim makes no sense, as you are more exposed to the currents that typically sweep along the wall face.

I'm not sure I understand how you've come to this conclusion. How does horizontal trim make you more exposed to current?

As with most things in diving, I tend to "dive like a fish" orienting myself horizontally, pointing in the direction of travel. (When was the last time you saw a fish swimming horizontally... but oriented vertically?)

 

[cwoco]

Sorry, what I meant was that position 2) seems to make less sense to me. This is based on the understanding that the current is stronger further out from the wall, and having your head to the wall and legs out towards the open ocean would expose you to the currents more than the other positions where your legs are closer to the wall. I may be wrong though.

MikkelBC that's an interesting piece of information - I had not considered that at all, and it seems to make sense. At the same time, I'm sure there are different current gradients characteristics depending on how near you are to the wall - slower closer to the wall, faster in the open ocean? And that difference should then have some effect on steering, right? Or is my logic completely broken..

All of my understanding is based on the concept that the current is weaker closer to the wall and stronger out in the open ocean, similar to how the current is weaker closer to the seabed. Please do correct me if I'm wrong, because it's definitely interesting to learn and it will help me (and maybe others) become better divers!

 

[KDAD]

(When was the last time you saw a fish swimming horizontally... but oriented vertically?)

Friday night at maclearie park. It was a seahorse though. Does that count? (Sorry couldn't resist )

Actually I do agree that trying to emulate a fish makes sense and I also try to do that.

I think that a lot of newer divers assume a vertical position because they are so used to being that way out of the water. When we enter the weightless environment we assume the position most familiar. The only reason that the seahorse can successfully do it is because they have fins on their back where our tank would be. We don't have that so we have to swim like other fishes.

Fish do orient themselves in all sorts of directions when at the wall to reach stuff but then revert to a normal position in open water.

 

[MikkelBC]

At the same time, I'm sure there are different current gradients characteristics depending on how near you are to the wall - slower closer to the wall, faster in the open ocean? And that difference should then have some effect on steering, right? Or is my logic completely broken..

Current gradients will certainly complicate the picture. As far as I can figure, the effect will be one of rotating your body rather than pushing it anywhere.