Yuri accident

hi all,

I was watching a tv program call Monty's diving mysteries i think and one of them was " the divers graveyard". It was about the Blue Hole in Dahab and why so many divers died there. The so sad accident of Yuri Lipski appeared on the show.

My question is , why was he sinking so fast ? is there any depth where your speed increases because of pressure? was he overweight? I dont seem to understand it.

 

The deeper you go, the less buoyant you are. The wetsuit compresses. That's why you have to add air to the BC once the descent starts. When we did the Blue Hole in Belize, the DM had to grab one of the divers and add air to her BC. She was sinking like a rock, and probably would have kept going if he hadn't gotten to her. I don't know the exact depth at which one has to add air -- it would depend on how much weight the person is carrying and the wetsuit.

 

well .... that doesnt make me feel any better ! i guess you notice as you descent that youre going too fast and have to add air on BC

 

As you learned in your OW class, all air spaces compress as you descend. This includes the air in your BC and the little trapped nitrogen bubbles in your wetsuit. The thicker the wetsuit, the more buoyant it is at the surface, and the more buoyancy you can lose as you go down. I have been told of a test where a 7 mil wetsuit was taken to 100 feet, and it had lost 23 pounds of lift! If you add to the equation the fact that many people dive overweighted, you can, indeed, become quite negative at depth. This is one of the reasons for proper weighting that is rarely mentioned, but it is quite important that the lift of your BC match the maximum amount you can become negative as you go down; if at any time, you are "heavier" than your BC can lift, then only the power of your legs can get you back to the surface. Careful weight checks are important!

 

It's not just the amount of lift, but the rate of flow though the power inflator. You can reach descent speeds where holding the inflator down does not stop your decent because you are losing buoyancy faster than you can add it. Especially if your inflator is clogged or your valve not fully open.

 

Dropping your weights would send you back up in that scenario, but you'd probably end up with very bad decompression injuries. It could still be fatal. Better to avoid it in the first place! I suppose that's why the blue holes are considered advanced dives?

On a related note, I was recently on a black water Pelagic dive in 5000fsw. They clip you to a tether that is designed to stop your descent at about 50fsw. I read someone's log of that dive where he lost buoyancy control on his initial descent, and was stopped by the line on his way down. I wonder if he realized that the line saved his life? That guy probably had no business being on that dive.

 

I think with regards to the Yuri dive and footage there is so much speculation. I've heard one account where it was believed he was doing a "bounce dive" where he intended to hit the bottom and come back up to break a personal depth record. The bottom line is that no one knows for sure the "why" that was in his mind.

The physics are just as others explained. As a new diver, I tend to read a lot of the accident threads in hope of reinforcing the skills that I was taught. If sinking, and air in the BCD does not stop that ascent, drop weight.

In Yuri's case, I don't know if that would have made a difference at the depth he was at. The air in his tank would have been compressed as well. I'm sure those more proficient in the calculations could chime in.

 

You start adding air to your BCD pretty early if you want to stay neutral. I usually stop my descent at around 5m to wait for my buddy and do the last check on each other before starting to dive, and already at that depth I have to add some air to my system to avoid sinking further. Once I'm neutral and everything checks out OK, I just exhale a bit to continue descending.