Problem with my Poseidon

[avi foox]

I own a 7 complete with the Poseidon harness M28 and new cpod.
Lately I'm having a problem - when I get to about 30 ft. Or lower after a deeper dive despite being on minimum volume and being on the heavy side on weight I shoot up like a rocket no control I'm about to do the deco 40 class and I'm afraid of an accident. Please help thanks

 

[JohnnyC]

You've gotta get way ahead of the ascent curve when ascending on a rebreather. You need to vent the loop much more than you'd think, plus wing, plus drysuit. Remember, minimum loop volume is only minimum at the depth you are at. As soon as you ascend, loop volume goes up. Because the pressure differential is greater the shallower you are, what you can get away with at 100ft and what you can get away with at 30ft is entirely different. I'd recommend finding a pool and just practicing ascents from the deep end. You'll torch through O2 like nobodies business, but it's great practice.

If you can get in a pool with a sloping shallow to deep end, the floor is your friend. Practice following the floor up.

 

[RainPilot]

I have, on occasion, forgotten to open the counterlung dump valve on an ascent and then min loop gets max loop fairly quickly. This is on my Mk6 so same lungs.

On a steady rate ascent, I usually exhale every second breath or so out of my nose, that keeps the lungs close to min loop and lets me focus on wing control for the rate of ascent.

How much dil are you using on the deep dives? With the standard aluminium tanks I find that dil-heavy dives lead to a fairly big buoyancy swing. I have a set of 3L steels as well and they have made my weighting a lot simpler.

 

[w3dge]

How much dil are you using on the deep dives? With the standard aluminium tanks I find that dil-heavy dives lead to a fairly big buoyancy swing. I have a set of 3L steels as well and they have made my weighting a lot simpler.

Surely the buoyancy change is the same on both ali and steel cylinders? The swing is caused by the amount of gas used, not the material from which the cylinder is made.

 

[RainPilot]

Indeed, what i meant was that it simplified my weighting. What I found was that the ali tanks get VERY tail-light in comparison, inevitably I would end up toward the end of the dive running a larger loop volume unconsciously to compensate. Once I switched to steel, it became a lot easier to notice that my lungs were making me head-light.

Brain-screen translation issue, thanks for the reminder.