Ascent / Descent - Safety Stop YoYo practice??????

[Phishboy]

Hi anyone...
I'm a newbie with a dumb question...
My girlfriend and I are newly certified OW divers and want to practice slow and safe ascents and descents (this is particularly important for my girlfriend's descents as she often has trouble equalising her ears).
We would like to practice in a local quarry where the depth is only around 10/15m and work on our buoyancy / trim skills but also getting accustomed to slow ascents.

Question: Can we practice going down to 10/15m then coming up to 5m (simulating a safety stop)... holding for 3 minutes then going down and repeating the exercise a few times.
I'm not sure if this is good or not to go up and down like a yoyo.
We just want to get a good grip on these basics so we can become more comfortable when we go diving 'proper'.

Thanks anyone who replies!

 

[seaducer]

I will leave it to someone who can explain the physics better than I, but keep in mind that the first 10 meters causes the partial pressure of all the gasses you are breathing to double in all your tissues. In other words the top 10 meters holds the single largest increase in pressure that you will experience on a dive.

Now, the NDL for 10 meters is long enough that you should run out of air before bottom time, so the amount of nitrogen you are going to absorb should be sufficiently low enough that you will not have any problems with that aspect of dcs, but air spaces are going to compressed, decompressed, recompressed, etc. This makes it possible to develop squeeze and possibly an embolism.

Controlled ascents and descents are important and you certainly should practice them. Holding your depth for a safety stop is no different at 10 meters than it is at 5, so you can practice hovering and holding your depth at depth, and practice your movement through the water column when appropriate. Keep in mind that controlling your bouyancy at depth is also practicing to control your buoyancy anywhere.

That being said a lot of people who need to log a certain number of dives do pretty much exactly what you are proposing with no ill effects. But for my money I would just simply dive, enjoy the dive, and pay attention to your skills along the way. With practice and a few dives it all becomes second nature...

have fun

 

[irishsquid]

I will leave it to someone who can explain the physics better than I, but keep in mind that the first 10 meters causes the partial pressure of all the gasses you are breathing to double in all your tissues. In other words the top 10 meters holds the single largest increase in pressure that you will experience on a dive.

Now, the NDL for 10 meters is long enough that you should run out of air before bottom time, so the amount of nitrogen you are going to absorb should be sufficiently low enough that you will not have any problems with that aspect of dcs, but air spaces are going to compressed, decompressed, recompressed, etc. This makes it possible to develop squeeze and possibly an embolism.

Controlled ascents and descents are important and you certainly should practice them. Holding your depth for a safety stop is no different at 10 meters than it is at 5, so you can practice hovering and holding your depth at depth, and practice your movement through the water column when appropriate. Keep in mind that controlling your bouyancy at depth is also practicing to control your buoyancy anywhere.

That being said a lot of people who need to log a certain number of dives do pretty much exactly what you are proposing with no ill effects. But for my money I would just simply dive, enjoy the dive, and pay attention to your skills along the way. With practice and a few dives it all becomes second nature...

have fun

Well said and good advice.

 

[MXGratefulDiver]

NDL isn't going to be an issue ... but depending on how you do the dive, compressing, expanding, re-compressing, and re-expanding the bubbles of inert gas in your blood stream could be.

My recommendations if you want to practice this ...

- Do it first dive of the day, and early in the dive ... before your body has time to accumulate a lot of excess nitrogen.

- Limit your depth to no more than 10 meters (2 ATA) ... keeping the tissue loading to a minimum.

- Make your ascents slower than the recommended 10 meters per minute ... giving your fastest tissues time to offgass more effectively as you ascend.

- Since you're doing this to develop ascent control, practice making a short (15 second or so) stop every 2 meters between your bottom depth and your safety stop depth.

... Bob (Grateful Diver)

 

[String]

I woudnt do it. The last 5-10m of a dive are when pressure changes over an area are greatest so its the most critical part. Its also the easiest to form bubbles.

Id say if you're going to yo-yo the LAST place you'd want to do it is in that 5-10m range.

Also the more ups and downs you have the harder and harder it gets to equalise per session.

 

[Thalassamania]

I you really feel the need to practice that sort of yo-yo, do so at the greatest practical depth that you can, where the percentage change in pressure is the least. I'd not recommend doing what you are planning, e.g., down to 15m then up to 5m.

 

[on_two_wheels]

If depth is only 10-15 meters, invest in some type of anchor & buoy. Do a short dive and practice your ascent on the line. Mark your safety stop point on the rope/line (tie line to buoy, roll out 15 feet and mark it with a streamer or other obvious mark). While it's not as many ascents it's safer to do this 3 or four times over a day at the quarry than doing the yo-yo. Plus you'll have a nice visual reference to practice holding your depth during safety stops. If you lose the hover you simply grab the line, regain control and continue practice. Additionally, you'll be able to use it as a starting point for your bottom time which is useful in practicing navigation skills.

 

[bracko]

seaducer... I would argue that holding your depth at 10m is significantly easier than at 5m. if there is a resultant buoyancy force at 10m it will result in a [proportionally] slower rate of ascent than the same force at 5m. threfore although you may still bounce at 10, but it might be the difference between a controlled bounce and uncontrolled acscent to the surface.

at least that's my opinion the reasoning behind why I find it harder, anyone agree/disagree??

 

[dumpsterDiver]

seaducer... I would argue that holding your depth at 10m is significantly easier than at 5m. if there is a resultant buoyancy force at 10m it will result in a [proportionally] slower rate of ascent than the same force at 5m. threfore although you may still bounce at 10, but it might be the difference between a controlled bounce and uncontrolled acscent to the surface.

at least that's my opinion the reasoning behind why I find it harder, anyone agree/disagree??

Yes of course it is harder to hold your stop the more shallow you are. Anyone who says hanging at 10 meters (in cold water and a thick suit) is the same as hanging at 5 meters is a little out of touch. Experienced divers can obviously do it, but new divers who need to practice, will probably find it much tougher to stop exactly at 5 m than at 10 m. For safety, it is probably best to do it with a well anchored, vertical down line or an accomodating section of vertical quarry wall, that way if you start to loose it, you can cheat and grab the rope or wall to prevent a blow up. Obvioulsy the goal is to not touch anything and eventually to do it free with no visual references.

As others have said. I would do the practice at the very start of the dive and if you do loose it and pop to the surface, i would dive very conservatively for the rest of the day.

 

[on_two_wheels]

For safety, it is probably best to do it with a well anchored, vertical down line or an accomodating section of vertical quarry wall, that way if you start to loose it, you can cheat and grab the rope or wall to prevent a blow up. Obvioulsy the goal is to not touch anything and eventually to do it free with no visual references.

As others have said. I would do the practice at the very start of the dive and if you do loose it and pop to the surface, i would dive very conservatively for the rest of the day.

GREAT idea!!