NauticalbutNice
Contributor
Diver0001:
Ach, you knew what I meant
Nauticalbutnice :fruit:
Drysuit Student
- Thread starter skeet
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Ach, you knew what I meant
Nauticalbutnice :fruit:
NauticalbutNice:Ach, you knew what I meant
Nauticalbutnice :fruit:
ye gotta love the scottish accent
But regarding buoyancy and a drysuit, i normally dont teach it that way. It's normally just to relieve squeeze, therefor not having to worry about over inflating the suit.
SF
In a pool, you don't have but a fraction of the gas in your suit that you would at say 110' if using it for bouyancy. So I would imagine a pool demonstrated summersault would be quite different from one performed at depth with a lot more gas involved.
BC's have more than one dump location which implies they are designed to do so in many different positions. A drysuit does not.
Agreed on the last point.
BC's have more than one dump location which implies they are designed to do so in many different positions. A drysuit does not.
Agreed on the last point.
Diver0001:
mempilot:
I'll admit to not doing summersaults at 110ft so I'll give you the benefit of the doubt. My first intuition is to say that it's easier deep because the gas doesn't expand as much. I'll do a couple the next time I'm down that deep and tell you what happend.
Once again I agree with your analysis but once again you see different things in practice....
I see a lot of new divers and divers in training and I would bet you 10 bucks that only about 1/2 of new divers (or divers new to dry suits) would think about a butt-dump during an inverted ascent and of the ones who think about it, most would remember too late. The default reaction I would expect to see based on my experience is to see people trying like hell to swim down and vent the bcd with the inflator hose held above their head, which is now the lowest point..... That's why I said that getting righted is primary and dumping secondary once you're inverted. Once your righted I'll give you the point that venting the bcd is easier and more efficient for most people.
R..
R..
The problem as I see it is this. While practicing summersaults in a pool is great procedural training, it leaves out the sequence of events that leads to the need to do so. Example. A diver descends to 130' for the dive, adding gas to the suit to compensate for squeeze. As they approach their desired depth, they add air to the suit slow the descent and establish neutral bouyancy. They complete the bottom of the square, and start to ascend horizontally. At first, the suit doesn't need much purging, but as they approach shallower depths, the gas expands more quickly. They end up inverted and the shoulder dump isn't effective. They do the summersault, but as they ascend, the gas is expanding more quickly. Watch a lift bag being shot from 70'. It starts to rise slowly picks up speed as it ascends.
The summersault, while performed in the pool at 10 feet while neutrally bouyant is much different than doing it while positively bouyant coming up from depth where you have loaded up on N2. I do stationary summersaults all the time at depth to play with control and positioning while wearing doubles. They are, as you say, easy and on a dime. Doing them on a runaway ascent is a different story.
People make working the bc and ds simaltaneously sound too difficult. One takes very little for squeeze, and the other works like it did in OW class. Not really all that hard. Put all the air in the suit, and you have much more to deal with in an emergency.
The problem as I see it is this. While practicing summersaults in a pool is great procedural training, it leaves out the sequence of events that leads to the need to do so. Example. A diver descends to 130' for the dive, adding gas to the suit to compensate for squeeze. As they approach their desired depth, they add air to the suit slow the descent and establish neutral bouyancy. They complete the bottom of the square, and start to ascend horizontally. At first, the suit doesn't need much purging, but as they approach shallower depths, the gas expands more quickly. They end up inverted and the shoulder dump isn't effective. They do the summersault, but as they ascend, the gas is expanding more quickly. Watch a lift bag being shot from 70'. It starts to rise slowly picks up speed as it ascends.
The summersault, while performed in the pool at 10 feet while neutrally bouyant is much different than doing it while positively bouyant coming up from depth where you have loaded up on N2. I do stationary summersaults all the time at depth to play with control and positioning while wearing doubles. They are, as you say, easy and on a dime. Doing them on a runaway ascent is a different story.
People make working the bc and ds simaltaneously sound too difficult. One takes very little for squeeze, and the other works like it did in OW class. Not really all that hard. Put all the air in the suit, and you have much more to deal with in an emergency.
Fly N Dive
Contributor
i just did my drysuit class 11/21 and was told to use the suit for boyancy and not the bc, at the time i didn't question it, because it sounded right. but i guess it would be harder to vent air through one drysuit valve vs the three on my bc. i guess you learn something new every day 
bcsean
Guest
the other problem with using the drysuit for buoyancy is dynamic instability. that big bubble of air moves all over and makes you incredible unstable. Your BC puts the air over your center of gravity and is quite stable empty, or full. I dive my suit quite snug, this also allows me to shed weight off the belt. I'm diving a shell drysuit, so when weighted properly, I really don't add much air during the dive. Less air in wing/suit means less air to expand. Much simpler to dive weighted properly.
Hal
Contributor
Can a wetsuit be a good undergarment for warmth when using a drysuit?
mempilot:
Agreed. 99% of scuba training is like this. Is this "treat the symptoms" or "be prepared"? I can never remember.....
I was following until you said this. I don't see how gas expanding causes "ending up inverted" unless you ignore everything else you learned.
OK, I see your point. I'll wholeheartedly agree that if you're trying to somersault your way out of an uncontrolled ascent you are too late. The somersault is intended to correct the situation before your ascent is uncontrolled. I'll also agree that doing things in the pool isn't always good practice for how it goes for "real". On this point we totally agree.
We don't have anything to discuss here either. I believe, in fact, that the whole idea of using the drysuit to control your buoyancy is an admission of defeat in teaching buoyancy control in OW. I think PADI does this mainly for two reasons: (1) when they first developed their drysuit specialty most of us were wearing horse-collar bcd's that would ride up on your front when inflated and were generally a pain in the patoot. Keeping the air in the drysuit was simply easier and more comfortable in that context. and (2) I think offers better legal protection becuase they can claim in court that minimum task loading is the least risky. Note that neither one of these has anything to do with the realities of modern sport diving.
R..
I think we're pretty much on the same page. As for the following, I didn't mean the expanding gas caused the inverted situation, but merely pointing out that some panicked divers would try to swim for the bottom on an uncontrolled ascent causing the inverted bubble situation. I just didn't explain my thoughts too well.
Diver0001:
Similar threads
