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#190
primary buoyancy ctrl
Diver123 - 9/10/2008 6:15 PM
Category: Equipment
Replies: 29

OK, I was just reading some of the surveys. One question was what type of BC to use. This guy Scouter JT, is telling another diver Deepsteel that he uses his dry suit for primary buoyancy ctrl. I’m not sure where this guy learned to dive or through what agency, but i don’t know of any agency that stands behind this method and you have to be an idiot if this is how you dive. I want to know when this guys next deep dive is, I’ll meet him at the hospital to say i told you so.
#227
Scout - 9/11/2008 7:36 AM
I know ScouterJT and have dived with him on several occasions. He is an excellent buddy, careful and considerate. If he uses his drysuit for primary buoyancy control, that’s OK with me.
#3936
seawolfdiving - 9/11/2008 7:10 PM


I dive with a drysuit when I’m diving local (Central Pennsylvania) cold water sites. Been diving drysuits for quite a while. When I am on the surface I use my BCD for floatation. As I submerge, I vent all air from my BCD and use my Drysuit as my primary buoyancy control. When I am coming back up, I do a safety stop at about 15ft, during which I vent all air out of my drysuit and switch back to my BCD. I realize that most drysuit divers wait until they are completely on the surface before going back to their BCD for buoyancy, but I figure I have to wait at the safety stop for a while so I might as well make the most of it.


 I have found that if I need more buoyancy than my drysuit can provide, while I am at depth, then I am overweighted, and I adjust my weights accordingly.


What it comes down to is that "Yes" I use my drysuit as my "Primary" buoyancy control during the dive , and I use my BCD while on the surface.


Although I am not the most experienced diver in the group, I can say that this technique has served me well. I have yet to make a trip to the hospital because of it, nor do I feal particularly like an "Idoit".


 


 


 
#3936
seawolfdiving - 9/11/2008 7:10 PM


I dive with a drysuit when I’m diving local (Central Pennsylvania) cold water sites. Been diving drysuits for quite a while. When I am on the surface I use my BCD for floatation. As I submerge, I vent all air from my BCD and use my Drysuit as my primary buoyancy control. When I am coming back up, I do a safety stop at about 15ft, during which I vent all air out of my drysuit and switch back to my BCD. I realize that most drysuit divers wait until they are completely on the surface before going back to their BCD for buoyancy, but I figure I have to wait at the safety stop for a while so I might as well make the most of it.


 I have found that if I need more buoyancy than my drysuit can provide, while I am at depth, then I am overweighted, and I adjust my weights accordingly.


What it comes down to is that "Yes" I use my drysuit as my "Primary" buoyancy control during the dive , and I use my BCD while on the surface.


Although I am not the most experienced diver in the group, I can say that this technique has served me well. I have yet to make a trip to the hospital because of it, nor do I feal particularly like an "Idoit".


 


 


 
#190
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Diver123 - 9/12/2008 5:38 PM
What happens if when the valve sticks, the good year tire man will shoot to the surface like a cork. If the inflator on your bc sticks, it is much easier to control, and vents air more quickly than a full dry suit. I guess what I was trying to get at is, don’t tell this to a new diver. Using your dry suit for primary control can be quite dangerous, your dry suit was intended to keep you warm, dry and releave squeeze, as i said I don’t know of any agency that endorses this technique, if you find one let me know. Until then you should learn to use you equipment as it was intended. Would you use one of your back up lights as a primary light going into the dive?
#4586
Jen-Michael - 9/12/2008 11:55 PM
If you properly weight yourself so that you have just enough negative buoyancy to stay submerged, and you happen to be wearing a dry suit, then when you put air in your dry suit you tend to become neutrally buoyant, and you don’t have a need to use a BCD to control your buoyancy. Some of the "ancient" divers up here, down here for you, still dive solely with a backboard, and dry suit.

Couple of disturbing things about what you said , disturbing because you claim to be a divemaster, and this seems like common dive sense:
From Diver123: What happens if when the valve sticks, the good year tire man will shoot to the surface like a cork.

The same thing you would hopefully do if your BC inflator is stuck, pop the hose, vent as necessary, and abort the dive. You don’t need to take a technical course to figure either of those out just common sense.

From Diver123: your dry suit was intended to keep you warm, dry and releave squeeze,

Your dry suit was not intended to relieve squeeze, your wet suit does a better job of doing that, as it equalizes without having to add air; because relieving squeeze, after all, is just equalizing the pressure between inside and outside the suit.

From Diver123: Until then you should learn to use you equipment as it was intended.

Yes, you should like weights, and how to properly weight yourself. And dry suits like what to do should you have a run on inflator, because whether you’re using your BC as a primary buoyancy control or not, if it happens and you don’t know what to do you’re S.O.L.

Just to bust even more.
From Diver123: Would you use one of your back up lights as a primary light going into the dive?

Yes, yes I would. It’s bright enough, why not?


#3936
seawolfdiving - 9/13/2008 1:05 PM
The following are quotes posted by [ Diver 123, TODD ,CHICOPEEMA ,United States] who claims, on his profile, to be certified or affiliated with the following agencies: NAUI, PADI, TDI. Also claims to be at certification level of: Divemaster or AI.

[Quote, posted 9/10/2008]
“This guy Scouter JT, is telling another diver Deepsteel that he uses his dry suit for primary buoyancy ctrl. I’m not sure where this guy learned to dive or through what agency, but i don’t know of any agency that stands behind this method and you have to be an idiot if this is how you dive”.

[Quote, posted 9/12/2008]
“Using your dry suit for primary control can be quite dangerous, your dry suit was intended to keep you warm, dry and relieve squeeze, as i said I don’t know of any agency that endorses this technique, if you find one let me know. Until then you should learn to use you equipment as it was intended.”
(CONTINUED)
#3936
seawolfdiving - 9/13/2008 1:06 PM

(CONTINUATION)
First of all, I wish to thank Diver 123 for his kind invitation to “learn to use my equipment as it was intended”.
As I certainly realize that my 30 years of very active diving experience, being certified at the instructor level for no fewer than 2 recreational SCUBA training agencies, both military & commercial dive training and experience and an degree in Dive Technology would, in no way, provide me with “all of the answers,”.;
I have accepted your most gracious challenge.

In doing so, I have decided to write an article and post it on the blog space of this website. The article will address Diver123’s specific “concerns” as well as emphasize the need for exercising “critical thinking” when dealing with the multitude of information available to us.
(CONTINUED)
#3936
seawolfdiving - 9/13/2008 1:07 PM

(CONTINUATION)
I have completed some of my research into the questions posed by our friend and fellow diver Todd from CHICOPEEMA, concerning the use of the drysuit as the “primary buoyancy control device during the dive phase of a drysuit excursion and the use of the BCD as “surface floatation” during such an exercise.

Although not complete, my research has yielded the following information:
PADI teaches this method of using the drysuit for buoyancy control during the submerged phase of the dive and the BCD as surface floatation. NAUI also agrees with this technique. These results were obtained directly from the training and lesson guides and instructional videos of the named agencies.

I have queried the training departments of YMCA, and TDI/SDI as well as the RSTC concerning their current policy on the subject. They have not yet responded.

My intention is to complete and post the article on this subject sometime within the next week. This will include citations of reference materials used, as well as rational behind both teaching and using the currently accepted techniques.

Ron sends
#190
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Diver123 - 9/13/2008 2:53 PM
From Jen-Michael: If you properly weight yourself so that you have just enough negative buoyancy to stay submerged, and you happen to be wearing a dry suit, then when you put air in your dry suit you tend to become neutrally buoyant, and you don’t have a need to use a BCD to control your buoyancy.
 
with doubles, stage bottles, lights and reels I’m over weighted as it is. I don’t see any way around the over weighting for the dives we do. If you do please enlighten me.
#190
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Diver123 - 9/13/2008 3:01 PM


From Diver123: What happens if when the valve sticks, the good year tire man will shoot to the surface like a cork.

The same thing you would hopefully do if your BC inflator is stuck, pop the hose, vent as necessary, and abort the dive. You don’t need to take a technical course to figure either of those out just common sense.



the same but different, yes disconnect air, with a drysuit you have one dump most bc’s have atleast 2. Oh yeah vent at the neck seal, good idea flood your suit get your buoyancy under ctrl and then complete deco schedual with 35 degree water in your suit for an average of 45 min. great idea.
#190
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Diver123 - 9/13/2008 3:06 PM


Your dry suit was not intended to relieve squeeze, your wet suit does a better job of doing that, as it equalizes without having to add air; because relieving squeeze, after all, is just equalizing the pressure between inside and outside the suit.


wet suit compresses under pressure, providing less insulation, but that isn’t the topic. The function of a dry suit, if it is not supposed to releive the squeeze than what is?
#190
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Diver123 - 9/13/2008 3:09 PM


Just to bust even more.
From Diver123: Would you use one of your back up lights as a primary light going into the dive?

Yes, yes I would. It’s bright enough, why not?



obviously you dive alot, common sense wasn’t a priority for you was it?
#8208
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GypsyDiver - 9/13/2008 8:21 PM
I hear "common sense" and I shiver. Common Sense is not Common! I have dove with PADI Instructors who advise to use the Dry Suit for bouyancy control and BC as Backup. I have dove with NAUI instructors they say just the opposite. I have dove with Army and Navy divers that say to just put enough air in the drysuit to prevent squeeze. It seems to some to make sense to put air in the smaller bladder as opposed to a large suit. It is entirely up to you, the diver. The instructor will give you the doctrine, but as we have seen in this discussion, you are going to do what YOU think is best! 
#7880
Kemperite - 9/14/2008 1:46 AM
Dove is for swimmers - we "have dived".
#7880
Kemperite - 9/14/2008 1:55 AM


So you’re a PADI DM/AI? Have you read the Specialty Instructor Manual that PADI puts out? You don’t know of any agency that stands behind this method because you don’t actually pay attention. When RECREATIONAL diving PADI says (and I agree with) that you should use your Dry Suit for your buoyancy at depth and use your BCD only in an emergency or while at the surface. I realize that you are a Mass diver and you probably believe in wearing 40 pounds of lead with your dry suit because no one ever taught you any better (not different - I’ll just say your training was flat out wrong in this instance). In recreational diving you should need butt loads of weight. In recreational gear with a dry suit I wear 8 pounds. No, I don’t expect you to have the buoyancy control I do. You’ve already shown you have little clue as to what is actually going on because you don’t even read the manuals to develop an informed opinion.


Technical diving is a different story. When equipped and trained as a Tec Diver you use the Dry Suit only to eliminate squeeze and you should use your BCD bladder for buoyancy if necessary. Again, I don’t use a whole lot of air for buoyancy and I wear NO weight when Tec Diving. I’d hazard a guess that you use doubles and aren’t adequately or even actually trained in their use.


The reason for the difference? Many. Primary reason given? Recreational Divers aren’t trained to handle that many items of buoyancy control. When you task load a Recreational Diver with remembering where they have air to vent you run a higher risk of injury.


Just a little bit of education for the unwashed masses.
#7880
Kemperite - 9/14/2008 1:59 AM
In Recreational Diving you "shouldn’t" need butt loads of weight. Typo on my part in above post - my apologies.
#190
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Diver123 - 9/14/2008 5:18 AM


The reason for the difference? Many. Primary reason given? Recreational Divers aren’t trained to handle that many items of buoyancy control. When you task load a Recreational Diver with remembering where they have air to vent you run a higher risk of injury.


Then why would you change the way they were taught in their ow classes, they didn’t have a dry suit then.


and yes i reread both naui and padi drysuit course guide lines and standards, and it actually doesn’t say how buoyancy is controled while wearing a drysuit, i tried to attach these pages for you but was unable to.


section 9 under specialty diver courses in PADI manual, NAUI was borrowed.


so if you as an instructor could tell me where to find this info it would be apperciated, not that i’m going to change the way i dive, but i would know where to find this information and address it with all the instructors that i have been taught by.
#7880
Kemperite - 9/14/2008 7:38 AM


PADI Specialty Instructor Manual - Dry Suit Diver - Page 22 at the very top:


1. BCDs for use with dry suits - although under most circumstances you maintain neutral buoyancy underwater with your suit (more on this later), you always use a BCD when dry suit diving.


a. The BCD provides emergency buoyancy if you get a substantial leak in your suit.


b. The BCD provides a more comfortable way to float at the surface.


c. Choose a BCD that fits over your dry suit - the one you have will probably work, but you may need to readjust it - and that does not cover or interfere with the suit valves.


Page 26 - Special Note - Overweighting is the number one cause of problems when dry suit diving. Take the time to determine the amoutn of weight you need.


Page 26 -


4. Adjusting your buoyancy underwater.


a. Underwater, you add air or argon only to the suit. Do not use your BCD.


1. This avoids a suit squeeze (severe pinching due to the compression as you descend).


2. You’re not having to control two systems - adding or releasing gas as you change depth.


3. It keeps the proper amount of air/argon in your undergarment for insulation.


As stated in the previous posts - this is for RECREATIONAL Dry Suit Diving ONLY! Tec Diving takes on the method of enough air in suit to prevent squeeze and then use BCD as necessary - Tec gear is heavier and therefore the dry suit would normally not support the Tec Gear at depth without going into balloon mode.


Bottom line is what actually works best for you when you are properly weighted and equipped.


Reality is that this is not a change from Open Water. Remember, the idea here is to control buoyancy - just like in OW. Difference being you use the Dry Suit rather than the BCD. You are still using ONE item to control buoyancy underwater. That’s how we treat a recreational diver. One item so as to not task overload.


Anything else? I have manuals and will happily look up lots of methods. Oh, I read them all too at least twice so it’s pretty easy for me to find stuff.
#8208
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GypsyDiver - 9/14/2008 7:49 AM
Thanks, Danny, YOU ROCK!!!!
#3936
seawolfdiving - 9/14/2008 11:35 AM
PADI Drysuit Diver Manual, PADI International 2003,
“…you will learn that it may be more efficient to control your buoyancywhile underwaterusing your suit. (pg 30).
&
Paragraph in the “Diving a Drysuit Section) “…At this point (excepting an emergency or problem) you will stop using your BCD until you return to the surface. Underwater, you typically control your buoyancy using your drysuit” (pg38).
&
PADI Training video also states clearly the use of the Drysuit as your buoyancy control device while underwater and your BCD for surface floatation.

NAUI SCUBA Diver Manual, NAUI Worldwide, 2004
When you dive with a Drysuit, you use the drysuit for buoyancy control and the BCD for surface floatation” (pg 40)

These are only a few citations from two major certifying agencies concerning the topic.
All citations continue to state that you should always wear a BCD and use it for surface floatation and in the event you need extra buoyancy or in case of emergency.


#170
rescue15 - 9/14/2008 4:28 PM


So what’s the deal? I have been diving dry for at least 10 years and was taught (by PADI) back then to dive with an empty BC. The same holds true today. As a matter of fact, I just bought a new dry suit this summer and for some unknown reason I read the instructions. (I know men don’t read the directions). In the directions it said to use the suit for primary bouyancy...hmmm.


And I don’t know but I think when Danny gets rialed up and starts rebuting your point, you should probably take what he says as the absolute truth.


Steve
#190
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Diver123 - 9/14/2008 11:42 PM
From Kemperite:

 this is for RECREATIONAL Dry Suit Diving ONLY! Tec Diving takes on the method of enough air in suit to prevent squeeze and then use BCD as necessary - Tec gear is heavier and therefore the dry suit would normally not support the Tec Gear at depth without going into balloon mode.



I stand corrected and I appologize, I spoke with my instructors today. In recreational diving a drysuit is used for primary ctrl. I was taught the other method from the begining. Again I’m sorry for the incorrect information.
#190
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Diver123 - 9/15/2008 7:21 AM


more info, padi dry suit knowledge review question 4.


How do attain positive buoyancy at the surface, attain and maintain neutral buotancy underwater, and prevent dry suit squeeze when dry suit diving?


At the surface, add air to BCD, not dry suit. Underwater, if you’re wearing a shell dry suit add air to the dry suit to adjust for neutral buoyancy. Underwater, if you are wearing a neoprene dry suit or if you are wearing a dry suit for tec diving, add air to your buoyancy compensator to adjust for neutral buoyancy. Add a little air to your dry suit on descent to prevent dry suit squeeze.


This is out of the "08" instructor manual
#2157
MouthBreather - 9/17/2008 8:36 PM
Wow! I think that was the most spirited discussion I have seen on dive buddy. Can’t resist to throw my two cents in after some of the bubbles have disipated. I’m a recreational dry suit diver and as I was instructed by PADI in their specialty course, I use the suit for below surface bouyancy control. As a recreational diver, I carry substantially more weight to offset the additional bouyance provided by the suit, but after I have eliminated the squeeze by adding air to the suit, I don’t need any more positive bouyancy. For me, the air in the suit is just enough to maintain neutral bouyancy at recreational depths-no need to inflate the BC. With the drysuit inflated then, I manage position of the bubble in the suit to attain my desired body position. A stuck inflater valve would be managed by disconnecting the inflater hose.
#190
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Diver123 - 9/18/2008 7:09 AM


From MouthBreather: but after I have eliminated the squeeze by adding air to the suit, I don’t need any more positive bouyancy.



I also spoke with Larry at PADI training services, he stated your dry suit is primarily to releave squeeze. if while at depth you releave the squeeze and achieve neutral buoyancy great, but if you do need to crtl buoyancy beyond that Padi says to use your BC. Now the only way I could get a more dircet answer is if the CEO of PADI would call me directly.


But this also poses the question, what is to squeeze? I dive with my suit tight to my body, but still comfortable to move.
#8208
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GypsyDiver - 9/18/2008 8:16 AM
From Diver123:

But this also poses the question, what is to squeeze? I dive with my suit tight to my body, but still comfortable to move.


Squeeze

By Fred Bove, M.D., Ph.D.

Perhaps the most troublesome part of diving is the continuous need to avoid the consequences of pressure changes associated with depth. The physical effects of pressure are described by Boyle’s Law, which defines the relation between pressure and volume. Boyle’s Law states that the product of absolute pressure and volume of a gas is constant: P¥V = Constant. If air pressure in body spaces cannot equilibrate with ambient pressure on descent, the forces produced will reduce the volume by squeezing surrounding tissues into the space. On ascent, air in the lungs must be allowed to vent or overinflation will occur. Tissue injury caused by Boyle’s Law effects is called barotrauma or squeeze. The accompanying table shows the changes a five liter volume undergoes as it is subjected to a dive of 100 feet. The greatest volume change is in the first 10 feet. Because the greatest volume change is at the shallowest depth, the most common time for squeeze to occur is during the initial portion of the descent or, in the case of lung barotrauma, during the final portion of the ascent.

SUIT SQUEEZE

Drysuit users may notice painful red streaks on their skin after diving. These are caused by suit folds lying against the skin during descent. Folds containing air are compressed against the skin, the skin is forced into the folds and local injury occurs. Always leave enough residual air in a drysuit so it is not tight against the skin. Wearing a light garment (thermal underwear) under the suit will prevent the suit from sealing tightly against the skin.

All divers will experience the effects of squeeze. Careful attention to equilibration of air spaces during descent and ascent, good dental hygiene, avoiding air swallowing, maintaining equipment and attending to the health of your nose, throat and sinuses are measures that will help avoid injury owing to squeeze or barotrauma.

Sharm el Sheik Emergency and Trauma Center: A new Emergency and Trauma Center in the well-known Red Sea diving resort area of Sharm el Sheik has recently been opened. The hospital, the first of its kind in southern Sinai, specializes in diving medicine and includes a physical therapy clinic and a pulmonary therapy clinic. Sharm el Sheik Emergency and Trauma Center is close to many hotels and the downtown area.

Further information may be obtained by contacting Dr. A.G. Hamada, 8841 Garden Grove Boulevard, Garden Grove, CA 92844 or call (714) 537-6780, fax (714) 537-6782.
#190
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Diver123 - 9/18/2008 6:14 PM

Squeeze

By Fred Bove, M.D., Ph.D.

Thank You, but I guess my point was what you consider being squeezed I my consider comfortable.
#3936
seawolfdiving - 9/18/2008 11:02 PM


The following is a direct quote from the response that I received from Mary Kaye at PADI T&E concerning the drysuit & buoyancy issue:


"In the PADI Dry Suit Diver Manual, Product 79901 page 30, under the heading BCDs, Weight Systems and Argon Inflation Systems, it states, “ …you’ll learn that it may be more efficient to control your buoyancy while underwater using you suit, not your BCD.” The text goes on to explain that a BCD is always worn with a dry suit primarily for safety in case the dry suit malfunctions, providing the ability to control buoyancy underwater while you abort the dive, and for surface support since fully inflating the suit at the surface is uncomfortable at best. “Therefore, you’ll use your BCD when swimming or waiting at the surface.”


Also in an e-mail from Tom Leaird of YMCA SCUBA:


"First, when diving with a dry suit it always advisable to use a buoyancy compensator in case of catastrophic zipper or other failure. For liability’s sake we would never teach diving without a BC.





Now, where to put the air during a dive is up to the individual but here is how I teach it and is generally acceptable.


At the surface the BC is used for floatation and dumped completely upon descent. As the diver descends, the quantity of air in the suit is compressed and therefore the amount of insulation is reduced. So, it is advisable to maintain a constant volume in the suit, thus maintaining both warmth and buoyancy.





In addition, the amount of weight worn should only compensate for neutral buoyancy on the surface with no air in the BC and a relaxed breath. Over-weighting will cause greater changes in buoyancy during the dive. Of course, positioning of the weight is important for trim and balance.





During ascent from depth many suits exhaust automatically and need no effort on the part of the diver. However, some suits must be manually purged making ascent air dumping more critical. "





Hope this helps...


 


Ron sends
#3673
Bigdogdown - 9/19/2008 11:25 PM
I dive a whites drysuit in michigan and I have to tell ya, that if you are diving with a single cylinder, then your drysuit becomes your BCD thats the way it is!! You have to start adding air to the drysuit after about 10ft of descent, and between the about 100lbs. of lift that my drysuit can provide and the 45 of my wing on my backplate that amount of air to just get rid of the "squeeze" on my suit just trims me out perfectly. I was trained by SDI/TDI and IANTD and they advocate this kind of training, I also know that NAUI advocates the same thing. When I come up to about 20 ft I have vented all of the air out of my drysuit and I am back on the wing on my bcd but till then the BCD is only a back up. Though when I am diving my double steel 130’s and 80 al stage and 40 cu. ft. O2 bottles for deco then the wing gets more excercise deep because I would have to inflate the drysuit so much that I would look like the michelin man, but that’s a different story.