Buoyancy question

TMHeimer · Sep 6, 2009

I've been diving 4 years and took the Peak Perf. Buoyancy course. Found my ideal weight, which has yet to change. When I did the OW course we we given standard lead shot weight belts based approximately on our height/weight, etc. I found during the check out dives (20-30 fsw) that I was up & down like a yo-yo. I assume some of that had to do with being a newbie, but when more exactly weighted the problem disappeared. I'm wondering how many others experinced this during their check out dives. It would seem that a buoyancy check (even if in the pool in fresh water- then add 5-7 pounds for salt) should be included in the OW course. Any comments?

DevonDiver · Sep 6, 2009

It is included on the OW course - both on confined session 2 and as a mandatory skill in each of the OW dives...

Confined Water Dive Two
Overview
Predive safety check
Deep water entry(s)
Snorkel clearing – blast method
Snorkel – regulator exchange
Descents
Surface swimming with scuba
Mask removal, replacement and clearing
No mask breathing
Disconnect low pressure inflator
BCD oral inflation and deflation at the surface
Proper weighting
.....

And here is how it is supposed to be taught in confined water...

13. Proper weighting — At the surface and in water too deep to stand up in, demonstrate and have students practice proper weighting for neutral buoyancy. If students do this with full cylinders, then add weight to compensate for air used during the dive — typically about 2 kg/5
lbs for a single cylinder.

OPEN WATER DIVE 1
Performance Requirements:
During Open Water Dive 1, under instructor supervision, the student will:
1. Listen to and participate in the briefing and dive planning session for the dive.
2. Prepare, and with a buddy don and adjust, scuba equipment with minimal instructor/staff assistance.
3. Enter the water in the manner determined during the briefing.
4. Adjust the weight so that the student floats at eye level with an empty BCD and holding a normal breath.
5. Descend in a controlled manner using a descent line or sloping bottom contour to provide control and reference to a depth not greater than 12 metres/40 feet.
6. Under direct instructor supervision, explore underwater to gain experience.
7. Exit the water as determined during dive planning.
8. Attend the instructor’s debriefing.
9. Log the dive for instructor signature.

OPEN WATER DIVE 2
Performance Requirements:
During Open Water Dive 2, under instructor supervision, the student will:
1. Listen to and participate in the briefing and dive planning session for the dive.
2. Prepare, and with a buddy don and adjust, scuba equipment with minimal instructor/staff assistance.
3. With a buddy, perform the predive safety check.
4. Enter the water in the manner determined during the briefing.
5. Adjust the weight so that the student floats at eye level with an empty BCD and holding a normal breath.
.......

OPEN WATER DIVE 3
Performance Requirements:
During Open Water Dive 3, under instructor supervision, the student will:
1. Listen to and participate in the briefing and dive planning session for the dive.
2. Prepare, and with a buddy don and adjust, scuba equipment with minimal instructor/staff assistance.
3. With a buddy, perform the predive safety check.
4. Enter the water in the manner determined during the briefing.
5. Adjust the weight so that the student floats at eye level with an empty BCD and holding a normal breath.
......

OPEN WATER DIVE 3
Performance Requirements:
During Open Water Dive 4, under instructor supervision, the student will:
1. Listen to and participate in the briefing and dive planning session for the dive.
2. Prepare, and with a buddy don and adjust, scuba equipment with minimal instructor/staff assistance.
3. With a buddy, perform the predive safety check.
4. Enter the water in the manner determined during the briefing.
5. Adjust the weight so that the student floats at eye level with an empty BCD and holding a normal breath. If this adjustment is made with a full cylinder, add enough weight to compensate for air used during the dive (usually about 2 kg/5 lbs).
.....

DevonDiver · Sep 6, 2009

The PADI buoyancy check, as stated in the instructor manual....

Recommended Techniques for Meeting Performance Requirements
5. Buoyancy/weight check.
Use the following steps to assist student divers in getting their weight set properly.
• Help students estimate the amount of weight to use initially.
• When possible, conduct buoyancy checks in water that is shallow enough to stand up in.
• Have students, with their regulators in their mouths hold normal breaths, squat to eye level, draw their feet off the bottom and hang motionless. With proper weighting, students will float at eye level. Add or remove weight as needed and recheck buoyancy.
Since you normally do this with full cylinders, add weight to offset the weight change from air use during the dive, usually about 2 kg/5 lbs with a single cylinder.
• Have extra weights on hand, perhaps in a float if you’re not near a dock or boat. You speed things by having students simply hold weights until you find the right amount, then make a single adjustment to the weight system.
• If you conduct the buoyancy check in water too deep to stand up in, supervise the students more closely. Be sure you or an assistant remains close enough to students who may be overweighted to assure they don’t sink too far with empty BCDs. You’ll probably need to have
students adjust their weight one at a time.
• On occasion, you may have a student who has trouble staying down even though “properly” weighted. Apprehension (high lung volume) and other factors may cause this; keep a couple weights handy so you can adjust for this if necessary during the dive.

spectrum · Sep 6, 2009

Sadly it's a topic that often gets glossed over.

Even if a good weight is established in training it can change a lot when a diver gets into their own gear and regular environment. This means that every diver needs to understand how the weighting relationships work. They don't need to know any physics math but being able to recognize the puts and takes then fine tune it with a check becomes an advanced skill many flounder with.

Pete

vladimir · Sep 6, 2009

TMHeimer:
It would seem that a buoyancy check (even if in the pool in fresh water- then add 5-7 pounds for salt) should be included in the OW course.

We can easily improve upon this approximation. Use total weight (diver+equipment) X 1.025 (or whatever the specific density of your saltwater is) and add enough weight to get to that product. If you and your equipment are 145 pounds and your gear is 55 pounds then you'd add 5 pounds. (145+55) X 1.025 = 205.

TMHeimer · Sep 6, 2009

Thanks guys. Actually, I was unaware the buoyancy test was part of the PADI OW course. I am slack, especially for a DM candidate. My LDS is 5 star PADI and by far the biggest for hundreds of miles here in Canada, with excellant Instructors. But we NEVER did any buoyancy checks either in the pool or on any of the 4 check-out dives. I guess I'll re-phrase the question: Who out there had a similar experience as myself at their LDS where the buoyancy check was NOT done in training and you were just given weight belts based on approximations?

oly5050user · Sep 6, 2009

if buoyancy checks were not done in pool -repeatedly and during the training dives what else did these "excellent" instructors leave out?

TMHeimer · Sep 6, 2009

Actually nothing else that I can think of. I have always felt confident in my dives (140+) and all of the other skills were covered thoroughly. I later figured maybe it was due to time constraints at the city pool or some other reason that we bypassed the buoyancy tests. It certainly seemed at the time that something was always being taught, either in the classroom or pool, so I figured to check all 6 of us for exact weighting may have taken just too much time... I have no buoyancy problems now due to the PPB class I took in Florida where we did ONE buoyancy test in the pool.

DevonDiver · Sep 6, 2009

TMHeimer:
Actually nothing else that I can think of. I have always felt confident in my dives (140+) and all of the other skills were covered thoroughly. I later figured maybe it was due to time constraints at the city pool or some other reason that we bypassed the buoyancy tests. I have no buoyancy problems now due to the PPB class I took in Florida where we did ONE buoyancy test in the pool.

It's worth cross-checking what you did/do against the requirements. A DM candidate should have access to an instructor manual, so that will clear away any doubts you may have. For OW (and above) divers reading this - just remember that the PADI manuals for the respective courses also provide a list of the skills that must be covered on the course.

TMHeimer - it may not mean you were badly taught. I do use the 'recommended' method, but I prefer to teach my students to assess and analyize their bouyancy in a more 'educated' fashion - by raising an awareness of how much air they need to add to achieve neutral bouyancy at/after the descent...and how well they can maintain a safety stop (with no/minimal air in the bcd at the end of the dive). It is possible your OW instructors used a different method, although it does seem they resoundingly failed to achieve the requirement to educate you properly on how to achieve/develop your bouyancy/weighting awareness.

powerofslack · Sep 6, 2009

I think correct weighting is the biggest thing you can do for beginning ow students- if they're not weighted correctly everything else will be twice as hard and exhausting- of course because we're cold water our first check out dives are in 7/7 suits that have people wearing 20 lbs or more of lead- We spend about 1/2 hour in the first pool session just working on weighting, and teaching students how to triple-check and fine-tune their weight as they learn to exhale more etc. Then we spend two skin dives before our first check out scuba dive to check and then fine-tune and re-check our ocean weighting, and again work with them on how to know if they need to add or subtract a couple of pounds as we go through the check out dives. Of the idiosyncrasies of how my particular course director liked to do things, this emphasis on weighting is the one I've become the biggest fan of, and of the things I notice when working with advanced students coming from someone else's OW class, being improperly weighted, sometimes by a good bit, is probably the most frequent uh-oh that we end up noticing.

Buoyancy question

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