PADI OW and BPW

[Eric Sedletzky]

Doing a 15’ weight check in a wetsuit at the beginning of a dive when the wetsuit is fresh and warm with a near empty cylinder is not the same as a 15’ wetsuit weight check at the end of a full length dive.
The wetsuit will be cooled so the gas bubbles will be smaller and the suit will still be somewhat compressed.
The only way to properly check the final buoyancy of a wetsuit at 15’ is after a full length dive to depth.

Doing the eye level with full tank thing at the beginning of the dive is a good start, but after the dive and you’re on your way up you still need to do the 15’ weight check and see where you’re at.

 

[boulderjohn]

Doing the eye level with full tank thing at the beginning of the dive is a good start, but after the dive and you’re on your way up you still need to do the 15’ weight check and see where you’re at.

...and that is exactly what I and every other instructor in the shop told our students.

With the PADI standards, you are supposed to do a weight check on every one of the 4 OW dives, with an understanding that it may take all 4 dives to get it truly right. I once had a student for local OW dives tell me he had purposely used a 7mm suit in the pool so he would get his weight right, so he insisted he needed 22 pounds. I looked at his slight frame and thought "no way!" By the end of dive #4, he was happy as a clam with 10 pounds.

 

[wetb4igetinthewater]

@boulderjohn

How many open water classes have you taught in sub 50 degree F water with air temps 40 degrees F or colder?

That pre dive weight check takes precious time and students wind up suffering in the end from being cold.

So in my area there are two things being done. Instructors come up with some formula to weight students prior (like I do). Or just give students a heavy weight belt and be done with it. They are winding up on their knees anyway.

Which brings up an issue. In order to place students on their knees, they have to be overweighted. The float test will show that they have too much weight.

I see two problems. First, all agencies allow students to be placed on their knees so all agencies allow overweighting.

Second, no agency requires that weighting is to be checked at the end of dives with nearly empty cylinders.

John,

If you are ever back in my area and ever observe an open water class with students in wetsuits not taught by the shop Eight at Cove 2, Redondo, or Edmonds underwater park, take a picture a weight check at the surface being performed and send it to me, I’ll pay for dinner at Canlis, Seattle’s most expensive restaurant, for you and your wife.

 

[tursiops]

@boulderjohn

How many open water classes have you taught in sub 50 degree F water with air temps 40 degrees F or colder?

That pre dive weight check takes precious time and students wind up suffering in the end from being cold.

So in my area there are two things being done. Instructors come up with some formula to weight students prior (like I do). Or just give students a heavy weight belt and be done with it. They are winding up on their knees anyway.

Which brings up an issue. In order to place students on their knees, they have to be overweighted. The float test will show that they have too much weight.

I see two problems. First, all agencies allow students to be placed on their knees so all agencies allow overweighting.

Second, no agency requires that weighting is to be checked at the end of dives with nearly empty cylinders.

John,

If you are ever back in my area and ever observe an open water class with students in wetsuits not taught by the shop Eight at Cove 2, Redondo, or Edmonds underwater park, take a picture a weight check at the surface being performed and send it to me, I’ll pay for dinner at Canlis, Seattle’s most expensive restaurant, for you and your wife.

PADI OW Standards:
Dive 1: (Surface) Check and adjust weighting. (Underwater) Participate in a trim check.
Dive 2: (Surface) Adjust weighting and trim, as necessary.
Dive 3: (Surface) Adjust weighting and trim, as necessary.
Dive 4: (Surface) Adjust weighting and trim, as necessary.

So, it is OK to NOT do this, because it is cold out and it takes time?

 

[MichaelMc]

PADI OW Standards:
Dive 1: (Surface) Check and adjust weighting. (Underwater) Participate in a trim check.
Dive 2: (Surface) Adjust weighting and trim, as necessary.
Dive 3: (Surface) Adjust weighting and trim, as necessary.
Dive 4: (Surface) Adjust weighting and trim, as necessary.

So, it is OK to NOT do this, because it is cold out and it takes time?

Bolding above mine of 'as necessary'. Given deviation from perfect and student comfort, safety and conditions?

If we measured the diver's buoyancy, and their gear's, and their wetsuit's in the pool and all those items weights on the pool deck, and we did the math, how far off could we be? Drysuit in this case. And we had done this with 10 prior students.

 

[boulderjohn]

Bolding above mine. Given deviation from perfect and student comfort, safety and conditions?

If we measured the diver's buoyancy, and their gear's, and their wetsuit's in the pool and all those items weights on the pool deck, and we did the math, how far off could we be? Drysuit in this case. And we had done this with 10 prior students.

You would do your calculations as usual and then check it on the surface on the first dive to make sure you were correct. Then on each subsequent dive you would adjust as necessary, meaning you are taking into account the experiences from the previous dive.

 

[MichaelMc]

You would do your calculations as usual and then check it on the surface on the first dive to make sure you were correct. Then on each subsequent dive you would adjust as necessary, meaning you are taking into account the experiences from the previous dive.

Right, and if we know the weight and freshwater buoyancy of the diver and all their gear, the amount we were off at the start of the OW1 dive is likely not detectable by the precision of the tools we have floating at the start of OW1 (how high do they float, how heavy do they feel to a floating buddy/DM/Instructor, how fast do they sink, how full are their lungs). So we only really see at the safety stop, so we make any small adjustments before the next dive. If we know all those things prior.

 

[tursiops]

Right, and if we know the weight and freshwater buoyancy of the diver and all their gear, the amount we were off at the start of the OW1 dive is likely not detectable by the precision of the tools we have floating at the start of OW1 (how high do they float, how heavy do they feel to a floating buddy/DM/Instructor, how fast do they sink). So we only really see at the safety stop, so we make any small adjustments for the next dive. If we know all those things prior.

So if you are going to make adjustments for Dive 2, and so on, then is it that important whether you are adjusting a few pounds based on a first guess, or less based on superlative mathematics? Also, you are describing weight only, not its distribution for trim.
It sounds like you are arguing for math skills over observational and instructional skills, and following standards only if time and inclination permit.

 

[wetb4igetinthewater]

PADI OW Standards:
Dive 1: (Surface) Check and adjust weighting. (Underwater) Participate in a trim check.
Dive 2: (Surface) Adjust weighting and trim, as necessary.
Dive 3: (Surface) Adjust weighting and trim, as necessary.
Dive 4: (Surface) Adjust weighting and trim, as necessary.

So, it is OK to NOT do this, because it is cold out and it takes time?

You’d have to ask the instructors on why they don’t. I have my hypothesis.

I guarantee you no trim checks are being performed on the on-the-knees students. Though admittedly I haven’t seen that, nor could I with the silt cloud that gets kicked up.

There is the “as necessary” part that allows instructors to say “nah, isn’t necessary.”

I don’t know what checking for trim at the surface means in a practical sense. Maybe you can enlighten me where in your agency documentation that is described. Don’t worry, while not an instructor for to IE agency, I can still get the materials.

I understand people like you want to defend the standards for your particular agency. However, this is a problem with all agencies. Give someone an inch, and they take a mile.

Another aspect of this is that instructors are often not taught the center of mass versus the center of displacement. RAID is the first agency to document this. How many instructors read training materials from other agencies.

Ultimately I want to see two things from agencies. Separation of approximate weighting at the surface with a full tank with checks at the end of the open water dives with specifically stating (emphasizing) that the student’s BCD/wing must be empty, the cylinder must be early empty, amd if a dry suit is worn then as empty as possible yet still keeping the student warm and comfortable.

I’m trying to address the reality of standards being violated. And no, I’m not going to report the instructors to their respective agencies. The energy to press those keys to write that email would be wasted.

 

[MichaelMc]

So if you are going to make adjustments for Dive 2, and so on, then is it that important whether you are adjusting a few pounds based on a first guess, or less based on superlative mathematics? Also, you are describing weight only, not its distribution for trim.
It sounds like you are arguing for math skills over observational and instructional skills, and following standards only if time and inclination permit.

The buoyancy is just math (+, -, *, /) that we have all the data we need for. Weight on land and weight in a fluid of know density of all the parts. And experience in freshwater for four dives in that gear, with known ending tank psi. I would not call that needing superlative mathematics. It is the math we expect of our students.

The trim could be math, but we do not have easy access to the density distributions of all the parts. (That would be advanced math). But, assuming they are our students, we just had them in the pool in scuba gear for four sessions. We should have it dialed by now.

It says as necessary. If you do not do the measurements prior, then you need to guess/estimate and then futz with weights out in OW on the surface to get close. If you have the data and do the math, the buoyancy should be very close, once you do the fresh to salt conversion.

Instructors taking someone else's students out for the first time are a different can of worms! Unless they pop them in a pool first. Or do a student in swimsuit buoyancy check dockside if tropical.

I am not saying only follow standards if inclination permits. I'm saying if you know all the weights prior, there should be nothing left to do on buoyancy. If they were your students, there should be nothing left to do on trim, short of Fundies level weight distribution precision for the fresh to salt change.

Just to calibrate the ballpark of 'as necessary' that I am talking about, I make 1 lb. weight shifts if I find my weight distribution is no longer balanced after gear changes. I have two lb. pockets at each shoulder and hip that I can shift between while underwater and horizontal by myself. They start with 1 lb. each. I've played with 1/2 lb. shifts, but don't find that necessary in OW. But that is not the precision I think you would get for trim going from fresh to salt without, yes, observation and adjustment.