How much weight?

[rstofer]

I'm looking at the PADI Adventures In Diving manual and on page 213 they have a neat little table for weight versus equipment configuration.

For the 7mm/1/4" wetsuit salt water diver they recommend 10% of your body weight plus 3-5 pounds. So, I weight about 210 so I would need about 21 plus 5 pounds and I dive with exactly that much. I have a 20# weight belt and a 6# backplate. If I replace the 6# backplate with a 2# backplate, I have to swim down until the suit compresses - about 3 feet or so. I guess I am pretty close to 'average'.

For the trasition to fresh water at my body weight I would remove 7# which turns out to be within a pound of what my old NAUI material recommended. They said 6#.

There is every possibility that a person of the same weight as me might require somewhat different weight. PADI prefaces their table with "Use the following guidelines to get you in the ballpark."

Here's the rub: PADI wants you to do your weight check with a FULL tank.

1) Enter the water fully equipped for the dive.
2) Go to water too deep to stand in (or at least deep enough that you can easily raise your feet off the bottom) and completely deflate your BCD. If you're using your dry suit, open the automatic exhaust valve all the way.
3) Hang vertical and motionless holding a normal breath.
4) Add/subtract weight until you float at eye level while holding a normal breath.
5) As your final check, you should slowly sink when you exhale.

Then they go on to say:

Ideally, check your buoyancy and set your weight with a near-empty cylinder, then switch to the same type cylinder, full, for the dive. This isn't always practical, so the alternative is to set your weight as you just learned with a full cylinder, then add about 5#. If you'll be making several dives, you may want to recheck your buoyancy at the end of the dive while you're wearing a near-empty tank.

It all seems pretty clear to me. Use the handy table to get in the ballpark and then refine it using either a full or empty tank as you wish. Actually, 7mm wetsuit divers can just use the full tank and leave it that way because their wetsuit will lose more buoyancy at 15' than the weight of air in the tank. But YMMV.

I don't have the OW manual so I can't quote from it. But it's pretty straightforward in the "Adventures In Diving" manual.

Richard

 

[TheScubaBOB]

Richard,

Thanks for posting that. I just finished getting my manuals out to do the same.

The OW Manual doesn't include the weighting chart but does have the process to fine tune your weights, including adding 5 lbs to counter an empty tank.

By the PADI Chart I should have started at about 28 lbs.

10 months later I dive with 14lbs for an AL80, 9lbs for my Steel LP120 with AL30 Pont bottle & 8lbs for my Steel LP120 only.

 

[MauiScubaSteve]

By the PADI Chart I should have started at about 28 lbs.

The question I've been hinting at is did you take into consideration the fresh water correction;

For the trasition to fresh water at my body weight I would remove 7#

Take a moment to think about it; a 7' tall 350 lb guy is going to be quite different in weight needed compared to a 5'10, 350 lb gal (or even a guy), and yet the formula result for 350 lbs might be way too much for him and not sink her at all.

10 months later I dive with 14lbs for an AL80, 9lbs for my Steel LP120 with AL30 Pont bottle & 8lbs for my Steel LP120 only.

If 28 lbs had been for salt water let's drop 8 lbs down to 20 lbs for fresh water. In that senario the diver would have improved 6 lbs from the starting recommendation, which is very common.

 

[TheScubaBOB]

The question I've been hinting at is did you take into consideration the fresh water correction;

And part of the point I was trying to make is that I wasn't given that option as in OW it only referenced the Recommended Beginning weight, which we were given by the Instructor & Dive Shop Staff.

By the time I got the Adventures In Diving Book I was in a completely different environment (OW Dives Cold Fresh Water in 7mm wetsuit, AOW: Warm Salt Water in 3mm wetsuit) I didn't take PPB so I didn't read that chapter. Personally I think PPB should be part of AOW just for the weighting issues.

Iconically the AOW Instructor put me in the same weight for Salt/3mm that the OW Instructor put me in for Fresh/7mm. Their goals were the same; for me to be able to rest on the bottom, not to hover effectively.

Take a moment to think about it; a 7' tall 350 lb guy is going to be quite different in weight needed compared to a 5'10, 350 lb gal (or even a guy), and yet the formula result for 350 lbs might be way too much for him and not sink her at all.

Heck even two guys of the same height & weight can need different weights. For example I'll admit that I have a "spare tire" so while I'm 6'2" & 240lbs (ish) there are guys out there at the same height & weight who have more of their weigh in muscle mass than I do therefore they are more negatively buoyant naturally than I am.

If 28 lbs had been for salt water let's drop 8 lbs down to 20 lbs for fresh water. In that senario the diver would have improved 6 lbs from the starting recommendation, which is very common.

Again I wasn't given the info or option to make such adjustments. Lucky for my daughter, she's dropping weight a lot earlier in her diving than I did.

 

[CalgaryDF]

I think that the important thing is that PADI's suggestions for weighting are meant as a guideline to get you close to the proper weight so that when you do a weight check you are not really heavy or really light.

Looking at their tables and assuming that they will give you the exact amount of weight you need is unreasonable and the only way to figure out how much weight you need is to do buoyancy tests.

Figuring out how to distribute your weight so that you are in good trim is the hard part. I keep floating head down or feet up and its absolutely crazy. I can't get it right.

 

[MauiScubaSteve]

From an Instructor perspective, looking at the '08 Digital Instuctor Manual with regards to weighting I find the following, in order. PADI Standards are underlined.

Adjust for proper weighting is a Confined Water Two performance standard,
which is defined as floating at eye level at the surface with an empty BCD and while holding a normal breath.

Adjusting for proper weighting is required to complete Confined Water 2.

In the Knowledge Development Two lesson plan outline we have the following wording;

II. Streamline Yourself
__A. How should you move underwater?
____5. As much as possible, move horizontally through the water.
_______[Discuss the trim-avoiding overweighting, and adjusting weight
_______for a comfortable, balanced horizontal swimming position.]

Knowledge Developement Performance Requirements have this entry in Section Two;

The student will be able to answer the following questions:
25. How do you determin how much weight you need for a dive?

Open Water Dive One Performance Requirements state this;

Under instructor supervision, the student will:
4. Adjust weight so student floats at eye level with an empty BCD and holding a normal breath.

In the Open Water Dives Recommended Techniques for Meeting Performance Requirements section, Dive One,
the Instructor Manual gives a full description of a weight check, including;

Since you normally do this with full cylinders, add weight to offset the weight
change from air used during the dive; usually about 2 kg/5 lbs with a single cylinder.

Open Water Dives Two and Three Performance Requirements similarly state;

Under instructor supervision, the student will:
5. Adjust weight so student floats at eye level with an empty BCD and holding a normal breath.

The Recommended Techniques for dives two, three and four are;

Redetermin weight if this dive is in a different environment or if students wear
a different equipment configuration from the previous dive. Otherwise, a quick
recheck should be all that's necessary.

Open Water Dive Four Performance Requirements change slightly, with additional information (but not Standards);

Under instructor supervision, the student will:
5. Adjust weight so 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).

Finally, in the Apendix we have the Knowledge Review keys:

Knowledge Review - Section Two
16. Explain how to check for proper weighting.
____You should float at eye level with an empty BCD and while holding a normal breath.

It would seem to me that if the instructor just followed the PADI Instructor Manual the student would have the opportunity to learn how to properly weight, even if no teaching was going on.

The Instructor Manual does not have the tables you mention; that's why we are also required to have a personal copy of the Open Water manual. I have a few, of varying revisions, all stored under the house. I may even pull one out tomorrow.

 

[TheScubaBOB]

Figuring out how to distribute your weight so that you are in good trim is the hard part. I keep floating head down or feet up and its absolutely crazy. I can't get it right.

Take note of how you mount your tank. I wear my LP Steel 120s High as I want as little weight as possible in my trim pouches (currently 1/2 of my 8lbs are in the shoulder trim pouches).

It would seem to me that if the instructor just followed the PADI Instructor Manual the student would have the opportunity to learn how to properly weight, even if no teaching was going on.

The Instructor Manual does not have the tables you mention; that's why we are also required to have a personal copy of the Open Water manual. I have a few, of varying revisions, all stored under the house. I may even pull one out tomorrow.

I can say that the weight checks were definitely abbreviated. It went something like "Let the air out of your BC... Did you sink? Ok, your good to go".

Now that I know better I choose an instructor for my daughter who actually started with less weight and spent the time to do it right. The biggest difference, I was one of 25 students my OW instructor had that weekend (thankfully we were split into 2 groups) and my daughter was 1 of, well 1 student.

 

[mksmith713]

Also be aware that when you make your ascent, you have to do something that defies logic.
You have to deflate your BC.
The puff or two of air you added at depth compensated for your exposure suits compression and loss of bouyancy.
Also,as you ascend, that puff or two of air you added multiplies depending on the depth you were at when you added them.
As you ascend, your suit decompresses regaining the bouyancy that was lost at depth.
Additionally, those puffs of air multiply making you positively bouyant.
To equalize, you have to ditch the air you added at depth to keep it neutral.
If you forget to purge air from your BC, you'll be positively bouyant and experience a runaway ascent.

 

[mksmith713]

Lest we not forget....your tank is more bouyant at the end of a dive vs the beginning.
Another thing to take into consideration.

All things not adequately covered in the PADI OW course.

Thank goodeness for Scubaboard and this forum.
You can learn alot here.

 

[DiveMom1]

Interesting day.. today I took the pool sessions for PADI-Peak Performancy Bouyancy AND SSI-Perfect Buoyancy. Vastly different classes ... PADI session was about 15 min in to pool [me overweighted] and the the SSI session was 2 pool hours with near perfect weighting. I'm finishing both classes in Monterey this weekend.. so then can compare. Both Instructors are great so lets just see the difference in the end, either way I HOPE to finally figure out this bouyancy "tweak" I can't wrap my head around ...