Trimming dive posture/weight position

[elan]

I found weight on the back with a steel tank makes the back way too heavy, I dive HP100 though. I put all my weight on the waist, pockets and the belt. This brings the center of gravity

I dive in skydive position all the time but can easily move to upside down or leg down position. But I dive dry which makes it much easier. I got to the point when I can manage my trim with my head and legs only and no fining. It took at least 10 dives to figure it out and get used to it. At first it was awkward. I do pretty much the same in 5/4/3 wetsuit easy.

 

[Teamcasa]

OK, that is three people who think he may be over weighted. He may indeed need more than 16 pounds but given the steel tanks and other equipment he seems a tad over possibly.

Frankly, to the OP, take your stuff to a pool---by yourself---and play around until you get close to what you like. Internet help is great but each person is a unique critter and in the end only you can get it right.

You will probably never get a perfect balance where you remain static/fixed in any given position over the course of a dive, learn to use your lungs to act as an auxiliary balance/BC, learn to move your legs in (up, bend at knee) or extend them to act as a pendulum to help adjust your center of gravity. Your arms as well, crossing them under your chest or moving the out front, crossed or even held along your side will also alter your balance/center of buoyancy. BTW, resist the tendency to use your arms and hands to swim and maneuver, do it all with your legs and fins.

These guys dismiss what I say, I have been a continuously active diver with hundreds and hundreds of dives for over 40 years, I might know a few tricks beyond what you learned in your Peak Buoyancy course. Remove every bit of weight you don't need, over weighting only compounds and magnifies other problems.

Good luck, hope you get it worked out to YOUR satisfaction.

N

This is more the response I'd expect from a diver with Nemrod's vast experience.

 

[TSandM]

I'd like to get to the point where regardless of the position I hover in (skydive, feet up, or feet down), I stay that way with no finning.

This can be a difficult thing to achieve in cold water gear. For a given position in the water, you are stable when immobile only if the heavy parts of you and your gear are precisely balanced, not only in amount but in location, by the lift you have. With heavy wetsuits, the amount of lift from the suit in very shallow water is great and distributed along your body; as you descend, that lift is reduced, leaving you with the air in your BC, which is centralized. Since the tank and weights are generally around your torso, the BC lift will counteract that pretty nicely in a horizontal position. But once you go vertical, the tank is hanging down on your back, and the lift from your BC is somewhat in front of it, so you may find you have a tendency to go over backwards unless your weights are well in front of your body (and perhaps even then).

It's fairly easy to adjust things with your body posture when you are wearing light exposure protection and an Al80, but it gets harder with cold water gear.

I've settled for ideal balance when horizontal, and you've gotten great advice about that. I just want to add that body posture plays a big role -- when I'm balanced, if I drop my head, I'll tilt forward; if I extend my knees, I'll tilt back. Flexing at the hip so that the knees are dropped will rotate one's whole body into a head up position. Posture is amazingly powerful -- I played with different backplates and weight arrangements for months with my doubles, only to discover that keeping my posture correct will let me balance out almost any tank and plate combination.

 

[mikemath]

In my 7mm suit with two hoods, boots, gloves, and 3mm short and vest under, I use 16 pounds fresh and 18 salt with an aluminum 80. You are over weighted.

I put two pounds in each camband pocket on my Oxy Mach V and the rest on a belt.

N

Interesting--those numbers sound strange to me compared to what I learned in the buoyancy class but I'm new to this so bear with me and correct me where I'm going wrong. From the PADI literature, here's the recommended differences in approximate weighting when going from fresh to salt water:

| Body Weight | Weight to Add |
| 100-125lbs | +8lbs |
| 126-155lbs | +10lbs |
| 156-186lbs | +12lbs |
| 187-217lbs | +14lbs |

Your 2lb difference sounds odd on this scale. I'm not going to list my weight, but I dive 32lbs in salt water and 14lbs in fresh--as I said, I'm a big guy. I've done normal breath-hold bouyancy checks on the surface and can do fin pivots with no air in my BC at 15 feet (need to add a tiny squeeze from my inflator when deeper due to compression). I'm pretty sure I'm not significantly overweighted, but please let me know what else I can do to check.

 

[mikemath]

OK, that is three people who think he may be over weighted. He may indeed need more than 16 pounds but given the steel tanks and other equipment he seems a tad over possibly.

Frankly, to the OP, take your stuff to a pool---by yourself---and play around until you get close to what you like. Internet help is great but each person is a unique critter and in the end only you can get it right.

You will probably never get a perfect balance where you remain static/fixed in any given position over the course of a dive, learn to use your lungs to act as an auxiliary balance/BC, learn to move your legs in (up, bend at knee) or extend them to act as a pendulum to help adjust your center of gravity. Your arms as well, crossing them under your chest or moving the out front, crossed or even held along your side will also alter your balance/center of buoyancy. BTW, resist the tendency to use your arms and hands to swim and maneuver, do it all with your legs and fins.

These guys dismiss what I say, I have been a continuously active diver with hundreds and hundreds of dives for over 40 years, I might know a few tricks beyond what you learned in your Peak Buoyancy course. Remove every bit of weight you don't need, over weighting only compounds and magnifies other problems.

Good luck, hope you get it worked out to YOUR satisfaction.

N

Thanks--all good advice, and the arm/leg position was illustrated well in a video link posted earlier in the thread. I will definitely try it. And I'm definitely not trying to use the internet as a complete fix to the problem, rather I'm looking for advice on things to try on my own. I've accomplished that thanks to the advice I've gotten from you and others.

I'm just trying to learn as much as I can about a sport I'm growing to love--the fact that I'm posting here should indicate that I don't feel like I know more than anyone else just because I've taken a class. I truly appreciate all the feedback I've gotten and will put as much into practice this weekend as possible, and share the results afterwards.

 

[JeffG]

I'm not going to list my weight, but I dive 32lbs in salt water and 14lbs in fresh--as I said, I'm a big guy.

You must be around a million pounds then. 14 lbs in fresh should be ~19 lbs in salt. If you were "really" big...maybe 22.

 

[gcbryan]

Interesting--those numbers sound strange to me compared to what I learned in the buoyancy class but I'm new to this so bear with me and correct me where I'm going wrong. From the PADI literature, here's the recommended differences in approximate weighting when going from fresh to salt water:

| Body Weight | Weight to Add |
| 100-125lbs | +8lbs |
| 126-155lbs | +10lbs |
| 156-186lbs | +12lbs |
| 187-217lbs | +14lbs |

Your 2lb difference sounds odd on this scale. I'm not going to list my weight, but I dive 32lbs in salt water and 14lbs in fresh--as I said, I'm a big guy. I've done normal breath-hold bouyancy checks on the surface and can do fin pivots with no air in my BC at 15 feet (need to add a tiny squeeze from my inflator when deeper due to compression). I'm pretty sure I'm not significantly overweighted, but please let me know what else I can do to check.

His numbers are wrong (the physics not what he may actually do) however you can figure it out yourself without the chart. Salt water is just under 3% more dense than fresh water so take your body weight and the weight of all of your equipment. Add 3% of that weight to compensate for salt water. If your are correctly weighted in fresh water and are diving the same gear in both fresh and salt then your weight in salt will only be 3% (of your total body/gear weight) more.

 

[mikemath]

You must be around a million pounds then. 14 lbs in fresh should be ~19 lbs in salt. If you were "really" big...maybe 22.

(sigh) Ok, f- it. I don't want it to be said that I put pride before knowledge. Here's the data and how I'm crunching it (directly from PADI Adventures in Diving, page 211 and 212):

Body weight: 240lbs

Basic weight guidelines:
7mm wetsuit w/ hood & gloves (10% of body weight +3 lbs) = 24 + 3 lbs = 27 lbs
Salt water, >217 lbs (not on table, projected out) = +7 lbs
AL80 offset (if I were using that instead of my steel tank) = 5 lbs
----------------
Total: 39 lbs

The steel 80 I use is a shop rental and dozens of people have used them and found that the difference between it and an AL80 is 4 lbs. That puts my starting weight at 35lbs. That was the weight I used when I first started, but I adjusted to 32 based on standard (normal breath-hold eye level) surface checks. As mentioned before my buoyancy checks and fin pivots work fine with this weight.

Crunching the same numbers in fresh water:

Basic weight guidelines:
7mm wetsuit w/ hood & gloves (10% of body weight + 3 lbs) = 24 + 3 lbs = 27 lbs
Salt water, >217 lbs (not on table, projected out) = SUBTRACT -7 lbs
AL80 offset = 5 lbs
----------------
Total: 25 lbs

Accounting for the steel tank, this gets me to approximately 21 lbs required. Again based on actual buoyancy checks, I adjusted this to 14. I believe the significant drop in actual weight compared to estimated weight needed is due to the fact that I have a very muscular build with the exception of my spare tire, while the typical body types at this weight are flabby all-around.

Anyway, that's more detail than I wanted to get into, but I'm hoping hard numbers will help get to the bottom of this discrepancy between what everyone thinks I need and what I have actually found to work.

 

[gcbryan]

(sigh) Ok, f- it. I don't want it to be said that I put pride before knowledge. Here's the data and how I'm crunching it (directly from PADI Adventures in Diving, page 211 and 212):

Body weight: 240lbs

Basic weight guidelines:
7mm wetsuit w/ hood & gloves (10% of body weight +3 lbs) = 24 + 3 lbs = 27 lbs
Salt water, >217 lbs (not on table, projected out) = +7 lbs
AL80 offset (if I were using that instead of my steel tank) = 5 lbs
----------------
Total: 39 lbs

The steel 80 I use is a shop rental and dozens of people have used them and found that the difference between it and an AL80 is 4 lbs. That puts my starting weight at 35lbs. That was the weight I used when I first started, but I adjusted to 32 based on standard (normal breath-hold eye level) surface checks. As mentioned before my buoyancy checks and fin pivots work fine with this weight.

Crunching the same numbers in fresh water:

Basic weight guidelines:
7mm wetsuit w/ hood & gloves (10% of body weight + 3 lbs) = 24 + 3 lbs = 27 lbs
Salt water, >217 lbs (not on table, projected out) = SUBTRACT -7 lbs
AL80 offset = 5 lbs
----------------
Total: 25 lbs

Accounting for the steel tank, this gets me to approximately 21 lbs required. Again based on actual buoyancy checks, I adjusted this to 14. I believe the significant drop in actual weight compared to estimated weight needed is due to the fact that I have a very muscular build with the exception of my spare tire, while the typical body types at this weight are flabby all-around.

Anyway, that's more detail than I wanted to get into, but I'm hoping hard numbers will help get to the bottom of this discrepancy between what everyone thinks I need and what I have actually found to work.

No one can tell you over the internet or in a book what your correct weight should be. Everyone is different even at the same weight/height. Those are just approximations.

However, if you do an actual weight check...for example get your tank down to 500 psi or less at the end of a dive and try to hover at 10 feet and keep removing weight until you can't hover this is your correct weight.

However much that is in fresh water it will not be more than 8 lb more for salt water. You are 240 lb and let's say the rest of your gear is 60 lb so 300 lb total. Take 3% (actually more like 2.8%) of that total ...weight....028 x 300 = 8.4 or basically 8 lb.

If 25 lb is correct for fresh water after a proper weight check then salt water should be no more than 25 lb + 8 lb. or 33 lb.

No one can tell you the actual numbers. You need a proper weight check but the difference between fresh and salt water weighting should be no more than 8 lb for your body weight and standard gear.

People generally estimate that one would add 5-6 lb because they are using 200 lb total weight with gear as an average but if you weigh more then using 300 lb total would be a good estimate for you.

 

[rongoodman]

Since the HP80 is a rental and you're not committed to it, I'd try a different tank. If it's a Worthington, it's less than 20" long, very stubby and heavy. Try an AL80 and deal with the extra 4 lb you need to sink it, at least for a while, and see if a longer tank helps. If so, you'll have another data point when you decide to buy your own.