Too much Weight

[Diver Dennis]

Sometimes having extra weight makes a diver think they are more comfortable as it is easy to get down and you have your BC to compensate right? An example of how much weight you can drop under the right supervision and still be comfortable is a fellow I was diving with over a 9 day period in Malaysia last year. The first day he insisted he needed 24 lbs. to be comfortable. After 9 days of diving with a very attentive DM, he was comfortable with 10lbs. A little coaching can go a long way and he was pleasantly surprised he could dive with an amount of weight that 9 days before he admitted he would have been too scared to try. The DM got a big tip by the way...

 

[danielt]

i was told in training that you need approx 1kg for every 1mm of wetsuit and a couple more kg's to account for the tanks etc?

 

[Rainer]

i was told in training that you need approx 1kg for every 1mm of wetsuit and a couple more kg's to account for the tanks etc?

Another "rule" that isn't any more helpful than providing a starting point. You can't figure this stuff out without getting in the water.

 

[Twiddles]

Thanks for all the input all. I spent quite a bit of time fiddling with my weights I have 5 to 1 lb bags and have tried multiple combinations. I currently carry 10lbs 5 each side in the pockets on my back close to my tank. I carry another 12lbs in each detachable integrated bcd pouch and the final 3.5 lbs is on my ankles. I use Mares Volo fins and ankle weights help me with my trim. I really enjoy the sensation of weightlessness so half of my diving fun is "playing" in the water as much as looking at things (IE given the chance to barrel roll with a sea lion or enjoy a beutiful reef wall, im still at the stage where the sea lion would win, not in a real hurry to grow up either).

I go "nicely" negative to the point where no further effort (I expel all the air from my lungs and hold it) is required between 7-9 feet (have watched my computer). At that point I can breath normally shallow, for about another 10' then I can breath full and have my bcd inflator in hand to begin slowing decent. I decend in skydiving posture (knees bent, back slightly arched fin tips pointed at surface) after about 12-15', for the first 15' im head up with hand above head height with deflator fully depressed till bcd is "empty". I have been told this is not exactly correct but it is the position that allows me to decend without pulling on the rope (if there is one) or waving my arms to help descend.

I have no idea why on a shore dive I need less weight then on a boat dive. I assumed that the time to get to the location before diving saturated portions of my wetsuit, hood, gloves, boots and this in turn allowed me to dive with less weight as opposed to the boat where within 30 seconds of hitting the water I am ready to submerge?? I dive a back inflate as opposed to the wrap around. I noticed I could compress the wrap around while it was on my body by squeezing my arms against my sides, with a wing the only reference I have is by reaching around by the dump valve and feeling the wing. I do know that I must be extremely carefull on ascent to prevent ascending through my safety stop (why I ascend negative). I assumed with time this would become second nature and I wouldnt need to be so attentive?

 

[Surelyshirly]

when I first learned to dive from a boat it took more weight. Try crossing your legs when you exhale to start your descent. Often you fin and dont realize it because you automatically tread water when over your head. Even the slightest of finning will be counter productive

 

[Piccola]

This is a very interesting thread. I too am new to diving and feel like I am 'overweighted'. I am trying to alter my weight and trim to determine the best 'fit' for me. I dive with a .5 skin and 7mm one piece along with hood/gloves/boots. I experience the same difficulties getting below ~10', then I feel like I sink like a stone and have to work at staying off of the bottom. I am just trying to patiently work the numbers since my gear is unlikely to change. It is frustrating when all the others in the group can just descend and I resort to do the head first manuever! My first ocean dive resulted in a frozen regulator which went into freeflow. I truly had to work at staying a float to inflate my BCD with the weight I was carrying. I know I could have ditched the weight but I stayed calm and tried to deal with the situation. I want to learn to better control my bouyancy and weight needs which I am sure will improve with practice.

 

[matt_unique]

....
I am curious how much of the weight issue is actually about skill and safety and how much of it is really about ego.

99% ego

1% to account for brand new divers who were told they need X lbs to sink when they learned to dive. The X lbs was derived from an instructor who decided to make the same heavy weight belt that would ensure all divers with all configurations would sink to the bottom for basic skills.

Short of grossly overweighted, the amount of weight you carry has little impact on measurable air consumption. If I need 25 lbs, and I do a dive with 35 lbs, you will not see a measurable difference in my air consumed. In a test tube you are pushing more mass, need more air in your air spaces to support the weight, thus more friction drag, etc., etc. None of that matters outside of a test tube because the decrease in efficiency is so small relative to everything else going on.

Using neoprene, you should *always* be overweighted at the depth the way you are defining it. The bubbles in the neo compress with depth and thus you need less weight for the same level of buoyancy. It's just a function of your suit. I dive a 7mm neo drysuit in cold water with thick thermals. All my weighting is about the first 20' of depth. The rest is excess I need to float for the rest of the depths/dive until I'm returning to the surface.

--Matt

 

[dave4868]

This is a very interesting thread. I too am new to diving and feel like I am 'overweighted'. I am trying to alter my weight and trim to determine the best 'fit' for me. I dive with a .5 skin and 7mm one piece along with hood/gloves/boots. I experience the same difficulties getting below ~10', then I feel like I sink like a stone and have to work at staying off of the bottom. I am just trying to patiently work the numbers since my gear is unlikely to change. It is frustrating when all the others in the group can just descend and I resort to do the head first manuever! My first ocean dive resulted in a frozen regulator which went into freeflow. I truly had to work at staying a float to inflate my BCD with the weight I was carrying. I know I could have ditched the weight but I stayed calm and tried to deal with the situation. I want to learn to better control my bouyancy and weight needs which I am sure will improve with practice.

You may have already done this, but here's a sure-fire way to tweak your weights.

Takes 5 minutes, but requires in-water adjustment. It's too simple to require practice.

For wetsuit diving, you only need the minimum amount of weight that will offset the positive buoyancy of all your gear, with the bcd empty.

Hopefully, that's something we can agree on.

The positive buoyancy is greatest at the end of the dive, when you have less weight of air in the tank. Keep that in mind when doing the adjustments below.

Do an in-water weight adjustment with an empty tank. You already know how to do this, but for the sake of clarity, it's: vertical in the water with an empty bcd, full inhale brings eyes level with the surface, exhale causes you to become negative and sink below the surface.

or

Do a similar in-water weight adjustment with a full tank and then add the calculated amount of weight equal to the weight of the tank air, since it will be gone at the end of the dive.

The tank air weighs approximately 0.08 lb per cubic foot.

For example, add about 6.4 lbs for an 80 cubic foot tank. (I'd round up to 7 lbs or so.)

Now, you also mentioned:

I experience the same difficulties getting below ~10', then I feel like I sink like a stone and have to work at staying off of the bottom.

If you add air to the bcd to compensate for the change in buoyancy (from compression of the neoprene) you'll be able to achieve "neutral buoyancy".

Then, you won't have to move a muscle to stay off the bottom, provided your trim is also okay.

I truly had to work at staying a float to inflate my BCD with the weight I was carrying.

Are you saying your free-flow was not allowing you to inflate your bcd adequately?

Or are you saying that you were overweighted? That's probably not the case, since you said you have difficulty getting down from the surface at first.

Are your bcd straps so tight that the chambers can't be adequately filled with air? Do tight straps cause your bcd to exhaust air out the exhaust valve when you try to inflate it?

I'm curious about how you're doing things and if you did an in-water adjustment of weighting when you started with your current gear.

Just trying to be helpful.

Dave C

 

[jviehe]

10% is a starting point, assuming a full set of gear and aluminum tank. You must then get in the water and test it. The PADI weighting check fulfills that. Empty your BC, hold a normal breath and adjust your weight till you float at eye level. Then add weight to compensate for the air in a tank that you will use during the dive, about 5 pounds. Do your dive, and when finished, write down how much weight you used, and what gear you used, and whether it was heavy or light at the end of the dive. Keep track of this and keep tweaking till you get it right.

FYI, for those new divers who think they would benefit, the PADI Peak Performance Bouyancy Adventure Dive or Speciality covers weighting in detail. [/end training plug]

 

[Matt_NJ]

I'm by no means a hugely experiences diver, but I remember when my wife and I got certified that she had extreme problems with boyancy control. This all stemmed from the fact that she was finning alot and would pop back to the top like a cork so the instructer kept dumping weights into her BCD to make her sink, then once she was on the bottom she could barely control her boyancy. Things got alot better once she was able to descend without needing ton's of extra led to get her past the first 10 feet or so.