You have it.
How to correct if you're overweighted?
- Thread starter guymenton
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northcoast_diver
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Charlie99:
How do you take off only a pound? Dont you need to take off even numbers, like 2 lbs minimum, or else wont you be lopsided?
starfish365
Contributor
fmw625:
Just curious how you can be negative naturally?
northcoast_diver
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He doesn't inhale.starfish365:
waterwraith
Contributor
starfish365:
Its possible the head of my department sinks in saltwater unless he is wearing a suit.
fmw625
Guest
Without any weight or gear I will sink to the bottom making me naturally negative bouyant.
I think you just have to experiement. This weekend I dediced to clean the bottom of my boat. Put on my wife's 1/2 empty AL 63 and realized that I'd left my weights on shore. Hey, no problem as I was just going to clean the boat. I was very surprised to learn that I had perfect bouyancy control. No wet suit and I'm 6'3" and 250.
starfish365:
By being heavier than 64 lbs per cubic foot. This is accomplished by having a low percentage of body fat. Bone and muscle will sink in salt water.
I would agree with the sentiment that you want to be neutral at the surface with your tank at 500 psi. and with a normal lung volume. This is most easily achieved by weighting yourself to float with a full lung volume and then sink slightly when you exhale.
Traditionally, divers weighted themselves with all their gear to float at eye level with full lungs and a near empty tank. This was in the pre-BC era where getting your weight right was important as any suit compression was going to have to be compensated for by the diver swimming the extra weight up and over weighting just made things worse.
The "weight yourself to be neutral at 15 ft" thing is not really correct for scuba divers. Freedivers on the other hand will weight themselves in this manner as it 1) allows a small degree of bouyancy on the surface to enable the diver to rest between dives, 2) does not present a large impediment to descending the first 15 ft and presents no impediment to descent below 15 ft., 3) minimizes the degree to which the diver is overweighted at depth and, 4) imcreases the likelyhood that the diver will float to the surface if they encounter a shallow water blackout and makes a rescue by the buddy easier.
None of this is really applicable for scuba diving as in scuba diving the ability to stay at the safety stop and them make a very slow ascent the last 15 ft is much more relevant. So it is much more preferrable to be neutral at the surface, not at 15 ft.
Prior to about 1980-85 when scuba started becoming big business and an every person sport, divers had to be very good swimmers and were all very comfortable in the water. Most also came from freediving (known as skindiving then) backgrounds and had bouyancy/weight issues nailed before they ever started scuba diving.
Today on the other hand it is common for rather weak swimmers with no freediving background to become divers. As an artifact of being less than fully comfortable in the water, many will be kicking or sculling with their arms even while trying to descend. This extra thrust is then offset by more weight and over weighting results from the effort to sink students with more weight rather than proper technique.
This is where people come up with the statement that your weight requirements decrease as your experience increases. It happens that way, but it shouldn't. The sad truth is that needing to be overweighted is indicitive of very poor technique and that the over weigthing itself in turn leads to additional bouyancy problems for the new diver. People should not even leave an OW class until they have become comfortable enough not to be unconsiously kicking on the surface when they want to descend.
Another related weight issue is the permanent compression that occurs in a realtively short time with a new wet suit. With a 7mm wet suit, this can result in the loss of a substantial amount of bouyancy. So while a new diver's bouyancy may be perfect with their new wet suit, several dives later they may be a few pounds to several pounds heavy and will again need to re-adjust their weight at the end of the dive with 500 psi in the tank.
It is always a good idea to check your bouyancy at the end of the dive now and then just to be sure nothing as changed.
Traditionally, divers weighted themselves with all their gear to float at eye level with full lungs and a near empty tank. This was in the pre-BC era where getting your weight right was important as any suit compression was going to have to be compensated for by the diver swimming the extra weight up and over weighting just made things worse.
The "weight yourself to be neutral at 15 ft" thing is not really correct for scuba divers. Freedivers on the other hand will weight themselves in this manner as it 1) allows a small degree of bouyancy on the surface to enable the diver to rest between dives, 2) does not present a large impediment to descending the first 15 ft and presents no impediment to descent below 15 ft., 3) minimizes the degree to which the diver is overweighted at depth and, 4) imcreases the likelyhood that the diver will float to the surface if they encounter a shallow water blackout and makes a rescue by the buddy easier.
None of this is really applicable for scuba diving as in scuba diving the ability to stay at the safety stop and them make a very slow ascent the last 15 ft is much more relevant. So it is much more preferrable to be neutral at the surface, not at 15 ft.
Prior to about 1980-85 when scuba started becoming big business and an every person sport, divers had to be very good swimmers and were all very comfortable in the water. Most also came from freediving (known as skindiving then) backgrounds and had bouyancy/weight issues nailed before they ever started scuba diving.
Today on the other hand it is common for rather weak swimmers with no freediving background to become divers. As an artifact of being less than fully comfortable in the water, many will be kicking or sculling with their arms even while trying to descend. This extra thrust is then offset by more weight and over weighting results from the effort to sink students with more weight rather than proper technique.
This is where people come up with the statement that your weight requirements decrease as your experience increases. It happens that way, but it shouldn't. The sad truth is that needing to be overweighted is indicitive of very poor technique and that the over weigthing itself in turn leads to additional bouyancy problems for the new diver. People should not even leave an OW class until they have become comfortable enough not to be unconsiously kicking on the surface when they want to descend.
Another related weight issue is the permanent compression that occurs in a realtively short time with a new wet suit. With a 7mm wet suit, this can result in the loss of a substantial amount of bouyancy. So while a new diver's bouyancy may be perfect with their new wet suit, several dives later they may be a few pounds to several pounds heavy and will again need to re-adjust their weight at the end of the dive with 500 psi in the tank.
It is always a good idea to check your bouyancy at the end of the dive now and then just to be sure nothing as changed.
Wristshot
Contributor
guymenton:
guymenton,
Not pretending to be an expert here, but since no one else answered your question: Yes, the size and material of a tank will make a difference. In my area, when you switch from an Aluminum 80CF tank to a steel tank, you use 4 - 6 lbs less weight. That would get you in the ballpark.
I have only used steel tanks a couple times so I won't swear by the numbers. Others here should be able to give you more exact details.
I would expect that larger tanks of a given material would be more bouyant (or less negative) but I could be totally wrong.
Hopefully my feeble attempt will trigger someone with more knowledge to answer your quiry. It would help if you were more specific about what tank sizes/materials you are interested in knowing about.
Wristshot
just an AL80 kinda guy. . .
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