archimedes73:
Since I got certified almost 5 years ago, I've completed around 40 or so dives including freshwater lakes in my home state of Minnesota and salt water dives in the Caribbean. I have always used what seems like to other people a lot of weight. Currently, I have done some diving in Minnesota using a Mares semi-dry suit, usually with a hood. The BC I am using is a Scubapro Accent. I've found that I need about 25 pounds with this suit to descend easily. The weight is distributed with 3 pounds split between ankle weights, 2 pounds in each back trim pocket, and 18 split between the two integrated weight pockets. When I dove in the ocean, I wore a 3/2 two piece suit with farmer john and jacket. I wore 18-20 pounds. Although I don't have a whole lot of experience, I feel like I've come a long way with my breathing and buoyancy control. I usually just need a small amount of air in my bc to be neutral at depth, and make any small adjustments with breathing. I also am much more relaxed with each dive now than when I was first starting. The current dilemma is that when I wear my semidry, my BC can barely hold enough air at the surface to keep me comfortably buoyant before the air release valve belches air. Once underwater all is fine. When I inquired about this issue at the dive shop we use, no one can believe I need that much weight to descend. I got the same response diving in Cozumel when I asked the dive master for 20 pounds. I have tried descending with less and have a very difficult time. I am about 5'9" and weigh around 150 pounds. I am currently working towards my dive master certification and don't want to feel like an idiot when I start helping out with classes because I have to wear "too much" weight. Am I way off here?
First of all, it is a common myth that the amount of weight you need is, by itself, an indicator of skill or accomplishment. I have heard people who were so proud they carried 5 pounds less weight than the next person. Forget that nonsense.
You need as much as you need and it is dependent upon many factors as pointed out above. Build, tank choice (alum vs. steel), other gear and its associated weight (heavy bc, titanium first stage, reel, etc.), and thermal protection. If you dive a 7mm neoprene drysuit with winter thermals you will need a lot more weight than someone diving with a trilam suit wearing thin thermals. Two piece 7mm wetsuit vs. a single layer 7mm wetsuit, etc., etc., etc.
With this being said, there are some other things to consider when determining how much weight you need. You need to be able to descend from the surface without kicking down, you need to be able to maintain neutral buoyancy at depth, and you need to be able to remain neutral for your safety stop and slowly ascend to the surface. The most important would be to ensure your weight is such that you can stop at 15' with a nearly empty tank AND slowly ascend to the surface. (Obviously don't end your dive on E - but for the point of this conversation - make sure you can - worst case scenario). Wearing neoprene you will always be heavier at depth as a function of the material. Remember it is always better to be a little heavy than a little light if being light means you can't stop at 5' for example because of an oncoming boat.
I suggest you have a buddy bring some extra weight while you try descending with 500 psi in your tank. Do this in the shallows obviously. If you can descend with 500 psi in your tank, making sure all the air is out of your BC, and exhaling fully, then you know you will be able to do a safety stop and slowly ascend to the surface.
This weight will be a little heavy with a full tank. An alum 80 goes from approx. 2 pounds negative when full to 4 pounds positive when empty. So over the course of the dive the tank will shift 6 pounds with the depletion of air. So to ensure a safe weight configuration you will be a little heavy when you descend with a full tank so you can ascend with sufficient weight to stop at your safety depth and ascend slowly to the surface.
--Matt
