Re: Proper weighting

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Posted by Ken Kurtis on September 11, 2000 at 12:28:58:

In Reply to: Re: Diver Injured/The Facts (long & detailed) posted by msblucow on September 11, 2000 at 07:05:00:

(msblucow asked) Ken . . . what's the best way to check if you're overweighted?

Here's the method I've been teaching for 20 years.

1. Put on your wetsuit (or drysuit), hood, booties, gloves, mask, snorkel, and fins.
2. Do not put on your tank or BC. kep them out of the equation. This way, we weight your for your personal buoyancy and that of the wetsuit, eliminating problems of trapped air in the BC or changes in the buoyancy of the tank 9which should be negative at the start of the dive anyhow).
3. Assuming you're wearing a 6-7mm suit, start with 10% of your body weight plus 2 or 3 pounds. (I think 6-8 over 10% is too much as a starting point.)
4. Float erect in the water, snorkel in your mouth, feet underneath you.
5. On a full breath of air, you should float at your chin.
6. On a full exhale, you should sink to the top of your head or even start to go under.
7. If you cannot sink on a full exhale, add some weight. Generally, from chin to top of head is about 10 pounds of buoyancy. If you only sink to your nose, add about 5 pounds. If you only sink to your eyebrows, add 3 pounds.
8. If on a full inhale you can't keep your mouth above the water, or if you start plummeting on a full exhale, you've got on too much weight. Take some off (3-5 pounds to start, then repeat #1-8.)
9. IMHO (although there will be exceptions) if you're wearing more than 15% of your body weight in lead, you've probably got too much on.

"I need more weight!!" is the cry of the chronically over-inflated diver, unable to descend. There are three reasons why you can't get down:

1. You are truly underweighted (which is why we have you do this drill in the first place).
2. You're trapping air in the BC.
3. You've got all the air out of your BC but you're holding air in your lungs. (Dump air from BC but take a big breath as you go under and you've just negated dumping the air from the BC. Remember that air in your lungs, depending on body size, can make anywhere from a 6-12 pound shift in buoyancy.)

Remember, too, especially in SoCal, you're going to get a lot of wetsuit compression which will decrease your buoyancy once you're underwater. (That's why the BC is called a bouyancy COMPENSATOR.) Even if you start slightly UNDERweighted at the surface (which is my personal preference) once you get down 10' or so, the wetsuit compression should offset any under-weighting.

As someone mentioned earlier, ideally at the end of your dive, if your tank's at 500psi, you should be able to be at 15' with no air in your BC and be neutrally bouyant.

You can also get a feel for how much air you're putting in your BC while on the bottom. If it seems like it's always a lot, you've probably got on too much weight.

And I will freely concede that we instructors, as a group, get you started on this over-weighting habit because it's easier for us to slap an extra 5-8 pounds on you to get everyone down quickly for class skills & drills than it is to wait for everyone to do a good surface dive and get down a few feet if they're slightly underweighted. But, unfortunately IMHO, it encourages bad weighting practices because most divers continue to dive with whatever weight they wore in their class.

Personally, I weight 175 and wear 14 pounds with my 7/5 Henderson one-piece and a hood, plus about 3 lbs from my steel 66. With my Zeagle neoprene drysuit (same tank) I wear 18 pounds.

Hope this helps.

Ken Kurtis
NAUI Instr. #5936
Co-owner, Reef Seekers Dive Co.
Beverly Hills, Ca.

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