How much weight?

[Deadeye]

OK,
As a relative newbie with few dives, I have a question.

The instructor I worked with felt most people use too much weight when they dive, and I guess I follow his lead so far.

I dive with only 4 -6 lbs of weight and I use a Henderson titanium suit. I'm not a small person and I wouldn't say I'm all muscle.

Reading the posts above it would appear that I use less weight than the buoyancy of my suit.

Even though I carry around a small spare tire around my waist, I have always been one of the folks in the pool who would sink to the bottom easily. In 'water survial school' safety training for my company I sank to the bottom VERY easily.

So what's up? Is this one of those, 'everyone's physique is different' issues?

Would I find it easier to equalize if I carry more weight? Also I've never gone saltwater diving yet so have no idea what to carry there.

I'm also one of those divers who probably won't dive without my wetsuit unless it's in a swimming pool.

Oh, yeah, and I know this has probably been hashed over more than once because it's probably one of the things we 'newbies' just have a hard time getting a handle on.

TJ

 

[kelpmermaid]

Hi Deadeye-

Yes, the bouyancy characteristics of salt water differ from fresh, and you will need more weight. Some people do sink more easily than others...

Weight has nothing to do with equalizing, unless you are so overweighted that you sink so rapidly your ears can't keep up...

 

[joewr]

I am not an expert in the field of buoyancy, but here is what I have found in my own diving...

I weight myself so that when I am submerged I use only my lungs for buoyancy control and there is, generally, no air in my BC.

To initially descend I evacuate my BC and my lungs. If I cannot descend feet first due to buoyancy, I invert. Normally I do not have to invert except on the first dive of the day when my all my gear is "dry" and I probably have a little adrenaline pumping. And, for the most part, I do not have to invert on the majority of first dives.

The compression of my wt suit and the opitimizing of air in my lungs allow me to do a safety stop without struggle, hanging onto the anchor line (unless there is strong current), or bobbing upside down with an Al tank.

The above technique probably violates all sorts of DUI, GUE, IRS and KGB rules...but they work for me............


Joewr...

 

[Deadeye]

I guess that is what I was really looking for more than anything else, the common sense approach from experienced people.

Ya know ya can read all the books,
see all the videos,
but doin' it is what really counts.

 

[socaldiver]

When diving with my steel tanks vs al80s I wear 5 lbs less weight.

When diving with my 3 mil vs 7 mil, I dive with 5 lbs less.

Going thru OW training my instructor "recommended" a certain weight for each student. I come to find out, after becoming certified, that I could go with 6lbs less weight.

I could probably shed another couple of pounds of weight but am very comfortable with my buoyancy as it is, and when I make my safety stop I can ascend without the use of the anchor line and know I can hover at 15 ft with no problems. Time and practice is the key.

Don't underweight, don't overweight they both could have ramifications. Relax and enjoy, stay safe, stay wet.

 

[artsprite]

Yeah, my instructor had everyone weighted too much in class. I think he did it for the pool because it's harder to stay under in shallow water. I don't know why he did it in the ow lake dives, but he told me I was wearing too much weight when we finished. I had to find out the hard way that 6 was enough without a wetsuit. It seems there's no easy answer, but you all have given good advice.

 

[rstone]

Here is some info i thought id pass along:


Step One: Calculate for your body (Typical range 1- 10lbs)

How much weight would you need to make your body alone neutral? There are two methods, one pretty accurate, the other a guesstimate.

Method 1: Take a few weights to a swimming pool. You will be perfectly weighted when you can hang motionless with half a breath and sing when you exhale. Using snorkel can make this easier. Assuming this is a freshwater pool, you can then make the saltwater conversion below. Remember to correct your total weight, body plus lead.

Method 2: Most lean adults are 1 to 4 pounds positive, although musclar, big-boned divers may be a few pounds negative. Remeber your weight when you were in your best physical condition as an adult? How much have you gained since then? How much of the gain is fat? For ever 10 pounds of fat you've gained add two pounds of lead. For ever 10 pounds of muscle , subtract 1 pound of lead.

Step Two: Calculate for your tank (Typical Range -7 to +5lbs)

Buoyancy characteristics of tanks vary. Find your tank below. Using the tanks weight when empty, add lead for positively buoyant tanks, subtract it for negative ones.

Step Three: Calculate for your exposure suit (Typical Range 2 to 20lbs)

There are several methods to estimate how much weight you'll need to compensate for the buoyancy of your weightsuit. Remember, its the buoyancy in shallow water (at your safety stop) that counts. Shell drysuits with full-thickness underwear normally require a few pounds more then a 7mm weightsuit.

Method 1: Take it to a swimming pool. Wearing your exposure suit and weight belt, figure your buoyancy as above in step one.

Method 2: Weigh it. Neoprene is 2 to 3 pounds buoyant for every pound it weighs in air, depending on the quality of the neoprene and age of the suit. (1mm neoprene skins, being proportionally more nylon, are less buoyant)

Method 3: How thick is it? A mans large fullsuit has 2 to 3 pounds of buoyancy per millimeter of thickness (a 3mm fullsuit has about 6 to 9 pounds of buoyancy; a 7mm fullsuit about 14 to 20 pounds). If you wear a differnt size, estimate an adjustment. Keep in mind that thinner suits and neoprene skins will have less buoyancy.

Step Four: Calculate for other gear (Typical Range 2 to 4lbs)

Regulators, gauges, knives, most fins and BCs are slightly negative. The total of your mandatory gear is probably 2 to 4 pounds. Optional equipment can change the equation by a pound or so. Most large lights are slightly negative. Cameras may be either negative or positive by about 1 pound.

Step Five: Total it up (Typical Range 2 to 40lbs)

This is your target weight and should be accurate to within 4 or 5 pounds.


Freshwater/Saltwater Conversion:

By how much do you have to change your weight belt when going from fresh to saltwater? To be accurate, you have to consider the whole package: diver plus equipment.

Stand on the bathroom scale with the equipment and weight that makes you neutral in one medium or other. Or you can estimate. A stand aluminum 80 tank weighs 32 pounds, a 7mm wetsuit is about 8 pounds. For regulator, mask, fins, etc, figure about 15 pounds. Include your weights.

Going from fresh to salt.. multiply by 0.025 and add that amount.

Going from salt water to fresh water.. multiply the total by 0.025 and subtract that amount from your weight belt or integrated-weight BC.

Tank Table: The Weight of Air

Type of Tank Full Empty Change
aluminum 50 @ 3000 psi -3.0 +1.0 +4.0
aluminum 63 @ 3000 psi -2.0 +3.0 +5.0
aluminum 67 @ 3000 psi -5.0 +0.5 +5.5
Steel 72 @ 2475 psi -5.0 +0.5 +5.5
Steel 76 @ 2640 psi -6.0 0.0 +6.0
aluminum 80 @ 3000 psi -2.0 +4.5 +6.5
aluminum 80 @ 3000 psi* -4.0 +2.5 +6.5
Steel 95 @ 3300 psi -15.0 -7.5 +7.5
Steel 95 @ 2640 psi -7.5 0.0 +7.5

* Super 80

This data is based on actual test and differs from mfg. specs, mfgs calculate specs for an ideal tank in fresh water with no valve.



:goofy:

 

[Ontario Diver]

Agree with all of the above (and Joewr - I do the same)

Where we dive, it is cold and deep; my philosphy is if I have too much weight, I can compensate for the extra weight by infalting my BC - even at the cost of air consumption, energy etc. But If I am light in weight, I haven't found any way of adding weight (well undewater at least; 6 days of DimSum will bash on a few pounds)

being light may become a serious safety issue. Especially after you empty the Al80

 

[artsprite]

good point about the safety issues of being too light. Thanks for the input everyone.