Too much weight on first dive

[perdidochas]

So if I got this straight, if you go from a aluminum tank to a steel tank there is virtually no difference in weight of the tank, but because steel is less buoyant you can reduce your overall lead by five pounds? thats a little hard to figure...

The main part is that conventional AL cylinders are positively buoyant when close to empty. That requires the carrying of extra weight to compensate for them.

on the subject of buoyancy, I was wondering, do wet and dry suits have buoyancy characteristic numbers associated with them so if you change suits, say from a dual 7mm to a 3mm, it is easy to recalculate your lead needed? If not can you figure this out by seeing how much weight it takes to sink your suit in a pool of water?...

Dry suits are a little more complicated, and I have no idea how you would do that.

For a wetsuit, you can do just that. Put your suit in a pool, and add weight until it sinks. You can do the same for all of your wetsuits. Then you would do the same for yourself without wetsuit, and could set up different weightbelts for different suits, for example.

 

[TravisD]

So if I got this straight, if you go from a aluminum tank to a steel tank there is virtually no difference in weight of the tank, but because steel is less buoyant you can reduce your overall lead by five pounds? thats a little hard to figure...

Ignore everything about "weight" - except when you're worried about if you can carry it from that car to the water or not..

The Buoyancy characteristics are what you're looking at with the tank change.

Comparing two "empty" tanks (which is what you're worried about, since you want to make sure you can can hold your safety stop at the end of the dive when the tank may be nearly empty - or even empty if things really went pear-shaped), an AL80 may be say 5 lbs "positively buoyant" - or +5. It would take 5lbs of ballast weight to make that tank neutral again. In the other corner, that Steel tank may be 2 lbs "negatively buoyant" when empty - It'll sink just like a 2lb lead weight would. The difference between those two tanks, buoyancy wise, is 7lbs, so you *should* need 7lbs less extra ballast in this example, when going between those two tanks. This is tank dependent of course!

 

[diver 85]

Everything you described, did that take place before or after your 4 checkout dives, in other words, have you gotten your C card----yet ??......

 

[RonFrank]

The short and long of it is, you need to do a weight check. It's not always easy for an instructor to make this happen before the first dive, especially if everyone wants to do one, but you need this to be done before you dive again.

It sounds like you were horribly overweighted.

To do a weight check you need a mostly empty tank, but you can use a full tank if necessary. I'm rather surprised that you did not do this in OW pool sessions.

So sluff on a 500psi tank, jump in/walk to the deep end, and exhale. If you can sink, take off some weight, if you sink like a rock take off a lot of weight. Do this until you can hover at the surface with a minimal amount of weight and keeping air in the lungs. If you exhale you should be able to sink. For comfort, add two lbs. If you are using a full tank, add 7 lbs of weight instead of two. This assumes a standard AL80. If using other types of tanks, adjust the weight as necessary to factor in the tank specs.

Good Luck

 

[MSilvia]

So if I got this straight, if you go from a aluminum tank to a steel tank there is virtually no difference in weight of the tank, but because steel is less buoyant you can reduce your overall lead by five pounds? thats a little hard to figure...

Okay, rather than steel and aluminium, imagine you had one tank made from 30 lbs of steel, and another made from 30 lbs of styrofoam. Obviously, they both weigh the same, but you're going to need a lot more weight with the styrofoam tank than with the steel. It's an exaggeration, but the principle is the same.

on the subject of buoyancy, I was wondering, do wet and dry suits have buoyancy characteristic numbers associated with them so if you change suits, say from a dual 7mm to a 3mm, it is easy to recalculate your lead needed?

It would be convenient, but no... not that I'm aware of.

If not can you figure this out by seeing how much weight it takes to sink your suit in a pool of water?...

Sure, but it may be just as easy to see how much weight it takes to sink the suit with you in it. At least that way you get to dive.

 

[mtrotterjr]

Wow, now i am new to diving and not and expert at all, but i dive cold water at milbrook, with al 80, 7mm, boots, hood and all. and i only wear 18 total in the pouches and 1.5 on each leg cause my legs float with a 7 on. so that is only 21 lbs. only had a problem one time on my descent because i was anxious, once i calmed down i sank like a rock. and i am 280, 5'11" and not in the best shape. Stick with it though, you'll get it all figured out.

 

[TSandM]

I wonder if the OP ever went through and got certified?

 

[Bob Vincent]

I'm 5'11" & 240. In salt water with a top I use 16 lbs. ( I don't dive in cold water) I have trouble believing that the 7 mill and 40 lbs requires 3.8 times more lead. And you were in fresh water. Get into a pool, get your tank down to 500 psi and get "dialed in". It's easy in those conditions. Additionally you will do much better if you get into good cardiovascular shape. Before every dive trip I workout in the pool with snorkel and fins and kick hard till I'm exhaused. I'm not ready till I can do that 45 minutes nonstop. I don't want to be the guy that makes everyone turn back on the dive becaus I'm the one who hits 1/2 air gone first. Amazing what some conditioning does to improve air usage. I do know a lady divemaster- instructor who is 5' and weighs close to 300 lbs. And she uses NO freaking air. She is as good as
ANY diver I've ever had the pleasure of diving with. Your size will be an issue but she proves it can be done (and I'm not talking about the air usage, women have an unfair advantage) but she is amazingly skillfull in the water. Her husband helps her gear up but in the water she is top dog.

I know someone like that but I don't believe she's 300 and gears up herself and is an amazing diver. I'd dive anytime anywhere with her period. And it might be the same person because it's like she doesn't breathe at all like you said. She is a fish ... period!

So I'm not on the small side either look at my picture lol I'm only about 5ft 6 1/2 inches and right at 296.