Negatively buoyant without weights

[brutus_scuba]

No, water is neutrally bouyant in water. What matters is just how much *air* is in the BC.

Water is nuetrally boyeant in water, but when you have somethign that is normally filled with air or even nothing at all and you add water the density of the object can increase. Take for example a rubber ball it will float when filled with air. It will even float depending on the material if you pulled a vacuum in the middle so there was no air in it at all. But if you fill it with water it will remain right at the top with all the ball in the water not floating on top anymore. With a BC there is more to it then just the material and bladders you also have to account for the tank regs and gauges so it is possible that the overall bouyancy is now negative.

 

[vondo]

Water is nuetrally boyeant in water, but when you have somethign that is normally filled with and you add water b/c the water is less boyeant then the air it brings down the boyeancy of whatever it is that is filled with water.

If after "with" you mean air, I agree. But it doesn't apply here because your BC is normally not filled with anything.

Sure, the maximum bouyancy of a BC with water in it is less than one that is empty, but a BC with no air in it and no water in it is the same as one with no air in it and some water in it. A BC with 1 litre of air and water is just as bouyant as one with 1 litre of air and no water.

A BC is not a fixed volume container like a tank. The amount of water in the BC does not matter.

 

[minnesota01r6]

you lost me there brutus...

EDIT: are you thinking about density??

 

[vondo]

I finished the pool portion of my OW class this past weekend, and I ran into an unusual issue with my weighting that I can't quite figure out.

We did the standard PADI "sink to eye level" exercise. On Saturday, 10 lbs of weight brought me to forehead level, which the instructor said was close enough. On Sunday I sank without wearing any weights at all.

I'm 6' tall and weigh 200lbs. I had the same BCD both days, and I'm pretty sure I was using the same tank. The only think I can think of is that my wetsuit was a size too large and air was getting trapped on Saturday. Either way, I'm uneasy about diving without being able to ditch weights and get buoyant in an emergency.

Any idea what's going on?

Thanks,
- Sean

Could it be that you didn't get all the air out of the BC the first time? I think I had problems with that early on. It moves around to the highest point and if that is not where you are dumping it from, some will stay in.

 

[brutus_scuba]

I dramatically edited my message up top. Sorry about that I was at work when I wrote it and I didn't dedicate near enough time to the message.

 

[Nemrod]

You either had trapped air in the BC (BCD PadIeze lingo is redundant BTW) or your suit was trapping air. There are actually quite a few people who are negative without weight. This is quite common especially with younger males with heavy bone structure and desnse muscle. To this day I need little or no weight even in a 3/2 suit and I don't quite fit that description anymore-lol. In salt water I now use some weight now that I am old and fat. I have had busy body know it all DMs insist I had to wear a weight belt--why? So, just be happy that you are one who does not need to lug all that lead around. Trust me, with a dry suit or a heavy wet suit you will need a weight belt, just not one with 40 lbs on it. N

 

[donacheson]

I finished the pool portion of my OW class this past weekend, and I ran into an unusual issue with my weighting that I can't quite figure out.

We did the standard PADI "sink to eye level" exercise. On Saturday, 10 lbs of weight brought me to forehead level, which the instructor said was close enough. On Sunday I sank without wearing any weights at all.

I'm 6' tall and weigh 200lbs. I had the same BCD both days, and I'm pretty sure I was using the same tank. The only think I can think of is that my wetsuit was a size too large and air was getting trapped on Saturday. Either way, I'm uneasy about diving without being able to ditch weights and get buoyant in an emergency.

Any idea what's going on?

Thanks,
- Sean

You want to be able to be neutral throughout your dive. You are lightest at the end of a dive - just below the surface with a near-empty tank. If you don't need weights with an empty BC under these circumstances, fine; just add enough air in your BC to be neutral and you can do your safety stop in comfort and control your ascent to the surface.

 

[bigred]

Hmmm. It sounds like I don't need to worry about it too much.

It's entirely possible that I had air left in my BC, but I think divingdj got it. We started the first day in the shallow end and I used a portion of my air before doing the weight check in the deep end.

We'll see how it goes next weekend for my checkout dives. I was wearing a 5mm full wetsuit in the pool, but the quarry is supposed to be pretty cold (50F). A hood, gloves, and 7mm wetsuit should add some buoyancy. If that doesn't work, well, I can always try diving in saltwater.

Thanks for the replies.

-Sean

 

[hdtran]

Sounds like you're one of these muscular and bony guys...

Don't worry about being a "sinker".

Now, if you *DO* worry, I've got this mixed bean stew recipe which is guaranteed to, umm, make you float