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Negative Buoyant Depth?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

LiquidRush

Fluid Funk Stylist
Jul 27, 2004
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5
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whoops.

A few times I've heard ppl mention this. Is there a certain depth where one becomes negatively buoyant? plz explain.
 

Bill

Baron of Breathold
Oct 17, 2001
1,805
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Most free diving is done with a wet suit. Everyone that I've seen will float(+ buoyancy) at the surface. If you dive, the air in your suit and lungs is compressed and your buoyancy decreases. For novices, it seems to be best to use enough lead to achieve neutral buoyancy at ten meters.
When you are neutral at ten, you will be negative at any deeper depth and positive at any shallower one.
Aloha
Bill
 

DeepThought

Freediving Sloth
Sep 8, 2002
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Well, since you're diving in Thailand I assume you freedive without a suit, so I wanted you to know it's the same for diving without a suit, though I think that in that case I'm negative at more depth... 15m maybe, never measured.
 

Skywalker

New Member
Aug 12, 2004
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Originally posted by DeepThought
Well, since you're diving in Thailand I assume you freedive without a suit, so I wanted you to know it's the same for diving without a suit, though I think that in that case I'm negative at more depth... 15m maybe, never measured.

Hmmm I guess you meant he is less positiv buoyant then with the suit and that for will be negativ at a smaller depth then with the suit?

Yours

Sky
 

DeepThought

Freediving Sloth
Sep 8, 2002
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No I didn't. :)
Suit gives bouyancy. Therefore you add weights. So in depth, when the suit loses bouyancy, you become more negative, on the surface you are more bouyant with a suit on.

If I empty my lungs without a suit, I will sink. which makes a good breathup (for me) with no bouy to hold on to kinda dificult - I have to give some propultion when I'm empty to keep my snorkel getting air instead of water.
If I empty my lungs with my 3mm suit and 3kg, I will not sink. So at surface I am more bouyant.
But at depth, this thing changes: not wearing a suit, I have only my lungs that have compressed.
Wearing a suit, I have my lungs and my suit that have comressed, and 3kg of lead. There's a depth in which the 3kg of lead sinks my suit, which doesn't happen at surface. That depth I guess is less than 15meters because when I was diving without a suit, I got negative deeper than I would with my suit.
You can also say that I don't inhale as much air with the suit on, though I'm not sure how much difference that can make.

This can be different for different body types lung sizes and suits, but there's a general rule that works for all: you have more buoyancy change when diving with a suit than without. And more change for a thicker suit.
That's why it's important that freedivng suits will be made from better materials and with a better fit to warm you more, so you could get rid of some mm's, because the bigger the buoyancy change you will have, the more energy you will have to spend fighting it (harder to get down, and harder to go up).

I guess I was in the mood for some writing. :)

Welcome to DB by the way. :)
 

Skywalker

New Member
Aug 12, 2004
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Thanx for welcome :)

I guess I forget to put the wight off without the suit. I reduced the circumstances just by the suit and in my mind there was still weight on even without suit which would give neg buoyence pretty soon I guess :D

Yours

Sky
 

donmoore

New Member
Aug 19, 2002
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One important goal is to be positively buoyant at the surface with no air in your lungs. To find out, just let all your air out without moving and see if you float or sink. Being neutral at 10 meters should do it for most people, but it’s a good idea to make sure. If your spearfishing in water less than 10 meters deep you might be tempted to weight yourself a little heavy so you can be neutral or negative where you want to hide and wait. It’s especially important in this circumstance to be positive at the surface with no air.

The reason surface buoyancy with no air is so important is that if you black out you will most likely let your air out. Maybe everyone doesn’t, but I know I do and there are a lot of dead divers who did too! Most divers that drown make it to the surface or close to it, but sink after losing their air and buoyancy.

Scott Turgent told how he blackout once and lived, because he floated face up. Both my regular dive partner and I purposely turn on our backs at the surface when ever we feel close and take our recovery breaths in this position. I don’t know if that is advisable or not, but I feel more secure when doing it. Even if I think I am being spotted, I still do it just encase he gets distracted or something.
don
 

donmoore

New Member
Aug 19, 2002
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That's why it's important that freedivng suits will be made from better materials and with a better fit to warm you more, so you could get rid of some mm's, because the bigger the buoyancy change you will have, the more energy you will have to spend fighting it (harder to get down, and harder to go up).
Actually the flexible and soft neoprene used in freediving suits hold more air and compresses more than traditional wet suits. Therefore they have more of a buoyancy change. My 3mm suit made out of Yamamoto 45 has significantly more buoyancy change than my 5mm double-sided nylon scuba suit.

I used to think that the less buoyancy change the better, but after getting used to my 3mm I miss it when it gets too warm for it. It definitely takes more effort to get started, but by using the arms for one stroke, like a lot of constant ballast competitors do, and really paying attention to the body position, I have been able to overcome it. The really nice thing is the expansion and large positive buoyancy I get as I near the surface. It feels so comforting and safe. Like a higher power saying, its okay, I’ve got you now! You would probably have to feel it to understand that last statement. :confused:
don
 

Skywalker

New Member
Aug 12, 2004
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I have a I think 3 mm neoprene which was supposed to be used for surfing should that be fine for the beginning?

And I bought the CRESSI, GARA 3000 today and can't wait to try them out :)

Yours

Sky
 

donmoore

New Member
Aug 19, 2002
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Sky,
Anything that keeps you comfortable in the water temp you are in is good enough for starting. As you get more addicted to the sport, you will eventually want to have a freediving suit with a built in hood. The streamlining and water flow a freediving suit with hood is much better allowing deeper and further dives. The hood will allow you stay warm with a thinner and less restrictive neoprene in the body.

Have fun with those new fins!
don
 

Skywalker

New Member
Aug 12, 2004
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So I am just starting that topic for me and will figure out the right training for me in the next weeks and months. I started to make a little dictonary for all the terms used and discussed here. Therfore I wanted to ask if something like that already exists or if someone has made something like that for privat use but would like to share. As I guess I am not the only newbie not knowing what negatives are (in the meanwhille I know) or samba, lung squeeze.

Yours

Sky
 

Roland

New Member
Mar 11, 2004
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For a start on a little dictionary on freediving terms you could look at:
www.freeapnea.nl --> Articles --> Freedive Slang Explained, 11-12-2003, English version

I am shure he would like to share it and any ideas or suggestions you might have.

I do not know of any others but I am shure there must be other little dictionaries out there. Are you also building a website? If yes, what is the link of the site you are building?
 

DeepThought

Freediving Sloth
Sep 8, 2002
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Originally posted by donmoore
My 3mm suit made out of Yamamoto 45 has significantly more buoyancy change than my 5mm double-sided nylon scuba suit.
Well, I think yammamoto might be an exception. Anyway, it is not what I noticed when diving with partners who wear scuba suits. Even when wearing only the top part of a 5mm scuba suit my partner had a FEW kg more than I did. And since we got out of the water atleast once because he was freezing while I was toasty warm, there was room for more neopren on him. :)
I don't think that our body types are that different, and I guess it is also a question of how new the suit is.

The really nice thing is the expansion and large positive buoyancy I get as I near the surface. It feels so comforting and safe. Like a higher power saying, its okay, I’ve got you now! You would probably have to feel it to understand that last statement. :confused:
don
:)

Skywalker, try the search option on 'glossary', you might find some more of those freediving dictionaries...

"Use the force Luke...."
 

donmoore

New Member
Aug 19, 2002
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Michael,
We both are probably right. The same thickness of scuba suit verses a freediving suit, the freediving suit will probably have more buoyancy change from the softer more compressible neoprene, but the fact that you can stay warm with a thinner suit would tend to offset this. I know I am a lot warmer in my 3mm smoothskin metallic lining freediving suit than I am in my 5mm scuba suit. I would probably need a 7mm scuba suit for the warmth to be comparable.

I also think the flexibility and comfort aids in the start and buoyancy part of dive which could allow a person to use less weight than a restrictive scuba suit.
don
 

Skywalker

New Member
Aug 12, 2004
70
3
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So the new fins worked fine. It was just like a huge difference to the scuba fins which I didn't expect.
Now it is time to start to increase my breathhold capability :p

Yours

Sky
 
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