Do you dive NEGATIVE without ditchable weight? As in "0" ditchable weight?

[100days-a-year]

Absolutely no ditchable weight when I am in 72degree+ water and S/S bp, S/S sta, AL80,polartec or skin ,no or little deco.Cold water ,doubles and/or stages= whatever weght it takes to be neutral empty at 10'(assuming deco on back gas due loss of stages or failure)I was light in the ocean once after a deep dive doing deco ...it really sucked until I got to 20' where we stash xtra weight to keep the hang line tight.

 

[BlueDolphin]

Yep.... being positive at the end of a dive..... happened. Scared the bubbles out of me. Not a lot mind you... but enough to make me lose control of my ascent for a few moments near the surface. I never want that feeling again.

So I would rather be negative, and have to swim it up, than have that happen again.

I am a new diver, as you can tell from my post(s).... and am working to find out what is the best way to weight myself. I do NOT want to have a lot of ditchable weight if possible. (10lbs. or less).

Anyway.... I appreciate the comments very much. It helps.

 

[ElectricZombie]

I can get down with no weight using a traditional "tech" style BC and a farmer john.


Now that I dive BP and Harness, I'm a few more pounds negative.

I went to the quarry today and wore the following:

Farmer John two piece - 3 mil on arms and legs, 5 mil on chest

Another wetsuit over that for a total of 5 on arms and legs and 8 on chest.

With my BP and harness and an Al 80, I needed about 6lbs to get down...maybe a bit less.

I would like to have some ditchable weight for warmer conditions but, I need to get an aluminum BP first.

 

[jrtonkin]

But I think you'll end up more than the 2-6lb negative that you're expecting...

Assume you're dead-neutral at the surface, with an empty tank.

If you've got an 80cf tank (steel or aluminum, doesn't matter), then at the start of the dive, at the surface, you'd be 6lb negative, just from the extra weight of air in your tank. For a 120cf tank, this would be 9lb.

You said you use a 7mm suit. My new 2-piece 7mm has about 20lb of buoyancy, pretty much all of which goes away by the time it's down to 60'. So if it's neutral at the surface, I'd be 20 negative at depth. Now if you only mean a 1-piece 7mm, you could probably halve that, depending on make, manufacturer, how big you are (a larger suit has more neoprene, which means a larger swing), how old it is (old suits compress a bit), etc.

So at depth, at the start of the dive, you could be 16 to 26 lbs. negative... A lot more than the 2-6 you asked about.

As for how much you can swim up... I'm an ex-lifeguard, in good shape, and have a strong eggbeater, and find:

10 lb: fairly easy. Most strong swimmers can handle this, although it's beyond what a lot of average swimmers can handle.

20 lb: takes effort. Certainly I wouldn't want to have to go more than 20-30 feet. Some lifeguards have difficulty with even this much.

30 lb: Quite hard. This is about the top weight I can consistently lift, and that still involves pushing off against the bottom of the pool, and only going another 6-10 feet.

40 lb: Only on a good day. A *very* good day. And even then, I'm jumping off the bottom of the pool, and just barely maintaining upwards momentum. I doubt I could do this from a hovering start, let alone if I had downwards momentum. It's also dead-slow. About 20sec, swimming as hard as I can, to get from the bottom of the pool to the surface, and it's only a 12' deep pool.

All of these are also based on using a kick called "eggbeater". A very slow kick, but one that provides quite high thrust... And not a kick I think you can do wearing fins (though I've never tried).

Practical upshot: if you're in good shape, and fairly shallow, you can probably swim 10lb. Anything more gets unlikely.

Jamie

 

[BlueDolphin]

Thanks JrTonkin for the swim scenarios. I would like to know if you think most could swim up 10lbs. - 12 lbs. or so WITH fins on. This would be assuming that there was a problem early on in the dive that required a slow ascent with lots of air still in the tank.

Thanks again for your input.

 

[Northeastwrecks]

Twin 104's, SS backplate, 4lbs of soft shot buried between the tanks to lower my legs, trilam drysuit, 55lb Explorer.

Weight is a necessary evil. I don't like to be positive, particularly at the end of a dive on a deco hang.

 

[The Chairman]

It's a comfort factor for each diver and there is no right or wrong. Wet suit or no, I feel comfortable with my HP 120s in fresh or salt. However, I feel a tad too negative with my doubles and SS Fred-T backplate. I will probably be getting a Fred-T AL backplate soon to help with that.

 

[nitroxbabe]

I've also become positively buoyant at the end of a dive and would much rather have a little extra weight than I need than not enough. Lucky for me I had a rock to cling to or I would have popped right up. My feet wanted to go over my head, however, and it was a long safety stop.

Besides, having ditchable weight could help you if you're disoriented in a silt-out or low vis situation - lose the weight, you'll ascend, don't need to see which way is up.

 

[lucid]

I am taking IANTD Tech and Normoxic Trimix and my instructor had me do a drill the other day. He asked me to tread water for five minutes with no air in my bc.

Exquipment: (I was task loading so I had a lot on).

1) 3mm Shorty with skin.
2) Double Neutraly bouyant 80's alum. (They are going bye bye)
3) Canister Light. (Wreck one 10watt HID).
4) Dive Rite ABS backplate and wreck wing.
5) Rest of normal gear.

No weights.

It was very hard. If I was actually at the surface in a real emergency I would of had to ditch a lot of $$$ in gear. You people that dive heavy should try it out. May start to understand why people say to kiss your family good bye before you dive with steels in the ocean etc. You never know.

 

[jrtonkin]

BlueDolphin once bubbled...
Thanks JrTonkin for the swim scenarios. I would like to know if you think most could swim up 10lbs. - 12 lbs. or so WITH fins on.

Depends on the person, and the fin I think. (Like that's not a fairly content-free statement.)

With split-fins, I'd have my doubts about most people being able to do so. This is because I believe (though I havn't tried) that split-fins are more optimized for higher-speed, lower thrust swimming.

With conventional fins, I'd guess that most people probably could, if they knew what they were doing. The extra 10lbs is a fairly significant load, and flutter-kick isin't really designed for low-speed, high-thrust... So if that's the only kick they know, then they probably couldn't (or it'd be a very hard task). For a strong swimmer, or someone who can do a good whip-kick then they probably could.

From what I've read about jetfins (or other short, broad, fins) they seem most likely to allow most people to lift that load. This is because they seem to be better for doing non-flutter-kicks than other fins, so it would take less training to have an effective whip-kick. (I've not been trained (or even seen videos of) frog or modified frog, which is why I'm sticking with the names I know from swimming instruction... A whip kick is probably similar to a frog kick, but I don't know for sure)

All this is just me theorizing though. <grin> Guess I'll have to haul my fins (Mares Quattros) down to the pool and give it a try some evening.

Jamie