Descent difficulty, even overweighted

[Russjstewart]

The similar threads links on this thread has a link Scubapro Yulex vs. Henderson Greenprene

where people are talking about the greater buoyancy oh greeprene wet suits which the op is using

 

[scubadada]

The similar threads links on this thread has a link Scubapro Yulex vs. Henderson Greenprene

where people are talking about the greater buoyancy oh greeprene wet suits which the op is using

So, you compensate for the buoyancy. I bought a Henderson Greenprene 3 mm and needed 2 lbs more than previous 3 mm. 2 dives and I was completely back on track, no big deal.

It's a very warm and very comfortable wetsuit, the extra buoyancy is the only drawback.

 

[rx7diver]

@Bubba_in_cali,

The approach I was taught (and recommend) for determining your "correct" buoyancy for single-cylinder, recreational diving using a wet suit, is similar to the approach @UofMI_Divegeek describes above:

... Try this to set your buoyancy:
Have ~ 500 psig in your tank
Place regulator in mouth
Deflate BCD ... make sure it is totally deflated
Add or subtract weight until you float at eye level
At this point, exhalation results in descent and inhalation results in ascent

If weight is set at end of the dive with ~ 500 psig, then at the start of the dive with a full tank you will be slightly heavy and should sink on exhalation. ...

though "my" approach differs in one significant way: I was taught to use a full cylinder (rather than a cylinder containing only 500 psig). My approach "guarantees" that you will never be too negative, which you might if you're using a large capacity cylinder and you use Divegeek's approach. For example, the 71.2 cf ft of air/nitrox in an old-school steel 72 weighs ~5.7 lbs. But the 122 cu ft of air/nitrox in a HP120 weighs ~9.8 lbs (four lbs more)!

Using my approach means you will weight yourself a bit lighter than you will using Divegeek's approach.

Using my approach, a diver can surface swim (in full gear, with fins and under snorkel power) a very long distance when wearing a completely full cylinder and a completely empty BC without having to shed his/her weight belt. For example, we had to swim three miles this way using a 72 (or a Luxfer Al 80). Absolutely no problem--except for the boredom (because deep fresh water). And I have never been a strong swimmer.

Actually, I personally remove a little bit more weight than my approach suggests I use, and I do a surface dive and kick down to descend.

rx7diver

 

[Brett Hatch]

@rx7diver interesting approach. What is the advantage of being able to float on the surface with a full tank and an empty BC?

And, what in the hell circumstances led you to surface swimming 3 miles in fresh water???

Not knocking your idea, I'm genuinely curious.

 

[dmaziuk]

And, what in the hell circumstances led you to surface swimming 3 miles in fresh water???

Not knocking your idea, I'm genuinely curious.

More interestingly, how long did it take?

 

[tomfcrist]

@Bubba_in_cali,

The approach I was taught (and recommend) for determining your "correct" buoyancy for single-cylinder, recreational diving using a wet suit, is similar to the approach @UofMI_Divegeek describes above:



though "my" approach differs in one significant way: I was taught to use a full cylinder (rather than a cylinder containing only 500 psig). My approach "guarantees" that you will never be too negative, which you might if you're using a large capacity cylinder and you use Divegeek's approach. For example, the 71.2 cf ft of air/nitrox in an old-school steel 72 weighs ~5.7 lbs. But the 122 cu ft of air/nitrox in a HP120 weighs ~9.8 lbs (four lbs more)!

Using my approach means you will weight yourself a bit lighter than you will using Divegeek's approach.

Using my approach, a diver can surface swim (in full gear, with fins and under snorkel power) a very long distance when wearing a completely full cylinder and a completely empty BC without having to shed his/her weight belt. For example, we had to swim three miles this way using a 72 (or a Luxfer Al 80). Absolutely no problem--except for the boredom (because deep fresh water). And I have never been a strong swimmer.

Actually, I personally remove a little bit more weight than my approach suggests I use, and I do a surface dive and kick down to descend.

rx7diver

Interesting, how does holding a 20’ stop with a near empty tank (4-600psi) work out for you doing it that way?

 

[rx7diver]

@rx7diver interesting approach. What is the advantage of being able to float on the surface with a full tank and an empty BC?

And, what in the hell circumstances led you to surface swimming 3 miles in fresh water???

Not knocking your idea, I'm genuinely curious.

@Brett Hatch,

You're not positive at the surface. (So, you don't float.) You're simply not too negative at the surface. If you jump in with a faulty or disconnected BC, you're not too negative; you'll probably be able to resolve things at the surface before you need to jettison your weight belt (to establish positive buoyancy). Or, if an emergency is happening at the surface (e.g., maybe you've passed out), hopefully you won't quickly sink out of sight before your buddy can swim over and drop your weight belt (since you'll sink only relatively slowly at first if you exhale).

The skill is called the "Three Mile Swim." The group swims 1.5 miles one way, pulling a dive flag. Buddies then stop and release each other's weight belt and inflate each other's BC. Then a diver deflates his/her BC and swims (tows, pushes) his buddy back half the distance. Then buddies exchange roles. The skill is meant to reinforce the absolute importance of proper weighting (and the utility of a snorkel).

Extremely boring, because you quickly lose sight of the bottom, and then there is absolutely nothing to see when you're looking down through the green water. (These man-made MO and AR lakes are formed in the Ozark Mountains by impounding the White River.)

Oh, and not "my" idea. This is how I was taught. Seems to work.

rx7diver

 

[tomfcrist]

The skill is called the "Three Mile Swim." The group swims 1.5 miles one way, pulling a dive flag. Buddies then stop and release each other's weight belt and inflate each other's BC. Then a diver deflates his/her BC and swims (tows, pushes) his buddy back half the distance. Then buddies exchange roles. The skill is meant to reinforce the absolute importance of proper weighting (and the utility of a snorkel).

Seems excessive…but whatever y’all are into.

 

[rx7diver]

More interestingly, how long did it take?

It takes awhile. Typically we would leave early morning from central MO to drive down to either Bull Shoals Lake or Table Rock Lake (~4 or 5 hours, depending). Set up camp. Get fully kitted up, establish "correct" weighting, remove regulator from cylinder, and then commence the skill by early afternoon. We would be back in camp by late afternoon, early evening.

All these years later, my daughter went through the same drill last spring.

Actually, it is fun, since you're doing this with a bunch of certies that you've just spent 16 weeks with in lecture and pool sessions. And your TA's are there, too, swimming along, just for fun, keeping you company, and laughing at the rediculously serpentine route you're swimming as you're attempting to follow your compass heading.

rx7diver

 

[rx7diver]

Seems excessive…but whatever y’all are into.

@tomfcrist,

My first ocean dive trip was to the Fl Keys a couple of months after I certified. A group of us, almost all of us freshly minted, drove down together. During our first night dive, a squall happened. We were too inexperienced to know that the increased surge we began experiencing at depth meant that the weather had changed. We surfaced to see our dive boat waaayyyyy over there, across the small whitecaps. Wind and current had swung our moored boat away from us. We snorkeled up and kicked to the boat, no problem whatsoever.

The crew had been a bit concerned because they knew we were all new divers. For us it was absolutely no big deal. That dive was an absolute blast!

So, yeah, excessive.

(You know, I must have written all this before, including the part about "correct" weighting, several times here on SB. I must be getting old, re-re-repeating stories.)

ETA: Our dive boat was actually shining a very strong spotlight (searchlight?) on our group as we swam back. I was a bit miffed, because night vision. It wasn't until I thought about it much later that I realized that we were in open ocean quite a distance away from our dive boat and its dive flag, and the captain was likely hoping to help keep us from being run over by another power boat! There! I've never written this before. I think.

rx7diver