Question about “balanced rigs” and having all ballast unditchable

[Storker]

The standard test for proper weighting is to be able to float at eye level

When my eyes are at the surface, my mouth and my nostrils are below the surface. I don't breathe through my eyes. And if there's just a a little bit of chop, I'd like my mouth and my nostrils to be significantly above the surface. YMMV.

 

[boulderjohn]

When my eyes are at the surface, my mouth and my nostrils are below the surface. I don't breathe through my eyes. And if there's just a a little bit of chop, I'd like my mouth and my nostrils to be significantly above the surface. YMMV.

I was responding to the emergency scenario described in which a diver fights his or her way to the surface with a failed wing and is unable to keep the head above water while kicking furiously. I am contending that this diver is overweighted, because keeping the head above water in such a situation should require only minor effort for a properly weighted diver.

That is an emergency. You keep talking about routine scenarios where you are waiting for a boat to pick you up at the end of a dive. In that case, your BCD should still be working. I know a recent post suggested that you routinely drop your weights at the surface if the boat that is going to pick you up is far off. When I am in South Florida, that is a common occurrence. Do you suggest I drop my weights each time that happens? I prefer to add air to the wing myself.

If we are talking about an OOA scenario with a failed wing, then the overweighting issue is even more pronounced. With an empty tank, a properly weighted OOA diver should have trouble submerging, not trouble staying afloat.

 

[Storker]

I prefer to add air to the wing

So do I. But if I'm OOG and more than a little stressed out, I prefer to have the option of ditching some weight. I have never done so, but ISTM that depriving myself of that option if SHTF is... suboptimal.

Again, YMMV.

 

[MichaelMc]

@boulderjohn,

Yes, diver was negative, but that is within the rules for a balanced rig is all you need, as described as able to swim it up. But we can go with a neutral diver. We are stepping out of all you need is a balanced rig land. Soon we might wind up in well you need surface buoyancy as well land. Which was the point....

Your surface neutral buoyancy test is inexact relative to a safety stop use. And it is accidentally conflating it with surface buoyancy. I'll go with the SS definition of neutral.

Neutral diver: neutral at SS with low air, neutral suit so depth does not matter, no ditchable.

Wing failure 30', weak vacation diver legs and fin but can swim moderate tank of 5-6 lb. air up. for 60 seconds. So balanced rig. All is wonderful. Swells, chop, no boat.

Head weight now matters. Must continue to swim up 5-6 lb. + head weight to try to see boat or breath after likely rejection of perfectly good regulator. Weak vacation diver legs. But balanced rig. Waving adds additional arm weight. Inexact kicking adds 1st stage and valve weight.

Legs burning... Waving drives you lower... But the rig was balanced...

 

[boulderjohn]

Head weight now matters. Must continue to swim up 5-6 lb. + head weight to try to see boat or breath after likely rejection of perfectly good regulator

I suggest you look up Archimedes Principle and give it a good read.

 

[MichaelMc]

From memory: A body, wholly or partially submerged, is buoyed by the weight of the water it displaces. (My undergrad was math, with a year of physics, physics is just math with units.)

You are describing 'overweighted', and I am responding to 'negative'. But I think your overweighted has a surface out of water component.

 

[Dan_P]

Are we not all working on an assumption of Proper Weighting here?

I mean, if hopeless overweighting is the motivation for ditching lead, I'm not going to acknowledge the need as it's quite simply malpractice - by, I believe, just about any agency's standards (right?)

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If I could be bothered to spend the time, it'd be... interesting to have a chat with you about what's right or wrong with my setup. Single tank BP/W, drysuit, thick undergarments, 16#/7.3kg non-ditchable, 12#+2kg (7.4kg) ditchable. Exclusively no-stop diving, and several (IMO) good reasons for having ditchable weight. Including the option of being able to ditch on the surface if the bovine manure should happen to intersect with the rotating ventilation device.

After all, we live in the same corner of the world. However, I believe I have better use of my free time.

I'm always open to sharing advice about equipment configurations, you're welcome to PM me any time.
And if you're up for a dive sometime instead, that'd be cool, too

 

[MichaelMc]

Inexact kicking adds 1st stage and valve weight.

This of mine is inexact. it adds the weight of the water the 1st stage, valve, and tank top displaced.

But the arms are big, and the head.

 

[boulderjohn]

But I think your overweighted has a surface out of water component.

When a cruise ship floats, part of it is out of the water. If you take the entire weight of the ship, it will equal the weight of the water displaced by the part that is at or below the water line. The weight of the part that is above water does not matter--it is the total weight of the system that determines how much of it is above water level. The same is true of icebergs. Ice weighs less than the water it displaces, so it floats; the part that is above the water line is not above the water line because it is lighter than the rest of it; it is above the water line because the weight of the entire mass is equal to the weight of the displaced water.

 

[Storker]

if hopeless overweighting is the motivation for ditching lead

AFAIU, in this thread it isn't. At least for me, having a bit of ditchable weight is just another tool in my toolbox. Me, I like having different tools available even if I don't use them at a specific time.

If I have to add weight to be properly weighted, I see no reason whatsoever not to be able to ditch that weight - or at least some of it. Depriving myself of that option seems... suboptimal to me.