BP/W for me and my son?

[stuartv]

Progress.

I have posted many 100's of times on the subject of wing sizing. Many include the following weighting recommendation for divers using normal sized single cylinders and buoyant suits:

Adjust your initial weighting so you are eye level at the surface with no gas in your wing and full cylinder. I may not include this information depending on the application I'm being asked about because it can confuse those using less buoyant suits.

If one is weighted as described, and has BC that offers more lift than than the initial buoyancy of their suit and enough lift to float their rig if they ditch it, which is *exactly* what I have recommended for years there will be no need to ever drop ballast.

One does not gain mass during a dive, we loose mass as the gas is consumed.

Having said that lets looks at the example I offered on a *Technical* diving forum in 2008…..


How deep does one have to go to zero out a wetsuit?

Do you recommend diving to these depths with a single cylinder?

How likely is it that drysuit will lose 100% of it's initial buoyancy?

Were you not breathing *any* gas on the way to the bottom while your drysuit suffered a total failure?

Would you ditch your belt or swim up couple lbs?

The reality is my recommendations have built in fudge factors. This is intentional on my part because I know not every diver will follow my recommendations with rigor. The number of failures that would have to occur near simultaneously to leave ditching ballast as the only alternative are many. The number of failures divers realistically plan for is few. This should be part of your technical instruction.

I'd again suggest that you refrain from offering advice until you have some actual experience and training, but I know that's pointless.



Tobin

Your ability to respond after only hearing/reading part of a question continues to astonish me. It also, apparently, caused you to (again) miss that I do have actual technical diving training.

Where does the question "how deep do you have to go to zero out a wetsuit" come from? My previous post posited a wetsuit that lost 24 # of buoyancy at the chosen depth - not that it had 24 # of buoyancy at the surface.

And "how likely is it that your drysuit will lose 100% of its buoyancy?" Here are a couple of quotes from "cool_hardware52" from TheDecoStop (thread I linked earlier):

You need in reserve enough capacity to deal with a total failure of your suit.

I would agree that total failure of a drysuit is a very low probability event, but none the less it is none zero.

Planning for failures seems prudent to me.

Also, how much gas do YOU breathe in a 2 minute descent to 120 feet? I estimate I would breathe about 3 cu-ft. That works out to being about 4 ounces less negative when I arrive at depth, I think.

Your fudge factor is why I have (in the example you posted) a 26# wing when you said I only need 24 # of lift. But, I'm still 6 pounds negative and you translate that to "a couple"?!?

And, since I'm asking questions, you have posted many times that dry suit buoyancy is to be measured with minimum gas. For example, here:

The Deco Stop

But, if the intention is to measure how much buoyancy I could lose, shouldn't I actually measure it with the maximum amount of gas I would ever actually use in my suit?

Let's continue your earlier example and suppose I'm the diver. Per your example, we stipulate that I am correctly weighted with my 13 # of ballast on my weight belt, in my dry suit. And we recognize that the 24 # of buoyancy that was measured for my dry suit was done using your method of "minimum" gas. Okay, so now I'm getting ready to dive. I know from prior experience that, when I get to depth, if I keep minimum gas in my suit, I am going to be cold. But, if I add a bit more gas to let my undies loft up a bit, I will be warm enough. And, from prior experience, I know that I need to add an additional 4 # of weight to my belt to accommodate that extra gas that I'm going to put in my suit. Again, that is presuming that the 13 # was the "correct" amount of weight for me with my dry suit with minimum gas. You have posted that, for single tank diving, you expect weighting to be based on having minimum gas in the dry suit at the safety stop. Words to the effect that the diver can handle being a little chilly for a 3 minute safety stop.

So, now, per your example, I arrive at depth with 17 # of weight on my belt and a 26 # wing. And, of course, that's when my newly installed neck seal pops it's big ole O-ring out of its channel and I have complete loss of buoyancy from my dry suit. So, now, I'm (19 + 17 =) 36 # negative and I have a 26 # wing. I've followed your protocol to the letter and you still say that your protocol is not based on any need to ever ditch my weight belt?

Or, perhaps your answer will be "you shouldn't add that 4 pounds of weight to your belt, you should plan to let that extra air back out when it starts to drag you to the surface at the end of your dive." Maybe that's how you would really do it. Personally, I would prefer to weight myself such that I can maintain my own comfort at all points of the dive - including the ascent and safety stop - so I think I will continue to carry that extra 4 # when I'm diving in cold water.

Or, really, I imagine that your response will be just like your previous one where you ignore the example (which you actually gave!) altogether. I mean, the example I cited and expanded upon had exactly one failure in it that results in the diver being at the bottom and 6 # negative and you still said this in your response:

The number of failures that would have to occur near simultaneously to leave ditching ballast as the only alternative are many

Bottom line:

- You advise people to buy a minimal wing where your definition of the "minimum required" does not allow for supporting the weight on their weight belt. If they bolt the same weight to their backplate, then your recommendation for wing lift increases to accommodate that. And you add that following your advice should result in never having to ditch their weight.

- You advise people to buy a wing based on the maximum buoyancy they could lose from their suit and then tell them to measure the max buoyancy loss potential using the "minimum" gas in their suit. That procedure seems to measure the minimum loss, not the maximum, in a 100% failure scenario.

I would genuinely like to know what I am missing that makes these two statements so hard for me to understand.

 

[jzipfel]

Disclaimer: I have been diving for less than a year and have less than 50 dives. Take any statements I make for their own intrinsic value (if any), not because of any presumed "expertise". I have only owned one BCD - a DSS stainless steel back plate and LCD 30 wing - so that is the only BC I have actual hands-on diving experience with other than the jacket BCs I used in OW training last year.

Yet you can't help but air your personal grievance with Tobin. It gets old.

 

[eelnoraa]

And, yes, I can remove my DSS wing from my DSS BP without removing the tank bands, but, looking at the DGX rig, if I were using it without an STA, I could do the same thing, right?

No, I don't think so. You will need to remove cambands to remove wing for DR travel wing, which is the same as wing in DGX package

 

[Patoux01]

- You advise people to buy a wing based on the maximum buoyancy they could lose from their suit and then tell them to measure the max buoyancy loss potential using the "minimum" gas in their suit. That procedure seems to measure the minimum loss, not the maximum, in a 100% failure scenario.

If you don't understand why he's saying you should have minimum gas in the suit, you have a serious issue for someone who's trained into technical diving, don't you think? A suit should never have more than minimum gas in it, except after a wing failure, hence the maximum loss of buoyancy of a drysuit is the minimum amount of air it requires to not squeeze your nuts.

 

[stuartv]

Yet you can't help but air your personal grievance with Tobin. It gets old.

I post facts and my experiences and I don't give the disclaimer about my experience and I get slammed for impersonating an expert. I do give the disclaimer and I get slammed. Hmmm...

Have I posted anything that was incorrect? If I have, I encourage you to set me straight - not just for my benefit, but for the benefit of the OP and anyone else who reads this thread. If I didn't post anything that was incorrect, then what is the actual motivation behind your post?

Also, maybe you can answer the two questions I've raised:

- If you're not supposed to ever need to ditch your weight, then why is it recommended to increase your wing capacity when you move the weight from your belt to your back plate?

- Why do you take a measurement to determine "the maximum buoyancy that your dry suit could lose" by filling it with "minimum" gas?

If there is no good answer to these two questions, then do you also think it's "old" to see those two things posted all the time (I mean, ALL THE TIME), steering new (and old) divers to buy wings that aren't as much lift capacity as the diver might really want?

No, I don't think so. You will need to remove cambands to remove wing for DR travel wing, which is the same as wing in DGX package

Right. The DGX and DR wings are the same. If there is not an STA on top of it, holding the wing on, then why would you have to remove the cam bands to take the wing off? The cam bands just slip through the big holes in the wing, right? DGX even recommends that you don't use assembly screws with this wing. So, with no STA, OR with the OMS soft STA attached to the BP first, I don't see what would prevent you from taking the DGX wing off the BP without doing anything with the cam bands other than unthreading the tail from the cam buckle - not removing the cam bands. When you said "remove" did you really just mean to unthread the one end from the buckle? In that case, yes, I see what you're saying. If you use something like the DGX QR tank straps (which I have recently switched to and love), then you wouldn't have to do anything at all to remove the wing after you remove the tank.

 

[jzipfel]

All right, I'll try once. But I am not going to go down this rabbit hole. These questions have actually been answered many times but maybe just did not sink in.

Also, maybe you can answer the two questions I've raised:

- If you're not supposed to ever need to ditch your weight, then why is it recommended to increase your wing capacity when you move the weight from your belt to your back plate?

The answer is in the many posts by Tobin. "Size the wing so it can float the rig." Hmm.. If the weight is on the rig, then I'll need more lift to float it. If there is less weight on the rig, then I'll need less lift to float it.

- Why do you take a measurement to determine "the maximum buoyancy that your dry suit could lose" by filling it with "minimum" gas?

One is not worried about the maximum buoyancy of the dry suit when sizing a wing. The second point is if you lost all buoyancy in the suit, can you wing support your needs. The assumption is that when you did your buoyancy check, there was probably some air in the suit (minimum air). You might want to review suit/wing in buoyancy and trim.

If there is no good answer to these two questions, then do you also think it's "old" to see those two things posted all the time (I mean, ALL THE TIME), steering new (and old) divers to buy wings that aren't as much lift capacity as the diver might really want?

Ahh! But there are good answers to these if one is willing to listen. The comment about what the "diver wants" is exactly the issue. If what they want and what they need intersect, then no problem. If what they want and what they need do not, then maybe they just need to be educated to remain safe.

 

[cool_hardware52]

I post facts and my experiences and I don't give the disclaimer about my experience and I get slammed for impersonating an expert. I do give the disclaimer and I get slammed. Hmmm...

Many have provided you with near endless answers to countless questions. Most of which you choose to argue with. That's why you get "slammed"

Also, maybe you can answer the two questions I've raised:

- If you're not supposed to ever need to ditch your weight, then why is it recommended to increase your wing capacity when you move the weight from your belt to your back plate?

Again, I hesitate to even try and answer your "questions" given your well demonstrated compulsion to argue with everything and and everyone.

No doubt I will regret this effort too, but into the breach once more......

Why *might* a larger wing be required if a diver moves ballast from their person (belt) to their rig? Ah, well if you ditch your gear, (you know remove you and your buoyant exposure suit from your rig) your wing now has to float more stuff, i.e. your plate, harness, reg(s), tank(s) *and* the ballast formerly attached to your person. Was this not covered in your technical training?

- Why do you take a measurement to determine "the maximum buoyancy that your dry suit could lose" by filling it with "minimum" gas?

Did your tech instructor teach you to start your dives in a vented suit or one blown up like the Michelin man?

Drysuits don't lose buoyancy because water can leak in, Drysuits lose buoyancy because gas can get out. The volume of gas that one needs to be able replace with wing lift in the event of a total failure of their suit is the "minimum" gas volume, essentially the gas trapped in the undergarments.

Should we determine required wing lift by filling a drysuit like this ?

If so please explain why.

Tobin

 

[Adobo]

I post facts and my experiences and I don't give the disclaimer about my experience and I get slammed for impersonating an expert. I do give the disclaimer and I get slammed. Hmmm...

Stuart, no disrespect intended but you have been diving for like 5 minutes. One thing you will realize in 1 year/100 dives is that you didn't know as much as you thought you did when you had 50 dives. At least, that is what I realized. The same thing will happen in 5 years/500 dives. And I am told, the same happens at 1000 dives.

I am not saying that what you are posting is incorrect. Frankly, I haven't bothered to read. But I think this is like the 4th thread I have seen you going back and forth arguing with experienced divers. Some of whom have done thousands of dives and/or have done dives where their first deco stop is deeper than the deepest you have dived.

My point is, you'll probably get more out of your time doing a little more listening and a little less arguing.

My 2 cents.

 

[stuartv]

The answer is in the many posts by Tobin. "Size the wing so it can float the rig." Hmm.. If the weight is on the rig, then I'll need more lift to float it. If there is less weight on the rig, then I'll need less lift to float it.

That is not an answer. That is smoke and mirrors - unless there is an explanation of why it only needs to float the rig. There is no explanation for why my rig is floating alone on the surface without me. Personally, my plan would be to never need to separate myself from my rig - especially if my dry suit has lost all buoyancy. So, why does my wing only need to float my rig and not me+my rig? If we agree that it needs to float me+rig, then how does it help me if my wing can't hold me up with my weight belt on? Well, unless you say "this wing is sized such that you might have to drop your weight belt."

If my dry suit experiences 100% loss of buoyancy, then it might mean I have to make an emergency ascent and come up well away from the boat, right? Which might mean I end up floating on the surface for a long time. So, how is "the wing just has to float the rig" an answer? Am I unique, because I'm so ignorant, in thinking that I want my wing to float me AND my rig?

One is not worried about the maximum buoyancy of the dry suit when sizing a wing.

Oh, really? Have you actually READ Tobin's posts? He always makes two points. One is that the wing needs to be able to compensate for the maximum buoyancy you can lose from your suit.

How is that anything OTHER than the maximum buoyancy you would be using from your dry suit? Not the maximum it could provide if you overinflated it until a valve popped off. Just the max it would ever actually be providing when you are using it. it seems to me that that amount (the largest amount I would actually ever use) is the "maximum buoyancy I could lose from my suit." How is that incorrect?

All of this discussion is predicated on the assumption that the diver is correctly weighted. So, assume I'm at my safety stop with an empty BC and tanks that are empty and I have chosen to stay warm, so my dry suit is inflated beyond the "minimum". I am neutral and holding my safety stop. I am wearing 4 - 6 pounds more ballast, on a weight belt, than I would need if my suit had "minimum" gas in it.

Now back up and assume that I got in the water that way and got to max depth and lost 100% of my dry suit buoyancy. With the example TOBIN gave, I'm now on the bottom and I am 36 - 38 # negative, with a wing that only has 26 # lift. And his words echoing in my head that using his approach does not produce situations where I would have to ditch my weight belt. How does that work?

In this scenario, are you asserting that I am incorrectly weighted because I chose to keep a little extra gas in my dry suit to maintain my warmth? If we agree I am correctly weighted, then, as Tobin is fond of saying, it's simple integer arithmetic. So, where am I going wrong? My suit was 24 # positive with minimum gas in it. It required an extra 4 - 6 # of weight for me to be correctly weighted when using the actual amount of gas in my suit that keeps me warm. That means the suit, as I'm using it (applying simple integer arithmetic), is providing 28 - 30 # of positive buoyancy. But, Tobin's rule # 2 is calculated using "minimum" gas, my wing is sized based on the suit providing 24 # of lift, when 28 - 30 (in this example) seems to be the correct answer to the question "what is the maximum change in buoyancy of your exposure suit?"

The comment about what the "diver wants" is exactly the issue. If what they want and what they need intersect, then no problem. If what they want and what they need do not, then maybe they just need to be educated to remain safe.

So, in your world, is there an intersection of "diver wants to keep their weight belt if at all possible" and "diver needs a wing with enough capacity to accommodate a total drysuit failure at any point in their dive"?

If there is such an intersection and someone gives the diver advice that doesn't fall into that intersection and also doesn't tell the diver that there is an option that would fall into that intersection, is the advisor giving good and complete advice?

Why *might* a larger wing be required if a diver moves ballast from their person (belt) to their rig? Ah, well if you ditch your gear, (you know remove you and your buoyant exposure suit from your rig) your wing now has to float more stuff, i.e. your plate, harness, reg(s), tank(s) *and* the ballast formerly attached to your person. Was this not covered in your technical training?

Actually, no. So far, I haven't had a situation explained to me where I would want to remove myself from my rig and have my rig be able to float itself while I'm sinking because of my weight belt.

Maybe that would clear all this up if you could do that? When am I going to want to remove myself from rig and just have it floating and me still wearing my weight belt?

My lack of adequate training and poor imagination is only letting me come up with scenarios where I want to keep my rig on, since it is my only source of buoyancy (presuming that we are still talking about a total dry suit failure), and I don't want to ditch my weight belt. Even if I'm on the surface, I would prefer to keep my weight belt, if possible, rather than dumping it and buying a new belt and new weights.

Did your tech instructor teach you to start your dives in a vented suit or one blown up like the Michelin man?

Well, neither. Are those really the only two options in your world? I was taught to put just enough air in it to be comfortable. That is more than the minimum, which I would consider to be the amount that eliminates discomfort from squeeze. The extra, beyond the minimum, is the amount needed to allow my undies to loft and provide the maximum insulating benefit that they can. In your case, you specify "minimum" and don't define it, so, if I applied your rules with true rigor, I would have so little gas in the suit that squeeze actually is somewhere between uncomfortable and painful, depending on the depth.

It seems to be axiomatic here on SB that, when diving dry, "lead is warmth." I have found that, for me, "minimum" gas in my dry suit yields no need for a weight belt. When I want to actually be warm and comfortable (in the same undergarments) I add a belt with 4 # of weight. And, actually, next time I dive in 38F water, I might try 2 more pounds, to see if I can add even a little more air to be a little warmer without putting on more undies.

You rules for wing lift capacity don't accommodate any of that 4 - 6 # of weight I might have on my belt. And your only explanation, so far, is "you don't need it to float your rig, since that weight isn't on your rig" without ever explaining when or why I would be trying to float my rig without me in it.

Should we determine required wing lift by filling a drysuit like this ? View attachment 215529

Who said anything about inflating to look like the Michelin Man? No one. So, this is just a deflection to avoid admitting that it would be better to measure the suit inflated to the maximum that you actually expect to use it, versus the minimum gas?

 

[cool_hardware52]

That is not an answer.

The fact that you can't grasp a concept doesn't mean no answer has been provided.

You have once again proven that one should not bother trying to enlighten you. Just not worth the considerable effort.

Tobin