BP/W for me and my son?

[Mark Lem]

Hi All
Thanks for all of the comments. First off, I have traded pm's with Tobin. He asked me for info he needed to make an educated suggestion, I provided said info, and I got great suggestions as well as good advice. I am more of an authority in a couple other fields but not scuba diving and don't presume to be. I like direct answers, for me they are usually the ones easiest to make sense of, and I received great answers from Tobin with no evidence of shortness or whatever has been attributed to him by a few others in this thread.
I do appreciate the give and take between several contributors in this thread though as it helps a newcomer like me sort out some important issues for myself, my family and our diving future. In addition to my son I also have two daughters that are certified but due to attending school or being injured (ACL tear on one) don't have the opportunities for now to do all the diving my son and I have. There were many good posts and I thank the many contributors on this board. I found it by a simple "google" of dive forums but will stick around for a good while to come. I like the simplicity and freedom of movement that a bp/w provides, hate the enclosed feeling a vested BC gives me nor do I like the squeeze from the air bladder on my sides and partial front. I will likely go with Tobin's suggestions.

 

[stuartv]

Hint: "the maximum you actually expect to use it" and "the minimum gas" are pretty much equivalent.

Hint: In an earlier post, I gave a specific example where they are 4 pounds different. I imagine (could just be my inexperience here) that if I had really lofty undergarments, that number could easily be 10 #, instead of 4.

I then asked for an explanation on why the "maximum amount of buoyancy I could lose from my dry suit" would be based on the lower number, and nobody has explained it to me yet.

If I measure my dry suit buoyancy using Tobin's method (i.e. "minimum" gas), and it is 24 #, and then I dive with it and find that I add a little more gas than that in order to allow my undies to loft up and provide additional warmth, and that additional gas causes me to add 4 # of weight in order to hold my safety stop, is my "max buoyancy I could lose" now 24 # or 28 #? If I switch to 700 fill power goose down undies, and they compressed with minimum gas so that my dry suit still measured 24 #, but, fully lofted required 10 additional pounds of lead to hold a safety stop, then is my "max I could lose" still 24 # or is it 34 #? Or is that scenario imaginary and unrealistic?

Am I wrong in thinking that accommodating really lofty undies could result in 10 more pounds of lead (for max warmth) compared to "proper weighting" in the same undies with "minimum" gas? What I'm hearing so far is that allowing undies to loft for maximum warmth would not ever increase my buoyancy that is provided by my dry suit, compared to the buoyancy the suit gives with minimum gas. If that's really what you experienced folks are saying, then I will scratch my head, say "huh" and go try to figure out why my simple undies seem to make me need 4 extra pounds (to be warm) compared to what I need with the same undies and minimum gas.

...

BTW, I do understand that there are situations where I might want to remove my rig. What I was asking about is, in the specific situation where my only problem is that I've just gotten to the bottom, with full tanks, and have a total dry suit failure. What about that would make me want to remove my rig? And, in any case, why would the wing lift only need to match the weight of my rig, versus my rig weight being the minimum, where the desired capacity would be the weight (i.e. negative buoyancy) of my rig plus any negative buoyancy that I might have?

I've already cited Tobin's own example and expanded on it to show a result of a diver being on the bottom with a 26 # wing and being 32 (or more) # negative. Nobody has yet to address this specific example and explain why you wouldn't, either, plan for this by having a wing with 32 # of lift, OR, by admitting that part of the plan is for the diver to ditch their weight. Tobin dismissed it by saying "swim a couple of pounds up", referring to 6 # as "a couple." And all the Tobin Fan Club has simply ignored the example, apparently agreeing the 6 = "a couple" and that the answer is "swim it up."

This big long discussion started with me saying that I understand Tobin's wing lift recommendation to be predicated on ditching your weight belt in some scenarios and Tobin saying that he would never recommend such a thing (thus implying that his wing lift recommendation is not based on ever having to do that).

...

I have give 2 simple examples as part of 2 simple questions. How many more posts will we have from Tobin and his fan club before someone uses Tobin's simple integer arithmetic to explain why either or both examples, and the implicit point in each, are wrong, or admits that the implied points are valid?

Ex 1: diver on bottom with fully inflated wing and still 6# (or more) negative. It SEEMS like the correct response would be "try to swim it up and ditch weight belt (if necessary)", but Tobin says his solution does not ever require ditching weight. It seems like proper planning would recognize this possibility and recommend a wing with 6 # more lift capacity, so you would know you could at least get neutral if/when this happens. Where have I gone wrong in understanding this? Why would it not be better/safer to have that extra 6 # of lift (allowing you to get neutral)?

Ex 2: diver is correctly weighted to reflect 28 # of buoyancy from his dry suit, but only gets 24 # of buoyancy when tested with minimum gas, per Tobin's instructions. Tobin says to base wing lift on 24 # as the maximum buoyancy one could lose. Why is this correct? Is it incorrect (i.e. impossible) that minimum gas could provide 24 # of buoyancy but actual proper use of the suit (with same undies) might result in 28 # of lift (that is also what Ray seems to be saying here)?

Tobin likes numbers and simple integer arithmetic. I like numbers and simple integer arithmetic. These examples have numbers and simple arithmetic. I have never said Tobin or anyone else is wrong. I am just asking somebody to take these specific numbers and explain which numbers are wrong and why, or what arithmetic I have done incorrectly. I am sure that, if you can explain it so that I can understand it, then ANYONE that comes along later will see it crystal clear, plain as day, so you'd be helping us all.

 

[cool_hardware52]

using Tobin's method

I've already cited Tobin's

Tobin dismissed it all

the Tobin Fan Club

Tobin's wing lift recommendation

Tobin saying that he would

will we have from Tobin and his fan club

Tobin's simple integer arithmetic to explain

but Tobin says his solution

per Tobin's instructions.

Tobin says

Tobin likes numbers and simple integer arithmetic.

never said Tobin or anyone else is wrong.

BTW Stu, please don't stop, the number of people contacting me for my expertise has leaped recently with more than one referencing you by name when they call.

Tobin

 

[JohnnyC]

Mark Lem, following Tobin's advice will be the best thing you can do. In fact, the only issue I have with Tobin is that he won't make me a wing in Multicam. The rest of his stuff speaks for itself, and the advice he has given is absolutely correct.

 

[kaspar.almayer]

I've been using DSS' set-up with the 26 torus all summer and have been very happy with it. Now planning on getting one for my daughter. I'm a newbie, but my (perhaps overly) simple understanding of the wing size requirement is that you need the greater of 1) buoyancy required to float the rig with full tank at the surface, and 2) the buoyancy required to give you positive buoyancy at depth WITHOUT REGARD to the buoyancy of your exposure protection. So, I'm not sure why you'd need to ditch weights at depth if you follow these guidelines.

 

[beaverdivers]

hate the enclosed feeling a vested BC gives me nor do I like the squeeze from the air bladder on my sides and partial front. I will likely go with Tobin's suggestions.

There are jacket BC's that don't give you that squeeze, but it sounds like you prefer a back floatation B.C.

A BP/W may be your best option depending on the answer to these questions:

Where are you going to do most of your diving? Tropical ( warm water ) or local ( colder water ).

What is the thinnest suit that you plan to wear for diving? No suit, lycra, .5mm, 1mm, 2.5mm shorty, 3mm or 5mm or thicker.

What is your percentage body fat?

If you plan to mainly dive in Ohio & your thinnest suit is a 5mm or thicker & you have a high % of fat, then a BP/W is for you.

If you plan to do most of your diving in the tropics ( warm water ), your suit is 3mm or thinner & you have a low % of fat, then a BP/W may be a poor choice and even hazardous.

It may be a poor choice because you may find yourself overweighted. This circumstance will lead you to having to put too much air in your wing ( B.C. ) making buoyancy more difficult.

A BP/W may be hazardous due to the fact that you will find yourself overweighted without the ability to drop weight in an emergency!

 

[eelnoraa]

....
If you plan to do most of your diving in the tropics ( warm water ), your suit is 3mm or thinner & you have a low % of fat, then a BP/W may be a poor choice and even hazardous.

It may be a poor choice because you may find yourself overweighted. This circumstance will lead you to having to put too much air in your wing ( B.C. ) making buoyancy more difficult.

A BP/W may be hazardous due to the fact that you will find yourself overweighted without the ability to drop weight in an emergency!

Why?? I think if anything bp/w is even more perfect for tropics. It is the only type of "BC" you can customized your wing size down to 18-20lb. Conventional BCD most have too big of wing for tropics, heck, they are even too big for cold water.

As to overweighted, how would a 2lb AL plate be over weighting anyone when AL80 is +4lb? If you are using a heavy steel tank with out suit on, maybe the tank is the wrong choice to begin with.

 

[elgoog]

If you plan to do most of your diving in the tropics ( warm water ), your suit is 3mm or thinner & you have a low % of fat, then a BP/W may be a poor choice and even hazardous.
It may be a poor choice because you may find yourself overweighted. This circumstance will lead you to having to put too much air in your wing ( B.C. ) making buoyancy more difficult.
A BP/W may be hazardous due to the fact that you will find yourself overweighted without the ability to drop weight in an emergency!

Uh, what?!?! This is true if you make bad weighting decisions with your gear - like diving a big ol' steel tank with a steel backplate in your swim trunks. Which you shouldn't be doing in the first place.
If you're diving primarily in the tropics, you would get an aluminum/kydex/plastic plate and dive with an aluminum tank. In this configuration, you might even need a pound or 2 to be neutral.

 

[scubadada]

There are jacket BC's that don't give you that squeeze, but it sounds like you prefer a back floatation B.C.

A BP/W may be your best option depending on the answer to these questions:

Where are you going to do most of your diving? Tropical ( warm water ) or local ( colder water ).

What is the thinnest suit that you plan to wear for diving? No suit, lycra, .5mm, 1mm, 2.5mm shorty, 3mm or 5mm or thicker.

What is your percentage body fat?

If you plan to mainly dive in Ohio & your thinnest suit is a 5mm or thicker & you have a high % of fat, then a BP/W is for you.

If you plan to do most of your diving in the tropics ( warm water ), your suit is 3mm or thinner & you have a low % of fat, then a BP/W may be a poor choice and even hazardous.

It may be a poor choice because you may find yourself overweighted. This circumstance will lead you to having to put too much air in your wing ( B.C. ) making buoyancy more difficult.

A BP/W may be hazardous due to the fact that you will find yourself overweighted without the ability to drop weight in an emergency!

With a Kydex or aluminum backplate you are able to dive perfectly well in warm water with a minimum of exposure protection with either a steel or an aluminum cylinder.

 

[Lorenzoid]

If you're diving primarily in the tropics, you would get an aluminum/kydex/plastic plate and dive with an aluminum tank. In this configuration, you might even need a pound or 2 to be neutral.

I would say a STEEL plate, not aluminum or kydex, is ideal for an aluminum tank with a 3 mm wetsuit. A steel plate plus harness is about 6 lbs, I think. With a steel plate and aluminum tank, in my 3 mm wetsuit, I don't carry any ditchable lead at all. (It's not like ditching a mere 2 lbs. of lead or so is going to make the difference between me being able to reach the surface or sinking into the abyss.) Maybe if by "tropics" you mean diving in nothing but a bathing suit then I might agree aluminum or kydex would be optimal, but I never go without a full suit for protection against abrasions, stings, etc.