BP/W for me and my son?

[Jim Lapenta]

What if he were carrying a laden swallow as well?

 

[decompression]

What if he were carrying a laden swallow as well?

African or European?


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[dumpsterDiver]

2) If there is a good chance the diver will be adding more exposure suit. When new divers get comfortable in their own well fitting BC bottom times get longer, and energy expenditure drops, both often lead divers to seek more suit, hooded vest etc. There are of course limits to trying to future proof divers, or the wings gets huge and some of the benefits of a BP&W are lost.

I also explain to my customers when the goods i've recommended for specific application are no longer appropriate. i.e. more buoyant suit, steel cylinders vs al 80s etc.


Tobin

do you mean to imply that if a diver uses a very thick wetsuit, that a BC rather than a BP/W would become advantageous for this situation???

 

[cool_hardware52]

do you mean to imply that if a diver uses a very thick wetsuit, that a BC rather than a BP/W would become advantageous for this situation???

No. I never said anything close to that.

People are attracted to a BP&W largely because they want a better performing BC. No inherent buoyancy, less clutter, easier to vent and less drag.

Diving with a wing several sizes larger than the application demands doesn't defeat all the advantages of a BP&W, but it will offer more drag, less stability and increase the effort required to fully vent then a correctly sized wing.

Very buoyant suits, as per your scenario, will require more ballast, and that means there will be substantial gas in the wing at depth and or when the cylinder is full. Larger wings vent reasonably easily when they have a lot of gas in them. Higher lift wings are an unavoidable necessity of cold water and thick suits.

Still preferable to Jacket BC.

Tobin

 

[Centrals]

African or European?


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African swallows are non-migratory!

 

[dumpsterDiver]

No. I never said anything close to that.

People are attracted to a BP&W largely because they want a better performing BC. No inherent buoyancy, less clutter, easier to vent and less drag.

Diving with a wing several sizes larger than the application demands doesn't defeat all the advantages of a BP&W, but it will offer more drag, less stability and increase the effort required to fully vent then a correctly sized wing.

Very buoyant suits, as per your scenario, will require more ballast, and that means there will be substantial gas in the wing at depth and or when the cylinder is full. Larger wings vent reasonably easily when they have a lot of gas in them. Higher lift wings are an unavoidable necessity of cold water and thick suits.

Still preferable to Jacket BC.

Tobin

Thanks... I figured you might say something like that.

You've gone into considerable detail to explain how the minimum required lift for a wing can be determined. You've also explained that having excess capacity in the wing is undesirable as well.

However, you seem to have not considered another potential factor. Namely, the potential for deliberately using a wing that has excess capacity which might be useful in a rescue scenario. Say with a diver (victim) who is over weighted on the bottom and has a wing/BC failure.

For me personally, I feel much more comfortable knowing my BC has maybe 10-12 lbs of excess capacity which could allow me to drag a victim to the surface with little or no kicking or exertion. Is that something that your customers inquire about with any frequency?

 

[cool_hardware52]

However, you seem to have not considered another potential factor. Namely, the potential for deliberately using a wing that has excess capacity which might be useful in a rescue scenario.

I've discussed this many times. Unless you happen to find yourself faced with

1) an overweighted diver,

2) unable to drop ballast

3) with a BC failure,

4) when you are at ~190 fsw or deeper

5) when your cylinder is full,

6) having selected a wing that *exactly* matches the surface buoyancy of your exposure suit

you will have wing capacity to spare.

In the *Real World* the wing selected will be a little larger than the suit buoyancy, the depths will be recreational and your wetsuit wont be fully compressed, and you consumed some gas getting down to your victim. All these mean you will have unused lift capacity should you need to use you own BC to rescue somebody else.

BTW how many angels can dance on the head of a pin?

Tobin

 

[dumpsterDiver]

I've discussed this many times. Unless you happen to find yourself faced with

1) an overweighted diver,

2) unable to drop ballast

3) with a BC failure,

4) when you are at ~190 fsw or deeper

5) when your cylinder is full,

6) having selected a wing that *exactly* matches the surface buoyancy of your exposure suit

you will have wing capacity to spare.

In the *Real World* the wing selected will be a little larger than the suit buoyancy, the depths will be recreational and your wetsuit wont be fully compressed, and you consumed some gas getting down to your victim. All these mean you will have unused lift capacity should you need to use you own BC to rescue somebody else.

BTW how many angels can dance on the head of a pin?

Tobin

Well the "real world" condition of excess capacity is what I was trying to get at..

Not to push it too far.. but it would not be that hard to imagine that you drop straight down to the bottom with a buddy, upon reaching the bottom, you find that HIS BC has failed AND he has a heavy steel tank and no ballast to drop and you are going to have to drag him up to save the day. I was presented with that EXACT situation less than a year ago. So it is not so far fetched.

As for assuming that this will only occur on a recreational dive, there will be ballast available to ditch and your suit won't be fully compressed and you will have used up an appreciable weight of air when the accident happens..... none of these "mitigating assumptions" were applicable to the actual situation I was presented with.

I had no ditchable lead either.

Am I being too cautious when I say I want an extra 10 lbs of lift for unforeseen contingencies... We haven't even gotten into a discussion of downcurrents either.

 

[eelnoraa]

Tobin, what is the significant at 190fsw? or it is just an arbiturary deep depth?

 

[cool_hardware52]

Well the "real world" condition of excess capacity is what I was trying to get at..

Not to push it too far.. but it would not be that hard to imagine that you drop straight down to the bottom with a buddy, upon reaching the bottom, you find that HIS BC has failed AND he has a heavy steel tank and no ballast to drop and you are going to have to drag him up to save the day. I was presented with that EXACT situation less than a year ago. So it is not so far fetched.

As for assuming that this will only occur on a recreational dive, there will be ballast available to ditch and your suit won't be fully compressed and you will have used up an appreciable weight of air when the accident happens..... none of these "mitigating assumptions" were applicable to the actual situation I was presented with.

I had no ditchable lead either.

Am I being too cautious when I say I want an extra 10 lbs of lift for unforeseen contingencies... We haven't even gotten into a discussion of downcurrents either.

Do what ever makes you happy.

I'd suggest avoiding teammates that apparently don't know what a balanced rig is…….

Tobin