Jacket BC or Wing BC

[danvolker]

"you need a diving technique that suits the conditions" I totally agree with that! I also agree that we should strive to be as streamlined as possible for any condition but especially in high currents. I watched and enjoyed your video! I confirm that you were in a high current situation (bubbles) but what a beautiful dive and you had many obstructions to "hide" from the current.

Thanks, I'm glad you liked the video....right around the 7:56 minute mark, in the morning dive, you can see the photographer ( Sandra) trying to hide from current in a big exposed area, by some rubble on the bottom. The Goliaths use the structures and contours just like we do, even though they are cable of short bursts where they can hit many times our speeds....most of the time, they move at closer to the speeds a slick diver can move at. Marine Biologist Sara Tores, says they run a very low metabolism, and expend very little energy....and actually do not eat very much ( considering their size), because of this avoidance of exertion behavior
The current in this area was not a problem for good divers in very streamlined vests, or any of the bp/wing divers...And really, there would be few dives a recreational diver could enjoy, with more current than this, so it shows pretty well that a Vest can be streamlined enough for virtually any condition a recreational diver can find themself in. All my "stressing" before, was just about the vest or other BC's that are the opposite of the vests worn by divers here...the vests that really are huge and open, and that "CATCH" water going by.

Yes the Rodeo 25 was a while ago for (more than 10 years) but I liked the drift in. Current was minimal and it was a very easy dive. I was actually very impressed when we drifted in to the top of the wreck without missing; I really thought for sure we would miss it. If you can drift into your destination and hit your mark routinely then I think that is a great way to go.

The high current drops are a skill that separates good captains from average captains, and allows exceptional captains to really shine.
One of the first wrecks ( kind of deep) we began diving around 1994, was the HydroAtlantic. In about 165 feet of water, it was the first somewhat deep shipwreck I had ever dived, and it was where I met George Irvine and Bill Mee, who would then get me into diving all the really deep wrecks of the area, down to the 285 foot depth areas. The first few times we had captains drop us on the hydro, some would want to anchor on it...the Hydro had a normal current around 3.5 to 4 mph ( my guess). It was well into Gulfstream intrusion. When anchoring in the big a current, even as a weight lifter and cyclist, massive exertion would occur on the way down to the wreck, as the hand over hand journey felt almost impossible--and for many it was. It would take too long, it would fry the arms of most, and cause enormous air consumption. Other Captains, the best of which was Lynne Simmons of Splashdown in Boynton, would drift us in to this wreck. Captain Lynne was like a Savant....she had had us on the boat many times before, and already had calculated our typical fast descent rate--and knew it precisely.....She would drop a group of 4 at a time, and tell us that the moment she said dive, to do our normal full speed descent to the bottom, and then look up, and the ship would be coming at us fast. This was a drop where you enter with the air sucked out of your wing or bc, and you swim straight down, but don't actually exert--just swim down at cruising exertion We never failed to have the ship come right at us, and with us at the right section of the ship to find perfect access to enter. Lynne was, and is, amazing at this!! As she got to know us even better on these deep wrecks, she would say--"do you want me to drop you on the wheel house, or the stairway, or things like that...and could do this without fail.....It is a combo of amazing captain, and a small dive team that the captain can estimate descent speeds of well. So the captain would do multiple drops, until each group of 4 or less, was in.

In the old days, when we were still anchoring, coming up the line for deco was even worse. The current could even pick up to closer to 5 mph....You can hang on for a while, but after 10 minutes at 50 feet, and another 10 minutes at 40 feet, with lots more deco to go, the deeper wrecks quickly became unmanageable to returning on an anchor line....wrecks like the skycliffe in 225, dove usually for a 25 minute duration, had just too much time at each deco stop for even an Olympic Athlete to be able to hang on for long enough, during each deco stop....and this ignores the constriction of tired muscles, and the poor offgassing this causes....Had we tied on to the anchor line, a jon line concept, the problem would still be that the divers are like trolled bait in the water collumn, being thrown all over the place like a bucking bronco ride, as the current blows past furiously. Regulators easily auto purging, and masks easily torn off by current....It was just no fun, it was really hard, and when we began our free floating decos, it was SO MUCH MORE RELAXING, AND EASIER!!
We would send up and SMB in the early days, and later sometimes would use a torpedo float with a flag on it...it could be tied off ( cave line) with little tug on the line, and on our leaving one of us would just grab it and the rest would stay with them....Drag compairison....take a big red float on a thick yellow line...toss it off the back of the dive boat going 20 mph....will you be able to hang on? with the torpedo, toss the torpedo at 20mph, and there is only a mild tug....this is holy grail stuff
We would come up several miles from the wreck, after deco, so we would need a reference from the boat the entire time....so we had to have an smb or a torpedo.

Even far shallower dives can become difficult here due to the environment. I would much rather dive in your waters, wish it was like that here.

Micheal Kane told us alot about the Doria diving he did, and I have done a few cold water sites similar....and yes, you do need your sh#t together to dive places like this, and to live and enjoy yourself.

I feel very lucky to live in a place with such good vis, huge marine life, and I have come to love the high current areas, because this is where the biggest swarms of baitfish, groupers, and all the cool stuff hangs out under water....by structures where THEY experience the differential of huge current and lee currents.

Plan a trip here and dive with Bill and myself

 

[kdsmithjr]

It does not matter what everyone else is using, use what makes you comfortable. Try both and decide which one suits you.

There is no better advice than this. I'm with you 100%.

 

[Teamcasa]

...Ok, I give up....what is rigging IMG style ?

It's My Gear..

 

[boulderjohn]

I have never seen anyone diving with a BP/W.

In all those trips, I have never seen a single DM or Instructor wearing a BP/W. Not once. .

Only a handful of my students have ever seen me in a BP/W, but that is because for the most part I have been required to wear different gear by the shops for which I have worked. Be very careful about judging a professional's gear choice while they are working. Not only might they be required to wear certain gear, they may also be able to get screaming deals on certain brands and kinds of gear. A DM working for a shop will likely purchase what is available for that reason. If I were a DM diving every day, I would be very tempted to use the equipment I got the best deal on, frankly. In typical OW recreational diving, a skilled diver can do well with anything.

Doug, if you want to see a person diving in a BP/W, just complete the class you started.

I can't tell how many dives you have on you, but you say you are a new diver. I'm new too, but i have about 130 dives and an advanced card. I don't disparage your plans...mainly because you say you are "ambitious"...but your question leads me to believe you still have some holes in your knowledge (we all do) so, at this point, i might borrow a phrase and say.....pump yer brakes.
...

I am guessing that in the 9 years that passed since he started this thread, Marcos ceased to be a new diver, and he probably made the decision on his gear. Since he has not posted in 6 years, he might have missed a lot of the advice he has been getting lately.

 

[BoltSnap]

I am guessing that in the 9 years that passed since he started this thread, Marcos ceased to be a new diver, and he probably made the decision on his gear. Since he has not posted in 6 years, he might have missed a lot of the advice he has been getting lately.

No John, He hasn't made up his mind yet. He keeps reading the new posts in the thread and gets more and more confused. When he thinks that he had decided on one type, he gets different information to buy the other type. Never ending cycle of indecision.

 

[-hh]

Well, you are wrong...

Not to worry, since the bicycle analogies that mictrik was criticizing were factually way off base: the first error I noticed is that basic immutable physics were overlooked: drag increases with the SQUARE of velocity, which means that in order to go 2x as fast, you need 4x as much power ... and to go 3x faster, one has to increase power to 9x.

The means that for the baseline swimming speed of 0.5mph, 1mph requires 4x the power, 1.5mph requires 9x the power, 2mph requires 16x the power, and so on: the 3.5mph claim requires 49x the power.

Yes, one can increase power by going on a huge fitness regimen. However, as pointed out, 99.9% of the diver population doesn't do this...and in any case, it really isn't possible to increase one's fitness by factors such as 9x or more, let alone 49x.


We can go further into all of the drag stuff, but the bottom line is brutally simple: until there's hard data, it is all just unsubstantiated opinions.

...but I will offer the following observation, based on my professional knowledge of several interrelated topics: based on the 50th percentile of an adult Western male's 19" x 9" thoracic cavity + 8" diameter tank, at a perfect trim angle, a typical diver's cross-sectional area is going to be greater 250 square inches, to which any BC design must then be added to ... its not going to be more than +20% in even the worst cases IMPO, and similarly, no amount of BC streamlining is going to alter the diver's total drag coefficient (Cd) by more than 10% either, IMPO, because the BC isn't that large in comparison to the entire diver.

What the numbers show is that even if we take the worst case of both of these factors against us, at the same input power level, there's only a 13% difference in max velocity.

And if we go a step further and allow for Mr. Fitness to have 50% more power available because he's a health nut, those numbers can be very easily cranked too:

In the hypothetical super gear, his max velocity would be +22% Not double, not 3x, nor even 3.5mph.
In the worst-case bad gear, his max velocity is +7% (actually +6.6%)


Here's a snapshot of the math:

Area	Cd	Drag	Velocity
250	0.5	125	1
300	0.55	125	0.87038828
250	0.5	187.5	1.22474487
300	0.55	187.5	1.06600358

Offline for my professional credentials.


-hh

 

[Teamcasa]

I think all this drag talk is a smoke screen anyway. I dive a drysuit with big pockets, carry both a video camera and a still camera with associated lights. Although I am switching to the GoPro If I need to go fast I'll use the scooter. BTW, my BC is the Apex Harness with a DiveRite 35# Wing.

 

[danvolker]

Not to worry, since the bicycle analogies that mictrik was criticizing were factually way off base: the first error I noticed is that basic immutable physics were overlooked: drag increases with the SQUARE of velocity, which means that in order to go 2x as fast, you need 4x as much power ... and to go 3x faster, one has to increase power to 9x.

The means that for the baseline swimming speed of 0.5mph, 1mph requires 4x the power, 1.5mph requires 9x the power, 2mph requires 16x the power, and so on: the 3.5mph claim requires 49x the power.

Yes, one can increase power by going on a huge fitness regimen. However, as pointed out, 99.9% of the diver population doesn't do this...and in any case, it really isn't possible to increase one's fitness by factors such as 9x or more, let alone 49x.


We can go further into all of the drag stuff, but the bottom line is brutally simple: until there's hard data, it is all just unsubstantiated opinions.

...but I will offer the following observation, based on my professional knowledge of several interrelated topics: based on the 50th percentile of an adult Western male's 19" x 9" thoracic cavity + 8" diameter tank, at a perfect trim angle, a typical diver's cross-sectional area is going to be greater 250 square inches, to which any BC design must then be added to ... its not going to be more than +20% in even the worst cases IMPO, and similarly, no amount of BC streamlining is going to alter the diver's total drag coefficient (Cd) by more than 10% either, IMPO, because the BC isn't that large in comparison to the entire diver.

What the numbers show is that even if we take the worst case of both of these factors against us, at the same input power level, there's only a 13% difference in max velocity.

And if we go a step further and allow for Mr. Fitness to have 50% more power available because he's a health nut, those numbers can be very easily cranked too:

In the hypothetical super gear, his max velocity would be +22% Not double, not 3x, nor even 3.5mph.
In the worst-case bad gear, his max velocity is +7% (actually +6.6%)


Here's a snapshot of the math:

Area	Cd	Drag	Velocity
250	0.5	125	1
300	0.55	125	0.87038828
250	0.5	187.5	1.22474487
300	0.55	187.5	1.06600358

Offline for my professional credentials.


-hh

HH, '
Your science sounds nice, but we see people trying to deal with currents all the time, and there are much bigger differences in power and kicking efficiency than you are describing, and much bigger differences in bc drag than you are estimating...We know this because of the brutally obvious departure from your projections, in what actually happens.

There are divers that have far more ethan 50 % more power..50% is really ridiculous. Just look at the power on the bike of an average human, topping out at around 18 mph....and then how much of an increase in horspower it takes to hit 23 mph....and then how much of a massive increase it takes to hit 25 mph and sustain it....and then 27 mph and sustain it....and know the world record is 30 mph for an hour.

In your world, people don't have much in the way of physical fitness differences or propulsive ability differences, and clearly your bc's are different than the ones we see in Palm Beach.

You can calculate with incorrect assumptions all day long, and still miss the boat....it would be alot easier ( and more meaningful) to just put several people representative of each group in an ocean environment, and have them all attempt a max speed effort for 1 minute, 5 minutes, 10 minutes and 30 minutes.

Hint, it is easy for an elite athlete to put out 4 times the power of a non-athlete. It is reasonable for an elite athlete to put out maybe 10 times as much power. The cycling math will prove this. And while the anaerobic activity of doing squats is too short of a duration to mean all that much, their are many divers that can not do one singe squat with no weight whatsover....There are divers that can do 225 25 times in a row, as one set....or, that can do 600 pounds or more in one repitition. Is this 600 times as powerful , if both weight the same amount? Of course, it is not really relevant, because the leverage is different. The cycling is much closer. And aerodynamic are huge in cycling time trials. This begins to approximate the issues underwater once you hit speeds over 23 mph ( in that horsepower needs to begin doubling for small increases in speed).

 

[-hh]

HH, '
Your science sounds nice, but we see people trying to deal with currents all the time, and there are much bigger differences in power and kicking efficiency than you are describing,...

They're still anecdotes ... you have no scientifically objective data with which to argue against basic physics.

And yes, I do agree that technique is a contributing variable through elements such as kick efficiency - - but the scientific process examines only one variable at a time. The only variable under discussion here is the BC.

...There are divers that have far more ethan 50 % more power..50% is really ridiculous. Just look at the power on the bike of an average human, topping out at around 18 mph....and then how much of an increase in horspower it takes to hit 23 mph....and then how much of a massive increase it takes to hit 25 mph and sustain it....and then 27 mph and sustain it....and know the world record is 30 mph for an hour.

Yes, there's variation based on fitness. For example, a Tour de France elite athlete can sustain ~300 watts for an hour, but a power lifters can output up to 1800 watts ...but only for a few seconds. An average person will typically only be able to output ~125W over an hour ... which means the elite athlete is roughly only ~2x better.

In your world, people don't have much in the way of physical fitness differences or propulsive ability differences...

Incorrect: I'm recognizing that elite athletes aren't representative of the 50th percentile human. They represent the 1% extreme.

Besides, haven't you noticed the obesity epidemic in the USA, Dan? If fitness were such a huge contributor, then shouldn't PADI be flunking more students?

....it would be alot easier ( and more meaningful) to just put several people representative of each group in an ocean environment, and have them all attempt a max speed effort for 1 minute, 5 minutes, 10 minutes and 30 minutes.

What's easier still is to drag each diver behind a boat ... it eliminates the variable of diver fitness and does a better job of testing just the dive gear. Of course, Lee Bell offered to do this ... ten years ago ... and the salesmen making the "Our Gear is Best" claims ran away.

Hint, it is easy for an elite athlete to put out 4 times the power of a non-athlete.

Hint: PAID OW, AOW, Rescue, DM, AI & Instructor standards don't require elite athlete performance minimums.

It is reasonable for an elite athlete to put out maybe 10 times as much power.

For mere seconds, such as a Power lifter.

The cycling math will prove this.

Unfortunately, scientific papers that have measured the performance elite cyclist athletes have hard data that says otherwise. Here's but one example. And here's another. The measured science says that the difference is nominally only 2:1.

Now if we apply that 2:1 ratio to diver swimming velocities, for the same technique, fin, BC, etc, etc, etc ... the elite with 2x the available power is only going to be able to be SQRT(2) faster: +41%. That means 1.41 knots if the average diver is only able to do 1 knot max.

Immutable Physics. That's what you're trying to argue against Dan, not me.



-hh

---------- Post added ----------

I think all this drag talk is a smoke screen anyway. I dive a drysuit with big pockets, carry both a video camera and a still camera with associated lights. Although I am switching to the GoPro If I need to go fast I'll use the scooter. BTW, my BC is the Apex Harness with a DiveRite 35# Wing.

The smoke screen exists because from a marketing standpoint, divers - - especially new ones - - believe the hype.

That's how we've had fads before for many other dive widgets before this: brightly colored wetsuits, changes in training course names, fins with special vents, wetsuits with special linings, Force Fins, Split Fins, plastic balls that you release into the water that ascend at exactly 60ft/min, BCs that have depth-sensitive auto-inflation devices on them, self-deploying SMBs, Spare Air, ... the list of new, supposedly "better" equipment for divers to buy goes on and on and on.



-hh

 

[danvolker]

They're still anecdotes ... you have no scientifically objective data with which to argue against basic physics.

And yes, I do agree that technique is a contributing variable through elements such as kick efficiency - - but the scientific process examines only one variable at a time. The only variable under discussion here is the BC.



Yes, there's variation based on fitness. For example, a Tour de France elite athlete can sustain ~300 watts for an hour, but a power lifters can output up to 1800 watts ...but only for a few seconds. An average person will typically only be able to output ~125W over an hour ... which means the elite athlete is roughly only ~2x better.




Incorrect: I'm recognizing that elite athletes aren't representative of the 50th percentile human. They represent the 1% extreme.

Besides, haven't you noticed the obesity epidemic in the USA, Dan? If fitness were such a huge contributor, then shouldn't PADI be flunking more students?



What's easier still is to drag each diver behind a boat ... it eliminates the variable of diver fitness and does a better job of testing just the dive gear. Of course, Lee Bell offered to do this ... ten years ago ... and the salesmen making the "Our Gear is Best" claims ran away.




Hint: PAID OW, AOW, Rescue, DM, AI & Instructor standards don't require elite athlete performance minimums.




For mere seconds, such as a Power lifter.




Unfortunately, scientific papers that have measured the performance elite cyclist athletes have hard data that says otherwise. Here's but one example. And here's another. The measured science says that the difference is nominally only 2:1.

Now if we apply that 2:1 ratio to diver swimming velocities, for the same technique, fin, BC, etc, etc, etc ... the elite with 2x the available power is only going to be able to be SQRT(2) faster: +41%. That means 1.41 knots if the average diver is only able to do 1 knot max.

Immutable Physics. That's what you're trying to argue against Dan, not me.



-hh

---------- Post added ----------




The smoke screen exists because from a marketing standpoint, divers - - especially new ones - - believe the hype.

That's how we've had fads before for many other dive widgets before this: brightly colored wetsuits, changes in training course names, fins with special vents, wetsuits with special linings, Force Fins, Split Fins, plastic balls that you release into the water that ascend at exactly 60ft/min, BCs that have depth-sensitive auto-inflation devices on them, self-deploying SMBs, Spare Air, ... the list of new, supposedly "better" equipment for divers to buy goes on and on and on.



-hh

We live in an age where science it mis-used far more than it is used properly. Science was used to prove cigarette smoking had no relationship to lung cancer for decades.
Science has been used to prove that a criminally predatory corporation like Monsanto, is "helping" the world with its GMO foods and "roundup" pesticides.....The next decade should show this lie as far worse than the tobacco example.

Science is often a tool wielded with little regard for truth, and with great regard for personal agendas.

Enjoy your science, and those who will listen to you. I will take my personal experiences over your formulas any day.