Warped Dive World Evolution - BP/W Subgroup Mindset

[MauiScubaSteve]

Why do you need depth to measure drag? Deep enough to completely submerge is deep enough for the test.

What about differing amounts of air in the bladder? Beginning of the dive tank air weight must be countered, 100' deep exposure suit compression might have to be countered, end of dive shallow not much if any air in the bladder???

And if it's C_D you are concerned with, then kicking styles and scootering positions are irrelevant. An endless pool or a water tunnel would be fine. So would a low-speed wind tunnel or an illicit copy of Fluent.

Why would we take the diver out of the equation? We are giving recommendations about gear for people to use while diving. Can you not see that a different body position would change the diver's overall drag? I dive, and teach, a mask slightly lowest body position, not a horizontal body position. Most of the leading edge of the Vest bladder, and all the chest clutter is drafting behind the shoulders and arms, which are crossed holding a wrist at the crotch, making the chest area more cohesive. It seems to me that the same diver, in the same rig, diving a horizontal body position with arms crossed in front, will have a different overall C_D.

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Exactly. This is an opinion based board (except maybe within a few subforums). I often disclaim my own posts ("in my experience," "for my dollar," etc.), but not always, and I'm not intending to purport unequivocal fact when I don't.

I imagine most users understand that and wouldn't take as gospel that a Jet Fin is better than a Twin Jet because I responded to a thread titled "what do you like better?".

Below is an example of an internet expert making unsupported statements as if they were fact;

Most will be slower, due to more drag inherent in the less streamlined form of the vest.

Dan states as fact that the vest BC "form" is less streamlined (more drag).

Now compare that to the most recent post by Dan.

A diver wearing a DIR style Halcyon type bp/wing will have a smaller profile in the water than the jacket wearer. I can beat big currents much better with the halcyon approach than with a jacket approach.

Still making unsupported statements as if they were fact.

Do DIR style Halcyon type bp/w's only come with 18# wings? Could one have a DIR style Halcyon type bp/w with larger than 27# wing? Do all vest bc's have the same frontal profile? Could you point to even one biased study of an 18# wing DIR style Halcyon type bp/w compared to any vest bc?

 

[Sas]

Did switching gear suddenly make you a better diver or was there some training involved? If you had to dive in your original gear would you suddenly not be able to maintain your trim?
- Let me answer for you. No. You have become a better diver because you decided to become one.
Gear selection is no replacement for proper training.
To be clear, I use a Apeks WTX Harness/with a plate and wing because it works well for me. Could I use a jacket BC and still gain control of my trim, yes.

BTW, This is not Marvel Comics. You can't just duck into a submerged cave, swap your jacket BC with a BP/W and come flying out all super ninja diver.

Sorry but you're wrong. It was the BP/W that made me a super ninja and just cooler in general.

P.S surprised you are taking me seriously...

 

[Teamcasa]

I think it would be interesting to gather a few of the people in this thread together with a variety of BP/W's and jacket BCD's in a nice tropical resort with excellent diving. The people diving would use different gear each time and just try to enjoy the dives. In the evenings sitting down to eat delicious food, only pleasant dive conversations about everything except BP/W/jacket BCD's would be permitted. Several divers with video recorders would be present on all dives.

Funny, that sort of thing takes place more often (here anyway) than you might think.
Just this weekend over 245 divers showed up on Catalina for the annual harbor cleanup. Just casually (nothing scientific) scanning the divers gear, the only BP/Ws I saw were in our group. I'm sure there were others but the overwhelming majority were jacket BCs but at dinner nobody cared, it was just pass the guacamole and cervezas. Great fun was had by all.

On the final dive day, a special series of events would be planned involving sudden opportunities to race for 100oz gold bars. Each diver will be allowed to select the gear they choose on the last day. On arriving home start a new thread entitled "What trim was like for me wearing xyz BP/W or jacket BCD".

The strongest diver will still leave with the gold.

 

[Teamcasa]

Sorry but you're wrong. It was the BP/W that made me a super ninja and just cooler in general.

P.S surprised you are taking me seriously...

Oops! My tongue was firmly place in my cheek when I made the Marvel Comics reference!

 

[Blackwood]

What about differing amounts of air in the bladder? Beginning of the dive tank air weight must be countered, 100' deep exposure suit compression might have to be countered, end of dive shallow not much if any air in the bladder???

I agree regarding the bolded bit, in fact I suggested in a later post that full versus empty bladders should be accounted for. That's easily done with weight. You don't need a 10m tall water tunnel.

Or you could use analysis software. For incompressible flow, most reputable finite difference codes will get on-order results.

Why would we take the diver out of the equation? We are giving recommendations about gear for people to use while diving. Can you not see that a different body position would change the diver's overall drag?

Same reason we take the fuselage (and span, for that matter) out of the equation in airfoil texts: because everyone has a different body, and we want to know the properties of the shapes themselves. Interactions are a much more complicated beast, and are best understood with a clear knowledge of the constituent parts.

Drag testing a variety of BCD's is kinda like missing the forest for the trees. But if it's going to be done, I'm simply making suggestions regarding how to accomplish it. Before I got stuck in mechanisms design, I could have honestly called myself an aerodynamicist. I still remember a thing or two about it.

Below is an example of an internet expert making unsupported statements as if they were fact;
Dan states as fact that the vest BC "form" is less streamlined.
Now compare that to the most recent post by Dan.
Still making unsupported statements as if they were fact.

I've seen all of the examples. But who cares? Do most people read the boards as gospel? Or as the opinions of mostly-anonymous strangers?

 

[Splitlip]

OMG.

My head hurts. What a worthless OP and subsequent thread. Definitely some agenda here I suspect.

IJS.

A BPW IS a BCD for crying out loud. I am a dumb old rec diver, but I like 'em. Do you have an ax to grind? Many, many threads here already. Is OP trolling?

 

[BDSC]

Is OP trolling?

Well if he is he sure had a lot of people take the bait.

I bet halemano is a heck of a fisherman! :talkingfish:

 

[CuNanoTube]

Well, my first BC was an awful mares travel BC that must be bottom of the line. I got it as a bonus in a craig's list deal and modified it to actually have D-rings, as well as adding a clip on the waist. This all this BC had to hold you in was one Velcro strap....
Anyways, in the scuba club I dive with most people use the BP & W set-up so that in conjunction to my reading here and the fact I can easily modify and fix the system convinced me to go this route. My first proper BC will be an Apeks WTX system with a SS backplate, integrated weight pockets, and a 40lb wing. It offers me the ability "upgrade" my system in the future as well.

 

[danvolker]

Below is an example of an internet expert making unsupported statements as if they were fact;



Dan states as fact that the vest BC "form" is less streamlined (more drag).

Now compare that to the most recent post by Dan.



Still making unsupported statements as if they were fact.

Do DIR style Halcyon type bp/w's only come with 18# wings? Could one have a DIR style Halcyon type bp/w with larger than 27# wing? Do all vest bc's have the same frontal profile? Could you point to even one biased study of an 18# wing DIR style Halcyon type bp/w compared to any vest bc?

Unfortunately, Halemano has the grasp of science common to many children and many octogenarioans. He believes that there is something almost magical about the scientific method, and that if he follows the rituals of using certain "scientific sounding words", and pretends well enough in following the "scientific method", that the critiques and ideas he puts out will be seen as superior to the "anecdotal" postings of other SB members. He does not recognize the rampant misuse of "science" as exemplified by the pharmaceutical industry, where for enough money, virtually any toxic drug, can be scientifically "proven" as absolutely safe, within the guidelines of the FDA ...with proper disclaimers...This is a world where big money can nearly always corrupt the scientific method at will, and provide consumers with a strong feeling that "SCIENCE" supports the product pushed by this money.

Bottom line... Science is constantly misused. For the purposes of this discussion on scubaboard, it is no better than smoke and mirrors, as "used by" Halemano.

Many of us on SB have opinions and beliefs borne out of many decades of diving, and with this experience, our ideas will often/usually be far more credible than the commercially biased pseudo-scientific findings of the Dive Industry...basically advertising strategy, flavored with the suggestion of a basis in scientific fact.

In plainer terms....lets look at Halemano. He is an instructor, and he has been teaching most of his students in vest style or non-bp/wings for at least a decade now....the shop(s) he has affiliation with are most likely primarily non-bp/wing...and Halemano dives in a place where the average skill levels of tourists in diving, is at a level that we should perhaps question.....Halemano has every reason in the world to want people to believe he has always been correct in teaching people with vest BC's, and in pointing them in this direction for purchase---and it appears to me there is an ego thing going on as well, where he wants people to associate his choices with the right choices. He has squarely tied his ideas to the prevailing DEMA disseminated dogma on the gear divers need...and he now invests an enormous amount of time in attempts to discredit opionions that differ from those he is invested in.

I would say, when you read Halemano posts, have a few grains of salt handy

 

[Kern]

snip

I would say, when you read Halemano posts, have a few grains of salt handy

As both Halemano & you, seem desperate to prove your point of views, I think I'll take everything out of both of you with a grain or three.

I think I'll continue to rely on the correct use of the scientific method over anecdotal evidence, an oxymoron, every time. Wake me up when someone publishes a peer reviewed article that proves there's any real, statistically significant difference.