From jacket BC to back plate and wing?

[diverrex]

I started with a Seaquest Balance, a nice back inflate BC and used that for my first 230 or so dives. I really liked it and had no problems with it but had also started to look at BP/W setups. One day I was on the boat diving at the oil rigs and out of 9 divers that day I was the only one wearing a BC, all the others including the two woman divers were in a BP/W. So I figured I had to join the crowd too and bought a Halcyon Infinity. Seriously I bought it with the idea that it I would be more streamlined and it would help me stay horizontal. I'm glad I bought it but truthfully I don't feel like it's a night and day difference, an improvement for sure but not earth shaking.

 

[MauiScubaSteve]

My Instructor is a hard core Florida cave diver. He gave me the following pros:

4. More streamlined

Did your Instructor give you anything but his anecdotal opinion on this?

I mean has anyone got a link to some data that shows which rig is most streamlined.

AFAICT, streamlining is a red herring discussion with regards to the three BC categories, since there is no scientific data on the subject. I'd venture to say there isn't even any non-scientific data on the subject. All I see on this subject is opinionated anecdotes.

My "other" job is pool cleaning, and I hope to someday find an "endless pool" that I can make some tests in.

My anecdotal opinion is that since a good majority of the leading edge of the vest BC bladder is drafting in the divers shoulder "shadow" and NONE of the other two BC's have any part of the leading edge of the bladder drafting at all, it is hard for me to imagine that either of the two that have the entire leading bladder edge dragging are going to have less drag than the one with the majority of bladder leading edge drafting.

I totally agree. Like you, I often see claims of BPs being much more streamlined but as far as I have seen there is no research on the subject. My bet is a well sized jacket BC with hoses properly stowed is actually more streamlined than any other with the exception of the horse collar which is most likely the most streamlined of them all. Now by streamlined, I am not talking about how it looks but how it actually cuts through the water. While the jacket style and to some extent most back inflates (BI)have pockets and other irregular surfaces on the front, the BP and BI have a large floppy bladder with a large surface area as opposed to the smooth transition from the shoulder down the bladder of a jacket style. The jacket style may have more actual surface area but it is more rounded and flowing than the bladder of a BP or BI. The actual surface area of the BC is not the surface area that needs to be considered. A couple of thin straps on a divers chest of a BP may look more streamlined but when you take into consideration the area of the divers chest covered in a wetsuit it is basically the same total area as the frontal area of a properly fitting jacket BC the difference becomes small. The real difference in streamlining between the 2 is in the rear of the BC and that is where the jacket style wins. From personal observation I do know (or maybe feel is more correct) that the bladder on a BP adds a huge amount of drag. I often remove the bladder -fairly small 24 lb one- from my BP and dive with no bladder. I can tell a big difference in how I glide between frog kicks. If anyone has links to a study on the streamlining of BCs I would love to read it.

 

[knowone]

A buoyancy compensation device has more resistance at Mach 1.

It's really about precluding the cylinder from clunking around like it does in the back of the clunker which is achievable with any quality system.

 

[InTheDrink]

My 0.02 psi would be that a BP/W makes the whole entity of the diver and equipment more streamlined in general. BP/W with crotch strap helps keep better horizontal trim. This presents much less overall surface area to the water in front of you.

I've definitely noticed since getting one that I am exerting myself much less and in fact having to deliberately hold back when I think I'm barely finning if at all, to stay with buddies. I'm pretty sure - anecdotal yes of course - that this is because I am a point to and thru the water, rather than a 45 degree large surface area. I guess if you get your trim down pat with a jacket BC then all things being equal it might have less drag, who knows. But I think that in general the way a BP/W acts is to promote better trim and this is what creates less drag.

J

 

[MauiScubaSteve]

I guess if you get your trim down pat with a jacket BC then all things being equal it might have less drag, who knows. But I think that in general the way a BP/W acts is to promote better trim and this is what creates less drag.

Well I think the vast majority of dives being made world wide are made in vest BC's and only the people who really do not know how to dive well are diving at 45 degrees so I might agree with you that IF a BP/W MAKES a bad diver more horizontal then for that kind of bad diver using a BP/W makes that diver more streamlined.

Seems like a crutch and more bang for the buck would be to learn how to dive well.

For someone who knows how to dive well, I can not see how a well designed BP/W or BI could possibly be more streamlined than a well designed vest BC.

 

[InTheDrink]

Well I think the vast majority of dives being made world wide are made in vest BC's and only the people who really do not know how to dive well are diving at 45 degrees so I might agree with you that IF a BP/W MAKES a bad diver more horizontal then for that kind of bad diver using a BP/W makes that diver more streamlined.

Seems like a crutch and more bang for the buck would be to learn how to dive well.

For someone who knows how to dive well, I can not see how a well designed BP/W or BI could possibly be more streamlined than a well designed vest BC.

Nice job on twisting my words

I've dived a jacket BC for a good few years. No bother and with fine trim and buoyancy.

It's not as nice to dive as a BP/W. A BP/W is easier to dive well in. Jackets tend to ride up and that's a pain and it means you need to make adjustments to keep proper trim, so it's inefficient.

Your argument seems to be that if you're driving a ferrari you must be **** cos you can drive a mini fine. Spurious or specious. Can't remember which. Specious I think

J

 

[MauiScubaSteve]

Nice job on twisting my words

I've dived a jacket BC for a good few years. No bother and with fine trim and buoyancy.

It's not as nice to dive as a BP/W. A BP/W is easier to dive well in. Jackets tend to ride up and that's a pain and it means you need to make adjustments to keep proper trim, so it's inefficient.

Your argument seems to be that if you're driving a ferrari you must be **** cos you can drive a mini fine. Spurious or specious. Can't remember which. Specious I think

J

Words do not have to be twisted when they are used so generally. You typed the following;

I'm pretty sure - anecdotal yes of course - that this is because I am a point to and thru the water, rather than a 45 degree large surface area.

I think I actually un-twisted those words.

I have owned a ScubaPro (adjustable shoulder strap vest? - circa '91) and numerous SeaQuest ADV's, as well as a SeaQuest Balance. I have worked students/customers with shop gear that included Oceanic vests (circa '02), ScubaPro Classic (circa '04), multiple SeaQuest vest operators and Mares vests which have just recently been discontinued; only a few Oceanics and the "new" ScubaPro's were integrated weights.

How many different vest BC's have you used and how many different BP/W's have you used?

It sounds like your one BP/W is easier for you to dive than your one vest BC, so now you claim on the internet that BP/W's are easier to dive than vest BC's?

I do not feel that my vest BC's "ride up" but perhaps that is because I am the rare HWP guy with a waste.

I am not making claims; I am telling you what I have experienced and seen with specific gear. I thought the current discussion was about streamlining. I also regularly state that from a physics perspective, a well designed vest has to release air easier than a well designed BI or BP/W, due to the position of the bladder being lower/closer to the body when horizontal.

Other than being streamlined and releasing air easily, what other criteria causes a Buoyancy compensator to be the best to dive well in?

 

[TSandM]

I also regularly state that from a physics perspective, a well designed vest has to release air easier than a well designed BI or BP/W, due to the position of the bladder being lower/closer to the body when horizontal.

Okay, I have issues with this. When you are in a horizontal position in the water, any air you have in your BC will go to the highest point, which is your back. Assuming you are properly weighted, and therefore have very little gas in the BC to begin with, what is there about the fact that the jacket bladder extends down around your body that is going to help you vent? If you have enough gas to have any down there, you've got too much air in the BC.

I don't think a backplate setup is the be-all and end-all of diving, and I don't think everybody in the universe needs to switch to some kind of back-inflate BC, whether it's standard or backplate. I think a good diver who has taken some time to balance his equipment can dive beautifully in any kind of BC. I do think back-inflate and backplate setups leave the front of the diver more uncluttered and can be more comfortable. (I can't imagine diving in a jacket; I hated the one I learned in, and went back-inflate from the get-go.) I think well designed BCs of ANY sort should vent easily; having dump valves where they are reachable and useful adds to that ease.

I think we argue a great deal about things that are either largely untrue (like the push your face in the water thing) or irrelevant. Most BCs work. If it doesn't fit you, it won't work very well. If you don't like being squeezed at the surface and you don't like the feeling of strapping yourself into an underwater life vest, you won't like jackets. If you don't like the tank slopping around on your back, you may prefer a back inflate with a rigid plastic plate component, or a backplate. If you want to strip your BC down to the minimum you can get away with, a backplate setup is for you.

Different strokes (did I say that) for different folks.

 

[EGad]

OK, I'm only going to jump into this conversation because it's in basic scuba and I think it pertains to me. (Also, I've had like a whole 3 beers, so I'll actually speak up on a topic rather than let the experts handle it.) I'm not certified yet. I've been dying to actually scuba dive for roughly 15 years. I spent a lot of time snorkeling in the Atlantic growing up and a lot of time studying diving while I was in the military and too busy to get my cert.

I will be buying a BP/W as soon as possible. It's not because it's the cool thing to do on SB. It's that it's infinitely adjustable and the physics behind it are sound.

I would prefer the lift component near my back, because it makes sense from a center of gravity standpoint.
The fact that a hogarthian harness isn't padded won't affect me much while I'm actually diving it. And where I usually go, I don't have to walk more than a few hundred yards and the terrain is usually pretty easy. Even with my usual sore back, I'd rather dive a one piece harness than hang from the parachute harnesses I trained with. I'll probably switch to a nice padded setup when it starts to bother me.

I just know that I'm going to be outside of the normal sizes (way outside if my old 7mm beavertail suit is any indication.) I'm 5'10" and 120 lbs. Kinda hard to put a vest on a pole. So I want the ability to just move a couple triglides and have my setup adjust. I might be diving U853 and CSSP in the same week. Don't want to have to have different BCs. I might start diving doubles. At any rate, I can change the configuration myself. Also, having your lift element as high as possible above your balance can only help lateral trim.

Anyway, those are just my thoughts, back to the argument at hand.

Eric

 

[Sas]

How many different vest BC's have you used and how many different BP/W's have you used?

I have used:
Ladyhawk BC
Knighthawk BC
Tusa Liberator BC
Transpac
an Oceanic BC (not sure of model)
Tusa Imprex Pro
ScubaPro Classic
about three or four others that I do not remember the names of

I have also used:
Halcyon BP/W (single tank one)
OMS BP/W 60lb lift bungeed, double bladder
OMS BP/W 45lb single bladder
OMS BP/W 32lb
Zeagle BP/W (single tank)
Dive Rite BP/W (doubles)
DSS BP/W (single)
Oxycheq BP/W (single)
At least one other, but I can't remember what kind

I found any one of those BP/Ws was better than all of those BCs. For the reasons gone over already in this thread.

How many BP/Ws have you tried Halemano? There's nothing wrong with disliking BP/Ws like you do, but there is a lot wrong with asserting incorrect things about them such as you seem to like to do.