The great back inflate vs. jacket BC debate
- Thread starter triggertravel
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
If properly weighted and trimmed the only time a back inflation BC tends to push you face down is when its over filled at the surface.
Ive observed that new students have more difficulty with back inflation versus jacket in a traditional kneel on the bottom or platform environment. However, this is more than made up for by the fact that its easier to swim horizontal; what divers spend most of their time doing.
Once you get a handle on buoyancy control and trim, or perhaps I should say if, as some divers never do, back inflation versus jacket will not significantly affect your ability to achieve any orientation you like. IMO back inflation, whether a BC or BP&W, results in less clutter in front.
This was subtle for MechDiver
, and I agree with him. There are no shortcuts to experience. For what its worth, my advise is to take your time, youre young. Get certified and see if you even like diving. If you do, you may not want to instruct or even DM. I know good divers that dive a lot and have no interest in teaching. Many take the technical route prior to or instead of teaching.
Good Luck,
Mike
Ive observed that new students have more difficulty with back inflation versus jacket in a traditional kneel on the bottom or platform environment. However, this is more than made up for by the fact that its easier to swim horizontal; what divers spend most of their time doing.
Once you get a handle on buoyancy control and trim, or perhaps I should say if, as some divers never do, back inflation versus jacket will not significantly affect your ability to achieve any orientation you like. IMO back inflation, whether a BC or BP&W, results in less clutter in front.
This was subtle for MechDiver
, and I agree with him. There are no shortcuts to experience. For what its worth, my advise is to take your time, youre young. Get certified and see if you even like diving. If you do, you may not want to instruct or even DM. I know good divers that dive a lot and have no interest in teaching. Many take the technical route prior to or instead of teaching.Good Luck,
Mike
XenoMorph2049
Guest
No. I, in no way, joined for tuition. I joined to go into the infantry. And did. The best 7 months I spent in the Army was in Kosovo. The thought of helping people and doing something that mattered was the biggest reward. The only thing stopping me from deploying with my unit in january, other than back problems at the time, was the fact that my daughter was only 3 months old. I wanted to go almost as equally as I wanted to stay, but my family became first priority the day my wife and I confirmed that she was pregnant.
As far as having 40-100 dives, the course is 60 plus dives, dealing in almost all aspects of diving including deep diving, technical diving, rebreathers, equipment maintenance, nitrox, rescue, navigation, night diving, resort managment, safety, and several other classes. The only one i can think of off the bat not included is cave diving, which I plan on getting certified after a bit of experience. So im not just taking OW, AOW, DM, and going straight into instructor. As far as the jobs I am considering, the range is large and I will not decide on which I take untill I have a list of current jobs available. The only reason I have been emphsizing instructor is it seems this is the most readily available. If i get a job at a shop, I will insist on doing assistant instructor, equipment repair, or managing untill the shop is confident in my skills/experience.
I appologise if I came off as defensive at first if you were honestly being subtle in your suggestion. I do know this is a technical job dealing with a life support system and will not even consider putting the lives of people into my own hands untill I feel confident that I am compitent enough in my field. It might seem as I am being over-zealous with my ambition, but please believe me this is not something Im taking lightly. I know first hand of jobs that put peoples lives into my hands and how big of a role expierience plays. I want to know I would be able to handle a situiation if all is not ideal before finding out the hard way.
Am I correct in assuming a BP/wing is dealing with the mounting plate for twins? Like i said, I want to know as much as I can befors getting into it. Please refrain from critisizing me, as I am only tryin to get a head start on the vast amount of info I know i dont have. Please help with info I might not know so I may improve my chances at being a decnt instructor if that is the job I end up with.
Once again I am sorry if I misinterpreted your initial post. The only excuse I have is it came across as arrogant to me. If this is your natural character, I appologize. I try my hardest to be receptive of every one and there views as they are.
SeaJay
Contributor
Before I address your questions (which a few have briefly already), let me try to explain to you what just happened here.
Imagine walking into a pilot's bar at the local fighter squadron (since you're military - or considering - perhaps you can relate to this) and announcing, "Hi, everyone. I'm not a pilot yet, but I want to be an instructor. Can someone please tell me whether I should learn to fly in a Cessna or Beech?"
Some of the people here have been diving for many, many years... Some are new. Few are totally off their rockers, and they're easily spotted and often thrown out of the "bar." Not by the bouncers... But by the pilots who take their sport seriously and don't generally warm up well to "announcers."
...So there's nothing wrong with your ambition - congratulations. Take it all the way. We could always use another good pilot - er, "diver." But take it easy, kid... Let's see you get up in that biplane before handing you the keys to the F-18, K?
We'd love to see you grow. Go get 'em.
To answer your question about the BC... Your LDS, I'm sure, is trying to fit you best for your needs. But their information is often "tunnel visioned" in pursuit of profit motive and small, local dive communities in their area. I've noticed a propensity for most divers in a given area to hold similar beliefs, whether they're correct or not... Simply because the ideas are enforced by the divers that surround them. For example, divers here in this area, who often dive shallow, zero-vis waters in search of fossils, tend to believe that radically overweighting themselves - in some cases wearing 50 lbs. of lead or more - helps them to "stick to the bottom" while they search for fossils. While that may be true to a degree, body positioning - that is, laying on the bottom, horizontal and streamlined - is much more effective at resisting current than kneeling on the bottom with lots and lots of weight. And if you're laying on the bottom, there's simply no need for all that weight - which can become a real problem when floating on the surface or anywhere in-between.
...So your LDSes are sorta pointing you in the right direction... It's true that the placement of the air cell has an effect on the diver's attitude or "trim" in the water, and this can be especially apparent at the surface, where divers tend to blow up the cell and make any existing problem much worse. What the LDSes apparently haven't told you is that the diver's trim is also a function of weight placement. Alone, neither of these variables have the net effect of poor trim... It's actually a function of both - or the difference between the two - that causes any sort of trim issue.
For more information on the topic, I recommend reading the article I wrote on the subject... It's at http://www.DeepSouthDivers.org/homebc.html . The article, as has been pointed out by a few experienced divers on this board, talks in terms of absolutes... Which is not always reality. I picture absolutely full bladders and absolute weight placement. However, with that knowledge, you should be able to estimate the effect of partially filled bladders and weight placement in different areas on the rig.
The article also gives you a brief introduction to backplates and wings, which you questioned about... Yes, the "plates" are the types that are widely accepted as "for doubles." However, many, including myself, find them equally ideal for use with single tanks.
The bottom line - and a quick answer to your question - is that, with the right weight placement (try three pounds in each of the "trim pockets" in the back of that Scubapro Knighthawk, and the rest in the quick-ditch pockets) any poor trim characteristics can be "tuned" out of a rig that forces you in any direction under a certain circumstance.
So no, it's not entirely accurate to say that back inflates push you face-forward at the surface... Nor is it entirely accurate to say that jackets always tend to bring you "face up." It's a matter of "tuning." It's just that most people aren't familiar with the techniques needed to do so.
Imagine walking into a pilot's bar at the local fighter squadron (since you're military - or considering - perhaps you can relate to this) and announcing, "Hi, everyone. I'm not a pilot yet, but I want to be an instructor. Can someone please tell me whether I should learn to fly in a Cessna or Beech?"
Some of the people here have been diving for many, many years... Some are new. Few are totally off their rockers, and they're easily spotted and often thrown out of the "bar." Not by the bouncers... But by the pilots who take their sport seriously and don't generally warm up well to "announcers."
...So there's nothing wrong with your ambition - congratulations. Take it all the way. We could always use another good pilot - er, "diver."
But take it easy, kid... Let's see you get up in that biplane before handing you the keys to the F-18, K? We'd love to see you grow. Go get 'em.
To answer your question about the BC... Your LDS, I'm sure, is trying to fit you best for your needs. But their information is often "tunnel visioned" in pursuit of profit motive and small, local dive communities in their area. I've noticed a propensity for most divers in a given area to hold similar beliefs, whether they're correct or not... Simply because the ideas are enforced by the divers that surround them. For example, divers here in this area, who often dive shallow, zero-vis waters in search of fossils, tend to believe that radically overweighting themselves - in some cases wearing 50 lbs. of lead or more - helps them to "stick to the bottom" while they search for fossils. While that may be true to a degree, body positioning - that is, laying on the bottom, horizontal and streamlined - is much more effective at resisting current than kneeling on the bottom with lots and lots of weight. And if you're laying on the bottom, there's simply no need for all that weight - which can become a real problem when floating on the surface or anywhere in-between.
...So your LDSes are sorta pointing you in the right direction... It's true that the placement of the air cell has an effect on the diver's attitude or "trim" in the water, and this can be especially apparent at the surface, where divers tend to blow up the cell and make any existing problem much worse. What the LDSes apparently haven't told you is that the diver's trim is also a function of weight placement. Alone, neither of these variables have the net effect of poor trim... It's actually a function of both - or the difference between the two - that causes any sort of trim issue.
For more information on the topic, I recommend reading the article I wrote on the subject... It's at http://www.DeepSouthDivers.org/homebc.html . The article, as has been pointed out by a few experienced divers on this board, talks in terms of absolutes... Which is not always reality. I picture absolutely full bladders and absolute weight placement. However, with that knowledge, you should be able to estimate the effect of partially filled bladders and weight placement in different areas on the rig.
The article also gives you a brief introduction to backplates and wings, which you questioned about... Yes, the "plates" are the types that are widely accepted as "for doubles." However, many, including myself, find them equally ideal for use with single tanks.
The bottom line - and a quick answer to your question - is that, with the right weight placement (try three pounds in each of the "trim pockets" in the back of that Scubapro Knighthawk, and the rest in the quick-ditch pockets) any poor trim characteristics can be "tuned" out of a rig that forces you in any direction under a certain circumstance.
So no, it's not entirely accurate to say that back inflates push you face-forward at the surface... Nor is it entirely accurate to say that jackets always tend to bring you "face up." It's a matter of "tuning." It's just that most people aren't familiar with the techniques needed to do so.
XenoMorph2049
Guest
Thanks! Good info! Yeah, the one thing I have learned from research is weighing the rear of a back inflate to adjust trim. Is there really that many peolpe who dont redistribute weight for trim adjustment? It seems like common sense to me even before i started trying to find the fine details. Is there any where i can find info/setups for the BP/wing? It seem that, properly set up, this would be the ideal rig. Thanks again for the info.
By the way, Im out of the military now. I miss it but have new and better things now, such as my daughter!
By the way, Im out of the military now. I miss it but have new and better things now, such as my daughter!
SeaJay
Contributor
Very cool.
Yes, there are many people who do not bother with the trim weights.
See, the problem really is how we are taught to dive... With rare exception, we are taught to dive vertically. In fact, often literally on our knees in a pool. The head-up, feet-down position is what the body is accustomed to on land, and so it tends to feel natural in the water. It's so natural, in fact, that on dives where there are other divers in the water, I've actually observed some of them literally standing on the bottom!
Divers who have been diving a long time know that there are some fundamental problems with this position. The body is most streamlined moving through the water lengthwise... That is, from head to toe. If the body is positioned vertically, then there is little resistance to depth changes, which you will learn is very, very bad. Consistent depth helps a diver's physiology from a variety of standpoints. Also, a vertical diver has the problem that it's difficult for him to travel horizontally... Because his body presents a large "face" to the water. This makes resisting a current, or even the act of swimming in general, very difficult.
There are other problems as well with the vertical diver... Fins pointed downward tend to push the diver upwards. To maintain depth, the diver deflates his BC... Which makes him sink the moment he stops finning. So... To maintain depth, a vertical diver tends to always fin, even when he's not actually going anywhere. This, of course, requires much more work, and the vertical diver uses up his air/gas supply much quicker than does the horizontal diver.
Lastly, the vertical diver tends to create a mess for others... The vertical diver who dives over a silty bottom tends to "cloud up" everything, reducing visibility badly. In the worst cases, a vertical diver's errant fin can impact and kill marine life... Especially hard corals, which may take hundreds of years to grow over the damage.
A better solution to all of this is learning how to maintain a horizontal trim when diving. It may seem simple at first, but the diver that has trim "nailed" is one that looks bizarre in the water... Simply hovering there, like a genie. It's very striking the first time you see it done successfully. The position is akin to a skydiver, and they often seem nearly motionless in the water column... Eerily unaffected by currents in the water which make other divers beat limbs frantically.
Divers who dive caves and wrecks - whose environments can be very unforgiving of an errant fin kick or otherwise uncontrolled flail - are often noted for this strange position in the water. Done correctly, it's truly a beautiful thing.
My recommendation for learning about this technique - as well as answering your questions about the BP/wing - is for you to obtain the "Fundamentals of DIR" book from http://www.extreme-exposure.com . Call them and request a copy of it. You may find that it has a lot of great information in there. As you go through your OW certification, see if what's said in the book applies to your specific circumstance.
To be perfectly honest, some of what you considered harsh criticism above can be attributed to what we've often seen in the past... Divers who are thrown through their basic classes by newly certified instructors so fast that they never learn how to dive horizontally. In fact, many instructors don't even understand the concept themselves - much less teach it. The result is hoardes of newbie divers who can seem at least dangerous in the water, and at worst damaging to the environment around them - either in terms of permanent damage (like in the coral example) or in terms of destroyed visibility.
Thus, these people tend to REALLY come down on you hard when they hear that someone wants to bolt through the classes to get their instuructor's license.
I would recommend the Fundamentals book... And a mind open to the idea that basic diving usually doesn't teach what the "old salts" would consider "the basics." Often their opinion of the introduction-to-instructor path is akin to PETA's opinion of puppy mills.
One more reference for you, which I would recommend... Go to my site again and click on "Look" to the left... Then "Videos" and finally, "Training Videos." There, you will see examples of proper body positioning - as well as some good gear instruction - that you aren't likely to find in your basic scuba courses.
Keep us posted on how it goes for you.
Yes, there are many people who do not bother with the trim weights.
See, the problem really is how we are taught to dive... With rare exception, we are taught to dive vertically. In fact, often literally on our knees in a pool. The head-up, feet-down position is what the body is accustomed to on land, and so it tends to feel natural in the water. It's so natural, in fact, that on dives where there are other divers in the water, I've actually observed some of them literally standing on the bottom!
Divers who have been diving a long time know that there are some fundamental problems with this position. The body is most streamlined moving through the water lengthwise... That is, from head to toe. If the body is positioned vertically, then there is little resistance to depth changes, which you will learn is very, very bad.
Consistent depth helps a diver's physiology from a variety of standpoints. Also, a vertical diver has the problem that it's difficult for him to travel horizontally... Because his body presents a large "face" to the water. This makes resisting a current, or even the act of swimming in general, very difficult.There are other problems as well with the vertical diver... Fins pointed downward tend to push the diver upwards. To maintain depth, the diver deflates his BC... Which makes him sink the moment he stops finning. So... To maintain depth, a vertical diver tends to always fin, even when he's not actually going anywhere. This, of course, requires much more work, and the vertical diver uses up his air/gas supply much quicker than does the horizontal diver.
Lastly, the vertical diver tends to create a mess for others... The vertical diver who dives over a silty bottom tends to "cloud up" everything, reducing visibility badly. In the worst cases, a vertical diver's errant fin can impact and kill marine life... Especially hard corals, which may take hundreds of years to grow over the damage.
A better solution to all of this is learning how to maintain a horizontal trim when diving. It may seem simple at first, but the diver that has trim "nailed" is one that looks bizarre in the water... Simply hovering there, like a genie. It's very striking the first time you see it done successfully. The position is akin to a skydiver, and they often seem nearly motionless in the water column... Eerily unaffected by currents in the water which make other divers beat limbs frantically.
Divers who dive caves and wrecks - whose environments can be very unforgiving of an errant fin kick or otherwise uncontrolled flail - are often noted for this strange position in the water. Done correctly, it's truly a beautiful thing.
My recommendation for learning about this technique - as well as answering your questions about the BP/wing - is for you to obtain the "Fundamentals of DIR" book from http://www.extreme-exposure.com . Call them and request a copy of it. You may find that it has a lot of great information in there. As you go through your OW certification, see if what's said in the book applies to your specific circumstance.
To be perfectly honest, some of what you considered harsh criticism above can be attributed to what we've often seen in the past... Divers who are thrown through their basic classes by newly certified instructors so fast that they never learn how to dive horizontally. In fact, many instructors don't even understand the concept themselves - much less teach it. The result is hoardes of newbie divers who can seem at least dangerous in the water, and at worst damaging to the environment around them - either in terms of permanent damage (like in the coral example) or in terms of destroyed visibility.
Thus, these people tend to REALLY come down on you hard when they hear that someone wants to bolt through the classes to get their instuructor's license.
I would recommend the Fundamentals book... And a mind open to the idea that basic diving usually doesn't teach what the "old salts" would consider "the basics." Often their opinion of the introduction-to-instructor path is akin to PETA's opinion of puppy mills.
One more reference for you, which I would recommend... Go to my site again and click on "Look" to the left... Then "Videos" and finally, "Training Videos." There, you will see examples of proper body positioning - as well as some good gear instruction - that you aren't likely to find in your basic scuba courses.
Keep us posted on how it goes for you.
XenoMorph2049
Guest
Which is one of the reasons Im here
I want to now, if im trained incorrectly, of better ways.Thanks, and once again, great info SeaJay. I am also a aqua culturist. To think of someone destroying corals is repulsive. Why destroy the one reason a lot of people dive? Not to mention an EXTREMLY sensitive ecosystem?
I dont see how struggling to maintain a posaition is comfortable. When snorkling, I have a tendacy to be a bit acrobatic, and seeing how most of the time Im on jetties, mainting a posture is critical to not getting smacked into the rocks. Maybe what seems like common sense to some is just not thought of by others.
How reef safe are jetfins, more specificaly liquid blue's? I figured they would have less down force compared to, say, jetfins.
Please correct me if Im wrong.
Ya know, I shouldn't be surprised by anything you post anymore, but every once in a while you come up with another one. Where in heavens name you dream this stuff is difficult to imagine.
While I'm being subtle. Don't ever presume to speak for me as to what or why I post. For one thing, you don't know enough, for another...well, lets just consider this a freeby.
MD
I would never take a scuba class from someone that went from not diving at all to instructor in only 3 months. That is insane.
In my personal opion it sounds like you are putting the cart before the horse. Take your time. Get ow cert, and dive, dive, dive. Then do AOW and nitrox, dive some more and some more, then rescue. Then after that do your DM course. I had well over 100 dives before I did DM.
Knowledge is good, but experience is vital and you will be in short supply of that even if you do dive on your days off.
In my personal opion it sounds like you are putting the cart before the horse. Take your time. Get ow cert, and dive, dive, dive. Then do AOW and nitrox, dive some more and some more, then rescue. Then after that do your DM course. I had well over 100 dives before I did DM.
Knowledge is good, but experience is vital and you will be in short supply of that even if you do dive on your days off.
Similar threads
