Are trim and buoyancy fundamentally related?

[Lorenzoid]

So, you dive without kicking? Maybe you can start the No Kicking Scuba School?. . .

If not for the inclusion of the word "fundamentally" in the question, I would agree. Talking about what is fundamentally related doesn't make sense in the real world, where various things are interrelated. To me, discussing whether two things are "fundamentally" related or not sounds like a high school physics problem.

Also, the other thread that I suppose was the impetus for this one related to the idea of maintaining trim without moving one's feet at all.

 

[The Chairman]

If not for the inclusion of the word "fundamentally" in the question,

We disagree. Both Trim and Neutral Buoyancy are fundamental to maintaining control while diving. Trim is often forgotten with disastrous results. Again, where's the upside to sculling, silting, kicking the crap out of the reef, hooving through your air and I could go on and on?

Most open water divers can decrease their SAC by at least 10% simply by clasping their hands together and getting their trim straight. I've seen improvements of over 25% on a few. If you don't get your trim adjusted you'll have to keep moving like a jet plane or else you'll crash and burn.

 

[NAM001]

They both work with the same principles. buoyancy is ----can you go to a depth and be motionless and stay at that depth... neither heavy or light. you can be vetrical or at a 45 (it does not matter)and have perfect buoyancy. now for trim. trim is the aspect you are in the water. virtical or horizontal or somewhere in between.

You first get neutran buoyant. then you move the weight on your body to make the natural position IE horizontal. If you need 10# to be neutral ,,, you then position that weight somewhere between you feet and head to allow you to become horizontal with minimum or no effort to stay that way. ,,,,, school yard teeter totter. it always is down on one side one way or the other , As a kid you probably put rocks on the high end till the till it lowered and became horizontal. The trick was,,, where do you put the rocks,,,, in the middle or closer to the end of the board to make it sit level. another example was a big kid sat closer to the middle of the board than a lighter kid. Some remember using a teeter totter with no one on the other end

so for a bit of math a 60# kid on a 12 ft teeter totter (6' on each side. sits on the end . he has 60# x 6' of force. or 360 foot #s. on the other side is a kid that weighs 80# and he has to slide closer to the center to ballance he has to sit at 4.5 ft cause 80# x 4.5' equals 360 ft #'s when the board is ballanced you can stop the board at any angle and it will remain in that position cause both ends have the same force on them. You as a diver go throught he water a little feet down , causing drag. so you move some weight from the hips to your shoulders. Now you lie flat and you reduce your drag.

Back to the teeter totter. the center is you solorplex. You either have to reduce the distance on one side or move to the other side with existing weights to trim.

Buoyancy is about putting on or taking off weight. trim is about where to put that weight.

when you first start the dive you are neg buoyant by about 4# because of the air in the tank you have to put air in the bladder to counter the 4# weight. as you use the tank air you need less counter lift till you get to 500 psi and you need no counter lift because at 500 psi you have the right amount of lead to hold you form floating up.

enemies of neutral buoyancy. change of wet suit. 3 mil to 5 mil / shorty to a full/ wet to a dry salt/fresh,,,, got to add or remove lead to counter that larger fixed amount of lift from the suit. idealy you need only enough BCD to adjust for the air you carry. That would be true IIIFFFF you were not wearing a wet suit. at 20 ft you need a BCD to comp for a full tank. At depth you need the BCD to comp for the tank of air and reserve for the loss of wet suit cause it shrinks from say 5mm to 1mm because of pressure and looses its lift. so a full tank can make you -4 at 20 ft and at 100 ft you become -15>20 because of suit compression,

Wet suit issues neopreme compression you loose about 90 % of lift at 100',,,,,,,,,,,dry suit. no compression but you need reserve lift in case you flood the suit and become 20-50 # heavy from the water taken on or lift being lost.

So wet suits....... only get enough suit to do what you need. If a 2 mil will work a 7 mill will only make life miserable in the world of buoyancy. If you dive both warm and cold then get 2 suits and know that the 2 mil needs 5# of lead and the 7 mil needs 20# of lead for buoyancy.

 

[Lorenzoid]

We disagree. Both Trim and Neutral Buoyancy are fundamental to maintaining control while diving. . . .

No, we agree. I was just examining the question as worded: "fundamentally related" (as opposed to are they both "fundamental to ...." Semantics over substance. Having participated in that other thread, I know what the OP is getting at. As my examination of the wording of the question doesn't add much if anything to the substance of this thread, I won't take up any more space on it. I agree with all who have pointed out the physics through which trim and buoyancy are related in real-world diving.

 

[NAM001]

No, they are not. The addition of forward thrust can impact buoyancy in relation to trim.

Your position is a tough one to understand. there are 3 components that allow you to carry weight. which your statement is relating to. as divers go it is speed body angle and sculling. In submaerines its called speed angle planes. Over all speed is not a real factor as you can not really change it enough to make an effect by its self. body angle is usually the culpret. when moving you are more horizontal than when still.
People will say speed is a factor but most people change angle when they chage speed so 2 factors are changing. If yo could some how maintain the body angle you would go shallow or deep depending on the stationary body angle. when you moved. most have 20-30 (normally looking up)degree angle when still and go flat when moving. The slower you move the more angle you get. That is an indicaton that the fundimental trim is off. SPEED is the neutralizer of trim problems. Speed hides the problem. The more gross the trim error is the more use of hand and feet sculling is to comp for it. feet when yo are head up and hands when you are head down;

 

[MichaelMc]

I think the list of concerns might be:

Buoyancy: Being heavy/light, an up/down force, affected by depth, air spaces, lead.
Static Trim: how you hang if nothing moves, affected by lead and air distribution.
Torque(?): Rotational thrust with hands/fins, done with little propulsion.
(Dynamic) Trim: Static Trim + Torque, horizontal is often handy.
Propulsion: Thrust that moves body, from fins.
Depth change: Sum of Buoyancy + Trim * Propulsion, affects buoyancy and thus trim.
(Maybe lift/plane, force of water on body that pushes it up/down from line of travel)

If you’re just floating, it’s not complex, except if you want a specific trim. If you alternate moving with stopping, it gets more so. Propulsion * trim can override buoyancy, until you stop. I think the kick and glide rhythm of frog kick can help drive the pieces home.

Edit: It is a complex system, the fewer imbalances you have -- like poor buoyancy, or kicking up while trying to move horizontal -- the easier it will be to manage. I think horizontal trim and frog kick help with that.

 

[RayfromTX]

If not for the inclusion of the word "fundamentally" in the question, I would agree. Talking about what is fundamentally related doesn't make sense in the real world, where various things are interrelated. To me, discussing whether two things are "fundamentally" related or not sounds like a high school physics problem.

Also, the other thread that I suppose was the impetus for this one related to the idea of maintaining trim without moving one's feet at all.

Just do the AOW as and when you can. I wouldn't sweat it. Diving in the ocean isn't as scary as some people are making out. I regularly dive in far worst conditions then you will experience and have a great time. AOW is experiencing 5 different types of diving and seeing if they are for you. It's meant to be 5 glorified fun dives. Nothing more and nothing less.

I'd also just trust the instructor. It's their judgment call. No one on the internet is in a better position than them.

And don't stress the neutral buoyancy and trim stuff. In openwater, it's a nice party trick but not the most important thing in the world. And the course might make you better anyway. As you develop and dive more it will happen. Diving with more experienced people will help. It's become a big thing on the internet as a marketing ploy - the reality is in open water is generally doesn't matter at all.

This is the post that started the whole argument. It has no reference to the other thread about maintaining trim without finning. As you can well imagine, there are many on Scubaboard that are not going to ignore the statement to the beginning scuba diver that "And don't stress the neutral buoyancy and trim stuff. In openwater, it's a nice party trick but not the most important thing in the world. And the course might make you better anyway. As you develop and dive more it will happen. Diving with more experienced people will help. It's become a big thing on the internet as a marketing ploy - the reality is in open water is generally doesn't matter at all."

The best thing that happened is that the off topic discussion was moved over to it's own thread. I suspect it will quickly grow to a longer thread than the one from whence it came.

 

[wKkaY]

In this photo, I am neutrally buoyant...

View attachment 410470

I actually want to learn that kind of diving... It comes handy when watching large schools of fish above!

Whenever I invert myself like that, my chest feels crushed, it becomes hard to breathe, and water goes up my nose... Eventually I lose my sense of neutral buoyancy, sink and hurt my ears due to equalization.

 

[Bogtrotter]

Also known as fundamentally drowning.

 

[The Chairman]

Whenever I invert myself like that, my chest feels crushed, it becomes hard to breathe, and water goes up my nose... Eventually I sink and hurt my ears due to equalization.

You have to acclimatize yourself to do that. It's not that prolonged of a process. I often invert and use the surface of the pool as the "bottom". Go slow and work on it.