Gear dependancy and additional training

[TSandM]

I am not going ot teach physics, been there and done that, simply put, if you are inclined and making thrust via your fins at that inclined angle and yet you are remaining at the same depth and moving horizontally then you are over weighted because some of your thrust is being used to buoy you upward--to maintain depth---and some is being used to provide forward thrust.

You do not have to be overweighted to kick upwards and remain at the same depth. You do need to be NEGATIVE, however. I can easily be negative at depth when quite properly weighted; all it takes is not having enough gas in the BC/wing to compensate for a) the gas I am going to use on the dive and b) any compression of my exposure protection.

When I get in the water with an LP95 tank, I have roughly six pounds of gas in my tank that I am willing to use. Therefore, I begin the dive about 6 pounds heavier than neutral at the surface. I need enough gas in the BC to counter that six pounds. If I don't put it there, I can kick upward and forward and remain at the same depth, but if I stop swimming, I will begin to sink. It has nothing to do with whether I am carrying the correct amount of ballast or not; as long as I am carry at least what is required, this is possible.

 

[Nemrod]

You do not have to be overweighted to kick upwards and remain at the same depth. You do need to be NEGATIVE, however. I can easily be negative at depth when quite properly weighted; all it takes is not having enough gas in the BC/wing to compensate for a) the gas I am going to use on the dive and b) any compression of my exposure protection.

When I get in the water with an LP95 tank, I have roughly six pounds of gas in my tank that I am willing to use. Therefore, I begin the dive about 6 pounds heavier than neutral at the surface. I need enough gas in the BC to counter that six pounds. If I don't put it there, I can kick upward and forward and remain at the same depth, but if I stop swimming, I will begin to sink. It has nothing to do with whether I am carrying the correct amount of ballast or not; as long as I am carry at least what is required, this is possible.

I will stick with what I said and I think you are saying exactly the same thing more or less, negative does not imply over weighted, you are trying to parse words and define "is" which I will not play that game. If you are finning upward and maintaining depth you must be negative. The inclined position is the result of over weighting and consequent extreme difference in the moment between center of lift and center of mass that rotates the body. Once the over weighting issue is dealt with then the secondary issues of trim can be addressed more easily.

What you guys want to do is put a bunch of weight on and then try to level yourself by shifting it around and adding even more, if that is what you learned in fungies then more power to you, you are wrong and they are wrong if that is actually what you were taught. I got at it from the other direction, I remove weight until no more can be removed and then move it around to get desired trim. The simple act of removing the un-needed weight often cures multiple problems, therefore it is job number one. The moment is reduced, the body tends to level itself as a result, trim is better as a result and requires less correction.

The goal is to move the center of buoyancy and center of body mass as close together and as equal as possible, then you can remain fixed in any position you desire, the goal is not horizontal trim--that is right--that is not the goal, the goal is balance, perfect balance. This fixation on some fictional Law of Horizontality blinds you from the actual end game, balance.

N

 

[TSandM]

What you guys want to do is put a bunch of weight on and then try to level yourself by shifting it around and adding even more, if that is what you learned in fungies then more power to you, you are wrong and they are wrong if that is actually what you were taught.

I don't know where you got this idea. One of the first things we did in Fundies was to make absolutely sure that everyone was properly weighted -- meaning carrying enough weight to be neutral in very shallow water with the tank as empty as you are going to tolerate it being (eg. 500 psi at 10 feet). Steve was very intent on making sure that none of us was dragging around weight we didn't need. However, he was unable to take any weight off me; I had already done the weight checking thing, and despite the fact that the numbers weren't what he wanted them to be, they were what they were.

I agree that keeping your center of gravity and center of lift close together is the way to make yourself stable in any position. That's the physics! And with cold water diving setups, it's quite easy to have them a long way apart.

 

[dumpsterDiver]

wrong thread...

 

[Peter Guy]

b1gcountry -- TSandM and I had recognized the geographic split and wondered if that was a part of the differences of opinion. And yes, I agree, Walter, with what is truly a wealth of knowledge and experience is MUCH more likely to be correct than I -- however, there still IS a chance I'm on the right track, if not, in fact, correct -- a very SMALL chance, but something greater than Zero.

(BTW, I really DO mean what I wrote about Walter's wealth of knowledge and experience -- I am truly a mere guppy.)

 

[b1gcountry]

(BTW, I really DO mean what I wrote about Walter's wealth of knowledge and experience -- I am truly a mere guppy.)

The other guppy would like to point out to Nemrod that just because you have poor trim doesn't mean your kicks are directed down or up. I can pretty easily swim head up at a 30-60* angle and still direct the force of my fin kicks straight back. That is how I read Lynn's original comments that you keep disagreeing about.

Tom

 

[D_B]

??????, I am not going ot teach physics, been there and done that, simply put, if you are inclined and making thrust via your fins at that inclined angle and yet you are remaining at the same depth and moving horizontally then you are over weighted because some of your thrust is being used to buoy you upward--to maintain depth---and some is being used to provide forward thrust.

I would like to point out (again) being overweighted is not the only way that could happen
Overweighted is not the same thing as being negitive

Edit: OK Lynn said it already ..

 

[Nemrod]

The other guppy would like to point out to Nemrod that just because you have poor trim doesn't mean your kicks are directed down or up. I can pretty easily swim head up at a 30-60* angle and still direct the force of my fin kicks straight back. That is how I read Lynn's original comments that you keep disagreeing about.

Tom

LOL, uh, you go ahead and think that. Is that the DIR seahorse kick, what kind of fins you need for that trick? I don't think so.

Strange kicking methods aside, if you are moving through the water inclined to your direction of travel you have several complications, your body will generate some lift since the path is at an angle to the plane of the body.

I am sorry, I am sitting here drawing out forces, you body is inclined to your direction of travel 60 degrees, and you are maintaining depth and yet your fin thrust is purely directed 180 degrees to your path? Now, explain that some more to me? Just curious, in this odd propulsion method, when you quit kicking, what happens?

N

 

[Nemrod]

I would like to point out (again) being overweighted is not the only way that could happen
Overweighted is not the same thing as being negitive

Edit: OK Lynn said it already ..

So did I, several times.

N

 

[John_B]

On another note, I find it interesting the locations of the people on different sides of the main argument between Peter, and Walter. The Florida folks don't think poor trim or weight placement matter. The cold, and silty group understands what happens when you kick downward, or have lots of weight in the wrong place.

Pay no attention to my location. I am a geographical anomaly. Consider me an outlier, or the exception that proves the rule.