Good Trim and the Fin Pivot?

[Boogie711]

I remember getting pissed off in AOW - at that point I could hold a stop at one FOOT depth - (as long as it wasn't choppy) without losing trim. I was bang on - and then they wanted us to do a fin pivot. I couldn't do it... I have this natural aversion to touching the bottom and silting it out. I don't swim with my fins below my chest anyway. I thought the entire exercise was stupid.

 

[MikeFerrara]

MikeS said "A fin pivot drill does not address weighting or trim. It’s a simple exercise to demonstrate how lung volume affects buoyancy"

And that's all it is. If you are on the bottom you can't be neutral, can you?
The real problem with this exercise is PADI's insistance that it be performed in open water, so a great many divers think this is some kind of real skill. You spend effort getting trimmed and horizontal in the pool, and then take that big step backwards. No diver should ever have spent more than 5 minutes in their life doing a fin pivot. Mike F., be careful with your back, you aren't getting any younger, you know .
Neil

The fin pivot standards for OW no longer require the student to touch the bottom. All they need do is get neutral.

Neil, my back can take it. LOL
When I teach a PADI class, which as of this month I no longer do, we do a fin pivot in mod three after we have practiced body position on land and talked about trim and balance. At this point some may not yet be trimmed and have no problem doing a fin pivot (sort of bad). When a student is allready trimmed out well and rises horizontal we just improvize. Howe in the world could I justify penalizing a student who is controling their buoyancy with their breathing and bc without touching the bottom.

BTW, the standards say that the student needs to touch the bottom with some part of their body when doing a fin pivot in CW.
I found that you need to read this stuff rather than make assumptions based on how you've seen it done.

 

[MikeS]

I remember getting pissed off in AOW - at that point I could hold a stop at one FOOT depth - (as long as it wasn't choppy) without losing trim. I was bang on - and then they wanted us to do a fin pivot. I couldn't do it... I have this natural aversion to touching the bottom and silting it out. I don't swim with my fins below my chest anyway. I thought the entire exercise was stupid.

I don’t understand. If you’re “bang on” you should easily be able to pivot from any part of your body. Why were you pissed off?

Mike

 

[neil]

The fin pivot standards for OW no longer require the student to touch the bottom. All they need do is get neutral.

I'm sure you're correct but please tell me where you saw the change in standards. Musta glossed over an update, fascinating reads that they are.

[/QUOTE]BTW, the standards say that the student needs to touch the bottom with some part of their body when doing a fin pivot in CW.
I found that you need to read this stuff rather than make assumptions based on how you've seen it done.[/QUOTE]

Same applies for OW. I have the students put one finger down on a rock or something and hover horizontal in that position. Meets the standard and keeps everyone honest.

Neil

 

[Capt Jim Wyatt]

I love seeing the dead horse beaten

 

[MikeFerrara]

I love seeing the dead horse beaten

Why do you call it a beating deag horse? Every day new people are exposed to it start trying to make sense out of it.

Buoyancy control, trim and how they're taught is, IMO, a pretty central issue. I think that the way it's taught and the average divers mastery of it pretty well defines the state of recreational dive trianing.

 

[RiverRat]

Hi,
I'm brand new to diving and trying to get my "trim" under control. I'm about to testdrive my new BP/Wings with tank weights. It occurred to me that the fin pivot drill just confirms that you're not weighted properly. You inhale, and your upper body (only) rises, exhale and you sink. Does this make sense? I've read that if you have proper trim/weighting, your body should be horizontal in the water. Any insight? Thanks.

ClassAction:
As a new diver I just went through the same learning experience you're embarking on now. I remember having horrible trim in OW and AOW class. With 7mm full suit, hood, gloves etc. it took 28# on the belt to get down. I swam around like the Concorde on takeoff. Now I know why the fin pivot went well Anyway, I'm glad I went with the BP/W setup. I did MAJOR homework running every buoyancy calculation I could find here on SB to figure out roughly what weight plate to get and how much weight would be "left over" for the belt. I dove my rig for the first time in salt in a 3mm shortie. I started heavy with 15# on the belt but my trim was still a million times better than my OW dives in the jacket BC (no trim weights). About half way through my dive trip I was down to 3#! One thing I would stress is to LOG everything on your first dozen or so dives. Weight, wing, start-end pressures, exposure suit, etc, etc. When I got to the correct weight of 3# on my belt (11# BP) I was truly neutral. Just exhaled to sink (horizontal or vertical) and inhale/fin to rise. I was truly awestruck when I was able to control my position throughout the water column using only lung volume and fin power. I was using no air in my BC. FredT here on the board has an excellent document on weighting/neutral diving. I was able to put that info into play on those dives. On my "final" tuneup dive I had a 6# belt. I dropped it at the mooring line, did the dive, then grabbed it on the way back up the line. At the safety stop, with the belt locked in my hand on the line, I felt a little light at 500 psi. With this I went back to 3# all was dead nuts at the stops after that. Once you get your weighting/trim nailed you'll be amazed at how your SAC rate improves big time without all the extra lead.

 

[Genesis]

This is one of the things that REALLY pizzes me off about dive training today.

I was taught to "fin pivot". Teaching me that was wrong, as it promoted incorrect trim and weighting (too much and in the wrong places!)

Of course its easier for the instructor to just throw lead at you rather than figure out WHERE you need weight and exactly how much. But without proper weighting, in the right place, good trim is almost impossible to achieve without MAJOR fighting all the time.

My g/f and her daughter also were shown this asinine exercise. We're still sorting out THEIR trim and weighting - they're CONVINCED they need more lead than they almost certainly really do, and of course it goes straight to their trim!

We WILL overcome..... Once the water warms up anyway (they're WWWs)

 

[donacheson]

In theory you're right. But reality is that as you inhale your lungs expand in multiple directions and exactly compensating for this is not humanly possible. Ergo there is no such thing as "perfectly horizontal".

There's a bit more than just the diver's lungs involved.

The changing weight of air in the diver's tank as the dive proceeds is a factor unless the center of buoyancy happens to be at the center of the tank. Also the variable amount of air in the diver's BC, changing either to compensate for the loss of air in the tank or changes in depth, is another factor.

An even finer point: If the diver is in good trim, tilting up or down will move the air in the BC or shell dry suit up or down and thus disturb the trim. Likewise, a neoprene foam exposure suit will expand slightly on the higher portion of the body and compress slightly on the lower. The best that can be said of perfect trim is that it's an unstable equilibrium.

 

[Boogie711]

Don - ever dove with a BP/Wing?

I find that when you're dialed in - properly trimmed and weighted, moving your entire body in the water column comes automaticaly. Some are better than others - I have an instructor friend who has been described as having an elevator button in her butt somewhere.

Once you're dialed in, it's quite relaxing, anyway... I would hardly describe it as an "unstable equilibrium." When I want to ascend, I can horizontally ascend, all of me, at once. It's not hard. (or vice versa.)

Hence the problems I had with a fin pivot - mentally, I had a real tough time putting my fins on the bottom in the first place... I normally dive with my legs bent and fins higher than my head. I saw no value to the exercise.