THE "PERFECT ( being horizontal ) TRIM" HOAX

[Neilwood]

A bit late to the party but my two cents worth.

I think it is important to separate buoyancy and trim ( and by extension the goals for each):
1) Buoyancy - the ability to maintain a position in the water column at a chosen depth. This should be done without any finning or skulling with hands and it should not matter what orientation the diver is in (head up, feet up, side on, facing down, facing up, vertical, horizontal or at 45 degrees).
2) Trim - the ability to maintain your orientation in the water irrespective of depth, direction of travel or finning/skulling. Flat trim is a good goal (for efficiency of moving from place to place) but to my mind should not be the only goal (apart from certain circumstances such as cave, wreck where a silt out could be life threatening). There are a number of situations where "perfect" flat trim is not necessarily the best trim for that moment. A few I can think of are drift diving along a reef wall (vertical or side on will allow you to see more of the wall without significant manoeuvring), current/swell (it might not be a flat current but have an element of vertical movement where adjusting trim might help counteract it), ascent to surface (last few metres/feet where looking upwards at the surface is critical), diving with predators (shark dives tend to be done vertical as that presents the biggest area to the shark and minimises the chances of attack), restrictions such as swim throughs where side on might be better etc.

The ideal goal IMHO is a diver that can maintain both parts independently and together when required. That way the diver has the skills to be able to chose the best position for the situation that presents itself.

Diving should be fun. "Perfect" trim is good but if it means diving is less fun then screw it - I will adopt whatever trim I need at the time to have the best time. If that means drifting along inverted to make my buddy smile then so be it!

I sometimes think that both new & experienced divers alike should read some of TS&M's posts as an exhibition of what diving should be about. She struggled but with perseverance became a very accomplished diver (who we lost too soon). My thanks go to @OTF who shared her post regarding her experience with some of GUE's finest (link) where it was all about fun.

 

[MichaelMc]

Balance also lets us talk more easily about the gear setup as input to our diving.

"My balance is way off with this gear, do you have some pockets to put trim weights higher up so we can get this squared away properly?"

Diving should be fun. "Perfect" trim is good but if it means diving is less fun then screw it - I will adopt whatever trim I need at the time to have the best time. If that means drifting along inverted to make my buddy smile then so be it!

The issue is if "whatever trim I need at the time to have the best time" means fins down kicking up the reef so I no longer have to fight gravity's rotation so much and can just enjoy the view in front of me, but destroy it and the reef for those behind me.

If you want to look under a ledge, then the perfect orientation is inverted, if that is what works for you then and does not destroy things. Or drifting along inverted for fun. Or drifting upright, clear of kicking up the reef, if you want and you are capable of maintaining other orientations.

Fins down kicking up the reef is never a good orientation, unless you are being chased by a great white shark and you are trying to create a smokescreen and dislodge fish from the reef as alternative bait.

 

[wetb4igetinthewater]

unless you are being chased by a shark

That's one of the problems with society today. No one is willing to be inconvenienced in the slightest to protect the environment.

 

[Lorenzoid]

The "balance" discussion brings to mind an exercise an instructor had me do when I was trying out a new set of doubles. The idea was to see if I would start pitching forward or backward when I got into the standard horizontal trim position--torso and upper leg horizontal, lower leg vertical, fins horizontal, arms out in front, etc. Being "balanced" meant that, depending on what I felt would be useful under the circumstances, I could achieve a slightly head-up trim by extending my legs slightly backward, or achieve a slightly head-down trim by bringing my feet slightly forward. As I believe others have been saying, a particular trim (pitch angle) itself is not the goal but rather the ability to adjust one's trim on-the-fly to suit the circumstances, which is most easily achieved when one is balanced in horizontal trim.

Oh to change one's trim! On a whim! No need to swim!
(Apologies to Dr. Seuss)

 

[The Chairman]

Maybe it's the most versatile orientation to start from?

It is.

Maybe just balance? Be in neutral balance?

There is such a thing as "natural horizontal trim". Unless your trim is effortless, you'll get neck and back pains staying that way. Once you achieve it, changing your trim is as easy as moving your legs in and out.

About walls. I stay pretty horizontal but slip over on my side. I do that looking under ledges too. Like a fish, I simply orient to the new 'bottom'.

I think it is important to separate buoyancy and trim

This is impossible in real diving. Trim affects thrust which then affects buoyancy. Divers who are constantly adding and removing air from their BC evidence this erroneous concept.

 

[Manatee Diver]

This is impossible in real diving. Trim affects thrust which then affects buoyancy. Divers who are constantly adding and removing air from their BC evidence this erroneous concept.

Trim and buoyancy are linked directly and IMO good trim is required for good buoyancy control unless you never want to fin level.

 

[The Chairman]

Trim and buoyancy are linked directly

Thus sayeth Reggie! RIP.

 

[Deepsea5]

The issue is if "whatever trim I need at the time to have the best time" means fins down kicking up the reef so I no longer have to fight gravity's rotation so much and can just enjoy the view in front of me, but destroy it and the reef for those behind me.

If you want to look under a ledge, then the perfect orientation is inverted, if that is what works for you then and does not destroy things. Or drifting along inverted for fun. Or drifting upright, clear of kicking up the reef, if you want and you are capable of maintaining other orientations.

Fins down kicking up the reef is never a good orientation, unless you are being chased by a great white shark and you are trying to create a smokescreen and dislodge fish from the reef as alternative bait.

That's one of the problems with society today. No one is willing to be inconvenienced in the slightest to protect the environment.

I agree with the sentiment of "whatever trim I need at the time to have the best time".
However, if a diver's idea of "have the best time" is to trash a reef or do their best impression of a crop duster and kick up silt; I question whether SCUBA is a good fit for them...

 

[Pressurehead]

I agree with the sentiment of "whatever trim I need at the time to have the best time".
However, if a diver's idea of "have the best time" is to trash a reef or do their best impression of a crop duster and kick up silt; I question whether SCUBA is a good fit for them...

A little off topic: The very worse damage I see done to the reefs in my area are done by boat anchors, saw one destroy a whole section of reef last dive, a fair size swell on the surface and dragging the anchor.
Not a private boat but a local dive charter.
99.9% of the local divers do the right thing.
'Fornication and wit' come to mind.

 

[Ayisha]

...there is also balanced rig, as in (roughly) not too heavy to swim up...

Remember that the term balanced rig refers to dealing with potential failures on both ends (beginning and end) of a typical dive, not only swimming up from depth.

So, diving with a balanced rig means that in the event of a BCD failure with a full tank, you can swim up your rig, and with a nearly empty tank, you can hold a stop at 3m/10'. A balanced rig may or may not include ditchable weight.

While head to fin or side to side balance isn't part of the standard definition, it's typical to observe the rocking in videos during courses when someone kicks while they are head/fin heavy or rotating side to side.

If someone is observed to be rocking, the person gets into a static trim position resisting the urge to correct and see which way they fall. It's often counter-intuitive and divers who think they're fin heavy are sometimes actually head heavy but over-compensating with their fins.

Of course this takes time and observation. Hopefully more instructors will work on having their students achieve neutral buoyancy and decent trim, whatever it's called.