Getting Horizontal Trim

[boulderjohn]

Years ago, after I had been doing technical diving with a backplate and steel doubles for a while, I did some warm water diving with an old back inflate BCD with trim pockets in the shoulder. I had learned in the past that distributing the weight evenly gave me excellent trim. I had also learned in the past that I was perfectly weighted with a 3mm suit with 8 pounds, hopefully distributed among 4 2# weights. Unfortunately, the boat I was on had nothing but 4# weights. So I had the choice of being badly over-weighted or badly out of trim. I decided to go with 16# evenly distributed, even though it would make me far over-weighted.

It was great! I could hover motionlessly on the reef, watching the sea life effortlessly. I could handle the extra gas in the BCD pretty well, probably because I had gotten used to being overweighted at the beginning of a dive with a steel back plate and steel doubles.

So, this will sound like a sacrilege to some, but if I have to choose between good trim and perfect weighting, I go for the good trim. It makes diving so much easier.

 

[DevonDiver]

I've found that POSTURE (body position in the water) tends to be a major culprit when divers are struggling with trim.

Obviously, I've not seen the OP in the water (photos?), but weak posture is always a factor that needs to be considered. Typically, weak posture involves laxity in the hip and lower-back areas, allowing the arse to rise and the knees to drop. Once the knees drop, the diver will rotate towards a more 'feet down' trim. This is common - even with experienced divers, who have never focused upon achieving proper trim.

The shoulders-hips-knees should be on a flat plane.... all at the same level. This allows the lower legs to be held upright, with a 90 degree bend at the knees. In practice, adopting this posture feels very akin to a 'free-fall parachutists' position - a definitive 'arch' in the back to bring the shoulders and hips up. It takes some practice...


Divers practice proper posture for horizontal trim

Some examples of weak posture:



When I teach trim, I normally over-exaggerate the posture - demonstrating a very big arch in my back. I am forever 'poking' my students' knees to remind them that they are dropping.

If your body forms a W shape, rather than a flat horizontal L shape, then your posture is weak.

If your arse is sticking in the air then, again, you have a weak posture... and that is degrading your ability to trim properly.

 

[GCullen94]

I had the same problem yesterday. I was fighting to keep horizontal.
I am in southern Cal diving wet 7mm with hooded vest 5lb plate and 16 on the belt with a steel 119 and jet fins which are similar to the f1's

My dive buddy made the most ridiculous suggestion I had ever heard, move the tank lower down. I looked at him like are you freaking nuts. It was a shore dive so I moved the tank down and then went back in to get trimmed out and hey presto I was horizontal. I would give that a shot and see what happens.

 

[dkktsunami]

Have been where you are.........raise tank (it will help), OMS Slipstreams will help a lot, arch your back a little bit. This takes practice, maybe a little like trying to balance on a fence rail. Also it might help to picture your body as a play ground teeter-totter and what would happen if you added or removed weight at the extremeties. Shifting the position of weight (buoyancy) is a big factor in achieving a comfortable and stable horizontal position in the water.

 

[rongoodman]

My dive buddy made the most ridiculous suggestion I had ever heard, move the tank lower down. I looked at him like are you freaking nuts. It was a shore dive so I moved the tank down and then went back in to get trimmed out and hey presto I was horizontal. I would give that a shot and see what happens.

It's not all that ridiculous, although it happens more often with doubles, which tend to put people head down because of the extra weight at the top. If your rig is too top heavy, you'll feel like you're going to fall forward when you are horizontal, so the natural reaction is to go head up, which has the effect of moving that weight to the rear.

 

[GCullen94]

It's not all that ridiculous, although it happens more often with doubles, which tend to put people head down because of the extra weight at the top. If your rig is too top heavy, you'll feel like you're going to fall forward when you are horizontal, so the natural reaction is to go head up, which has the effect of moving that weight to the rear.

I meant the ridiculous in a joking way, because it worked. I think that was it I was too top heavy and fighting it, over compensating and then I was foot heavy. I moved the tank down and it seamed to work so I'd give that a shot

 

[kylehorn]

I'm having the same issue as the OP. I went this weekend to try some different single tank configurations in a pool. I was wearing my dry suit with medium undergarments, a HP100 and 4 lbs (2 in each weight pocket). I took video of the pool session and noticed that in this configuration I could sort of force myself to be horizontal by leaning my head forward but I would inevitably end up with negative feet. I tried to move my BC down on the tank and it was to the point where I could feel my first stage with the back of my head when it was tilted back and looking forward. I found that when I forced myself forward the air in my dry suit would pool in my feet and while I didn't necessarily start an uncontrolled ascent it was uncomfortable and not the type of solution I'd like to put to use on an actual dive. So I'm wondering...should I put weight in the rear weight pockets? What happens if I needed to ditch weight for some reason on a dive? With 4 lbs of lead I was just getting down so I feel pretty comfortable adding an extra couple of pounds on my back but I'm not sure that will help all that much.

 

[Scott L]

In most fundies class, they would say you are seeking a equipment solution to a skills problem. The rest of humanity would simply switch out to the Slip Streams or shift a few pounds forward in order achieve true blissful trim...

 

[TSandM]

Posture is the first step. If you are nicely flat from shoulders to knees, then get yourself horizontal (feedback from buddy) and then STOP MOVING. Don't do anything but breathe, and see where you tilt. If you do go feet down (and you may, because that rig sounds as though that's what it would do) then the only option you have for fixing it is to change weight distribution. You CAN add more weight than you need, but you will be dealing with extra air in your wing and the concomitant complications to buoyancy management, especially in the shallows. Or you can buy an aluminum or Kydex plate, and then move weight up to the neck of the tank, and move the tank up.

Moving the tank down to solve feet-down issues rarely works with single tanks. That's much more commonly a doubles thing.

Those very large, very negative fins are the culprit here, and the problem is that they are on the end of a very long lever arm from your center of gravity, which means you have to move a significant amount of weight as high as possible on your body to compensate for them (since the lever arm in that direction is very short). I know you love your fins, but you could probably solve the entire issue by switching to Slipstreams or EXPs (and your luggage would be lighter, too).

 

[KD8NPB]

Move your wing to the lowest bolt position while keeping the tank valve even around your upper shoulder blades.

Other than that, your options are to switch fins, switch to an aluminum BP, oorrr.

You could add some usable weight : Sling an AL19 or AL30?