Trimming for a leg heavy diver

[justinthedeeps]

View attachment 860286

• the forces from CoL and CoG are no longer balanced because the bubble moves forwards the divers feet as they flatten out, I’m a dry suit gas starts to move to the feet exaggerating this effect. Thus resulting in the head dropping due to static imbalance.

View attachment 860288
• This diagram represents the other position of static stability where the CoG is directly below the CoL.
• In a dry suit this likely ends up with the diver hanging by their boots as the dry suit bubble shifts.

Yep this was me years ago, the moment the regional GUE guru tore off my heathenous hip weight pockets (from Halcyon, with the special D ring, no less) at the start of a course to "streamline the rig"

Then promptly criticized "you're too head down" on the dive without doing anything else to help (had to discover the v pouch tricks on my own)

Oh the countless hours of back kicking in formation, elegantly twiddling valves that almost never in reality get twiddled

 

[Gone for diving]

I’m going to try to explain. Credit to gue.com for the image of the diver. Scribbling on it courteousy of yours truly.

View attachment 860285

• In this diagram, the diver’s Center of Lift (CoL) is positioned above their Center of Gravity (CoG).

• However, if the diver try’s to flatten their trim, the misalignment between CoL and CoG causes a downward head tilt due to gravity pulling on the CoG.

View attachment 860286

• the forces from CoL and CoG are no longer balanced because the bubble moves forwards the divers feet as they flatten out, I’m a dry suit gas starts to move to the feet exaggerating this effect. Thus resulting in the head dropping due to static imbalance.

View attachment 860288
• This diagram represents the other position of static stability where the CoG is directly below the CoL.
• In a dry suit this likely ends up with the diver hanging by their boots as the dry suit bubble shifts.


By moving the weights forwards the divers feet. You create flat static stability

View attachment 860289


And if this exist when the diver is flat the diver will always try to return to thus position versus falling through flat into a head down position.

With a manifold and 2 first stages. The cg is almost always to close their head. Loosening the shoulder straps and tightening the crotch strap. Tail weights and weight belts solve a lot of problems.

If you fail to diagnosis the problem correctly you keep adding weight higher on the diver and you just keep making them more head up it the water

Makes more sense when you explain it.
But I assume most divers have noticed a shifting air bubble in their wing, (drysuit it's more extreme)

Not gue or anything like that.
But I find I naturally compensate.
I do have long legs so depending on how far you bend your knees you can tweak your center of gravity.

 

[crofrog]

Makes more sense when you explain it.
But I assume most divers have noticed a shifting air bubble in their wing, (drysuit it's more extreme)

Not gue or anything like that.
But I find I naturally compensate.
I do have long legs so depending on how far you bend your knees you can tweak your center of gravity.

Agreed it’s like an airplane you have a forward and aft CG limit if it’s outside of that window you’ll have a really hard time compensating for it.

I personally like to keep my weighting low enough that I can stick some air in my drysuit and let some gas get into my feet without it being really hard to recover from. It also helps a lot when you need to go head down to descend into a cave or opening on a ship.

I also like negative fins because as you move your legs in and out they’ve got a greater effect on your CG. If they’re neutral they won’t have much an an effect.

 

[crofrog]

Yep this was me years ago, the moment the regional GUE guru tore off my heathenous hip weight pockets (from Halcyon, with the special D ring, no less) at the start of a course to "streamline the rig"

It seems sort of an open secret that quite a few people up in GUE BC have small weights in their drysuit pockets to compensate for how head heavy the double 100s are.

Then promptly criticized "you're too head down" on the dive without doing anything else to help (had to discover the v pouch tricks on my own)

Oh the countless hours of back kicking in formation, elegantly twiddling valves that almost never in reality get twiddled

And yes Train hard fight easy.

 

[grantmac]

DR XT are supposed to be an excellent neutral fun. They are the next on my list to try

 

[addohm]

Two suggestions for sidemount. Try moving your wing down on your body. Even an inch of adjustment can be a major improvement.

You may also find that moving weight down can help.

Making these changes helped me quite a bit and I'm extremely leg negative.

Is the problem consistent throughout the dive? What kind of tanks?

This was the fix. By moving the wing down I was able to have some flexibility in where I add weight on the spine to perfect the balance point. Thanks! Good information in this post regardless.