Trim and Buoyancy

[Mike Klieb]

That particular model the buoyancy varies by color. If they are black they are negatively buoyant and the other colors are slighly positive. If they are negative that may be contributing in a small way to your trim issues. You may just test it by putting your fin in the water and seeing what happens and then doing the same with the boot in the fin.

The fins are Blue and they do tend to be ever so slightly positive

A couple of other thoughts.

1. Are you using a jacket BCD with integrated weights or a BP/W? If jacket I assume the weights are in ditchable pockets near waist? Do you have trim pockets higher on your back? Moving weight higher (even though you don’t have a lot to play with) may help.

I have the ScubaPro Go so it is more of a vest/ Jacket type just the with integrated weights

2. Breathing. Do you take large full breaths or do you breath out of the middle or bottom of your lung capacity? How you breath may have an effect on your trim.

My breathing is usually controlled to help me maintain a certain depth I am learning to breath in the middle of lung capacity that way if I want to go down I let more air out up just the opposite.

3. Leg/Foot position. Do you keep your legs out straight or do you pull them into an L-shape with your fins above you and directly above your knees. How you position your feet can have an effect on weight distribution and effect your trim. If you do a regular flutter kick with your fins straight out you may try out bending your knees and seeing how/if that changes your trim when kicking and resting.

Normally I am flat legs out straight haven't really tried with my knees at a 90 degree because I haven't mastered the frog kick yet still trying but as log as I am moving forward with my legs out straight I can maintain a good level trim @90 I may trim negative (legs slightly down) when I'm still legs out straight they will slowly fall and cause me to "stand up" when I bend them that happens a lot faster

 

[Ayisha]

While out at Diving Sunday I was trying to work on trim and buoyancy I noticed that as I was swimming I was staying flat in a good diving position but when I stopped and was attempting to just hover my legs would invariably start to sink so I figured id move my tank up on my back to no avail... any suggestions ??? I had 2Lbs one in each weight pocket I could hover it would just end up being hovering in the standing position.

It might help to think of your centre of gravity as your fulcrum. Body positioning, placement of the tank, placement of ballast, type of exposure protection, and equipment all contribute.

I'm assuming you're stretching out horizontally and seeing where your body naturally goes, no compensating. That way you can accurately tell whether you're head heavy or foot heavy, and many people are surprised.

Stretch out while neutral with your arms out in front of you, your head looking forward, your glutes clenched, knees up, legs a bit apart. This should tilt you more horizontal with a "stable platform".

With your arms in front and all of the above, experiment with how straightening or bending your legs affects your trim. Often, taller people can bend their legs more, while shorter people may bend only slightly.

If you discover that you are head heavy, you moved your tank up, which helps, and if you have shoulder trim pockets, you can move your weights there. If not, there are trim weight pockets that you can slide onto your upper cam band if you have 2, otherwise onto your single cam band. Integrated weight pockets by the waist are often too low for many people.

Be conscious of where "the bubble" is in your BC. If you tip head down slightly momentarily, the bubble will move to the bottom of your BC. Stretch out and keep the bubble there, which will keep you in position.

Body positioning is very important in maintaining trim, but heavy fins can increase your struggle in a thin wetsuit or especially with no exposure protection.

Just keep practicing, keep analyzing, keep tweaking. Hope that helps...

 

[happy-diver]

The reason your rotation accelerates when you bend your heavy legs is probably that when your legs are out straight, your fins were acting as retardants. That water resistance disappeared when your knees bent and your fins became parallel to the direction of rotational movement.

Wow this must be why I get less propulsion when my fins are anything but parallel to the surface