Another weighty question: Diving with a 19CF pony-much much weight to substract?

[CraigCarter]

A novice diver with a novice question....To date my dives have been salt and fresh coldwater with a 7m WS,80A tank, BC is jacket type-Scubapro classic. I carry 18 lbs in the side pockets (9/9) and 4 lbs (2/2) on the back trim pockets (saltwater). (I suspect I'm carry too much weight, I weigh 195.)

I just purchased a 19 CF pony as a redundant air suppy (14 lbs w air). The unit is connected to the right side d-rings of my BC. I am wondering how much weight to remove for buoyancy control.
Thanks for your help!

 

[spectrum]

My similar rig tested at just over 4 pounds negative all dressed to sling.

The next question is do you want to reduce weight or just offset the pony? Assuming that you have correct weight to begin with how do you plan to utilize it? For solo diving it dosen't matter much. In the case of buddy diving you may have need to hand your pony off to the buddy. If that leaves you a full 4 pounds below ideal then making a controlled ascent on a near empty cylinder may be a challenge. Diving 4 pounds "heavy" for this reason is not the end of the world and splitting the difference is always an option.

Whatever you do be sure to rig yourself to be balanced in your normal configuration. Diving with a 4 pound offset is noticeable.

As for correct weighting here is a suggestion:

Remember to set your weight so that you bob vertically at eye level at the end of your dive with an empty BC, an average breath, your feet still (crossed) and about 500 PSI in your cylinder. A deep breath should get your mask out of the water and a deep exhale should sink your mask. Do all of this while breathing from your regulator. The end of the dive is the defining moment for your weight requirement and you want just enough to let you stay down in the shallows with a light cylinder.

You can make the same test pre-dive with a full cylinder and add 5 pounds to compensate for the buoyancy gain you will experience as you breathe the tank down. Be sure to repeat at the end since you are apt to have some stowaway buoyancy (trapped air) in your gear early in the dive. You are safer being two pounds heavy than 2 pounds light.

Pete

 

[Mayor]

Trim your self out with the tank empty (500psi) and with all the gear you will be diving with. I'm not a big pony fan but I would think you should empty that as well. Some others might have to help with that. For me a pool is the best place to get close to what you need for salt water. Drop some weight on the bottom and add till you can hold at 6 or 8 feet with out any air in the wing / jacket. Then add 2lb to 4lb for salt.

 

[BigTuna]

I tied a line to my (full) 19 cuft pony, rigged for slinging, submerged it in salt water, and weighed it with a battery-powered "fish" scale. It weighed 3.5#. I treat it as part of my ditch weight.

 

[drbill]

I actually added two pounds when I switched to a 19 cu ft pony... placed it on the opposite side of the tank-mounted pony to give me better balance.