Drysuit Diving Buoyancy as it relates to your BCD

[tylerinflorida]

I am sure there are probably reasons for this ... but when I tried to use the suit for bouyancy i would get light feet. When in Good trim with proper body posture, feet are the high point. The center of mass and weight is not the feet, the legs are functioning as a lever. Using the bcd for bouyancy seams right. lift where the center of moment/mass is and not at the lever end that primarily controls trim angle. When trim is controled by head movement and feet tucking or extending (equivilant of .1 lb changes in weighting at the feet area), shifting a couple of lb's of lift to the feet is overkill and counter productive. I use the suit air to counter suit squeeze, and the bcd for bouyancy for the center of mass that equally lifts both the head and feet without changing aspect in the water. I would guess that there are very few that have dry suits that have legs so snug that it precludes an air volumn from migrating to the feet. There are those that are strapped such that it retards greatly the movement of air to the feet. I look at the suit as a exposure suit and not a bouyancy device. The dry suit besides providing exposure protection also provides a BACKUP bouyancy function. So dry or wet the purpose of the bcd does not change. The only changes are the price you pay for the selected type of exposure protection. Wet= changing bouyancy and brrrr in coldwater and dry = toasty warm but you have to counter the increased overall bouyancy fo the suit with weight. Granted every time you put air in or vent air you are geting the effects of the bcd nature, however what little air you put in for squeeze comtrol is only restoring the baseline bouyancy of the suit. Another thing is that if i want some lift i want it from the tank area not the body area where it will (by phisics) try to roll you belly up when the suit is used. normally this effect is so minimal it either doesnt count or is well within you ability to compensate for it. the auto rlief valve in the suit when properly set is there to minimize the air volumn in the suit, and as such minimize the suit as a bouyancy device. One last thing to think about. Your bcd is about say 20" long. your dry suit is about 6 feet long. air moves along the full leignth of the air vessel. soooooo, take a slight up angle and the air rises by ging to the highest end. in the suit it is a 2-4 ft shift in center of lift. in the bcd it is much less than a foot. One other thing. Another poster said that if you are probperly ballasted you wont need the bcd. you still have the weight shift of air consumption, say 6-8 lbs. if the tank changes then the cpmpensation of the weight should be limited to the same area as the change ie the tank and therelies the bcd.

What he said.

 

[NAM001]

i agree 100 percent and because of that it is my belief that some use the suit for bouyancy and not the bcd. i would guess that like many i lack the 100 percent dicipline of always keeping my knees lower that my core body.especially when going deeper with a down angle or mauvering to get through a tight spot. that is when air goes to my feet. tuck and roll works fine once you get a problem. i just cant guarentee i can precvent the problem to start with so i minimize the cost by not using the suit as a lift device. i admire those that can do it though. it is definately not the thing to do if you have trim issues.

Although your feet is the highest point doesnt mean the air flows there.. The knees can be the lowest while the feet is the highest

 

[TSandM]

It depends on your trim issues. I have been in setups where parking a bunch of air in my feet was the perfect way to balance myself (and it's the only way I've found to avoid a backache when scootering). I've also dived rigs where I had to park air in my shoulders, or in the upper arc of my wing, to balance properly.

But I'll certainly agree that there are few things more annoying than having to go head down for some reason, getting a bunch of air in your feet, and then never having an opportunity to drop your feet to get it back OUT. (This is why I run the suit tight when cave diving.)

 

[Bogie]

Getting the squeeze off and using the BCD is best for buoyancy control. It is what GUE teaches and they know.
PADI teaches to use drysuit only however if you read your drysuit manual (DUI) they teach a limited amount of air in the drysuit (elbow to wrist bubble) and if you need more air for buoyancy add it to the BCD. Drysuits vent more slowly than BCD so you need to stay active and release air proactively. Getting the right undergarment is important for venting. Some just don't allow proper venting. Bare undergarments are great.

I use my drysuit only for buoyancy because it is warmer and more comfortable but you are not as stable as using your BCD. I have hundreds of dives in my suit so buoyancy becomes second nature.

 

[RonFrank]

There is no right way, if it works for you so be it. I dive with my BC for buoyancy and my Drysuit for squeeze control. That works for me. Others may choose to dive the drysuit for everything, so be it. Who cares what PADI or DUI has to say. Do what best works for you.

If I had to recommend one way I would of course go with ....

 

[j yaeger]

.....my way.....?

enjoy the sQueeze!!!!!!!

have fun
yaeg