Drysuit and weight issue.

[fisherdvm]

I read frequently about how much weight you need to carry to dive dry. My question is, is it feasible to use a vacumm device to empty your drysuit of excess air before you go in.

I was thinking of like using a 60cc syringe and a cathether or a 3 way valve. You probably could deflate the suit pretty quick ... and decrease its bouyancy. Have anyone done this before?? Of course, problem is, if you added a little too much air to your suit at the bottom, you might not be able to get back down??

 

[Dive-aholic]

There's a technique for emptying the air without the use of a syringe. A syringe would take way too long. You can either squat down while holding your neck seal open to let the air escape. The purpose to squatting it to minimize the air space by bending your knees and elbows. The other option if you're shore diving is to walk into the water while holding your neck seal open.

The weight issue with dry suits is not the excess air. It's the undergarments that create the buoyancy. As you descend you will need to put air back into the suit to prevent suit squeeze. So you need to make sure you're wearing enough weight to be neutral during your safety/deco stop.

 

[fisherdvm]

So in the case of the 2 USCG divers who drowned wearing 60 lbs of weight each is because they had too much insulation on, and not able to ditch it at depth? I am going to start drysuit class in a few weeks, and just trying to understand the issues.

 

[The Kraken]

Open up your vent valve and I guarantee you that as you enter the water, the air will get squeezed out of your suit. Before entering the water, you can always squat down and sort of hug yourself. The air will exhaust through your neck seal.

The thing is to have the valve adjusted so that it keeps the right amount of air IN the suit yet vents as you ascend and the internal volume of air in the suit starts to increase.

Squeeze not good . . . . .

the K

 

[mikerault]

The problem with the USCG divers was they over weighted themselves (by at least 30 pounds), didn't have a proper dive master, didn't have a proper dive plan, didn't have proper topside support (their line enders had been drinking), didn't hook up their BCD inflator and didn't have proper equipment maintenance (their stuff hadn't been PM'ed in years).

 

[Dive-aholic]

So in the case of the 2 USCG divers who drowned wearing 60 lbs of weight each is because they had too much insulation on, and not able to ditch it at depth? I am going to start drysuit class in a few weeks, and just trying to understand the issues.

Noone, especially in military service, should need 60lbs of lead. I wear no lead with an AL bp and doubles in my dry suit in fresh water. With an AL80, I need 10lbs. That's with a crushed neoprene suit and undergarments.

 

[tterry1]

I read frequently about how much weight you need to carry to dive dry. My question is, is it feasible to use a vacumm device to empty your drysuit of excess air before you go in.

I was thinking of like using a 60cc syringe and a cathether or a 3 way valve. You probably could deflate the suit pretty quick ... and decrease its bouyancy. Have anyone done this before?? Of course, problem is, if you added a little too much air to your suit at the bottom, you might not be able to get back down??

At one time, DUI's catalog showed a battery-powered vacuum pump to remove air from suit. I haven't seen it in the catalog in years, so I have no idea whether it's still being made. It always seemed like a solution looking for a problem.

 

[steven_bennett]

Hi,
Seems to me that this is not an issue. Why would you want to vacuum the suit before diving?
As soon as you are in the water, all exces air will exit the suit as soon as you press your shoulder purge. Basic physics here.
Dry suits usually have an exit purge on wrist or shoulder, and an inflator on chest.
I dive with a compressed neoprene dry suit with 4 kgs (11 pounds) lead in fresh water and add a couple kgs (6 pounds) in seawater, with a 15 liter (approx. 100 in US size, I think) tank. Enough weight for me.

PS: when you guys going to go metric like the rest of the world ;-) ;-) ??

 

[TSandM]

The last thing you want is to vacuum pack yourself in your suit. If you haven't dived in a dry suit yet, you're about to meet the phenomenon of "squeeze". Squeeze begins with uncomfortable, goes on to miserable and ends with immobilization You need a certain amount of air in a dry suit to dive it at all, and more if you want to stay warm in it. And it just requires the weight it requires, is all.

Rob, your undergarments must be T-shirts. With my double 85s and my new crushed neoprene dry suit, it looks like I'm going to have to carry 22 or 24 pounds

 

[spectrum]

I find that as I gear up with my vent valve wide open most movements expel air through the check valve. The rest comes out as I wade into the water column. I have never really needed to do the squat let alone use a pump to evacuate the suit. Pre and post dive I am just as likely to close the valve and blow it up for comfort.

What you need for weight is what you need and it will vary widely with your body and your gear. Be sure to take you time figuring this out for good safe results.

There is one wild card with a drysuit and that is the air in the suit. In a wetsuit the buoyancy will change with depth, with 100% consistency it will rebound as you ascend and compress as you descend. In a drysuit all of the same effects of Boyle's law are at work except that the venting of the expanding air from the suit is subject to the vent being at the high point. This means that a diver who is not paying attention to his or her position of attitude in the water can find themselves overly buoyant with trapped air in the suit. This is exacerbated by the fact that a drysuit vent is very slow compared to something like a pull dump on a BCD. Make slow ascents and be sure to feed expanding air volumes to where your vent is located. My point in going down this road is that many divers will choose to carry a couple of extra pounds (2-4) just to keep them tolerant of a little bit of extra air in the suit. Other than alleviating squeeze manage all of your buoyancy with your BCD.

Pete