My wife won't sink
- Thread starter CycleCat
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I honestly thought this was going to be some kind of a confession.
Eric Sedletzky
Contributor
The title was somewhat Scott Petersonesque?
OP, the way to determine exact proper weighting is to do the 500 psi test at the safety stop making sure the BCD is completely empty of any air. She should be able to hold a stop using breath control alone. Once you have this baseline you can add some if you want. But at least you will know where the hard line is.
The other thing I should mention is that wetsuits prior to their first dive will always be very buoyant. They are heated by the sun which inflates the cells and they have not been compressed yet by depth. It might be possible that she may have to tip head down and kick down until a little pressure takes over and squeezes the suit.
Over the length of the dive the suit will cool making the cells in the neoprene shrink. Pressure will also squeeze the suit down so on the return trip to the surface the suit will have lost a lot of buoyancy. Suits don’t always re-expand at the same rate as your ascent. You have to factor all this in. It’s not always just about initially getting down.
In this day and age there is too much emphasis on push button elevator diving. Descending feet first is one such example. That doesn’t matter. What matters is where your weighting is at the end of the dive after temp and pressure has had it’s effects on your gear. Chances are with a 5 or 7 mil wetsuit with that criteria in mind you will float on the surface with a full tank. In that case you/she would have to tip forward and swim down.
Those BC’s you mentioned also will require some additional weight just to sink themselves. Add an aluminum tank and the weight just went up again.
Steel tank and a BP/W will relieve a lot of her weighting issues.
Just be careful, overweighting is probably the biggest equipment related safety concern in modern scuba diving.
Eric Sedletzky
Contributor
7mm suits suck. There is so much air in the neoprene that the standard of being neutral at the safety stop with around 500 psi in the tank means you will be a couple of pounds light at the surface as the gas expands.
Which in turn means you'll only be 2 or 3 pounds negative at the start of the dive provided there are no air bubbles trapped inside the suit which there absolutely are.
So you'll have to work around this. You can try one or a combination of the following. First is to take a hose or bucket and try to fill up the suit before you go in. Be mindful of the water temps though as you didn't want to start a dive chilled. Another is to fully exhale and duck dive like a freediver to get down the first 5 or 6 feet until the neoprene compresses a little. It may also be necessary to be a couple of pounds overweight (if measured at the safety stop).
BTW, 14# is not that much weight with a 7mm, especially for a petite diver where the highly buoyant suit makes up a relatively large percentage of the volume of the vessel that is diver plus the suit.
I understand that a 7mm is the cheapest way to keep yourself warm in colder water, but it might be worth exploring layering neutral exposure gear like Sharkskin, Exoware or Lavacore with a 3 or 5mm suit.
Which in turn means you'll only be 2 or 3 pounds negative at the start of the dive provided there are no air bubbles trapped inside the suit which there absolutely are.
So you'll have to work around this. You can try one or a combination of the following. First is to take a hose or bucket and try to fill up the suit before you go in. Be mindful of the water temps though as you didn't want to start a dive chilled. Another is to fully exhale and duck dive like a freediver to get down the first 5 or 6 feet until the neoprene compresses a little. It may also be necessary to be a couple of pounds overweight (if measured at the safety stop).
BTW, 14# is not that much weight with a 7mm, especially for a petite diver where the highly buoyant suit makes up a relatively large percentage of the volume of the vessel that is diver plus the suit.
I understand that a 7mm is the cheapest way to keep yourself warm in colder water, but it might be worth exploring layering neutral exposure gear like Sharkskin, Exoware or Lavacore with a 3 or 5mm suit.
Rose Robinson
Contributor
Hello CycleCat,
Two suggestions:
Ensure your spouse is neutral in the shallows, pre dive. Follow neutral buoyancy procedures that were taught in basic training.
Suggest switching from aluminum to steel cylinders, If she is using aluminum 80's, suggest switching to HP steel 80's, or HP steel 100's.
As a third suggestion, ensure BCD is completely evacuated pre dive.
All the very best,
Rose
Rose Robinson
Contributor
CycleCat,
I'm reading here that the problem may be related to your wife's 7mm suit. The suit is not a factor if your wife sets her neutral buoyancy pre dive.
Kit/suits are all irrelevant if the diver is neutral at the commencement of the dive.
I'm approx 125 lbs, dive full time with a drysuit, commonly to depths in the 150 ft range, I own no lead ballast, never have, and again my kit is irrelevant, as I aways commence my dive being neutral.
In the beginning getting neutral takes a little work and a little time, and having someone to assist you is always the best way.
Getting yourself dialed in will come pretty quick.
All the best,
Rose
This is unhelpful, completely. If she was neutral negating the suit there would not be a problem.
You cannot dive in cold water with a drysuit (BC right?) without weights unless you are using gigantic steel negative doubles or the like. It's not at all relevant to the situation.
What does "sets her neutral buoyancy pre dive" mean?
Neutral at the start means 4-5 pounds light once you breathe down your gas. Good luck holding a safety stop.
And "no lead ballast" with a single tank and a 7mm suit? You could maybe get there with stainless steel in the form of a really thick backplate and a big steel HP tank, but that's not relevant to this situation.
Boarderguy
Chief Narctopus Wrangler
I'm just interested in seeing someone in a drysuit not require any lead regardless of kit... just wow
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