Cold water Wing lift - again

[cool_hardware52]

And my experience tells me that if I dive shrink-wrapped with minimum weighting I'll freeze my butt off,

Other than 3 minutes at your safety in the unlikely event of an emergency that requires you completely empty your tank when have I *ever* advocated diving shrink wrapped?

Tobin

 

[decompression]

I can't believe how much warmer I am by just adding air.....


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[eelnoraa]

decompression, you own me a keyboard

 

[ams511]

I'm not confused about any of it. If you or he think it is appropriate to carry so little lead that the diver will float to the surface from less than 15 feet, then I disagree.

You are confused whether you want to admit it or not. If you look at title of the thread, it says "cold water wing lift", which is what we were talking about. In fact you pointed this out in a previous post. You are now shifting the conversation to weighting which is a different topic.

My point is that once a diver is properly weighted, the buoyancy swing of the tank does not get taken into account when calculating the wing lift requirement. What is taken into account is 1) the ability to float the rig without the diver in it, and 2) to compensate for the loss of buoyancy of the wetsuit at depth.

I never said to dive with so little weight that the diver will float to the surface from 15 feet. What I did say it that wetsuit compression at 15 ft (using the example you gave) will more than offset the reduced buoyancy of the tank. I am not sure how much cold water diving you have done in a thick wetsuit but advocating adding another 6 or so pounds when the diver is already carrying 20 + just adds to the diver's discomfort and could be potentially dangerous.

 

[dumpsterDiver]

You are confused whether you want to admit it or not. If you look at title of the thread, it says "cold water wing lift", which is what we were talking about. In fact you pointed this out in a previous post. You are now shifting the conversation to weighting which is a different topic.

My point is that once a diver is properly weighted, the buoyancy swing of the tank does not get taken into account when calculating the wing lift requirement. What is taken into account is 1) the ability to float the rig without the diver in it, and 2) to compensate for the loss of buoyancy of the wetsuit at depth.

I never said to dive with so little weight that the diver will float to the surface from 15 feet. What I did say it that wetsuit compression at 15 ft (using the example you gave) will more than offset the reduced buoyancy of the tank. I am not sure how much cold water diving you have done in a thick wetsuit but advocating adding another 6 or so pounds when the diver is already carrying 20 + just adds to the diver's discomfort and could be potentially dangerous.

I learned to dive on NJ shipwrecks in the mid-70's and did that for several years and did a few summers in Maine - diving -snorkeling and scuba frequently. I was diving solo, to 130 in a dry suit (unisuit) and double steels, on a wreck in NJ before I was old enough to get a driver's license. But I admit, the vast majority of my diving is in water that is warmer than 65 degrees.

I'm really not interested in getting in a pissing match over all this. I was asked to give specific examples of WHY a diver might not want to be buoyant from a depth of 8 feet to the surface. Answer: I've know two people who have gotten whacked by boats on the surface while scuba diving, one I recovered from the bottom with prop marks exposing his brain and the other lost both legs below the knee. I'm not sure if buoyancy was an issue in either situation or not, but I would always want to have enough ballast to stop an ascent at any depth - even with an empty tank - since I am fearful of boats.

The statement was made that you can just figure the bouyancy of your suit at the surface and then have that much lift in the BC. So simple... I asked about the air in the tank and was pretty much ridiculed.

A simple analysis leads me to believe that air weight needs to be considered under this very simplistic assumption. The assumption that the cold water suit will lose 100% of the buoyancy at the surface is not something I have ever verified and to be honest, I would expect that some residual lift would remain at depth - possibly enough to account for some air in the tank.. but who knows? That is why I asked.

I can give some example of how I know that suit compression is a big deal.

I used to FREEdive with a 7 mm step in jacket, a 3 mm hooded vest, a 5 mm short hood, a 7 mm FJ pants, 7 mm mittens and boots. In this configuration I would need about 24-26 lbs of lead on my belt. I don't remember now exactly.

This was the absolute minimum amount of lead I could use and would have to fight to descend and would be very heavy below 30 feet with suit compression and lung compression.

When I would scuba dive with an 80 or 100 ft aluminum tank, I would add about 4 lbs of lead to the BC. So total ballast was around 30 lbs. Any less and I was too light.

When I dove to a depth of around 75 ft in scuba gear, I was heavy. I had a Sea Quest BC that was rated for (I think 35 lbs) of lift. Maybe the actually capacity was less, but several times, upon reaching the bottom, I would have to fill the BC COMPLETELY with the OPV valve venting.. It never was a problem, but it really showed me that I had no reserve lift to pick up anything heavy.

I'm not advocating anything with respect to weighting other than to be able to hold your depth with an empty tank, without doing anything difficult - like not inhaling, kicking down etc.

My personal belief is there is not freaking way I want to dive with other people without having excess lift capacity to haul their ass to the surface or to support them at the surface.. but I was very interested in the simplistic idea of just figuring what it takes to sink the suit.

 

[danvolker]

I learned to dive on NJ shipwrecks in the mid-70's and did that for several years and did a few summers in Maine - diving -snorkeling and scuba frequently. I was diving solo, to 130 in a dry suit (unisuit) and double steels, on a wreck in NJ before I was old enough to get a driver's license. But I admit, the vast majority of my diving is in water that is warmer than 65 degrees.

I'm really not interested in getting in a pissing match over all this. I was asked to give specific examples of WHY a diver might not want to be buoyant from a depth of 8 feet to the surface. Answer: I've know two people who have gotten whacked by boats on the surface while scuba diving, one I recovered from the bottom with prop marks exposing his brain and the other lost both legs below the knee. I'm not sure if buoyancy was an issue in either situation or not, but I would always want to have enough ballast to stop an ascent at any depth - even with an empty tank - since I am fearful of boats.

The statement was made that you can just figure the bouyancy of your suit at the surface and then have that much lift in the BC. So simple... I asked about the air in the tank and was pretty much ridiculed.

A simple analysis leads me to believe that air weight needs to be considered under this very simplistic assumption. The assumption that the cold water suit will lose 100% of the buoyancy at the surface is not something I have ever verified and to be honest, I would expect that some residual lift would remain at depth - possibly enough to account for some air in the tank.. but who knows? That is why I asked.

I can give some example of how I know that suit compression is a big deal.

I used to FREEdive with a 7 mm step in jacket, a 3 mm hooded vest, a 5 mm short hood, a 7 mm FJ pants, 7 mm mittens and boots. In this configuration I would need about 24-26 lbs of lead on my belt. I don't remember now exactly.

This was the absolute minimum amount of lead I could use and would have to fight to descend and would be very heavy below 30 feet with suit compression and lung compression.

When I would scuba dive with an 80 or 100 ft aluminum tank, I would add about 4 lbs of lead to the BC. So total ballast was around 30 lbs. Any less and I was too light.

When I dove to a depth of around 75 ft in scuba gear, I was heavy. I had a Sea Quest BC that was rated for (I think 35 lbs) of lift. Maybe the actually capacity was less, but several times, upon reaching the bottom, I would have to fill the BC COMPLETELY with the OPV valve venting.. It never was a problem, but it really showed me that I had no reserve lift to pick up anything heavy.

I'm not advocating anything with respect to weighting other than to be able to hold your depth with an empty tank, without doing anything difficult - like not inhaling, kicking down etc.

My personal belief is there is not freaking way I want to dive with other people without having excess lift capacity to haul their ass to the surface or to support them at the surface.. but I was very interested in the simplistic idea of just figuring what it takes to sink the suit.

I would argue that it is bad technology, for the industry to make such high buoyancy wet suits commonplace, without "warnings".
The smarter treatment would be to publicize how dangerous such highly buoyant suits are at depths from 70 feet deep and greater, due to the potential threat to the diver if their BC/wing fails, and their inability to swim back up to the surface without assistance of a bc/wing.

Another way of discussing this usefully.....If a freediver can use a wetsuit to any given depth, then a scuba diver should be able to.
And there are plenty of freedivers in cold water --- the kelp freedivers off Catalina come to mind....So here is a great quality wetsuit that these guys wear in winter....see how deep they can go with it before these suits are dangerously negative for them--and then make this the max "safe" depth for the suit....Each wetsuit can have an MOD rating, just like a nitrox tank

As to a buoyant stop at 20 feet.....feet can be over the head, and you can swim down and hold the stop, even with a large amount of buoyancy. Heading to the surface, without the protection of a professional dive charter boat protecting you ( what most scuba divers pay for), should indicate the diver would be smarter to remove their hood so they can hear well, and NOT surface until no sounds of approaching boats are heard. If they are hard of hearing, or in a very high boat traffic area, then they could be towing a bright yellow or red kayak, as if it was a dive flag ( and the flAG would be on the Kayak) ... Then the diver comes up next to the kayak. Even drunk boaters do their best to avoid running over kayaks...they damage the props. Small private boats taking some scuba divers out, could use a rack to hold the kayak out of the way--on top, like a roof rack for bikes on a car.

 

[cool_hardware52]

My personal belief is there is not freaking way I want to dive with other people without having excess lift capacity to haul their ass to the surface or to support them at the surface.. but I was very interested in the simplistic idea of just figuring what it takes to sink the suit.

As you know well from the many many many times I've discussed this exact matter with you a diver following my recommendations for weighting and lift will have at a minimum at the surface 100% of their wings capacity available for what ever purpose they choose.

A diver following my weighting and lift recommendations at recreational depths will have some portion of their wings capacity available through out the dive, and this available capacity will increase as the dive progresses.

It's false to suggest otherwise.

Tobin

 

[dumpsterDiver]

I like to weight myself so that I'm neutral at 10ft with a near empty tank. This puts me slightly positive on the surface, and a little negative on the surface with a full tank. It works well for me. This is in warm water, 3 or 5 mil suit.

For a typical single tank diver, the difference between "eye level with full tank" and "eye level with near empty" is 4-5 lbs. With a thick wetsuit, I think it's possible that over the course of the dive the suit will get soaked and compress enough so that at the surface at the end of the dive it's a few pounds less buoyant.

Theoretically, you are correct that the air in the tank should be included in the ballast calculation, but in actual practice it can result in some divers in some wetsuits carrying a few more pounds than they need.

Sounds like somebody gets it. I was trying to understand the recommendation and the whole discussion gets into dying because the diver has 5 lbs of lead more or less.

 

[cool_hardware52]

Sounds like somebody gets it. I was trying to understand the recommendation and the whole discussion gets into dying because the diver has 5 lbs of lead more or less.

How long can you tread water holding a 5 lbs weight?

Why not be neutral at the surface?

Tobin

 

[danvolker]

Considering that Dumpster diver IS a freediver.....the real thinking for him may need to be about..."why should a scuba diver be weighted DIFFERENTLY than a freediver?

As long as I have been diving, I am pretty sure I have always used freedive style weighting for my scuba diving....with the exception of a few 300 foot deep tech dives where we had to drop at about 300 feet per minute, to hit a wreck in a huge current...and even here, it was instantly ditchable weight--and had I ditched it, I could still easily hold the 20 foot stop without exertion.

Matching very thick buoyant wetsuits, to heavy tanks and very negative bp/wing set ups, looks too much like an invitation for Darwin to visit.


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** As I think about this, one of the boats I use alot, likes to give me an hp120 to dive, instead of an al 80.
When I use this, I am weighted much heavier than a freediver would allow themself to be....but I do NOT actually need the wing to swim the 120 up from any depth.....I do however, need the 18 pound wing to be dead neutral a foot off the bottom.

The wing can easily lift this bp and tank , but technically, a tank this negative is not ideal for wetsuit diving in the tropics. I don't like the wing needing to act like an elevator for the tank.