Cold water Wing lift - again

[ams511]

We are not talking about weighting for the dive, but rather the lift needed. In order to be neutral with an empty tank at the end of the dive, at a depth of 1 foot, the diver will need to carry extra ballast to offset the weight of the air used. If he does not, then he will float up. Proper (or minimum) weighting will make him neutral with an MT BC, and an MT tank at the surface. So, this means that when he starts his dive, with a full tank and at a depth of zero he MUST be over-weighted by an amount exacty equal to the weight of the air in the tank. So when he descends to 130 ft, (in zero seconds, without using any air ) ,, what will be his buoyancy situation? The answer is ... he will be negative by an amount exactly equal to the suit compression AND the weight of air in his tank(s). So in order to establish neutral condition - the wing MUST have the capacity to offset the negative force generated by suit compression AND the weight of the gas in the tank(s).

Tobin, already answered your question so I will try to keep it brief. If the diver takes time to descend to 130 ft (and uses air) he will just be less negative and need to inflate the wing less. I was trying to keep the math simple. As Tobin already mentioned at 15 ft a + 25 lb wet suit is around + 17 (25/1.5=16.67). So it already lost 8 lbs. (25 - 17 = 8) of buoyancy. This 8 lbs should cover the weight of air in most tanks. In fact the diver may need to inflate the BC a bit.I think where you are getting confused is the difference between warm water and cold water diving. If you are diving with a skin in warm water, there is no compression in the skin so the only thing you need to worry about is if the wing floats your rig. However when doing the weighting the diver should be able to hold a stop at 15 ft with 500 PSI in his tank. This would translate to being roughly maybe 5 lbs heavy during the start of the dive. As the air gets used up the diver becomes more neutral and needs to vent. Remember the weighting is done first and then the wing size is determined.

 

[dumpsterDiver]

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.

 

[Storker]

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.

This thing that you should always strive to minimize weight, preferably to the extreme, must have been invented by wetsuit divers. Any drysuit diver who has spent more than half an hour comfortably warm in sub-10C water knows that weight = warmth. Shaving your weighting to the absolute minimum means you can't sink the air you have to put in your undersuit to stay reasonably warm. I'm not the only diver around here who puts an extra kilo or two on their weightbelt in the fall when the water gets cold.

Also, with a DS you'll be either quite buoyant, very buoyant or very, very buoyant before you don your rig and belt. Unless you want to carry all that lead - which may easily be more than 10kg in addition to the steel tank and the other hardware - around your hips, you put quite a bit of it on your rig. Which again means that you may need a decently sized wing to float the rig on the surface. I'd hate to see my rig sink like an anchor if I should choose to doff it in the water, so I can't rely on my own buoyancy in that calculation.

 

[danvolker]

I'm thinking that maybe these cold water Drysuit divers, might be better off using an Umbilical hose from the surface.....all the weight they want, and walking on the bottom like a hard hat diver. This could solve all the cold water and dry suit problems

Example of umbilical hose diving.....or Hooka.
Dry suit diver could have all the air they wanted, and with the well weighted walking along, they could stay warm with lots of air in the suit.
They could use a BC of sorts to surface, and the hose could be like a rope they could climb up, as a backup plan on regaining the surface.
Speed walking on the bottom, would be similar to most cold water dry suit diver swimming speeds....and they don't believe in going fast, anyway

 

[buddhasummer]

I'm thinking that maybe these cold water Drysuit divers, might be better off using an Umbilical hose from the surface.....all the weight they want, and walking on the bottom like a hard hat diver. This could solve all the cold water and dry suit problems
View attachment 218472
Example of umbilical hose diving.....or Hooka.
Dry suit diver could have all the air they wanted, and with the well weighted walking along, they could stay warm with lots of air in the suit.
They could use a BC of sorts to surface, and the hose could be like a rope they could climb up, as a backup plan on regaining the surface.
Speed walking on the bottom, would be similar to most cold water dry suit diver swimming speeds....and they don't believe in going fast, anyway


View attachment 218473

Except I like diving not walking.

 

[Storker]

I'm thinking that maybe these cold water Drysuit divers, might be better off using an Umbilical hose from the surface.....all the weight they want, and walking on the bottom like a hard hat diver. This could solve all the cold water and dry suit problems

Now you're being sillier than normal, and I think it would be insulting to believe you don't know that.

Look at the thread title. It contains the words "cold" and "water". This thread is about cold water diving. You're welcome to join me one day. I won't deny you using your streamlined WS setup with minimal weighting. And while you're still shivering and sipping hot cocoa, wondering how long you'll have to sit down to pee, I'll be sitting admiring the sunset, nice and warm, savoring my post-dive beer.


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[danvolker]

I was kidding

But....You have to admit, some walking on the bottom, ala 20,000 leagues under the sea....would be kind of fun!

---------- Post added October 23rd, 2015 at 09:06 AM ----------

Storker, one day I may well take you up on that offer !
But I would be using a very high tech heated wetsuit...the entire wetsuit heated, powered by a Can light style battery.
I'd be using an 18 pound lift wing, the system would be slick and very low drag... and I am sure I would enjoy your favorite areas.

When I get to DEMA next month, I will be pushing a few mfg's I know to get busy on making this happen soon !

 

[halocline]

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.

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.

 

[cool_hardware52]

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.

Divers in thick suits weighted as I suggest can easily control their ascent from 15 ft *using* their lungs. Anybody that's used a thick wetsuit knows they don't "snap" back during ascents, in fact it's quite common for suits to lose some buoyancy from the first dive to the second because the rebound is so slow.

Having said that why does a single tank, no deco diver who has completed their shallow stop need to be concerned about stopping at 1 FSW? Please do be specific.

Tobin

 

[danvolker]

And what is so wrong with having your feet over your head, with a gentle swimming down force at the safety stop?