A better freediving wet suit

[donmoore]

One problem facing freedivers when using constant ballast is the negative buoyancy in the last half of their dive. Now granted I like the feel of gliding down at this stage, but I also have the fear that if something happened down their, even if I dropped my weight belt, I may not come back up.

I read an interview by Tanya Streeter who said she felt nobody should free-dive with less than a 3mm wet suit, so that they would have more buoyancy at depth if they needed to drop their weight belt.

Now I’m no scientist, but my basic understanding of buoyancy is that lift is created when the weight of the amount of water displaced is greater than the weight of the object. Negative buoyancy is created at depth because our bodies, and soft floatation materials such as neoprene, compress because of greater pressure. The more compression, the less water displacement and the greater the buoyancy change from surface to depth. In other words -- more difficulty, exertion, and noise you have in starting your dive and the sooner you reach negative buoyancy and more negative the buoyancy at the bottom.

Compression of the body cannot be reasonable dealt with, but compression of the suit could be. I would say that a better freediving wet suit would deal with body warmth using materials that compress little and then use non-compression flotation material for flotation. Materials such as styrene or urethane foam are much stiffer and compress less than neoprene.

I think we have been given a bit of scuba diver mentality that drastic bouyancy change, due to compression, is just a fact we must live with; but do we really have too?

What your opinion? I’m thinking of sewing in some non-compression flotation material into my 1 mm suit, probably in small pieces to not obstruct movement, and then increasing my weight on my belt from the current 2 lbs to maybe 10 lbs..

Don

 

[efattah]

Been there

I had been toying with such ideas last year. In fact, my goal was to build a suit which increases in buoyancy as you descend, cancelling out the compression of the body, resulting in neutral buoyancy during the dive.

The secret lies in certain crystals, which undergo a phase transition at a certain pressure. This phase transition results in a greater volume than before. In water, such a phase transitions occurs with temperature; when the temp drops below 0C, the volume of the water increases in the form of ice.

Such a suit would thus have crystals embedded in the neoprene/rubber, or alternatively carried in a small flask somewhere. Ideally, the phase transition would occur near the midpoint of the dive, resulting in a sudden increase in buoyancy. Then, during the ascent, the phase transition would occur again, in the opposite direction.

The issues preventing such a suit from being built were:
- No crystals had the correct phase transition pressure (most would undergo phase transition around 600-2000m of depth)
- The % volume change of the crystals was small, about 5-10%

However, it is possible to build a pressure amplifying device, so it might not be impossible.

Otherwise, I investigated various flesh-like Shore A-00 urethane materials. They are extremely stretchy, somewhat insulative, neutrally buoyant, but they are very heavy; a 3mm suit would weigh 10+ lbs. They also tear very easily.

Eric Fattah
BC, Canada

 

[Tom Lightfoot]

Spermacetti?

I recall hearing a CBC radio show a number of years ago that described how sperm whales use that big bulb of spermacetti in the head to aid their ascent. Like water, spermacetti expands when it freezes but unlike water, it freezes at sea water temperatures. Sperm whales use their blood to melt the spermacetti on the surface, sink to the bottom, flood their sinus passages to freeze the spermacetti, and then float back to the surface.

I wonder if it would be possible to have a wetsuit with a streamlined backpack of synthetic spermacetti that could be flooded at depth.

Of course, having said that, it's probably much more practical and effective to have a mini air bottle and lift bag.

I've also heard of attempts to create wetsuit materials with microspheres as the insulating material. Microspheres don't compress so you wouldn't get a buoyancy shift. The trouble is that the rigid spheres don't bond well to the stretchy rubber matrix.

Tom

 

[Bill]

Hey Guys
I thought about this a bunch and even ran numbers for various configurations. The problem that came up is lungs. On the surface, +7 kilo. At 60 meters, +1 kilo. For tropical waters, the suit is about 1/2 of the lungs. More body fat and less neoprene? For northern waters, simulate the whales with a sandwich suit filled with oil. That's probably an engineering migrane.
I have a better solution, better for me. Have Tom and Eric and a few others join the 'Snow Birds' in Kona as often as possible. Warning, some of us didn't go home.
Aloha
Bill

 

[Tom Lightfoot]

Snow birds in Kona

Hi Bill,

I've already bought my plane ticket to Kona. See you in October/November I hope!

Tom

 

[Bill]

Tom
Win, lose or draw it'll be a blast. Just watching the best in action makes my day.
Aloha
Bill