Diving Performance - Beyond Drag (article Series And Discussion)

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Also, looking over the same diagram, a nylon tank strap and the huge clamp is a disaster as far as drag is concerned. Times 2 in a lot of setups.
Perhaps a single stainless steel band wth a latch placed out of the flow? Has to be better.
SS
Yes. This is how it used to be done in the old days. I have some old Daycor back-plates from the early '60s that used a single SS strap that's probably only 0.020" thick to secure the tank. It tightens down with wing nuts that are under the back plate and completely hidden from the flow. This is a reason why some people are attracted to the vintage gear. Back then, they knew that hydrodynamics was an issue, but they were limited on what they could do about it. I think the manufacturing tech exists to do something better now, but the people who remembered that it is an issue have all left the industry or just gotten old and died. Those who took over the industry, grew up accepting that drag is normal and believing that we just need to live with it. My whole message is that this is not true. There are things we can do that are effective for both performance and cost.

PS - I actually used these old Daycor back plates as a design reference for designing my back plate. I also reused the webbing from one of them. However, I used a standard CAM band for convenience, as the SS straps are sized for steel 72 tanks and too small to accept an aluminum 80.
 
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I don't know what kind of speeds I was able to achieve when I decided to streamline my kit just beyond the basics.
But what I ended up with was basically a plate, a tank, two hoses run off a small compact Conshelf 1st stage with the hoses run down at an angle, one was the first stage hose which went under my right arm and the other was for the SPG which went down the left side and either clipped off on the waist belt or later I got rid of the clip and just tucked it under the waist band up front. This minimized any and all hose drag I could think of the best possible way. The only other solution would be to rely 100% on electronics and go AI hoseless on the SPG thus eliminating another hose so That would take it down to one hose. For the dives I do I would be OK with that. For right now I just use a wrist computer, and of course a compass on the other wrist. That's the other thing, a really nice wireless PDC will have a built in compass so another item could be eliminated. Next, I picked a freediving suit because the beaver tail cut with attached hood is the most streamlined and warmest configuration I could come up with. For fins I use Picasso freediving fins, which will be changed in the future at some point for a better fin. I use homemade 7mm rubatex socks that I made from an old wetsuit (cut appart a set of other socks and used the panels as patterns). I'm also using fin keepers with those.
Then a rubber weightbelt with all the "tails" trimmed back so there isn't any loose flopping material sticking out.
No ankle weights, don't need them. No snorkel unless it's a kelp crawl dive to get out, and then it's the most basic "J" style I could find.
So that's about as basic as it gets. If I plan to go deeper I put a wing on and that adds another hose, but I suppose a guy could orally inflate when needed if desired eliminating the hose.
I do notice I am faster without a wing just by looking at the ground go by, but I have no way as of yet to measure speed. I thought maybe a speed wheel could be used somehow mounted somewhere to measure water speed, that would be cool just for giggles.
I like the option to go slow or fast. Just because somebody is set up for speed doesn't mean they have to go fast every dive. But it does make going slow even more effiecient. More air saved is a good thing right?

I also feel that a very minimized configuration is safer for me. I like being agile and having the ability to move freely enough to be able to get out of a wash by some rocks, or if I pop up in a bad spot to have the speed and manueverability to get the hell out of Dodge fast! So in this respect less is more. With a standard configuration I feel like someone threw me in the water in a straight jacket or tied me up, I can't move and I get really unnerved. I can only imagine how unnerving it must be for a new student to be be packed into all that crap plus overweighted and find themselves in such a position.
But this could be unique to where I dive too.
Not everywhere in the world is like the CA north coast.
 
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And Revan, if you can get a reg to self purge under your own power, dude! That's bad ass!!!

I think your market will be young guys looking for the newest cool stuff.
Forget about the fat old farts that only care about going slow. The reason they like slow is because they CAN'T go fast. The problem is the sport is kind of dominated by the middle aged right now (me included). But at least I'm young at heart, in shape, and a forward thinker.
 
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There was a company that used to make speed measuring impellers for kayaks. There were a few people who would better waterproof the electronics for operating underwater at pressure and use them while scuba diving. It was a great way to measure how fast you are swimming. GPS receivers eventually got so cheap that it was less expensive to use GPS and they no longer make these nice kayak instruments. If they were available and people were getting feedback on how fast or slow they are going for a given effort, they may be more aware of performance metrics and care about the results.
 
And Revan, if you can get a reg to self purge under your own power, dude! That's bad ass!!!

I think your market will be young guys looking for the newest cool stuff.
Forget about the fat old farts that only care about going slow. The reason they like slow is because they CAN'T go fast. The problem is the sport is kind of dominated by the middle aged right now (me included). But at least I'm young at heart, in shape, and a forward thinker.
I've found that the Scubapro A.I.R. I regulator is almost immune to free flow from forward movement. This is because the diaphragm is behind the body, and not in front of it. I have used the A.I.R. I since it was new, in about 1985, and it is a wonderful breathing machine.




It performs extremely well, as the entire diaphragm is the exhaust valve. When I do my underwater swimming in the Clackamas for speed, this is the regulator I use. It is also very streamlined in my mouth, and the current has no effect on the second stage. I have stuck my head in a creek flow that was quite fast (Steamboat Creek, North Umpqua River) to see trout in the creek. The flow was more than 3 knots, by far (I was holding onto rocks when I stuck my head up into the current to see above the pool).

It has a "Dive/Predive" switch, which is why there are two different measurements above. The switch can be used on the surface to prevent free-flows.

SeaRat
 
I'm finding that my regulator is far from ideal for the setup I'm now using it in. If I make it back to DEMA this year, maybe I'll start looking for something more appropriate to use with this kit.
 
As far as modern regs go I would guess the Poseidon style sideways reg would be the best anti self purge reg. Other than that a double hose (Kraken) would be the other option? I don't know what kind of drag two corrugated hoses would create but it may be more than a thinner single hose. I would also think that the larger floppier hoses may develop a wobble at higher speeds.
 
As far as modern regs go I would guess the Poseidon style sideways reg would be the best anti self purge reg. Other than that a double hose (Kraken) would be the other option? I don't know what kind of drag two corrugated hoses would create but it may be more than a thinner single hose. I would also think that the larger floppier hoses may develop a wobble at higher speeds.
Eric,

I'm not sure of the Poseidon for currents, but it would be better than a double hose regulator. Here is Bill High describing diving on trawl nets for research in 1958:
I dove on a trawl from the University of Washington's fishing research vessel Commando in 1958. Dale Dean and I used state-of-the-art double hose regulators. We promptly discovered that design could not supply adequate air at the three knot towing speed. Those soft hoses bent closed from the force of passing water. Mostly, our objective, once we got onto the net, was to survive that first dive. Our meaningful observations were few indeed. Later, on loan from the IPHC, I made a number of dives with McNeely's Bureau of Commecrial Fisheries (BCF) team.

The BCF divers did not make direct contact with the trawl. They rode in an undersea sled desgined by Dick, towed from th efishing vessel. By considerable maneuvering, the sled was guided near the net, allowing some direct observations to be made. Having previously dived directly onto a net by hanging onto the web, I was confident even if not proven by test, that I could freely and quickly move to any part of the net worthy of study. However, most people, even other members of the BCF dive team, considered that too dangerous because the variety and magnitude of possible dangers had never been identified.

I considered the sled unacceptable. It couldn't go quickly to where I wanted to be. From the sled we were lucky to make one meaningful observation per dive and I felt sure that by pulling ourselves over the dynamic net, we could reach all parts on one dive. The boss still said no in spite of my rationale. Finally, I couldn't stand the limitation any longer. While Dick piloted the sled along side of the net, I reached out, firmely grasped the net and bailed out of the sled. I'm certain Dick was horrified. However, the freedom to move was complete. Hand over hand I roamed far and wide as the ship pulled the net through the ocean.

Watching me convinced Dick that riding the trawl was a better way, especially if we could eliminate the sled altogether. Later I tied big floats to the net leading wing tips with enough line to reach the surface. The dive team jumped into the water ahead and in the path of the already set net. We descended down the buoyline until the net was reached. Then our detailed examination of the net and fish entering the net's influence occupied the entire available bottom time. Surfacing was too simple. By releasing our hold of the net web, the net pulled away leaving us free to routinely ascend to the waiting skiff.

On one early occasion, I pulled myself forward on the net, moving slowly against the strong water force, until I reached one otterboard (door). cautiously, I proceeded onto the door itself, a spot we believed could be disastrous dfor a diver because of the great turbulence it created. The dangers were real but presumably predictable so I accessed them as carefully as my experience would allow. Next, I moved hand-ove-hand ahead of the door and discovered that by good training, careful planning and strict attention to the obvious davgers, we could descend directly along the net tow cables from just behind the fishing vessel down to the door, past the door with its dense silt cloud and onto the net, thereby cutting out a great deal of lost time and prematurely consumed air.

At long last, we could quickly and efficiently study an entire trawl on a single dive. We science divers thereafter jumped into the water from the fishing vessel, descended olang the tow cable, assessed the function of the door as we passed and continued on to the leading edge of the net. Mnay hundreds of net divel were safely performed using that technique and I trained numerous other fishery scientists to conduct trawl dives in their own regions. Well, that is the background to trawl diving, now let us deal with some of the noteworthy events that happened while carying out those dangerous dives.
High, Willaim (Bill) L., Beneath the Sea, A Sampling of Diving and Other Adventures, Best Publishing Company, 1998, pg 161-2.
There is a photo of two divers on the trawl using single hose Calpyso regulators, and single steel 72 tank, sans BC or vest.

SeaRat
 
https://www.shearwater.com/products/peregrine/

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