Diving Performance - Beyond Drag (article Series And Discussion)

[REVAN]

Now, now, that's not being very nice.

Sorry, but that popped into my head and it was a little too funny to pass up; (dangerous, because humor can easily be taken for cruelty on a forum).

I've always felt that the great thing about having speed is that it makes all your swimming easier, even if all you are intending to do is swim around at 1/2 knot or less. Just because you have speed, that doesn't mean you have to use it.

Think of it like a seat belt in your car. I imagine you will put it on every time you drive somewhere even if you are intending to not get in an accident. You clip on the belt just so that it is there in case it is needed. Besides, it doesn't really interfere with your driving. Similar, it can't hurt to strap on some faster scuba gear, even if you are intending to swim slowly. Like the seat belt, it shouldn't really interfere with your diving. Even if your camera is big an makes a lot of drag, at least you will have less which still lowers the total, and the fins will still be more efficient. I have a hard time seeing the downsides.

 

[John C. Ratliff]

I need to chime in here. Why? Because I have been scuba diving and achieving that cruise of over 2 knots for the last 30 years. I dive unconventional scuba configurations, including my own design of a BC. I will get into that later, but first we need to see what is possible for speed in the water. In the 1980s, I was finswimming director for the Underwater Society of America. Here is a bit about finswimming. How about you engineering types figure out the speed in knots of swimming 400 meters in 2:24.83, as this team from Ukraine just showed?


SeaRat

 

[ronscuba]

Holy cow they were going fast !

Tell us more about your scuba gear and BC ?

I understand some are not really interested in speed, but I think many are. I wonder what kind of diving and fins does fjpatrum use for him to think most scuba divers don't care about speed.

 

[REVAN]

How about you engineering types figure out the speed in knots of swimming 400 meters in 2:24.83

That would be 5.4 knots, and yes it looks very fast. But, think about that cold blooded sea turtle going the same speed. That should really drive home just how important streamlining is when you are in the water.

I'd like to see more about your custom gear if you want to share. What did you think of my kit?

 

[John C. Ratliff]

Okay, before we get into my configuration, take a look at immersion Finswimming, or Finswimming with scuba.


2:42.09 was the winning time for a 400 meter swim I underwater with scuba (this is not the world record though). Note that the very small scuba bottle is held in front of the fin swimmer, for streamlining.

What I'm going to do is to show some of my configurations over the weekend, then discuss where I think diving could go in the future. It's hard to do this on my iPad; I need to wait until I am on my main computer to do what I want.

Let me say that I have "skipped" the entire tech diving configurations because I don't like the lack of streamlining in those configuration. The emphasis is on redundancy and slow, cautious swimming due to the highly hazardous overhead environments. While I was a beaststroke swimmer in high school on the swim team, I find the frog kick in tech diving to be a very inefficient means of swimming underwater. But it serves tech divers very well in caves and shipwrecks where stirring up the water can be life-threatening. I say "skipped" because I have been diving since 1959, and could easily have gone into the tech diving kits.

However, for the last 30 years I have been river diving, working in high currents and under river rapids, so streamlining has been very important to me. For this reason, I don't dive a dry suit--too much drag. I usually dive either my own design of BC, the Para-Sea BC (see. My avatar), or no BC whatsoever. In the 1970s I dove a BC that was built into the back of my wet suit by Bill Herter of Deep Sea Bill's in Newport, Oregon (Bill's now passed away, but I want his name remembered by those in the diving community, as his ideas on buoyancy compensation have been used by the diving community).

I'll put more up tomorrow afternoon. By the way, just so you'll know, I just turned 70 years old, and am not only still diving, but also chasing fish. I can keep up with some of the slower swimming fish, such as suckers, the red-sided shiner, and northern pike minnows (which can be a rather large fish).

SeaRat

PS--I have uploaded two images, both taken in Clear Lake, Oregon. The first shows Bill Herter's wet suit BC, when I was diving twin AL 72s (yes, the ol' floaters). The second image shows me using my Para-Sea BC. Note how much more streamlined this BC is than a wing BC. The Para-Sea BC is also more streamlined than many BCs, being built to "hug" the diver's chest. I patented it, but have never sold it, so it became a very expensive BC (two prototypes, and I'm still diving them). The Para-Sea BC is Patent #4,623,316.

 

[John C. Ratliff]

That would be 5.4 knots, and yes it looks very fast. But, think about that cold blooded sea turtle going the same speed. That should really drive home just how important streamlining is when you are in the water.

I'd like to see more about your custom gear if you want to share. What did you think of my kit?

I like your kit, REVAN. I would enjoy trying it out in my dive site at the Clackamas River. I think the cowling helps on both sides of the tank (use longer hoses for the second stages). For those who are worried about access to the valve/regulator, turn the tank over so it can easily be manipulated by the hand swinging down, rather than reaching behind the head. (European divers used that configuration for a while in the 1950s, and at least one USA manufacturer, Scott, used it too.

When I'm diving configured for fast swimming, I use a single tank, my Scubapro Mark V/A.I.R. I regulator, with the regulator on the top plug and not on the side. This allows the regulator first stage to "look" directly into the direction of travel. I use a single steel 72 tank, which is the best tank in the water, in my opinion, right now. If I'm really into streamlining, I'll take the tank boot off it.

By the way, I do have a UDS-1 system from U.S. Divers Company, and it is a great system, and the tank's valves are reversed, being below. It is perhaps the best-designed open circuit scuba (after two defects were corrected--harness problems and buoyancy imbalance--6 pounds of weight on the top of the unit was required to keep it hugging the back of the diver) ever. Unfortunately, I can no longer dive it, as it has a much larger valve opening than anything else, and those are the older AL tanks, which require eddie current testing, but there is no eddie current tester for them.

For my underwater swimming, I do not usually use a monofin--though I have a training monofin left over from my finswimming days. But I find it very uncomfortable to dive. (Finswimmers must train for literally years to be able to swim as in these videos.) I swim with my scoop fins (my own modification), and use the dolphin kick a lot. I also use what I call a "Hammerhead Unit," which I'll get into in more detail later.

SeaRat

 

[Monofin]

Okay, before we get into my configuration, take a look at immersion Finswimming, or Finswimming with scuba.

2:42.09 was the winning time for a 400 meter swim I underwater with scuba (this is not the world record though). Note that the very small scuba bottle is held in front of the fin swimmer, for streamlining.
..........

I need to chime in here. Why? Because I have been scuba diving and achieving that cruise of over 2 knots for the last 30 years. I dive unconventional scuba configurations, including my own design of a BC. I will get into that later, but first we need to see what is possible for speed in the water. In the 1980s, I was finswimming director for the Underwater Society of America. Here is a bit about finswimming. How about you engineering types figure out the speed in knots of swimming 400 meters in 2:24.83, as this team from Ukraine just showed?

SeaRat

Revan calculated 5.4 knots. (Post #54.) That includes several reversals in the pool, decelerate, turn, accelerate. Top speed would be higher. I'm impressed. The 5 knot speed is achieved and that is with scuba gear. I like the streamlined face mask. Where do you find those?

Last week, on this thread, the technology to do this did not exist. This week, thanks to the speed of internet communications, not only are we swimming fast; technology is advancing fast.

I can see that revan and SeaRat have a lot of common ideas. Stay tuned here to see future developments. I expect the use of revan's Dol-Fin Orca could improve these speeds. Are there competition rules that limit fin design? I am not familiar with dive fin scuba racing.

Edit: Finswimming - Wikipedia, the free encyclopedia Yes there are specified mono and bi fins in addition to other equipment requirements.

PS: Note that SeaRat calls 5+ knots cruising, not sprinting. 400 meters in water is a bit of a swim even if it is not long range cruising.

 

[REVAN]

Last week, on this thread, the technology to do this did not exist. This week, thanks to the speed of internet communications, not only are we swimming fast; technology is advancing fast.

It did not (and still doesn't) exist for recreational scuba diving. While impressive, a 13 cubic foot pony bottle is not going to cut it for the divers on this forum. Also, I referenced underwater orienteering equipment in my paper. That is similar, but with a larger tank and navigational equipment. Orienteering equipment is closer to what recreational divers need, but you can't really do anything other than navigate and swim as the hands are slated to hold the tank for the entire dive, and those hyperfins are notorious for destroying feet. For recreational diving, the gear needs to become more user friendly and utilitarian.

 

[REVAN]

This is a CMAS event that I haven't seen before, until now. This is pretty cool and looks to be a great venue for people to hone their skills as a diver and to develop training skills and techniques that will actually make them better and more proficient divers. We should have this here in the Americas.

 

[John C. Ratliff]

Revan, you are correct, in that the finswimmers do not help finding this for recreational divers. But I wanted to show the outside limit on swimming speed. Your look at underwater orienteering was a great example too. Not too many people know that in Europe, Asia and other areas of the world these games are very competitive. Underwater hockey is popular in pools in Canada, as they cannot get into the water much in the winter. Here are the finswimming records from CMAS (the World Underwater Federation).

Records
The World Record for 800 meters immersion looks like this:
800 05:46.96 VILHELM Szilard 1983 HUN 28/07/2010 KAZAN
That (05:46.96 for 800 meters) is probably the outside limit for humans for a cruising speed.

Before talking about the Hammerhead Unit, I'd like to spend a few minutes on swim fin design. I started experimenting with a different type of blade in the 1960s. I was convinced that the flat blade that we used then, and actually still use today, was not the most efficient way to move a diver through the water, independent of the type of kick used. I developed what I now call the "scoop fin" design. With the scoop fin, which anyone can duplicate, I removed the flat blade, and replaced it with a tapering flexible membrane. Several years later, when I was looking to patent the concept (it was already patented, by Mucdock, Patent #3,411,165), I made this analysis:

I converted a pair of AMF Voit A66 fins to the scoop design and made these photographs of how the water flows on the fin:

Note that the water flows down the blade, and out. It doesn't roll off the edges like with normal flat blades.

Freediving fins have a longer, flat blade, and work differently, using a rolling motion to ensure that the water flows back. But even today's "channel" fins do not duplicate what I did years ago, and continue to use today. You can see some of my more recent blade modifications below.

I have also enclosed an Excel spreadsheet with three headings. The Fin trails 3-12-2010 were conducted using identical fins, except one was the blade, one was modified to be a split fin design, and one was modified to be a scoop design. You can see these fins below.

The second heading wis "Fin Trails 3-13-2010" and included the Quattro Excel, Jet Fin, White Stage Super Stag, and that Super Stag fin modified to be a scoop design, the Jet Fin & Jet Split Fin combined (I found that fin in the river, with a spring heel that had caught on a rock and the spring was then about 3 feet long after being subjected to the river's floods over a winter), USD Rocket fins, and the Apollo Split Fins (full-foot variety).

The final tests were using the full-foot PlanaPlus fins, which were the same fin modified twice (split and scoop). Take a look, as I would be interested in your feedback.

SeaRat