Diving Performance - Beyond Drag (article Series And Discussion)

[John C. Ratliff]

Eric,

I'll only show you one, and then you need to buy Bill High's book.

I have some observations of double hose regulators in high current areas too. I have used them in what I would call extreme current in the Clackamas River, and they can be used. But the type of hoses are critical. The style used for U.S. Divers Company regulators were pretty flimsey, which is what Bill High was talking about. Thicker hoses, such as the "super-flex" hoses seem to work better. But the brand new, silicone mouthpiece doesn't work well in high current, as the mouthpiece itself bends and tries to remove itself from your mouth. The hoses of a double hose regulator provide significant drag when compared to the single hose regulator.

As I said, my best single hose for high current work is the discontinued A.I.R. I from Scubapro, but the D-300 through the series (D-450, I believe) will also work well. The only down side to the A.I.R. I is that it tends to retain a small amount of water in the regulator second stage, and if you go completely upside-down, that can become a mist going right down your throat. But in normal swimming position, it really holds well in a current, without free-flow.

SeaRat

 

[lowviz]

...//... I look for fins that have a soft floppy tip even on a stiffer fin blade (ie - it should have a lot of taper to the stiffness along its length). That soft tip is what makes the fin efficient. If the whole fin is stiff, it will absorb a lot of power, but won't efficiently convert it to thrust. ...//...

This post has gnawed at me since I first read it. Been messing with the concept ever since. In my world, it is called "impedance matching". Same reason why you can't remove your reg and holler at your buddy. You need an efficient way to transfer energy between two mediums. Blow up your glove and holler into that.

Given that, your fin tip should end up like water. I took a die grinder to my Mako's just to see. I'm sold. Notified Dano as he is one of the very few manufacturers who actually listens to and responds to customers. Let's see if he goes there.

REVAN, You are on to something...

 

[REVAN]

This post has gnawed at me since I first read it. Been messing with the concept ever since. In my world, it is called "impedance matching". Same reason why you can't remove your reg and holler at your buddy. You need an efficient way to transfer energy between two mediums. Blow up your glove and holler into that.

Given that, your fin tip should end up like water. I took a die grinder to my Mako's just to see. I'm sold. Notified Dano as he is one of the very few manufacturers who actually listens to and responds to customers. Let's see if he goes there.

REVAN, You are on to something...

The fins I made have a true composite blade construction. It's not just fiberglass. Its fiberglass where the properties of fiberglass are needed and plastic where the properties of plastic are better than fiberglass for the fin's dynamics.

Efficient blade dynamics will look fluid like this:

 

[lowviz]

I totally get that.

Do you know anyone who works in an aquarium? I'd so love to see a family of curves taken from a seal. Totally non-invasive. Just the curve of its "fin" vs. the applied force. Probably could be estimated from a good swimming vid.

I'd go straight to the experts for the stiffness profile...

 

[lowviz]

I neglected to point out a most important fact in my approach to all this. I'm not into chasing fish, I'm not into momentary acceleration.

I'm an older diver who is most interested in constant and efficient swimming. I have an upcoming project where this really counts. I wanted to love jetfins and their kin, but have come to see that they aren't for me. Dive Rites are the closest match to my requirements that I have found. However, not even they are perfect for open water trekking. The perfect long fins for me would likely not be ideal for a twenty-something hunter.

I would encourage the freediving suppliers to come up with an offering for the marathoners, you have the rabbits well covered...

 

[REVAN]

I'm an older diver who is most interested in constant and efficient swimming. I have an upcoming project where this really counts. I wanted to love jetfins and their kin, but have come to see that they aren't for me. Dive Rites are the closest match to my requirements that I have found. However, not even they are perfect for open water trekking.

I have found hydrodynamic efficiency to be useful everywhere. It's not just for chasing marine life. It pretty much makes everything better.
Please elaborate on what functional characteristics you are looking for in your ideal fins or other equipment. What do you hope to accomplish in your upcoming project that may be decreased by your present equipment limitations?

 

[lowviz]

OK, imagine I have a fixed amount of power to give to a propeller. Case 1 is very high speed, case 2 is very low speed. Two very different propellers would be needed for optimum power transfer.

I've been working towards diving a mountain pond that requires everything to be carried in. Thus, gas is a severely limited resource. The water is very cold and fins get stiffer. I hope to accomplish the best match in fins for this environment (slow swimming) in order to preserve gas.

 

[REVAN]

What depth are you planning?

I had a similar project long ago in the Cascade mountains (Snow Lake from Snoqualmie Pass). I worked on equipment for quite some time and practiced hiking with the scuba gear to try to get strong enough to get in there. In the end, I only dove the lake freediving. It was just too far a hike and too much elevation change to handle the equipment weight. I was able to explore down to 85ft freediving. The lake is a lot deeper than that, but by how much, I can't really say.

I grabbed this image from the internet of Snow Lake. It's deep and cold and an absolutely beautiful place in August.

I dove in Crater Lake several years back. I want to do that again, as all the video I shot in the lake got corrupted in the file transfer and I lost it. That one is a bit of a hike as well, but not nearly as bad as Snow Lake.

 

[lowviz]

We have a slightly different idea about what constitutes a "mountain" around here.

Still, a lovely place: https://upload.wikimedia.org/wikipe...e_Forest,_New_Jersey.JPG/1200px-thumbnail.jpg

 

[ronscuba]

I neglected to point out a most important fact in my approach to all this. I'm not into chasing fish, I'm not into momentary acceleration.

I'm an older diver who is most interested in constant and efficient swimming. I have an upcoming project where this really counts. I wanted to love jetfins and their kin, but have come to see that they aren't for me. Dive Rites are the closest match to my requirements that I have found. However, not even they are perfect for open water trekking. The perfect long fins for me would likely not be ideal for a twenty-something hunter.

I would encourage the freediving suppliers to come up with an offering for the marathoners, you have the rabbits well covered...

Have you looked at the softer blade freediving fins ?