Diving Performance - Beyond Drag (article Series And Discussion)

[caseybird]

As far as putting the kit on, it's not much different from a standard kit. It free stands on its own, probably with more stability than a typical kit because of the tripod foot on the tailcone. I can put it on with it sitting on the ground, at bench level or table top level. I've tried each of these and all these options are viable.

Do you have any images of the tank/tailcone set up for donning? I'd love to see it in practice.
Thanks

 

[REVAN]

Traveling has become a big concern and it is one of the hangups people have to long blade fins. In the water they are awesome, but they don't fit in the standard gear bag. I made my fins modular to fix that. Two screws removed and my fin is the same length as a regular scuba fin. If I want to remove more screws, I can get it down to fitting in a carry-on bag.

DPVs don't travel well at all. If you are going to dive currents while traveling, what I'm doing is a lot less expensive and less headache than trying to take a DPV along on the trip.

 

[REVAN]

Do you have any images of the tank/tailcone set up for donning? I'd love to see it in practice.
Thanks

I'd have to take some picks. What do you want to see? Just the kit freestanding and ready to put on from the strap/harness side?

 

[John C. Ratliff]

...What would be really cool would be a ballast system that was hidden or somehow integrated into the torso area of wetsuit. I think for optimal drag resistance even a small wing produces some drag. I found that the channel in between the tank and the bare back of the no BC diver is an important area for water to channel through. This would be the area that the wing would normally occupy.
I know for most divers this is really splitting hairs, but for drag obsessed divers this is a problem.
Maybe at some point in the future hydrodynamics and efficiency will make a comeback, who knows?

Eric,

The wet suit with a built-in BC bladder has already been done, in the 1970s. I owned one and finally gave it to the Winston-Dillard Fire Department's Water Rescue team in the 1980s. Bill Herter built these into his custom wet suits. He started out with an inverted "U" in the back of the suit, which I bought. He then went on to make the back of the wet suit (all the white part in the below photos) into a BC. He did that by sandwitching two 1/8 inch neoprene skin-one-side layers and using seam tape and neoprene cement to make them air-tight (seam tape, for those who have never seen it--it doesn't exist anymore--was open-celled neoprene about 1/8 inch thick on one side, with closed surface on the other side). He would use the tape on the inside and adhere it to both sandwitched layers, which also had been glued together. It formed the most streamlined, best back-mount BC ever designed, IMHO. In the photos below, I am using it is the Siletz River, Oregon and at Edmonds Underwater Park, in Washington State. I wrote a paper for IQ6 (the Sixth International Conference on Underwater Education) and included the following drawings for my paper, "Comments on Buoyancy Control and Emergency Procedures." That drawing (Buoyancy Control001) was re-drawn by Jim Mitchell for the published paper (Buoyancy Control002). You can see that Jim Mitchell, when he re-drew my drawing, went from Bill Herter's concept of a wet suit integrated BC to a tank-mounted BC wing with much greater drag. I don't think anyone out of our small group ever know much about Bill Herter's BC. If you wish, I can make a PDF of that paper and post it here.

SeaRat

 

[ronscuba]

There has been a lot of discussion of fun pocket design, why do you prefer full foot?
Are there any paticular issues with a full fit that a strap design doesn't have?
Are there any widely recommended models?
Thanks

A full foot fin has better energy transfer since there is no slop between the foot and the fin. Open heal fins use a boot. Take a look at your open heel fins. Most have openings shaped like a square. For warm open water diving from a boat, a flutter kick and full foot fin is much faster and efficient.

Downside is finding a proper fitting full foot fin is not as easy as open heel, they are not meant for cold water or shore dives and their softer blades work best with a flutter kick. You want full foot fins to fit like a glove. Some wear a lycra sock to prevent chafing. Mares Superchannel are a popular full foot fin.

Speaking of the flutter kick and softer blades, I think the popularity and performance increases that we saw with split fins was mainly due to the blades flexing more easily. Flutter kickers saw a performance increase. Frog kickers generally hated split fins because frog kicks work better with stiff blades. Now I see flutter kickers using hinge fins. IMHO, it's not the split or the hinge. It's the end result of the blade flexing easier that makes people go faster when flutter kicking.

 

[caseybird]

I'd have to take some picks. What do you want to see? Just the kit freestanding and ready to put on from the strap/harness side?

I would like to see it rigged, ready to don.
Thanks

 

[John C. Ratliff]

The one thing that Ronscuba did not say is that full-foot fins do not have the drag created by the foot pocket of the open heel fins. The water parts around them without forming current eddies around the foot, allowing more of the force to be applied to forward motion.

Concerning the straight blade verses the split fin, the split actually "channels" more of the water rear-ward than the stiff blade fins. I took the same fin, an Avanti full-foot fin (I'll have to check that--this is from memory) and tested the three exact same blades against each other (unmodified straight blade, split (by splitting the blade), and scoop designs, and the split blade out-performed the straight blade, but was not quite as good as the scoop design. The reason tech divers like the straight blade is that they use it differently, with a frog kick, that uses the entire back-side of the blade to push water backwards.

SeaRat

 

[caseybird]

I'd have to take some picks. What do you want to see? Just the kit freestanding and ready to put on from the strap/harness side?

I would like to see it rigged, ready to don.
T

A full foot fin has better energy transfer since there is no slop between the foot and the fin. Open heal fins use a boot. Take a look at your open heel fins. Most have openings shaped like a square. For warm open water diving from a boat, a flutter kick and full foot fin is much faster and efficient.

Downside is finding a proper fitting full foot fin is not as easy as open heel, they are not meant for cold water or shore dives and their softer blades work best with a flutter kick. You want full foot fins to fit like a glove. Some wear a lycra sock to prevent chafing. Mares Superchannel are a popular full foot fin.

Speaking of the flutter kick and softer blades, I think the popularity and performance increases that we saw with split fins was mainly due to the blades flexing more easily. Flutter kickers saw a performance increase. Frog kickers generally hated split fins because frog kicks work better with stiff blades. Now I see flutter kickers using hinge fins. IMHO, it's not the split or the hinge. It's the end result of the blade flexing easier that makes people go faster when flutter kicking.

thanks, very helpful.
I was looking at those fins online. Seemed to fit the descriptions of an ideal fin at a good price point.
I've been diving splits since my first dive trip in warm water in 2000, twin jets I think. I find them very easy to dive with, and I can perform a good helicopter and back water with them. I am interested in some of the points you mentioned about the full pocket fins.
How do these fins handle turns and backwater? Or is the main advantage better speed?
Thanks

 

[REVAN]

I would like to see it rigged, ready to don.
Thanks

@caseybird : I think that Dan Volker said that his Dive-R long blades back-kick better than his jetfins.

 

[REVAN]

This is what Dan had to say about my fins:

I dove Ron's new Bi-fin prototypes yesterday.....And I have to say WOW!
They are faster than my DiveR's when I want to go "scooter cruising speeds"...and when I want to go medium speed or slow, they feel very comfortable.
They are best at flutter and dolphin, obviously with their heritage....but Frog kick just fine....not quite as good as Dive R's( which frog kick as well or better than jet fins) and Ron's fins Helicopter turn well....Reverse kick will require me to develop a different kick shape....which is something I had to do with the DiveR freedive fins also....Ron's fins are different enough, so that I can't use the same kick shape I am used to for reverse kick, so at some point when I have more time, I'd see about what angles and articulations work the wing technology blade better for this.
I see these fins for hunters, or videographers, or even photographers doing wide angle of large marine life.
I spent some time following Sandra while she was doing a macro dive at the BHB with these, and going dead slow or hovering was very precise with them...It would be nearly impossible for a decent diver to silt with them. You would have to really try and do something stupid. But I don't see macro divers , or divers that insist on swimming as slowly as they can, wanting Ron's tech, or even freedive fin tech. They just won't use it.


All in all, this is a fin I want to add to my "Golf-bag" of fins....and hope to in the near future. There are a lot of dives where this would be the "right club" for me

Today, the plan is to do some freediving with Ron, and I will be using the bi-fin with the extra stiff bade attachment....just to see if there is a benefit with this. As of this moment, we will do either the BHB, the pump house, or possible go out on Keylypso with Jim Abernethy....will know in a couple hours if anyone wants to join us