Diving Performance - Beyond Drag (article Series And Discussion)

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Over on the Vintage Scuba Supply (VSS) site, we have a discussion going about different fin designs from Eastern Europe, and how that influenced current designs.
http://vintagescuba.proboards.com/thread/4032/back-basic-gear-european-dimension

Concerning the Jet Fin foot pocket, it was a lot better than the AMF Voit Duck Feet fins, which at the time of their introduction were its main competitor. But it does have a large dead area, and the "jets" don't do much of anything. The Jet Fin did not do well in my own fin trails.

SeaRat
 
Now, BCs are "standard equipment" needed on all dives, tropical or not. A thin wet suit doesn't loose buoyancy, and therefore doesn't need buoyancy compensation by an external device. We dove tropics with an inflatable vest or LPUs (underarm life preservers), but no BC. BCs now cost more than regulators, which is quite odd in my way of looking at things. I don't think there has been a decrease in fatal accidents for divers because of BCs either, and BCs were implicated in a significant number of fatal accidents:
http://www.rf30.org/final2012/wp-content/uploads/2013/02/Denoble-Diving-fatalities-by-numbers.pdf

I really don't mean to be an ass, but I think there's quite a bit more dives done per year nowadays than in 1970. Even then, you can see that the average value on the first 15 years or so is higher than on the last 15 years, which is also much flatter (for some reason).
However, didn't the first BCD pop up in 1970? Can't tell when they became mainstream though...
Not saying it's linked to BCDs, as I believe it has more to do with the training and reliability of gear.

As for reversing your Hammerhead, I'm not sure how well that'd work, I think your fins/body will be working against it and you might end up not moving at all.
 
Over on the Vintage Scuba Supply (VSS) site, we have a discussion going about different fin designs from Eastern Europe, and how that influenced current designs.
http://vintagescuba.proboards.com/thread/4032/back-basic-gear-european-dimension
That first fin shown is a nice looking fin design ("Гигант" (Giant) fins). I'd prefer to use it that over a Jetfin. Except for the aging issue, natural rubber is one of the best materials for diving fins with unparalleled toughness and great energy return. It's biggest issue is its relatively soft modulus which constrains the design parameters, but these fins look to me like they have a pretty good balance of design characteristics for a rubber fin. It looks a lot better than some of the gimmicky plastic fins we see in scuba shops these days.
 
In general, I like to use fairly small kick amplitudes. Comparing your kick in the picture above to my kick in the videos shows your kick is quite large by comparison. I don't know if this is your normal kick, or just happens to be what was going on when the picture was taken, but you may want to try smaller amplitude kicking to see how it goes. Different fins may respond differently as well. What kind of fin blade do your fins have?

As for blade stiffness, I think a scuba fin will lean toward a slightly stiffer blade than a freediving blade. Not all fin blades are the same. There is more to a good blade design than just blade length and an expensive FRP material. 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. It just feels powerful while bombing the bottom with off-axis waste momentum instead of pushing you forward.

This is the main reason most scuba fins are so poor at thrust efficiency. Take a pair of jet-fins and add an extra 8 inches of soft floppy fin blade on the end and it would probably make for a decent fin (except the foot pocket is still pretty cheesy).

I don't remember when the picture was taken. I do use a wider kick when changing direction or starting. My fastest swimming is done with a very quick narrow width kicks. Just swimming around it falls someplace in the middle. Looking at free divers, it looks like they use a slow rhythm medium width for almost everything.

I use fiberglass Leaderfins in medium flex. Their fiberglass medium blade combined with their foot pocket is considered the equal of other mfr. soft. Very affordable fin at $ 150 shipped to US from Europe.

What are your thoughts on blade materials ? Plastic, rubber, fiberglass, carbon ? Carbon fin fans claim the lighter weight and faster/stronger snap have a big effect.
 
What are your thoughts on blade materials ? Plastic, rubber, fiberglass, carbon ? Carbon fin fans claim the lighter weight and faster/stronger snap have a big effect.
I believe the design of the fin blade is much more important than the material it is made from. One could certainly make a totally crappy fin from carbon fiber by using a bad design. I was not impressed with these at all: Umberto Pelizzari Momodesign Omer

Personally, I think fiberglass is a better material for making diving fins than carbon fiber. I think it's structural properties allow for better functionality with a proper layup of the laminates. Carbon fiber is so stiff, that the material gets fragile before it gets the right amount of flex. Keep in mind that many "carbon" fins are actually fiberglass fins with a layer of carbon in there for aesthetics. IMO, carbon is more effective for marketing than functionality.

I went the route of making my own fins. That's what I like to do. If I were going to buy fins, I'd probably be looking at Alemanni fins, as some of my trusted bi-fin diver friends have very good things to say about them. I have not used them myself, but they closely follow the design characteristics that I found were important in my research. I have used and been impressed with Dive-R fins also.

Speedy fins - white - Fins | Alemanni Sub

The best fin design would probably not use just one type of material. I like rubber. It is tough and scratch resistant, but it limits the fin's design parameters because it is such a soft material elastically. It would be interesting to see a rubber fin with fiberglass spring parts molded into the rubber to overcome those limitations. The bigger problem is probably that it would be heavy, but maybe not much worse than other rubber fins like the Jetfins. By comparison, a pure fiberglass fin blade is pretty lightweight.
 
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In the 1970s and 1980s, the bifins and monofins used it competition finswimming in Eastern Europe were made with a rubber foot pocket and a tapered fiberglass blade (custom designed by the finswimmer). They used circuit board fiberglass (which was substandard by Western standards), which because of its quality could be "peeled." They would cut a segment, and peel off that layer of fiberglass. this became a custom-tapered blade that the finswimmers would use in finswimming competitions. These are still available (foot pockets for monofins):
Monofin Foopockets – Finswim World
Nemo pockets – Finswim World
Fiberglass Blades -Flat – Finswim World

We at the Underwater Society of America (USA),and I as Finswimming Director, presented the case for making Finswimming an Olympic Sport. We did not succeed (probably due to a lack of number of competitors in the United States, and possibly lack of commercial aspects to the sport). But the U.S. Olympic Committee was intrigued that we had a world-wide sport using mostly home-made, hand-made equipment during international competitions.

SeaRat
 
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The best fin design would probably not use just one type of material. I like rubber. It is tough and scratch resistant, but it limits the fin's design parameters because it is such a soft material elastically. It would be interesting to see a rubber fin with fiberglass spring parts molded into the rubber to overcome those limitations. The bigger problem is probably that it would be heavy, but maybe not much worse than other rubber fins like the Jetfins. By comparison, a pure fiberglass fin blade is pretty lightweight.

Interesting you mentioned a spring. I think that is part of the theory behind a longer blade plus fiberglass and carbon over plastic and rubber. They say fiberglass and carbon will spring or snap back faster/stronger. In a flutter kick, our legs up kick and down kick, but if the fin blade has some of it's own built in spring, it might make you go faster. I can feel my fiberglass blade snap back if I kick in one direction and then release without kicking in the other direction.

Many crazy very high priced carbon fins out there. Leaderfins offers a carbon and fiberglass sandwich blade like you describe, but also a pure carbon blade. Both are substantially cheaper than other mfr.. I know there is more to a quality blade than just the raw material, but their pure carbon fins are cheaper than other mfr. fiberglass fins and have been getting decent reviews.
 
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I really don't mean to be an ass, but I think there's quite a bit more dives done per year nowadays than in 1970. Even then, you can see that the average value on the first 15 years or so is higher than on the last 15 years, which is also much flatter (for some reason).
However, didn't the first BCD pop up in 1970? Can't tell when they became mainstream though...
Not saying it's linked to BCDs, as I believe it has more to do with the training and reliability of gear.

As for reversing your Hammerhead, I'm not sure how well that'd work, I think your fins/body will be working against it and you might end up not moving at all.
Controlling buoyancy has always been an issue ever since even the first wetsuits came out. Wetsuits crush down at depth and get heavy at depth, always have and always will no matter how trick the material was or is. Even Rubatex crushes down, maybe not as bad but it does, I know I have several of them.
Before some sort of marketable BC came along divers were always trying to figure out how to fix the heaviness problem. There were some pretty ingenious devices invented back then that never made it out of the garage like ballast tanks like a submarine would have. Then horse collars were modified and later made to use at depth to offset heaviness.
Most divers just compromised and would weight themselves light enough that they would start to get really light at a out 20' at the end of the dive. Safety stops weren't really considered for no deco profiles and divers would just float up as slow as the expansion of the suit would let them. Depths were limited to avoid crawling around on the bottom, even though there was a lot of that. Diving was hard you had to keep moving and streamlining was actually a consideration in that regard. Just look at all the covers and shells invented during that time that Cousteau used.
At some point the soft bladder dominated as the go to design for ballast and from there the first recognized poodle jacket came on the market. Some say it was the SP Stab jacket, that orange thing that was a sewn up vest with an air cell and it had a plastic pack sewn into the back of it which held the tank but the strap slots in the pack portion were not used. Instead the vest fabric was supposed to support the tank but it worked pretty poorly. For some reason this was overlooked and that style of product took off. They all copied each other and went to the wide panels of fabric to hold the tank to the diver but it never was very stable. At the same time as all this was going on scuba was being marketed to a whole new group of people, families and just regular people. It was no longer just for alpha type young males and a few women that could keep up. So this new style of gear was perfect for marketing and also relieved a lot of the "hard work" that was associated with scuba just a few years back. And it made it easier for instructors to teach since with push button ballast if a diver was a tad too heavy all they had to do was hit the elevator button and they were all set. Unfortunately this new device also IMO got badly abused throughout the years to what we have today, and yes, it bas been documented that people have indeed died because of abusing the BC in the form of gross overweighting. Not only have these new BC's gotten so complicated and over designed, they are also really expensive and they are very cumbersome. I think they are way too bulky, I think integrated weights are a horrible idea, and I think they are very counter productive to efficient scuba diving. Streamlining and all considerations for a smooth slipstream went out the window many years ago. All the obsessions with efficiency died out with the old crew many years ago. The newer divers who stepped in to the sport recently have no idea what scuba configurations used to be.

At least the BP/W is a step in the right direction, but I also think the flat or slightly bent doubles style plate is not completely optimal for single tank diving. IMO the tank needs to be dropped down into the grove in between the shoulder blades and the tank set a little lower. The modern doubles plates are too square and wide on top and don't allow the tank to snuggle in close enough, the plate rests across the high points of the shoulder blades. Those older plastic packs that narrowed down were actually a perfect design but unfortunately they went out in the garage sale along with all the rest of the old knowledge. If only someone invented a simple wing back then to go into one of those packs or a metal version I don't think we would be dealing with the abortion known as the modern poodle jacket today.

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?
 
We are seeing people cross over equipment and setups from different types of UW activities.

BP/W and octo on necklace is not just for tech divers. Recently changed my reg hose routing to under right arm with a 90 deg adapter after seeing a Dive Rite video. Very streamlined now.

Most of my diving is warm water on a boat. I switched to full foot fins yrs ago. Previously, people considered them only for snorkeling. On most of my trips, I now see boat crew all using full foots. My last trip, about 25% of the dive guests were using full foots. Faster, lighter, easier to kick, no stinky difficult to dry booties.

I see the above on my recreational dive trips more frequently than I used to. I think what is driving the changes is a combination of better functionality, less complication, better performance and ease of travel. The internet and people sharing their experiences/opinions has made it better for divers choosing equipment. Manufacturers have to have more than BS marketing for their equipment to be successful.
 
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
 

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