Why don't split fins work so well in current?

[Mavric]

I have read up extensively on fin types as I am trying to decide between SP Gorillas and either Apollo XTs or Atomic Smoke on the Waters. My confusion arises because all the tests and reviews that I have read with quantitative results show Apollos and the Atomic SOTW to generate the greatest thrust and speed. However so many (like pughio 83's post responders) advocate paddles for current. Am I missing something here? I dive mostly off the East coast of Africa so current will always be an issue. As a last Question I have pretty large feet UK size 12 (US 12.5) and currently wear XL SP Jetsports with 5 mm Akona booties which are a good fit-anyone else with larger feet had experience with the Atomic and Apollo sizing relative to SP please kind divers?

 

[dumpsterDiver]

It is due primarily to the Coriolus Effect. They will work reasonably well in the northern hemisphere, but almost no pwer at all below the equator, unless of course you are swimmingly co-lineat with the axis of rotation of the earth (either east or west).

 

[The Chairman]

We were having this discussion in another thread, and a few of us believe that your knowledge and skill in how to handle current is more important than the fin you use. Think of it as a game of Chutes and Ladders only you get to pick where you're going to land. You can use reefs and other objects to block the current or even use the current to your advantage. If you're working so hard that the fins make a difference, you're probably doing it wrong.

For me, fins should be fitted to your body type, style of kick and function on the boat. Big guys prefer non-splits because we can kick the hell out of the fin and we move. Unfortunately, if you kick a split fin really hard, the blade just collapses. To go faster, as in handling current, you have to kick tighter and faster and avoid kicking too hard. My legs aren't cut out for those high RPMs as they get their torque at much lower RPMs. Also, I frog kick almost exclusively and splits aren't the best fin for anti-silting techniques. That doesn't mean you can't do them and I actually developed a scull when I was diving Twin Jets, but backing up is next to impossible. They also aren't the best fin for towing, at least for me. When I want to move two divers through the water, I need to be able to kick hard and move. Again, the split fins are designed to minimize resistance in the water and so they are very soft and pliable. Not so good for a guy with tree trunks as legs especially with the amount of teaching and guiding I do. I have to be able to rescue people when THEY get caught out in current.

If your legs are always cramping, you have three choices. Exercise, change your technique or go with split fins. The easiest is probably split fins and there's no shame in that. In the end, personal preference and how you kick are the most important criteria in selecting a fin. In either case, you should learn how to manage currents in a way so that it doesn't really matter what fin you are wearing. Watch out for the chutes and learn how to find the eddies. Hug the bottom and dive smart.

 

[jar546]

What the heck, I'll chime in too.

I use my Apollo splits in a quarry and low, no current situations where we are on long dives and my knees need a break. I have also developed a technique with splits that allow me to do just about every kick but a backwards kick.
When I have students, I use OMS slipstreams because they are light and give good thrust up front. Sometimes with students you need some thrust.
In current conditions I use OMS slipstreams but have had the Apollo splits on and it was manageable due to my technique and abilities.
If you will be wearing doubles or need lots of lead to get you down, splits may not cut the mustard. Again, "may not"

If I was in a race, I would use the Apollo splits but I am not diving to race anyone. I have raced others and the Apollo splits clearly come out on top. I can generate serious speed with the splits even though you are a bit slow of the start until you get moving forward.

The bottom line is that fins are a very personal item and technique, ability, strength and conditions will vary performance so there are a lot of variables to contend with.

Some will swear by free diving fins and I can easily see why. They just don't travel very well.

The best thing to do is the try the fins out for yourself in different conditions and make your own decision.

 

[danvolker]

I have read up extensively on fin types as I am trying to decide between SP Gorillas and either Apollo XTs or Atomic Smoke on the Waters. My confusion arises because all the tests and reviews that I have read with quantitative results show Apollos and the Atomic SOTW to generate the greatest thrust and speed. However so many (like pughio 83's post responders) advocate paddles for current. Am I missing something here? I dive mostly off the East coast of Africa so current will always be an issue. As a last Question I have pretty large feet UK size 12 (US 12.5) and currently wear XL SP Jetsports with 5 mm Akona booties which are a good fit-anyone else with larger feet had experience with the Atomic and Apollo sizing relative to SP please kind divers?

NetDocs answer to you was right on. Beyond that, I would say DEMAND the ability to DEMO any fin you are interested in. You don't buy snow skiis without doing a demo first...you don't buy a car without a test drive.....When you want a pair of fins, you need a DEMO far more than you do for skiing or for a car. Whether the dive shop has to reach out to it's staff ( to let you borrow a personally owned pair) or their customer base, OR, you have to find a store that has demos available, I really don't think any diver should be willing to buy fins without this..... Particularly with this split fins issue. My feelings are that if you have muscle and aerobic power from training at cycling or another sport, you could not be happy with splits....they would just fold up under your power....If you really want fins great in currents, then check out what is popular in a place known for currents...i.e., in Palm Beach, the birthplace of "Drift Diving" in the world, freedive fins are commonly found on the divemasters or guides of charter boats, and on long time divers that like using what has been found to be optimal in currents. However, like NetDoc said, even with freedive fins, you need to learn to read the bottom to see where you should be at any given moment....optimally, you handle this like a whitewater kayaker handles reading a river....looking for places to edy out, for where they will traverse, and where they will travel quickly and easily.

 

[kidsdream]

The tough thing about comparing fins, is that various fins perform differently depending on the kicks stills and loading. Traditional blade fins are the most flexible when it comes to style (scissor, frog, shuffle etc.), but if currents are low, the better Split fins are more efficient due to their length and the impact of the flexibility etc.

I am basically a "frog kicker in nearly all cases, except when I need to move more swiftly in high current (or flow). I dive OMS Slipstreams for wreck and cave diving as this SP Jet style fin is good for this type of diving and are lighter than the SP variants. I use the Apollo's diving Key Largo. IMHO kick for kick in calm water you go farther per kick that than any other fins I have ever tried. They are very heavy so I usually don't travel with them. For non tech (or drysuit) travel or in current I go with Atomics.

For me, fins are like golf clubs, different fins for different diving.

Jeff

 

[diverdoug1]

Pendergast, DR; Mollendorf, J; Logue, C; Samimy, S (2003). "Evaluation of fins used in underwater swimming". Undersea Hyperbaric Medicine (Undersea and Hyperbaric Medical Society

This study showed that when the split fin designs were fused at the split, there was no degredation in efficiency, and will improve efficiency in some types of kicks. Divers with moderate to high levels of conditioning are better served using a stiffer, paddle style fin. Split fins will be easier for a poorly conditioned diver to kick, but will not be more efficient in current, and will need more kick cycles per unit of forwrd motion. A good way to think of it is to think of split fins being 1st gear on your 10 speed bike. It is easier to pedal, but you don't go as far with each cycle of the pedals.

 

[Mavric]

Thanks for the advice all-Dumpster, having studied physics at university I can only assume your post is a joke! Any advice on the size question though please?

 

[flots am]

Am I missing something here?

You will never get a straight answer on fin efficiency in actual use, because nobody I'm aware of has ever performed a study across various styles and brands of fins, using a machine designed to simulate a human diver, using equal energy input and motion for all the fins.

All you find are users that find a fin they like and swear they're "the best".

It's like Lake Woebegone. All the children are "above average."

The real trick to swimming into a current is "try to avoid it". Current is what boats and scooters are for.

flots.

 

[Orlando Eric]

My sherwood long splits are fast in non current short swimmers flutter kick but other than that my SP Jet paddle fins are more versatile. I have been training with the different kicks for the past two years and lobster diving is way easier with the paddles. Jupiter has some serious currents and I am now able to hold in place and use both hands for snare and tickle stick. This has made a huge difference in my catch to loster ratio.