What's wrong with Split Fins??

[JeffG]

Perhaps because they produce less fatigue, less cramping, greater comfort, and a more enjoyable dive?

(oh... that's based on diving... I don't have any propeller head data on the cramping/comfort factor...)

I don't disagree...But why do they have that effect? and what is the consequence of that?

 

[Bobby]

I have both, atomic splits and turtles(and oms slipstreams wich are pretty much the same thing...) splits are easier on the calf muscles, and I equate them to a car with no 1st gear but a real nice overdrive. You can swim real fast but it might take you a little while getting up to speed. Paddle fins have a lot of torque, imagine an work truck that can haul a lot of gear and will smoke the tires a block long but max out at fairly low speed. If you only plan on tropical vacation style diving (chasing the pretty fishies) with color coordinated gear, you would PROBABLY be happier with splits. If you get into tech diving or possibly photo(better fine control), you will want paddles.

Very good question. First there is nothing wrong with split fins, they are a tool and if applied for the right reason they are the tool for the job. Having said that lets look at the difference between split fins (hinged has the same function) compared to blades.

Most divers and especially new divers tend to over kick (use too much leg action) when they use their fins. This puts strain on leg muscles that are not used in the same way when we walk on solid ground. This quickly tires divers and causes leg cramps. Split fins release energy put into the fin that can not be imparted to propulsion. For new divers or divers that have not put time into fin technique they are a very usefull tool. NOTE!! I am not saying that all divers that dive split fins have not put time into their fin technique, I am saying that they have a lot of benefit for those divers that have not. It also takes more practice to master other more advanced fin techniques such as the frog kick, helicopter kick and back kick. It can be done but requires more practice to make them work.

Now having said everything above most technical divers prefer a short wide stiff blade style of fin. There are a couple of reasons for this prefrence. Technical divers tend to have more gear and mass in the water. They also tend to get into environments that stirring up silt can be hazardous, the shorter stiff blades tend to be easier in not stirring up silt. With practiced and proper fin technique the blade style of fins will give more efficient propulsion with less effort. On longer technical dives any small amount of saved energy results in less gas consumption which is more critical on more taxing dives.

Sorry for the long winded response, I hope that it gives you a better understanding for your fin choices. In closing I would suggest making your decision on what you feel fits you best for what you are doing now. There are many different types of diving that may attract your interest, as you progress and learn more there will be times that you replace equipment that no longer fits your needs.

Combined from an earlier post of mine and someone elses post to make it a more clear thought process.

Bobby

 

[JeffG]

Paddle fins have a lot of torque, imagine an work truck that can haul a lot of gear and will smoke the tires a block long but max out at fairly low speed. If you only plan on tropical vacation style diving (chasing the pretty fishies) with color coordinated gear, you would PROBABLY be happier with splits. If you get into tech diving or possibly photo(better fine control), you will want paddles.

and what might be more important than much of this is the fit of a fin.

I had Turtle blade fins that didn't fit very well. The transfer of power from leg to fin sucked (to say the least).

 

[RonFrank]

Luckily for me I don't usually have to fight the currents, rather I just go with them.

I can't imagine that any fin is really good to fight a strong current if it's sucking you down, or sideways, or anyway.

In Coz I kicked into the current on a few occasions. I was able to do so more effectively than some, but I have no idea if that is due to using BioFins, or because of many other variables.

I agree with Howarde, if you are fighting current, you are loosing, I don't care what type of fin you have. A Barracuda can strike at 40+mph. Dolphins have also been clocked at 40mph. The best we can hope to achieve is MAYBE 4mph for VERY short spurts. You kinda see how LAME we are UW, and how silly all this debate is?

If the current grabs you, unless you have a motor attached to your feet, you are not going to do much!

I have dove both, and continue to dive Apollo BioFins. I agree they do NOT have the traction of Jets, but I can do every kick I want with them with one exception, backing. I can back up with them, but it's very difficult and I'd have to work a lot more to become good at that. They also flop around more, so one has to be careful about kicking, and hitting the bottom.

If Scubapro made a foot pocket that was even close to as comfortable as my Biofins, I'd buy a pair tomorrow. They don't and I find Jet foot pockets uncomfortable, so I won't ever buy a pair.

Comfort is a KEY factor to fins, just like most personal gear.

 

[SelkieDVM]

Comfort is a KEY factor to fins, just like most personal gear.

Very good point.

 

[BKP]

I don't disagree...But why do they have that effect? and what is the consequence of that?

Couldn't tell you "why" they're easier on the calves and SAC -- I simply don't know... Perhaps it's the much lauded 'propeller vs. paddle' effect...
Apollo has a litany of reasons posted on their site, having to do with the 'propeller' effect of the twin/split blades.
Some of the dive mags, Scuba Diving in particular, have posted similar results...

As for consequence, I believe you give up some of the fine tuning in turns (not especially consequential for me), and perhaps frog and back kicks (also not especially consequential for me).

Comes down to the same old end-game... whatever works for you...

 

[Web Monkey]

Web Monkey - I had SP yellow and grey ones. They are very, very soft.

They're all really soft, except the black ones.

Terry

 

[SparticleBrane]

Couldn't tell you "why" they're easier on the calves and SAC -- I simply don't know... Perhaps it's the much lauded 'propeller vs. paddle' effect...
Apollo has a litany of reasons posted on their site, having to do with the 'propeller' effect of the twin/split blades.

I'll bet it's because there's a hole down the middle, and they're floppy so they're easy to push.

 

[CBulla]

Question:

To all of those who say that split fins suck... have you ever even tried them, or do you just regurgitate the rhetoric you hear elsewhere?
...how about some real comments?

I have tried them and found the kick cycle to be mushy. For frog kicks it felt (I can't see my legs, so I'm guessing here) as if I were having a hard time getting a solid cycle with that as well. Backing up happened at about 1/3 speed as did the helicopter turns. They actions did occur, but it took considerable more thought and time to create the result. I came to the conclusion that for me they would be a suitable fin for drift diving but not for dives where more movement is required.

Conversely, I have a dive buddy (Reefguy) who is rather proficient with these fins.

 

[SelkieDVM]

Here is the response I got from my engineer friend at Duke. Ok, so he's actually my brother. He attached three studies in pdf format which are too large for me to attach here, even compressed, unless someone who is more computer-savy can tell me how to do it. Two are in the 400-500 kb range and one is 700-800 kb. I personally only skimmed over the studies but his email below explains the gist of them.

Hi Lilla,
Here are a couple of papers I have handy. Split fins (with the split running the length of the fin) are inefficient. The split fins place the shed vorticity in the water in an orientation that serves no useful thrust purpose. BUT other fins are not much better. Most fins fall in the 8%-12% efficiency range.