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split fins for freediving?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Oct 14, 2003
i have never used split fin scuba style fins before, but i was reading some marketing propaganda about them and supposedly they help with fatigue and lessen o2 consumption but are slow on acceleration. i am curious as to why this concept has not been developed into super crazy long ass split freediving fins from some space aged composite... because the idea is bunk, and all marketing or what?
I tried several makes and models of splits awhile back. Slow cruising they felt nice, like nothing at all, kick a little harder and they go a little better. Turn up the juice and the more you put into them the less you get in return:head. This would not be good in current, or a surge and I'm usually towing something when I'm in the water, they're no good for that.

The short answer is, for my purposes splits inhale vigorously and standard SCUBA fins aren't much better, but I'm currently wearing O.ME.R BAT 40s if that information has any value.:)

The BAT 40s are a quite stiff fin. I suggest not getting them unless you're sure that's what you need.:)
In my own, humble, opinion:

Split fins suck

They are just flashy dive industry window-dressing to get people to drop their cash on somthing they don't need. Any basic full foot fin will work better than spit fins, and you can get a nice pair of freediving fins off of the Deeper Blue store for less money than you'll spend on a new pair of splits.

Again, this is just my opinion.

I do not think indole is asking whether split fins on the market are good for freediving. I think he is trying to get some opinions if the concept were extended to a new type of split fin that utilized freediving fin concepts, would it not be a more efficient fin?

I have asked this question of people before as well and the only answer I received was that freediving fins need to be able to move large amounts of water. Well we know this but it does not address whether a split fin could be made that moves the appropriate amount of water and at the same time takes advantage of the water vortex concepts.

Most split fins are very short because they were made for scuba with the intention of making the whole experience less exhausting. As far as I am aware they were not made for performance or fast swimming. However, in freediving we need efficient strokes that move lots of water. Well if the fin is actually more efficient (25% more some say) then why can the concept not be extended to freediving fins/monofins?

I have a pair of plastic blades that cracked at the base but are still connected to my footpockets. Maybe I will take a cut out of them and see if it changes the dynamics of the blade much.

Lets explore the concept of split fin as opposed to just voting on whether the industry did the right thing or not. :)


Most split fins are very short

Not the ones that I have seen. Some of the new spilt fins are approaching freediving fins in length!

I have used them both and will take a normal fin over a split fin anyday. A good test would be to play a quick game of underwater hockey in them and watch how people with shorter snorkeling fins swim circles around you.;)

So at what length do you imagine the split fin would have to be to get the same force out of the fin as compared to a non-split? Expressed in an relative term. Ie. 75% longer.
tylerz hit it on the head. i am not interested in current scuba style split fins for freediving, but more the vortex concept being applied to performance freediving fins. a lot of people say that the split fins they try are great for cruising and are more efficient, but cant go fast enough when pushed. basically, performance freediving can be seen as a proper ratio of O2 consumption to velocity, top speed is not as much of a consideration. So since split fins address using water vortex dynamics to increase _efficiency_ (see FREEDIVING), why and how could this be applied to OUR fins? as you may have noticed from other posts i am currently trying to make my own carbon fiber fins and i am trying to figure out if this concept will work for my purposes, but i have no idea how to do the calculations behind it.. i would assume the fins would have to be significantly longer like tylerz, but i have no idea. lets brainstorm....
How much longer do you want to go?

IF you look at a pair of Picasso Spinners or a pair of C4-80's you'll see that they are pretty darn long already, without even putting the split in them- although the Spinners have a slight V-shape at the end of them. There must be a point where 5' long fins just aren't practical for diving.

I think that real area to study would be in improving foot pockets desgins on monofins- that is an area that could use some help. OR you could try and come up with a custom moldable foot pocket for bi-fins. The ski industry has had them for years and I bet the dive fins could benefit from similar technologies.

The problem I see in applying a split fin to freediving comes from the properties that most folks require out of a freediving fin.

If you try the split fin in a pool or trial setting (like the fin line up over at rodales) they do show an efficiency increase in air consumption. I think that this is mainly due to the fact that there is less actual strain on on the leg when pushing through the water. So for steady swimming through calm water (like the tests) and an unlimited air supply (scuba) it's great. If you look at how someone swims with them they use a shorter, faster stroke similar to using an uphill gear on a bicycle. They are pedaling faster with less effort and when breathing regularly use less air.

Jon has brought up the shortcoming of the fins with his first hand knowledge via u/w hockey. Split fins do not generate much much "umph" from a standstill (or in general, like in a current) and this also results in difficulty in changing directions. All things required for u/w hockey.

When you look at freediving, most people like a stiff fin. I think this is because most freediving is done by short bursts of finning for power/locomotion, and then maximizing the glide phase for decreased oxygen utilization. For example, in a a cb dive down there is generally a hard kick at the surface to and a hard kick to turn at the bottom to change direction. In addition I try to limit the number of kicks coming up to to conserve air. I can do this because I have a large surface area on my fin that moves a resulting significant mass of water. To return to the bicycling analogy this is like pedalling on a straight patch of road. You want long, slow strokes to maximize the rest period between pedals. With a split fin I would have no rest time and would be constantly making short, fast strokes to produce the same net result. With scuba this probably results in lower total air consumption, especially since they can maintain their aerobic energy pathways longer because the load on their legs is less even though they are stroking more. In freediving, it's the opposite. The slower, harder strokes are more efficient especially since we drop to an anerobic energy pathway for most of the dive.

Please bear in mind this is just my conjecture based on my experiences with splits. Everyone is entitled to their own opinions. Even though I don't think that a freediving split fin would be beneficial I have to admit that I am interested in seeing a prototype for in-water test results.
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Interesting chit-chat guys,

Like the rest of ya, I'm not schooled in fluid dynamics. All I have is my experience. And my experience tells me that the split fin concept has no chance (at least using present-day materials). Truth is, I also think split fins are a gimmick, designed to appeal to [newbie] divers who have not learned proper finning technique. They are easier to push, so folks think that they are more efficient. If all this vortex talk is real, then why don't they make split-split fins, or split-split-split fins, or prehaps we should all be diving with a fine-toothed comb attached to our feet :). I just don't buy it -- how can a bunch of lateral movement thrust you forward :confused: .

That said, if you do make a prototype, don't be afraid to show it to us sceptics. I'd still love to see it :).

Originally posted by tmyers73
The opening sequence to the game has the main character freediving with a pair of split longfins

......and a mask he can't equalize - and without a nose clip. Seems that Santa's Workshop didn't do their research :D.
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