Split fins

[Douglas]

When diving, one can't really compare efficiency over split fins as generally one is recreationally diving for fun, but in the pool (I do this once a week as the sea is a long way off), my (Space Frog One) fins beat the socks off the split fins.

'cause that's just my opinion, I could be wrong - or just stronger


Doug

 

[budgy]

I have never tried split fins they don't seem to have made much impact on our club scene yet. Atomics are distributed by Seac Sub over here and the Force Fins by Poseidon, I would like a chance to try them.
Regards kicking up silt could it be more to do with our fin stroke?
I observed a diver with paddle fins finning over a sandy bottom about 4 to 5 ft above the bottom and noticed small craters appearing on the bottom. I thought the fin stroke was long perhaps 12 to 18 inches or more. I wonder what the effect would be if the diver had used a short stroke flutter kick, or scissors.
I tried a flutter kick with old style jet fins and was pleased with the result, I seemed to get good speed and did not get cramp.
I have not been able to get the rhythm right with quattro's, but its early days.

 

[devjr]

Yo, Pug, do I blow out the bottom with splits? Don't know, that's why I'm here, to learn something or at least learn what to look for.

It's not a personal issue because I rarely swim a few inches off a sea bottom. Moreover, any silt generated would not be a concern. There was a time when I dived deep Chesapeake wrecks which were covered with silt and rusty crud. Silt was a nettlesome thing and difficult to control. It aggravated the diffusion from our lamps and dropped the already low vis to near zero at times.

For some reason, all issues surrounding splits rouse up a lot of noise. I'm trying to figure out what's going on technically with the new fin, how and why it works and if any of these anecdotes, yours for example, are based in fact or are defects of observation, or imply some unknown parameters of the fin. Also, I would like to know if the company is truthful. Sofar, I have the Rodale report and the Biofin infommercial. Among thousands of members one might suspect some answers are out there.

Ciau.

 

[Uncle Pug]

Originally posted by devjr
For some reason, all issues surrounding splits rouse up a lot of noise.

Hi Devjr...
Seems as though all issues surrounding anything rouse up a lot of noise but hey, were still havin' fun right?

I don't complain in person to folks who are using split fins just here on the board.... and I will freely admit that the blade bangers are just as bad at blowin' out the bottom.

It is kinda fun in a way to go to the local hole and listen to the guys~n~gals whine about the crappy viz.... it actually was much better before they all got in and started diggin' for worms but they never seem to realize that.

I am not really sure whether correct technique to prevent silting up the dive site is possible with the splits but I am going to try them again just to see.

The reason I sold the ones I've tried is because I couldn't get the big burst of speed to broach water like an Orcinus Orca.... well I can't actually do that with the Jets either but at least I could make the swim step on the boat... and the Turtles absolutely excel in reverse.

Does anyone here with splits do the reverse???
How do you work it???

 

[MikeFerrara]

UP,
Rodale's says they work with any kind of kick or scull. Isn't that good enough?
Mike

 

[Uncle Pug]

Originally posted by MikeFerrara
UP,
Rodale's says they work with any kind of kick or scull. Isn't that good enough?
Mike

Shoot Mike,
You're right....
I didn't know that...
Now I feel sheepish....


Baaa baaaaaa

 

[devjr]

Pug, think about that. If the splits are not generating enough thrust to lift a diver up to the gunnel it implies that the fins lose forward thrust when the diver is stationary. In other words, a flow of water over the fin is necessary to produce max thrust. This is way different from paddles and suggests something that Rodales is either not aware of, or is but hasn't reported. It just makes those who are naturally curious to wonder if this fits with the "official" explanation of the wing principle (whatever that may be). Certainly, an aircraft wing requires forward motion. A bird seems to resemble a paddle or an aircraft wing depending on whether it's soaring or flapping.

We divers can pontificate on complex mechanisms like regulators and computers but can't understand, much less explain, how a bloomin' fin works.

Yeah, having fun.

 

[Uncle Pug]

Originally posted by devjr
Pug, think about that. If the splits are not generating enough thrust to lift a diver up to the gunnel it implies that the fins lose forward thrust when the diver is stationary.

OK, I'm thinking....
But it is not as easy as it sounds!

Hmmmmm....

OK, you might have a point there.... and that would be why for example they take a while to get you moving.... and why they are not good at helicopter turns and direction changes, much less backing up.

So what you are suggesting is that the splits work fine once you get them moving and as long as you keep them going in a straight line they work just fine. Did I get that right???

 

[Fishkiller]

The splits work at gradual changes in direction.. Yes I would believe that you guys have come close to explaining how a fin works..:bonk:

 

[devjr]

Yep, we're on the same page. Another implication of the wing theory; it may be that splits stir up more silt when the diver is slow moving or stationary. In other words, without the flow of water over the blade, splits act like inefficient paddles, not wings.

The Biofin video only shows divers who are moving over the bottom at high speed, not typical slow speed that one expects of some wreck and cave diving situations. Yet, these are the very divers who require silt control.

Incidently, I'm not calling the splits "propellors" unless I can understand the analogy. A propellor has plenty of stationary thrust.

Right now, it's all speculation.