Split Fins

[Charlie99]

As far as the silting... Check out one of the videos on Apollo's page http://apollosportsusa.com/Products/Fins/Videos.htm

They show a diver darn near dragging themselves along a silty bottom with no disturbance.

Look at the clip that shows both paddle fins and split fins. Look closely at the angle of the feet and of the fin at the end of the stroke. The diver with splits is doing a modified flutter kick with the knees slightly bent so that the foot is still above the knee at the end of each kick. That isn't true for the paddle blade diver.

Surprise, surprise. The manufacturer has a video which isn't exactly an unbiased test!

Splits are amazingly efficient. If you maintain discipline and kick properly, they work much better than paddle fins in a current. Split fins are like other finely crafted tools. For the right situation, and used properly they are very good. Used clumsily or for the wrong job, they are horrible.


Unlike the video by the manufacturer, my experience has been that split fins, when pointed down at the bottom by a negatively buoyant diver, can stir up sand and silt even when the diver is several feet from the bottom. Kind of like that old toy that would pulse a rubber diaphram and shoot a smoke ring or vortex of air all the way across the room.

I have never seen this long range vortex with any fin other than the splits, and always assumed that it was in some way related to the very high efficiency of the fin.

 

[scubatoys]

Unlike the video by the manufacturer, my experience has been that split fins, when pointed down at the bottom by a negatively buoyant diver, can stir up sand and silt even when the diver is several feet from the bottom. Kind of like that old toy that would pulse a rubber diaphram and shoot a smoke ring or vortex of air all the way across the room.

I have never seen this long range vortex with any fin other than the splits, and always assumed that it was in some way related to the very high efficiency of the fin.

I believe you are exactly correct. I'm not a hydrodynamic engineer, but in my experience, biofins send more water backwards, and less up and down. So since they are faster and more efficient, it makes sense they push water behind you farther, since they are not shoving as much water up and down, so if the fins are pointing down - the vortex would hit the bottom. No fin can correct poor buoyancy, but by simply getting the students to have proper trim, I find no silting problems - and again... less than standard paddles.

 

[dbombtek]

Splits work as good as paddles if not better. Always try before you buy because you need to be happy with what you are using.:mooner:

 

[drew52]

I vote for split fins.

Not sure about the silt thing but I lead and teach numerous divers. Bad trim causes operation desert storm no matter which fins are being used.

Learn proper buoyancy and trim and there is no issue. I also believe the problem is less with split fins but who knows I've done no scientific experiments...

 

[Adobo]

but by simply getting the students to have proper trim, I find no silting problems - and again... less than standard paddles.

Just like you wouldn't use split fins to do helicopter kicks and back kicks, you wouldn't use paddles to do flutter kicks while that close to the sand.

Instead of pushing divers towards only one solution, why don't we talk about the different ways that a problem could be solved? As an example, if you are gonna teach a diver proper trim and bouyancy anyway, why not teach them that there is more than one propulsion technique? You know, like the modified flutter kick that the split fin diver is using in that video? Why don't we talk about how to do a back kick or a helicopter?

In caves and wrecks where divers lives are put at huge risk when silt outs happen, it strikes me as odd that the overwhelming majority use paddle fins.