Bi-fins: T-shaped railing along each side of the blade

[morgan000]

fellow freedivers,

I'm buying my first pair of bi-fins and there is one thing I can't wrap my head around: do I need to add the T-shapped 'railing' along each side of my blade on models that don't have it?

From what I understand this strongly helps your finning technique, hence your performance, so that got me asking why all manufacturers don't include it on their fins?
What part did I miss...........

Thanks guys

 

[cdavis]

Depends on what you want to do with your fins. Rails are great for efficiency, not so good for quick maneuverability. Sometimes I wish my blades had them, sometimes I'm very glad they don't.

Connor

 

[azapa]

think of those T rails like this:
- YES they push more water backwards, and therefor the diver forwards, far better that no rails
- NO they don't slide (slice sounds better) sideways through the water very well if you are trying a sharp turn.

All in all, my personal recommendation is to get them.

 

[hteas]

Morgan,

The rails will help move water backwards, but I doubt they will improve your finning. To improve that, spend time in the water working on your finning.

 

[morgan000]

Thanks soooooo much guys!!! I love this forum, everyone is so helpful!

My decision is taken, I will get them and can always remove them if need be.

Cheers

 

[cdavis]

Just a caution:

Blades are designed for the rails they come with. Remove the rails and you are very likely to end up with blades that are very different from what you started with, probably a lot softer and maybe with other characteristics you might not like. .

 

[azapa]

...and if you are wondering why carbon and fibre fins seem to have longer and more pronounced rails: its because these materials are produced FLAT an need them. Many plastic fins have shorter rails and pseudo compensate by having channels molded along the blades.

 

[peacenluv]

I'm curious about the effect a rough surface blade has compared to a smooth surface blade. It seems a lot of carbon blades have a rougher surface lately, like the stingray and trygon carbon blades. If the blade is rougher, will it "grab" water more? and if so, would it require smaller rails?

Before, I used the first version Beuchat Mundial Carbon fins where the rails were very small and low profile like the Trygon rails now. They felt very easy to kick, though the blades might be considered medium-stiff. When the new version came out using the same blade but with more protruding rails (even though the rails were still rather small compared to some manufacturers'), the fins felt much stiffer and seemed to require much more power to kick. It's obvious the rails have quite a huge effect on the fins. But it would also seem that trying out fins without rails may give you the wrong idea of how efficient the fin is, so to speak. Of course there are a lot of variables such as kicking technique, etc. But i'm curious what others' thoughts on this are.

 

[cid]

I'm curious about the effect a rough surface blade has compared to a smooth surface blade. It seems a lot of carbon blades have a rougher surface lately, like the stingray and trygon carbon blades. If the blade is rougher, will it "grab" water more? and if so, would it require smaller rails?

I think the blades have a rough surface because of the manufacturing process. Omer stingray fins are made by vacuum infusion and with vacuum infusion at least one side of the fin needs a peel-ply which has a rough surface. There is a thread on deeperblue with nice videos about homemade fins by vacuum infusion.

 

[Vov]

During paddling water 'turns over' on the sides of the blades - from the higher-pressure zone to the lower-pressure zone. That flow creates the so called induced drag which is a mere loss of energy. Rails significantly reduce the induced drag by decreasing the water flow around the blade.
The difficulty is to mach the blade hardness+the rails added hardness with the personal strength, durability and way of paddling of a diver...
I believe one could add some more efficiency if one can spend some time training with no rails fins, and learn the right way to paddle without sliding... Then start diving with fins with rails.