Removing side rails from footpockets

[twentytwomonk]

I was going through some pictures, and Cesar Prieto from the Carbontek team removes the rails from some of his footpockets and just glues them into the foot pocket themselves. Anyone ever tried this before? Seems like it might take away from the tension the side rails put on the blade, but that also might not be a good idea. Any thoughts?

http://www.carbontek.net/fotos/probadores/prieto014.jpg

 

[Bill McIntyre]

What would be the advantage?

 

[trux]

I do not think it is a good idea. The side rails keep the fin and the water flow over it straight, and reduce turbulences. By removing them, water will flow over the blades sideways instead of backward, reducing greatly the efficiency. Also, if you swim behind colleagues with small or no rails on blades, or with too wide fins, you can easily see the vertical motion of such fin during the kick - it slides sideways similarly to a falling leaf. I observed it many times, and that's also I prefer the concept of C4 with quite narrow blades and relatively high rails. The only problem with C4 is that the rails are from soft rubber and tend to tear off very easily.

 

[twentytwomonk]

No, not the rails from the blades, the rails from the footpockets...

 

[trux]

No, not the rails from the blades, the rails from the footpockets...

They have the same functionality too. Additionally they are also usually calculated with to improve the flexibility / geometry of the blades - for the optimal propulsion, the blades need to have variable stiffnes (softer at tips, stiffer at roots). By removing the rails, the blade may bend too much and too close to the footpocket, possibly negatively influencing the efficiency.

 

[Bill]

'the blades need to have variable stiffnes (softer at tips, stiffer at roots).'

This would make a great topic Trux. I think the Avocet design is working on this as it goes against everything I've seen in boat and airplane props.

 

[Bill]

Be carefull of using the blades without the support of the side rails unless the fins are designed for it (Mustangs). I've had the side rails come off while diving and it's easy to feel but once it happened when I turned on a deep dive and all the first kick produced was a sickening crunch. Fortunately I had a rope to pull up on but I sure felt the pain in the pocket book.

 

[trux]

'the blades need to have variable stiffnes (softer at tips, stiffer at roots).'

This would make a great topic Trux. I think the Avocet design is working on this as it goes against everything I've seen in boat and airplane props.

Yes, sure, Bill, there are also other ways possible, but I was refering to classical long fins.