Best type of fins for current

[elmer fudd]

I also have to wonder to what extent those fish fins are actually split and how much of them are joined together by a translucent membrane.

 

[diggerled]

I know that some split fins work very well, but I really doubt that has anything to do with them being split up the middle. I think it has everything to do with them being floppy. The fins easily bend to 90 degrees and that allows them to push the diver ahead more directly.

Hmm, this may add up. floppy, 90 degrees equals low gear. To get you moving. Stiff, slighter angle equals high gear. once you are already moving as in making headway in a current.

Look at the cant on a window fan blade as opposed to the propeller on an aircraft.

 

[elmer fudd]

I wouldn't correlate the 90 degree part to high or low gears, it's just that by bending the fin 90 degrees the vector of force applied to the diver pushes him straight ahead. If your fin is angled less than that it means you are also applying force in other directions that don't propel you forward.

Imagine an oar turned 45 degrees from vertical. While it would still provide resistance to the rower and it would still propel the boat in a forward direction, it would also direct much of it's energy in either an upward or a downward direction depending on the angle making it less efficient.

I don't think it's really comparable to the pitch of a propeller because the speed of a diver is so slow relative to the speed of a boat. I'm not enough of a physics whiz to really explain this one, but it seems to me that a diver moving forward at between 1 and 2 knots just doesn't have the forward motion necessary to make a forward angled fin efficient.

I think one of the things that we also need to keep in mind when it comes to high vs low gear debates, is that the speed of divers is VERY limited. A diver that's really racing balls to the wall might get up to 3 knots, but generally 1 knot is a comfortable traveling speed and 2 knots is serious finning. This would be a little like having a truck that you never got out of first gear in 4L. Multi-speed transmissions or derailleurs never would have even been invented under these conditions.

 

[MauiScubaSteve]

But why are you swimming into current?

There are numerous threads here on SB that take issue with the supposed lack of gas management education in the PADI OW course. As a new PADI DM, do you know / remember the gas management / dive planning from the PADI OW manual?