Cave diving fins

[Johanan]

It’s worth to notice that even though heavy fins loose part of their weight when submerged, they do not loose their mass. Imagine waving a massive object on the surface. You have to overcome the inertia on both ends of every kick. This has an effect on tiredness and gas consumption.

 

[Preach]

Really? Nearly all European cave divers whom I have met dive RK3s.

Maybe i should change that to "in the Netherlands" then. But also other tech divers i met in Europe, almost all had SP jet fins.

I cant remember even seeing apeks rk3 fins over here.

 

[aquacat8]

It’s worth to notice that even though heavy fins loose part of their weight when submerged, they do not loose their mass. Imagine waving a massive object on the surface. You have to overcome the inertia on both ends of every kick. This has an effect on tiredness and gas consumption.

This mass can also work in your favor. I had to slow my flutter, and flutter is their worst kick, but if you slow your flutter they work fine and the increased power still adds more speed. Slow kick cycle=less air consumption. In a frog kick and glide scenario the mass makes you go and go. In a helicopter or other tight move the mass gives you something solid to pry off of, almost like kicking off a friendly wall that somehow materialized underwater. I was really surprised by this. In Dolphin it is almost like pushing off a wall, then the momentum takes over and you glide and glide. Actually they are really fun to freedive in if you like to dolphin, and you can’t afford a $450 monofin. Few talk about their superiority for “skin diving” but most of those early Scuba divers were “goggle divers” first and the jet fin works well for that.

And as we all know they are THE fin for swimming backwards. The mass and ability to push off it helps here too. There really is a technique to swimming them. You have to work with, not against, the mass and momentum. There’s a certain amount of “wait for it, wait for it, ahhhhhhhhhh! POWER!”

 

[Johanan]

This mass can also work in your favor. I had to slow my flutter, and flutter is their worst kick, but if you slow your flutter they work fine and the increased power still adds more speed. Slow kick cycle=less air consumption. In a frog kick and glide scenario the mass makes you go and go. In a helicopter or other tight move the mass gives you something solid to pry off of, almost like kicking off a friendly wall that somehow materialized underwater. I was really surprised by this. In Dolphin it is almost like pushing off a wall, then the momentum takes over and you glide and glide. Actually they are really fun to freedive in if you like to dolphin, and you can’t afford a $450 monofin. Few talk about their superiority for “skin diving” but most of those early Scuba divers were “goggle divers” first and the jet fin works well for that.

And as we all know they are THE fin for swimming backwards. The mass and ability to push off it helps here too. There really is a technique to swimming them. You have to work with, not against, the mass and momentum. There’s a certain amount of “wait for it, wait for it, ahhhhhhhhhh! POWER!”

You entice me to try the Jetfins. I normally dive with UK cave divers. May be they choose Apeks out of patriotic considerations as it is a British manufacturer. Most of them dive Otter dry suits as well. But IMHO RK3's are great fins.

 

[aquacat8]

Well I’d like to try those RK3’s too. They look very similar. I wonder how the performance would vary. One thing I notice is the long under foot pocket. I think that might give more power transfer. At first I thought the short under foot pocket was a flaw in the Jets as you don’t get thrust from the heel. However when I was researching blade angle on freediving fins I realized the short under foot on my jets allows me to point my toes farther, pointing the fin tip down more as the heel is not involved. I like this for precision and for flow. I see the RK3’s also have vents, though they are different too. With the jet fins the vents provide a “jet” of power if you drop your foot from a raised position as in modified flutter (cave flutter)... Do you feel that with the RK3’s too?

 

[EireDiver606]

What do people think of Hollis F1s and LTs? Do you think the F1 is too heavy? I know the Hollis F1 LT is very strong and powerful but I can imagine the F1s are very heavy?

 

[KevinNM]

It’s worth to notice that even though heavy fins loose part of their weight when submerged, they do not loose their mass. Imagine waving a massive object on the surface. You have to overcome the inertia on both ends of every kick. This has an effect on tiredness and gas consumption.

The reason you typically use heavy fins is the balance the heavy weights of the back-plate, tanks and regs that are mostly above your center of gravity. As your fins are very far from your center of gravity their relatively small mass (compared to a pair of steel tanks) allows you to maintain trim. Swimming around head down 30-45 degrees also has issues on gas consumption and tiredness.

If you are diving sidemount or otherwise don't have lots of weight high on your body then maybe you should choose different fins.

 

[LPA]

Went ahead and got dive rite xt fins. Just spent two weeks cave diving with them and totally love them, so much more control than with my recreational fins! Definitely not too heavy (diving wetsuit). Also not as stiff as e.g. RK3 fins, but that was great to save my ankles after a full day in the water.

 

[mainedvr]

I'm not doubting that Jet fins, Hollis F1, Apeks RK3 etc. are all great and proven cave diving fins. But in the end they're all based on a design from the 60s. DiveRite XT is definitely more modern, but is there a reason that the most modern fin designs, e.g. a Scubapro Seawing Nova is not commonly used in cave diving, or is this just a question of time...?

may have already been answered, but anyhow on the seawing nova's there is a spot that flexes between the blade and the foot pocket could be a failure point I suppose. Never heard of it happening but if you look at it I suppose it could. I use F1s and the DR XT's not at the same time of course

 

[Capt Jim Wyatt]

Dive Rite XT fins for me. I used Scubapro super jets for decades until I tried the dive rite fins....I'll never go back.