Force Fins and DIR diving

[meesier42]

I'm not a DIR diver but the Force fins (people use them for wreck diving up here) look like they are designed flutter kicking and direct thrust downward, which isn't always optimal for silty situations.

its amazing to me that you think they LOOK like they would direct thrust downward, which tells me a couple things about you.
1) you have never used them
2) you have little or no knowledge of how fins actually work

being that I have used them extensively inside wrecks, many styles, Foils, Pros, Excellerators, Hockey, Extra Force, SD-1 all of them work excellently in high silt tight quarters, but technique has a lot to do with that.

 

[billgraham]

its amazing to me that you think they LOOK like they would direct thrust downward, which tells me a couple things about you.
1) you have never used them
2) you have little or no knowledge of how fins actually work

being that I have used them extensively inside wrecks, many styles, Foils, Pros, Excellerators, Hockey, Extra Force, SD-1 all of them work excellently in high silt tight quarters, but technique has a lot to do with that.

Hey, I'm happy to try a pair of the new ones in the caves. I probably don't know much about how fins work, you're right. You probably don't know much about cave diving. The dive I described was almost ten years ago and I remember the fins as being the flat short ones, I'm sure they were an old design even then. Those who know me well will tell you that I'm always up for trying new and innovative gear so I'm all for it. I've got a couple of friends who invent and manufacture dive gear so I'm an experienced test dummy and if there's a way to break it, I'll find it!

 

[danvolker]

Bill,
The real issue for what you are discussing, is how much control surface is on the fin for precise control, and "How effectively" the control surface works -- how "tight" is the steering .... and for Frog kick, the 2 main things that are critical is that the fin is a stiff enough platform to PUSH on, along with allowing easy ankle articulation so that you can roll the blade after the push, and slide it back to the start phase without resistance.

( the push is like you are climbing a ladder, and pulled your legs up to 2 rungs higher, and then put your feet on these 2 rungs and push....which directly moves you higher.....ideally, with almost no fin bending, so that it really feels like the push is against a solid object like the rungs)

Worst for the resistance, are fins like the Mustang C4 freedive fins, which have a rail on the blade edge, and do not slide back easily.
Worst for the big PUSH, are sloppy fins like Apollo bio splits, which don't feel as though there is anything at all to "push" on....

Scubapro Jetfins are stiff to the point of being a nice platform to push off of...and, they have a good control surface that allows them to be slid sideways with an articulated ankle, and have very little resistance on the way back to the start of the push phase of the frog kick.... The Excellerators are almost identical to the large jets on push, and slightly easier to articulate and slide. This ease in the sliding and articulation, is what makes them superior for the Reverse Kick....something nice to have in-cave.

Unlike the jets, the Excellerators become more efficient as more torque and higher cadence is appied in a flutter kicking scenario, when a high speed is required to deal with some critical event. The jets lose efficiency if anything, as you approach maximum speed with them.

 

[billgraham]

Bill,
The real issue for what you are discussing, is how much control surface is on the fin for precise control, and "How effectively" the control surface works -- how "tight" is the steering .... and for Frog kick, the 2 main things that are critical is that the fin is a stiff enough platform to PUSH on, along with allowing easy ankle articulation so that you can roll the blade after the push, and slide it back to the start phase without resistance.

( the push is like you are climbing a ladder, and pulled your legs up to 2 rungs higher, and then put your feet on these 2 rungs and push....which directly moves you higher.....ideally, with almost no fin bending, so that it really feels like the push is against a solid object like the rungs)

Worst for the resistance, are fins like the Mustang C4 freedive fins, which have a rail on the blade edge, and do not slide back easily.
Worst for the big PUSH, are sloppy fins like Apollo bio splits, which don't feel as though there is anything at all to "push" on....

Scubapro Jetfins are stiff to the point of being a nice platform to push off of...and, they have a good control surface that allows them to be slid sideways with an articulated ankle, and have very little resistance on the way back to the start of the push phase of the frog kick.... The Excellerators are almost identical to the large jets on push, and slightly easier to articulate and slide. This ease in the sliding and articulation, is what makes them superior for the Reverse Kick....something nice to have in-cave.

Unlike the jets, the Excellerators become more efficient as more torque and higher cadence is appied in a flutter kicking scenario, when a high speed is required to deal with some critical event. The jets lose efficiency if anything, as you approach maximum speed with them.

Cool, thanks for the explanation. I went and looked at the exellerator and it's a lot different from the ones my friend brought down back in the day. I've used the jets a lot and my problem with them was the weight--I tend to be foot heavy to start with. When I did my rebreather training in '04, Griffith was buddied up with me and had a pair of the slipstream prototypes which are the same shape and solved the weight issue. Your description of how the frog kick works is dead on, the blades have to be stiff enough to push a lot of gear through the water into current, and the ankle twirling part of it is where you have problems on a really long swim. Anything to make that transition back to the power part of the kick easier would be great. I am interested to try them.

 

[danvolker]

I just took my inflatable Kayak out today, and paddled a couple miles to a good freediving area.... I brought the Excellerators instead of my freedive fins, because I was mostly doing a paddle trip..the diving was just to see how it looked ( vis was expected to be poor today)....
What I was blown away by, was how fast the excellerators were for snorkeling, with none of the drag from tank or BC.
I was hitting scooter speeds!
So the next time someone asks if these are good for snorkeling on top of the water....yes, they are fantastic, or for freediving..they are better than scuba fins....they still require more kick turnover than a real freediver wants for 2 minute bottom times--a non-issue for snorkelers....