IMO, the attraction to Force Fins has generally been that, in a flutter kick, the Force Fins convert more work into thrust than most other fins. This has to do with both the dynamics of the fin blade flexure and also the material used. This is my answer for the original question posed at the start of the thread.
As for the questions of, "if they are so good then why haven't others copied the design?", my answer to that is more involved.
First, materials:
The Force Fins are made from expensive materials that the mainstream manufacturers cannot use and still maintain their cost to profit ratios. Fiberglass fins are also far superior to plastic fins. However, we don't see any mainstream fin manufacturers making fiberglass fins either. Fiberglass fins are very popular with freedivers because they work better than plastic fins and freedivers are willing to pay for that additional performance.
Second, customer economics:
In spite of the fact that diving involves, first and foremost, swimming; for some reason scuba divers are not actually willing to spend any money on the swimming part of diving. Freedivers rarely spend less than $200 on their fins, and it is not uncommon to spend 6x that amount on a high-end monofin. But, scuba divers want fins that cost $40. I think it has to do with a lack of understanding how important the swimming is to what they are doing, because most of the time you can get by with a $40 fin and survive. If you dive enough, you will eventually run into a situation where you will wish you had invested in some better swimming technology.
Third, customer use:
A lot of divers have found a work around for the low efficiency aspect of paddle fins that takes away much of the force fin advantage. The force fin is IMO noticeably superior to most paddle fins in a flutter kick mode. However, paddle fins can be as hydrodynamically efficient when using a frog kick instead of a flutter kick. So, you can swim both comfortably and efficiently with paddle fins by doing a frog kick. The down side is that you cannot input much power or go quickly with this mode of swimming. However, few divers actually think much about the efficiency of their fins when swimming at high speed. They just transition from the frog kick to the flutter kick and think that because they are working hard, then their fins must be working hard as well. That perception tends to hold because they are going faster than they were with the frog kick. However, if they are diving with someone wearing efficient fins for higher power swimming modes when they are stuck in a situation where efficient speed saves the dive, they sometimes learn from the situation and convert (ie - change their perception of what it is worth to be able to swim well when diving). Those tend to be the people that form the small but dedicated followers of some of the fringe diving fin technology available (fiberglass freediving fins, force fins, or hydrofoil diving fins).
As for the questions of, "if they are so good then why haven't others copied the design?", my answer to that is more involved.
First, materials:
The Force Fins are made from expensive materials that the mainstream manufacturers cannot use and still maintain their cost to profit ratios. Fiberglass fins are also far superior to plastic fins. However, we don't see any mainstream fin manufacturers making fiberglass fins either. Fiberglass fins are very popular with freedivers because they work better than plastic fins and freedivers are willing to pay for that additional performance.
Second, customer economics:
In spite of the fact that diving involves, first and foremost, swimming; for some reason scuba divers are not actually willing to spend any money on the swimming part of diving. Freedivers rarely spend less than $200 on their fins, and it is not uncommon to spend 6x that amount on a high-end monofin. But, scuba divers want fins that cost $40. I think it has to do with a lack of understanding how important the swimming is to what they are doing, because most of the time you can get by with a $40 fin and survive. If you dive enough, you will eventually run into a situation where you will wish you had invested in some better swimming technology.
Third, customer use:
A lot of divers have found a work around for the low efficiency aspect of paddle fins that takes away much of the force fin advantage. The force fin is IMO noticeably superior to most paddle fins in a flutter kick mode. However, paddle fins can be as hydrodynamically efficient when using a frog kick instead of a flutter kick. So, you can swim both comfortably and efficiently with paddle fins by doing a frog kick. The down side is that you cannot input much power or go quickly with this mode of swimming. However, few divers actually think much about the efficiency of their fins when swimming at high speed. They just transition from the frog kick to the flutter kick and think that because they are working hard, then their fins must be working hard as well. That perception tends to hold because they are going faster than they were with the frog kick. However, if they are diving with someone wearing efficient fins for higher power swimming modes when they are stuck in a situation where efficient speed saves the dive, they sometimes learn from the situation and convert (ie - change their perception of what it is worth to be able to swim well when diving). Those tend to be the people that form the small but dedicated followers of some of the fringe diving fin technology available (fiberglass freediving fins, force fins, or hydrofoil diving fins).
