Aloha John
There is a huge amount of interplay between all the parts, but not enough time to disect them all and it is hard to do in print no matter how fast I can type! Ha! So… We gotta assume some likely agreed details and stay on point as much as possible otherwise as is typical of swaylocks…this will quickly drift into a political discussion of where the fins are made and an environmental discussion of how those materials are made. So please everyone, lets all agree to stay on point here.
It is my opinion that he most misunderstood and under valued part of why a tri fin thruster works so well is the fact that it is flying (hydroplaning) on the fins.
In my world, a surfboard fin is primarily a keel to keep the board from sliding sideways. The amount of surface area needed to resist a particular surfers turning force will depend on many factors. Too many to detail here so again lets not go there yet.
The most important ones are how much force a surfer can exert and therefore how much fin area is needed to resist it.
Yes, I agree that different foils can effect this but lets not go there and complicate the simple dynamics until they are well laid out.
Assuming an average turn, the laying up of the board on the rail will put the inside fin at a particular angle to the horizon. (horizon is just a base line for discussion, the fin doesn’t recognize horizon it just recognizes water flowing around it) If the fin has too much tilt then it can’t “catch” against the water as effectively and won’t have as much side drift resistence as a fin with no tilt.
So we have 2 important and conflicting issues. More Tilt allows hydroplaning on the fins, creating more lift without increasing wetted surface, thereby creating more thrust and speed. But more tilt also allows the board to drift sideways losing holding power in the turns and sacrifices the thrust and speed normally generated from turns. More of one creates less of the other and visa versa. Assuming normal fins and boards, then the solution is to find the best balance between them.
The reason I would like to infinately adjust the tilt, is because for every surfer, wave, fin, and board. There will be an optimum tilt that will create the highest amount of lift from the fins and the greatest amount of thrust from the turns. All with the least amount of drag and mass from the board.
It would be so cool to catch a wave, ride it, flip the board over and click the, yet to be invented “tilt clicker”, on the finbox one click for each .5 degree of fin tilt. Within couple of waves we would be riding the ultimate tilt angle for any circumstance.
Toe in is important but 1 degree of toe in on a 6’ board is less then 1" at the nose. Someone can check this. I didn’t run the numbers on my Cray Supercomputer! Ha! But I know someone on swaylocks will and please do.
1 " of toe in is less significant then 1 degree of tilt and… I hate to go there …but the template of the board matters more than the amount of Toe in. For example if the toe in is at the nose and the board is 19" wide the effect of the toe in will be much different if the board is 20" wide which creates a much bigger fulcrum point for the board to rotate on, while the effect of the tilt will be the same. Additionally, if the tail is super wide, the Toe In angle is now increased and you may begin dragging the fin too much sideways through the water. Like I said there are so many interacting factors we have to be carefull not to stray too far off course just to say, HEY. Look!! I thought of another one!!
So assuming a reasonable template and toe in of within 1" of the nose. The board won’t drag too much and will turn easily. But too little tilt and the board will not be fast and lively. Or too much tilt and it will drift and lose power in turns.
I should note here that if you tilt the fins far enough, toe in is eliminated as it is a vertical issue that exists less and less the more toward horizontal the tilt becomes.
These problems are often “sort of” corrected by different fin templates which surely can help, but imagine if you could get the tilt right for any fin template. Then you could begin to reduce the fin sizes until you were riding on the least amount of fin but getting maximum holding power and fin lift.
Then, if you could also adjust the Toe in angle on the fly, you could get that right also.
And now, we could effectively design fin foils that might enhance all the above and we would really be on top of our game.
The 4way system could do this, though not on the fly and they only advertise a 0 degree and 4 degree disc to adjust tilt. This is not sufficient.
The ProBox only adjusts tilt in 2 degree increments. This is still not enough but much better and their system doesn’t allow adjustment of the Toe In. And you can’t adjust any of this on the fly. But their routing system is very trick and way ahead of FCS and Futures which require too much pissing around.
I didn’t rate fin placement high on my list nor fin templates because we have those adjustments already. It is not that they aren’t super important, just that we have those options in some boxes now. And where you get the tabs located on your fin sets is another way of moving the fins around. So it shouldn’t be too hard to determine where the best location is. But Tilt and Toe In. That is a real problem. And adjusting tilt or toe within the construction of the fins is a big hassle.