Effective toe in ?

Does anyone know how to calculate the effective toe in angle on asymmetrically foiled side fins ?


Hey Bloke,

A truely pure arithmetic approach to a rail fin toe in formula probably doesn’t exist. Placing the trailing edge at a standard distance from the rail and up from the tail followed by aiming the fin at a given point at the tip has been used for some time. The within limits the further you move the fin up toward the nose and toe it in the more bite it gives. The more tail rocker a board has the less toe in the fins need to facilitate turning so in the end the world of mathmetics will always remain somewhat muddled when it comes to appropriate toe in. Board foils remain infinite in their variety and fin placement and attitude have to suit the board configuration ~ enough said.

Aloha, Rich

Thanks Rich, what I am trying to figure out is when asymmetrically foiled fins are running effectively parallel (i.e no effective toe in or toe out) I know that if I just run the flat inside surfaces of the fins parallel then the result is effective toe out, so I want to toe the fins in just enough to make them effectively parallel from a water flow point of view.


I getcha Roy, tough ask, the variables are huge, starting with are you using any of the NACA foil profiles? They are familiar ground to me ( and a well researched basis to start from) but the 3D fluid environment of a wave makes the final analysis a minefield of variables and surfing conjecture…( speed, angle, cavitation, ventilation,totally submerged/surface piercing and what percentage of each fin or both )

Not forgetting the turn arc, wave aeration variables, chop, water density,fin and board flex…

Could’nt you ask a simpler question like… why do women do what they do?..or if theres no air in space- then whats up there?..or why politicians arent shot on sight?

Keep at it Roy- it’ll happen.

But I think you are looking for a fin design configuration with minimal drag? Yes?

Hey Roy

I’d be using the midline of the lead part through to the tip of the trailling section…

Prease excuse clappy dwawling

Sort of averaging things out…seems logical…to me anyway…