Thickness is also directly related to flex.
Perhaps thick fins work better due to much less flex.
Perhaps thick fins work better, as it is easier to achieve a more accurate foil with a thicker fin, and/or perhaps a thicker fin is more tolerant of an inaccurate/imprecise foil.
Less flex, more accurate foil, happier surfing.
Possibly.
I have been experimenting with MrMik’s 3d printed high aspect ratio turbucled fins of various thicknesses. No errors in foiling, perfectly symmetrical, just Different thicknesses. The thinner stiffer fins have been the most engaging and rewarding when pushed hardest, the thicker fins are smoother through turns and more forgiving and rock solid predictable, especially at lower speeds, they have more grip and response. The Thinner fins have presented noticeably less drag paddling into waves and are just all around quicker, more precise, engaging, and less tolerant of user error, Kind of like too much engine, not enough tire thrilling, where thicker is plenty of tire, but lacking torque.
This impression was formed in relatively weak waves 3 foot overhead and under on an old school longboard design. A 25Lb 9’7" x 23 x 3 round pin that I have been riding for 15+ years. The thinner fin performance was unexpected. I was expecting the thinnest fin to be a dog, and it did turn weird, until I moved it 3/4" forward in the fin box and it then quickly began to blow my mind, until It snapped off after ~ 200 rides. The next day I rode a 1mm thicker version in very similar conditions and that Extra torque and top end was gone, replaced with more solid more predicatable turning.
So I am on the opposite mindset, at least with his turbucled leading edge super high aspect ratio GW fin design in this specific board…
How thin is too thin?
And I will be exploring this, with the thinnest and among the stiffest of the MrMik’s 3d printed fins yet, very soon.
That said, I had one traditional shaped wood fin I broke near the base, which worked OK before it broke being 1/2 inch thick. I rebuilt it ~5/32" thicker, and it worked so much better. Significantly better. But was It due to less separation of flow at higher angles of attack, or because being thicker it was less flexy, and easier to achieve an accurate foil when hand foiling?