I’ve encountered humming fins various times in the past and recently I heard it again on a brand new set of fins with an inner foil on the outer fins (the vector-style fins). Back in the early eighties, when I used to make fins, I used to think that it had to do with the vertical stiffness. If we didn’t use the nornal number of layers of fibreglass (at the time I think we used fourteen layers), the tip of the fin was very flexible, and we thought that it was vibrating back and forth in the flow. This would tipicaly start happening when the surf was more substantial (4-6 foot).
More recently, though it happened when surfing 10 foot down in France on these new fins, and they are very stiff. I guess that it means that this whole idea of having an inside foil on the outer fin will need to be consided/designed very carefully in order not to get the humming, as I am also guessing that energy which is used up in humming is adding to the drag/slowing the board down?
Howzit Nick, Rick, CB & Plus One… the board I have with fin hum is an older Dick Brewer mini gun. I’ve tried sanding those fins 19 ways from Sunday and it just won’t be fixed. One of the fins is misaligned (a tad too much toe-in) but I don’t think I’ve ever heard anyone suggest that as a cause. I’ve been able to change the “note” (frequency) of the fin hum but have never been able to eliminate it. Just one of those puzzles I guess… by the way the board is plenty fast but it does feel like it loses just a bit of speed when the fin hum is worst…more noticeable in weaker waves than bigger ones.
I have looked at the fin again.I think one side where the fin meets the board,has more glass build up.Starting just before the fin and going just past it.It is only slightly noticible,but thats the only thing i see it could possibly causing humming after reading all these posts.
I am not going to start messing with it,but i am interisted to see what it does the next time i surf.Most likely i will just live with it.
The first and only time i rode the board ,the waves were a foot or two overhead and hollow.