Re: [DougSchuch] FIN ?: Best High-
Posted: July 16, 2004 -
Quote:Glide, I have a stack of fins that I try out on my new boards, until one tells me, "This is the right fin for this board."
Two fins keep outperforming the others: Guy Takayama Orca model (for drive and performance, and the Manta model (to loosen up the tail). I don't know a lot of theory behind fin design, but Guy thinks out his designs very carefully and they work.
Both of those fins use flexibility of the fin tail to advantage. If you look at the image carefully, you can see the substantial chord length increase at the tip. Tip chord lengths are over 4 inches, whereas the fins have 3 to 3.5 inch chord lengths further up. This generates drive NOT through a normal foil action, but because the tip changes its AOA, stores energy, and then releases it.
You can make the whole fin do that, it makes a BIG difference.
Normal wings would not increase their chord length near the tip because of the penalty
in induced drag. Minimizing induced drag comes from an elliptical lift distribution
If you load the fin in a rotating system, you can make the whole fin turn like that, more easily control the force/AOA relationship, and avoid the induced drag penalty from having almost the longest chord length at the tip by using an elliptical, raked, foil. [wink]
Note: I like the Takayama designs, they are well thought out IMHO.