What I do not like about the OEM 70 cm wide chord fin that is supplied with the Serenity boards is that this particular fin design makes the Serenity very "unforgiving".
For sailing upwind on very flat water in < 10 knots of wind, it's a bit draggy, but pretty good overall.
I get better light wind speed on smaller 56-62 cm fins and do not believe I give up very much, if any, upwind angle and speed.
The big wide blade 70 cm stock fin does not handle any sort of "transition" easily.
If you jibe the Serenity the stock fin goes from "loaded" on the down wind side, to neutral as you head straight downwind, and then BANG it grabs all of a sudden as the pressure shifts to the other side.
Even std. 70 cm race fins (such as are supplied with Formula boards) are more forgiving than the Serenity fin.
I don't even use the stock fin in the Serenity unless it's a deep water demo and someone specifically asks to try the big fin.
I normally equip the demo Serenity with a 60 cm race fin or a 32-42 cm weed fin.
You could cut your 70 cm down to 60 cm but I'm not at all sure that this is going to make it any more forgiving.
Planing the tip down to give it more flex would most likely destroy the foil in the lower part of the fin, so I'm pretty much against that idea.
You should be able to find a used 58-62 cm formula/slalom fin for next to nothing and I think this is a better solution to this issue.
Borrow a 60 cm and give it a try and see if your feeling about the difference between the big wide 70 and a 60 cm race fin isn't similar to mine.
If I were to race the Serenity against other Serenitys in a one design class race, maybe I'd chose the big fin, but my experience suggests that falling off in the transitions would put me further back in the fleet than some tiny bit of upwind performance with better speed in a straight line with the shorter slipperier 58-62 cm race fin..
Hope this helps,
Last edited by Roger; 21st September 2008 at 08:17 AM.