http://www.windsurfermag.com/magazine/pro-slalom-windsurfing-fin-tuning-tips-kurosh-kiani-vector-fins/?params=M3w2Mnww
Great find choco,answers all your basic fin questions.
AAA ebay rating for that one. 
Hey guys, good article but I'm hoping for some advice that could narrow it down a little more for me. I've just bought an 06 Starboard Go 155 but the fin that came with it looks like it's had a pretty major repair job so rather than getting caught out i figure I'd get a new (or secondhand) fin or two. Would really appreciate some suggestions if anyone can help
So here is my situation,
Making a windsurfing come back after about 15 year. I've done most of my sailing on lake Illawarra, NSW in the past. I'm 90kg and have bought an 06 Starboard Go 155 and a 7.8 Naish redline. I chose this size kit hoping to be able to get out on the water in moderate conditions and not have to wait purely for the good old black northeasters. But in saying that I'd always prefered to sail overpowered and hang on for grim death rather than go in and change down, so i guess i should take that into account when making fin choices.
So what do you say, any suggestions? size? brand? shape?
I think people over think fins.
For most beginner - intermediate sailors fins choice isn't going to be that noticeable as long as its around what it should be for the board.
Good technique is more important than having a fin for every sail and board combo you have.
For most people i'd say stay with the stock fin the board came with until you get to a level when you need that extra 2 knots of speed.
Spending time on the water and learning how to do things correctly with the board is far more beneficial than sitting on the beach worrying about fins.
The stock fin that comes with a Starboard Go is @#$% ,badly shaped and manufactured and its why most people sell them with the board. Check the fin in the light for all the bumps and dips in the shape. A good fin never has this. Good fins that i have used. C3, Select,MFC. For someone starting out something thickish that will produce early lift, not to much rake and with a soft tip to help in chop.Cost $200 new, 2nd hand $100
Yours are just a lump of glass and fibre shaped with a hacksaw and jambed into an end of the board to make it go slower. 
I also think that manufacturers tend to compromise on a fin size for the range of the board. They often under fin to increase the range of the board.
I know I've had a couple of boards now that I barely used the stock fin because they were so underpowered. So even as a beginner you'd be missing out on a good part of a boards versatility with a underpowered fin.
Yeah, sometimes they get it very wrong.
I bought a nice F2 a few years ago, that had a too small stock fin that just did not work for me.
After fitting a much bigger fin, that board just came to life.
An intermediate that stuck with that fin would have missed out on a lot of fun.
I agree with wespyyl to a point, i've lost count of the number of people i've seen with say 2 boards and 6+ fins, swapping them all the time and generally faffing about. When you're a beginner or intermediate sailor I think this can become a distraction and 'the wrong fin' is more often that not used as an excuse for poor technique.
That said, it's also totally discipline dependent imo. For example on my freestyle board i'll run pretty much anything as long as it's <20cm, it helps if the chord is pretty wide, obviously since it's so short. That said i've run a wave fin cut down to 15cm in it and it still works fine, a bit slidey but given the technique you use to sail a board with a fin like that it's a non issue.
Likewise all my wave boards have super short fins, the longest fin I have on my single fin board is a 23, once again they aren't the sort of boards you 'sail off the fin' so I go for something that is as loose as possible.
Lastly I think slalom and general freeride etc is a different ballgame as most people don't have the technique required to sail a board with such a short fin, nor would you want to if your bread and butter is blasting back and forth.
Like flicky spinny i've just joined the Freestyle ranks and so can get planing in about 17 or 18 knots on with a 5.8 and 16cm fin.
But I was more meaning that any intermediate sailor who comes in to the beach and puts a 2 or 3cm different size fin on and then says
"OMG the board is so much easier to control now, that's why I wasn't pointing properly/ couldn't get planing/ whatever"
Is doing it wrong.
Granted a dramatic fin size change like 8 or 10 cm will change the board a lot.
Okay thanks guys, i think???
I guess I'll try to pick up a something 46-48 and see what happens
