Longboard fins - desperately need help

[catsandboots]

I'm extremely new to surfing and recently acquired a used 10' longboard without fins. I know absolutely nothing about fins (and I mean NOTHING). It is a tri-fin setup, and I have no idea what to do. As I said, I am a beginner, and don't really care about performance. I'm looking for whatever is the cheapest, most standard fin setup. The board has a typical fin box, with "10.5" marked inside.

-Do I need a "longboard" fin?
-When you buy fins do you need tools to install them/do these tools come with the fins?
-Do I have to buy all three fins (thruster + longboard fin), or can I just get the centre fin?

Please help me, I am very lost, and the internet is only confusing me further.

[jaffa1949]

There is a whole section on fins "Uncle Jaffa's fin primer."

Here is an easy answer there are several brands of fin set ups, we need to know which one... Typical fin box? Little round plugs on the outside fins? Are they all fin boxes?

If they are little round plugs, do they have grub screws in them? If so a normal fin key (Allen key) is the tool for them? Buy at surf shop!

Centre fin in most boxes requires a screw and plate set up.

I'll explain your centre fin ( 9 or 10" is suitable size) has a metal pin through the base which slides into a groove I the box at the other end of the fin is vertical hole in the base. You buy your fin and buy a fin screw that is special stainless steel screw with a square plate that goes into groove in the fin box. This screw can tightened be tighten either by a suitable screwdriver or in more modern screws the same fin key.
Place pin in groove slide fin downto one end to give space, remove screw from plate , place plate in groove at the right end of fin. Place screw in vertical hole screw it into plate lightly .slide fin along the box to where you want it to be. Tighten screw so all is firm.
Forward in the box makes the board loser in turning back makes it tighter.

See how you go , you only need one fin, the centre one would be best!

[waikikikichan]

With a long center box and two fin mounting things to the side, it's called a 2+1 fin set up. Not Tri-fin ( although it's possible ) The fins to the side are normally called side bites. Not Thruster fins which have all three fins same sized b ( although you could two of the Thruster fins there and leave out the center fin ). If you're just starting out, save your money and just get a single fin for the center. Maybe around 9 inches. Which to others will seem to be to small, but fine now for going straight in the whitewater. Those side fins won't matter for a newbie and less things to get hit/cut by. Later when you start turning, add side bites ( FCS uses the GX model, Futures Fins uses the SB1 ). If you got something else like BIC or non standard fin system, post a picture.