What sized fins to use for a 2+1 fin setup. Help!

[OldMudjimbaIsland]

Hi, I have been surfing for the last few years, but I still know little about fin sizes, materials and their effect on the board. My favourite 7,2ft mini-mal/longboard is running a 2+1 fin setup since I bought it, with a 6.8 inch centre fin. I have just recently bought new 4.5inch fins to replace my old "byte" fins. I have now realised that my old "byte" fins were 3.5's and are much smaller then my new fins. I am now wondering is it okay for me to use the 4.5inch "byte fins" with the 6.8 inch centre fin. Or do I need to return these fins and get smaller ones. I am just really confused when it comes to fins.

I put "byte fins" in averted comma's because I am not sure if thats the right word for them.

Thanks.

[waikikikichan]

Let's say fins come out to an area of "135" for the amount of fin that feels right for you. So your 2+1 fins set up had a 6.8" center with 3.5" side bites, so that was still in the area of 135. If you had a Thruster fins set ( say FCS go to fin, the M-5 ) where all three fins are the same at 4.5", then you get 135. But once you increased the sides from 3.5" to 4.5" then you have to lower the center fin length to stay with in that area number.

Most longboards running a 7.5" center use the GL side bites that are about 3.8" tall, so maybe that is what you had. ( or if Futures Fins, the SB1 )

[jaffa1949]

There is a whole fin primer on the forum that may help!
Imwrote it!
Some help rough rule of thumb centre fins usually about 1 inch per foot of board.
Side bites , the ones you bought are probably too big particularly if the base measurements base of fin from front to back is large when you add all three up. Centre fin positioning changes a lot, if it has a long box rather than plugs you have quite a few options.
So the question is what did you want to change in your surfing that made you want to change fin set up?
Another question about your surfing, what are you capable of doing consistently when you surf?
Do you paddle out to Old Mudjimba , good surf spot

Oh final thought don’t worry about spelling too much, it’s about surfing

[jaffa1949]

You could also,try single finning it!